CA2595719A1 - Image transformation means including user interface - Google Patents
Image transformation means including user interface Download PDFInfo
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- CA2595719A1 CA2595719A1 CA002595719A CA2595719A CA2595719A1 CA 2595719 A1 CA2595719 A1 CA 2595719A1 CA 002595719 A CA002595719 A CA 002595719A CA 2595719 A CA2595719 A CA 2595719A CA 2595719 A1 CA2595719 A1 CA 2595719A1
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Abstract
This patent describes a user interface for operating a device. The user interface comprises a card which is inserted in a machine and on the face of the card is contained a visual representation of the effect the card will have on the output of the machine.
Description
DEMANDES OU BREVETS VOLUMINEUX
LA PRPESENTE PARTIE DE CETTE DEMANDE OU CE BREVETS
COMPREND PLUS D'UN TOME.
CECI EST LE TOME DE _2 NOTE: Pour les tomes additionels, veillez contacter le Bureau Canadien des Brevets.
JUMBO APPLICATIONS / PATENTS
THIS SECTION OF THE APPLICATION / PATENT CONTAINS MORE
THAN ONE VOLUME.
THIS IS VOLUME OF _2 NOTE: For additional volumes please contact the Canadian Patent Office.
IMAGE TRANSFORMATION MEANS INCLUDING USER INTERFACE
Field of the Invention The present invention relates to an image processing method and apparatus and, in particular, discloses a Digital lnstant Camera with Image Processing Capability.
The present invention further relates to the field of digital camera technology and, particularly, discloses a digital camera having an integtal color printer.
Backpõt outtd of the lnvention Traditional camera technology has for many years relied upon the provision of an optical processing system which relies on a negative of an image which is projected onto a photosensitive film which is subsequently chemically processed so as to "fix" the fiim and to allow for positive prints to be produced which reproduce the original image. Such an image processing technology, although it has become a standard, can be unduly complex, as expensive and difficult technologies are involved in full color processing of images. Recently, digital cameras have become available. These cameras nonmally rely upon the utiliration of a charged coupled device (CCD) to sense a particular image. The camera normally includes storage media for the storage of the sensed scenes in addition to a connector for the transfer of images to a computer device for subsequent manipulation and printing out.
Such devices are generally inconvenient in that ali images must be stored by the camera and printed out at some later stage. Hence, the camera must have sufficient storage capabilities for the storing of multiple images and, additioinally, the user of the camera must have access to a subsequent computer system for the downloading of the images and printing out by a computer printer or the like.
Further, PolaroidTm type instant cameras have been available for some time which allow for the production of instant images. However, this type of camera has limited utility producing only limited sized images and many problems exist with the chemicals utilised and, in particular, in the aging of photographs produced from these types of cameras.
When using such devices and other image capture devices it will be desirable to be able to suitably deal with audio and other environmentai information when taking a picture.
Further, the creation of stereoscopic views, with a first image being presented to the left eye and second image being Presented to the right eye, thereby cresting an illusion of a three dimensional surface is well known.
However, previous systems have required complex preparation and high fidelity images have generally not been possible. Further, the general choice of images has been limited with the images normally only being specially prepared images.
There is a general need for being able to produce high fidelity stereoscopic images on demand and in particular for producing images by means of a portable camera device wherein the stereoscopic image can be taken at will.
Further, it would be highly convenient if such a camera picture image production system was able to create automatic customised postcatds which, on a fust surfaee contained the image captured by the camera device and, on a second surface, contains pre-paid postage marks and address details.
Recetttly, it has become more and more popular in respect of photographic reproduction techniques to produce longer and longer "panoramic views of a image. These images can be produced on photographic paper or the iike and the strucn,re of the image is normally to have longer and longer lengths in comparison to the width so as to produce the more "panoramic" type views. Unfortunately, this imposes a problem where the photographic paper to be imaged upon originally was stored on a roll of small diameter.
Recently, it has become quite popular to provide filters which produce effects on images similar to popular artistic painting styles. These filters are designed to take an image and produce a resultant secondary image which appears to be an artistic rendition of the primary image in one of the aetistic styles. One extremely popular artist in modem times was Vincent van Gogh. It is a characteristic of art works produced by this artist that the direction of brush strokes in flat areas of his paintings strongly follow the direction of edges of dominant features in the painting.
For example, his works entitled "Road with Cypress and Star", "Starry Night"
and "Portrait of Doctor Gachet" are illustrative examples of this process_ It would be desirable to provide a computer algorithm which can automatically produce a"van Gogh" effect on an arbitrary input image an output it on a portable camera system..
Unfortunately, warping systems generally utilised high end computers and are generaily inconvenient in that an image must be scanned into the computer processed and then printed out.
This is generally inconvenient, especially where images are captured utilising a hand held camera or the like as there is a need to, at a later stage, transfer the captured images to a computer system for manipulation and to subsequently manipulate them in accordance with requirements.
Further, new and unusual effects which simulate various painting styles are often considered to be of great value. Further, if these effects can be combined into one simple form of implementation they would be suitable for incorporation into a portable camera device including digital imaging capabilities and thereby able to produce desire filtetrd images of scenes taken by a camera device.
Unfortunately, changing digital imaging bechnologies and changing filter technologies result in onerous system requirements itt that cameras produced today obviously are unable to take advantages of technologies not yet available nor are they able to take advantage of filters which have not, as yet, been created or conceived.
One extremely popular form of carttera technology is the tradidonal negative film and positive print photographs. In this case, a camem is utilized to image a scene onto a negative which is then processed so as to fix the negative. Subsequently, a set of prints is made from the negative. Further sets of prints can be instantly created at any time from the set of negatives. The prints normally having a resolution close to that of the original set of prints.
Unfortunately, with digital camera devices, including those proposed by the present applicant, it would be necessary to permanently store in a digital fona the photograph capntred and printed out if ftuther copies of the image were desired at a later time. Ihis would be generally inconvenient in that, ideally, a copy of a"photograph" should merely require the initial print. Of course, altematively, the original print may be copied utilising a high quality colour photooopying device. Unfortunately, any such device has limited copy capabilities and signal degradation will often be the result when such a form of copying is used. Obviously, more suitable forms of producing copies of camera prints are desirable.
Further, Ahnost any artistic painting of a scene utilises a restricted gamut in that the artist is limited in the colours produced as a result of the choice of medium in rendering the image.
This restriction is itself often exploit,ed by the artist to produce various artistic effects. Classic examples of this process include the following well known artistic works:
LA PRPESENTE PARTIE DE CETTE DEMANDE OU CE BREVETS
COMPREND PLUS D'UN TOME.
CECI EST LE TOME DE _2 NOTE: Pour les tomes additionels, veillez contacter le Bureau Canadien des Brevets.
JUMBO APPLICATIONS / PATENTS
THIS SECTION OF THE APPLICATION / PATENT CONTAINS MORE
THAN ONE VOLUME.
THIS IS VOLUME OF _2 NOTE: For additional volumes please contact the Canadian Patent Office.
IMAGE TRANSFORMATION MEANS INCLUDING USER INTERFACE
Field of the Invention The present invention relates to an image processing method and apparatus and, in particular, discloses a Digital lnstant Camera with Image Processing Capability.
The present invention further relates to the field of digital camera technology and, particularly, discloses a digital camera having an integtal color printer.
Backpõt outtd of the lnvention Traditional camera technology has for many years relied upon the provision of an optical processing system which relies on a negative of an image which is projected onto a photosensitive film which is subsequently chemically processed so as to "fix" the fiim and to allow for positive prints to be produced which reproduce the original image. Such an image processing technology, although it has become a standard, can be unduly complex, as expensive and difficult technologies are involved in full color processing of images. Recently, digital cameras have become available. These cameras nonmally rely upon the utiliration of a charged coupled device (CCD) to sense a particular image. The camera normally includes storage media for the storage of the sensed scenes in addition to a connector for the transfer of images to a computer device for subsequent manipulation and printing out.
Such devices are generally inconvenient in that ali images must be stored by the camera and printed out at some later stage. Hence, the camera must have sufficient storage capabilities for the storing of multiple images and, additioinally, the user of the camera must have access to a subsequent computer system for the downloading of the images and printing out by a computer printer or the like.
Further, PolaroidTm type instant cameras have been available for some time which allow for the production of instant images. However, this type of camera has limited utility producing only limited sized images and many problems exist with the chemicals utilised and, in particular, in the aging of photographs produced from these types of cameras.
When using such devices and other image capture devices it will be desirable to be able to suitably deal with audio and other environmentai information when taking a picture.
Further, the creation of stereoscopic views, with a first image being presented to the left eye and second image being Presented to the right eye, thereby cresting an illusion of a three dimensional surface is well known.
However, previous systems have required complex preparation and high fidelity images have generally not been possible. Further, the general choice of images has been limited with the images normally only being specially prepared images.
There is a general need for being able to produce high fidelity stereoscopic images on demand and in particular for producing images by means of a portable camera device wherein the stereoscopic image can be taken at will.
Further, it would be highly convenient if such a camera picture image production system was able to create automatic customised postcatds which, on a fust surfaee contained the image captured by the camera device and, on a second surface, contains pre-paid postage marks and address details.
Recetttly, it has become more and more popular in respect of photographic reproduction techniques to produce longer and longer "panoramic views of a image. These images can be produced on photographic paper or the iike and the strucn,re of the image is normally to have longer and longer lengths in comparison to the width so as to produce the more "panoramic" type views. Unfortunately, this imposes a problem where the photographic paper to be imaged upon originally was stored on a roll of small diameter.
Recently, it has become quite popular to provide filters which produce effects on images similar to popular artistic painting styles. These filters are designed to take an image and produce a resultant secondary image which appears to be an artistic rendition of the primary image in one of the aetistic styles. One extremely popular artist in modem times was Vincent van Gogh. It is a characteristic of art works produced by this artist that the direction of brush strokes in flat areas of his paintings strongly follow the direction of edges of dominant features in the painting.
For example, his works entitled "Road with Cypress and Star", "Starry Night"
and "Portrait of Doctor Gachet" are illustrative examples of this process_ It would be desirable to provide a computer algorithm which can automatically produce a"van Gogh" effect on an arbitrary input image an output it on a portable camera system..
Unfortunately, warping systems generally utilised high end computers and are generaily inconvenient in that an image must be scanned into the computer processed and then printed out.
This is generally inconvenient, especially where images are captured utilising a hand held camera or the like as there is a need to, at a later stage, transfer the captured images to a computer system for manipulation and to subsequently manipulate them in accordance with requirements.
Further, new and unusual effects which simulate various painting styles are often considered to be of great value. Further, if these effects can be combined into one simple form of implementation they would be suitable for incorporation into a portable camera device including digital imaging capabilities and thereby able to produce desire filtetrd images of scenes taken by a camera device.
Unfortunately, changing digital imaging bechnologies and changing filter technologies result in onerous system requirements itt that cameras produced today obviously are unable to take advantages of technologies not yet available nor are they able to take advantage of filters which have not, as yet, been created or conceived.
One extremely popular form of carttera technology is the tradidonal negative film and positive print photographs. In this case, a camem is utilized to image a scene onto a negative which is then processed so as to fix the negative. Subsequently, a set of prints is made from the negative. Further sets of prints can be instantly created at any time from the set of negatives. The prints normally having a resolution close to that of the original set of prints.
Unfortunately, with digital camera devices, including those proposed by the present applicant, it would be necessary to permanently store in a digital fona the photograph capntred and printed out if ftuther copies of the image were desired at a later time. Ihis would be generally inconvenient in that, ideally, a copy of a"photograph" should merely require the initial print. Of course, altematively, the original print may be copied utilising a high quality colour photooopying device. Unfortunately, any such device has limited copy capabilities and signal degradation will often be the result when such a form of copying is used. Obviously, more suitable forms of producing copies of camera prints are desirable.
Further, Ahnost any artistic painting of a scene utilises a restricted gamut in that the artist is limited in the colours produced as a result of the choice of medium in rendering the image.
This restriction is itself often exploit,ed by the artist to produce various artistic effects. Classic examples of this process include the following well known artistic works:
- Camille Pissaro' L'le Lacroix - Rouen, effect de brouillard" 1888. Museum of Art, Philadeiphie - Charles Angrand "Le Seine - L'aube" - 1889 collection du Petit Palais, Geneve - Henri van de Velde "Crepuscule" - 1892. Rijksmuseum KrSller MQller, Otterlo - Georges Seurat. "La cote du Bas-Butin, Honfieur" 1886 - Muse des Beaux -Arts, Toumai It would be desirable to produce, from an arbitrary input image, an output image having similar effects or characteristics to those in the above iist.
A number of creative judgements are made when any garment is created. Firstly, there is the shape and styling of the garment and additionally, there is the fabric colours and style. Often, a fashion designer will try many different altematives and may even attempt to draw the final fashion product before creating the fmished garment.
Such a process is generally unsatisfactory in providing a rapid and flexible tum around of the garments and also providing rapid opportunities judgement of the final appearance of a fashion product on a person.
A number of creative judgements are made when any garment is created. Firstly, there is the shape and styling of the garment and additionally, there is the fabric colours and style. Often, a fashion designer will try many different alternatives and may even attempt to draw the fmal fashion product before creating the finished garment.
Such a process is generally unsatisfactory in providing a rapid and flexible turn around of the garments and also providing rapid judgement of the final appearance of a fashion product on a person.
Binocular and telescope devices are well known. In particular, taking the example of a binocular device, the device provides for telescopic magnification of a scene so as to enhance the user's visual capabilities_ Further, devices such as night glasses etc. also operate to enhance the user's visual system. Unfortunately, these systems tend to rely upon real time analog optical components and a permanent record of the viewed scene is difficult to achieve. One methodology perhaps suitable for recording a permanent copy of a scene is to attach a sensor device such as a CCD or the like so as to catch the scene and store it on a storage device for later printing out.
Unfortunately, such an arrangement can be unduly cumbersome especially where it is desired to utilize the binocular system in the field in a highly portable manner.
Many forms of condensed information storage are well known. For example, in the field of computer devices, it is common to utilize magnetic disc drives which can be of a fixed or portable nature. In respect of portable discs, "Floppy Discs", "Zip Dises", and other fotms of portable magnetic storage media have to achieve to date a large degree of acceptance in the market place. Another form of portable storage is the compact disc "CD" which utilizes a series of elongated pits along a spiral track which is read by a laser beam device. The utilization of CD's provides for an extremely low cost form of storage.
However, the technologies involved are quite complex and the use of rewritable CD type devices is extremely limited Other forms of storage include magnetic cards, oRen utilized for credit cards or the like. These cards normally have a magnetic strip on the back for recording information which is of relevance to the card user.
Recently, the convenience of magnetic cards has been extended in the form of SmartCard technology which includes incotponition of integrated circuit type devices on to the card.
Unfortunately, the cost of such devices is often high and the ootnplexity of the technology utilized can also be sigaificant Traditionalty silver halide camera processing systems have given rise to the well known utilisation of a "negative" for the production of multiple prints. The negative normally fotnis the source of the production prints and the pntctice has grown up for the independent care and ptotection of negatives for their subsequent continual utilisation.
With any form of encoding system which is to be sawed in a fault tolerant manner, there is the significant question of how best to encode the data so that it can be effoctively and efficiently decoded- It is the.refore desirable to provide for an effective encoding sysiein.
Summary of the Invention A user interface for operating a device, said user interface comprising a card which is inserted in a machine and on the face of the card is contained a visual representation of the effect the card will have on the output of the machine.
Further aspects disclosed herein include:
An alternative form of camera system which includes a digital camera with an integral color printer. Additionally, the camera provides hardware and software for the increasing of the apparent resolution of the image sensing system and the conversion of the image to a wide range of "artistic styles"
and a graphic enhancement.
In acondance with afinthQ of the asped presatt invention, there is provided a catnera system canprising at least one area itoage sensor for imaging a soene, acunem processor means for processing said imaged scene in accordance with a predetermined scene transformation requitnment, a printer for priating out said processed image sceue on print medis, print media and printing ink stored in a single detachable module inside said catneta system, said camera system comprising a portable hand held unit for the imaging of scenes by said area image sensor aag prklttng said soenes dneWy out of said camera system via said printa.
Preferably the camera system ineludes a print roll for the storage of print media and priniing ink for utilization by the printer, the print roll being detachabie from the camera system. Further, the print noU can inchtde an authentication chip containing authentication infonnation and the camera processing meaas is adapted to interrogate the authentication chip so as to detenmine the authenticity of said print roU
when insarted wititin said camera system_ Further, the , printu can include a drop on demand ink printa and guittotitm means for the separation of Irinted Pltotogniphs.
In accordance with a first aspect of the present invention, there is provided a camnera system comprising at lad one atea image sensor for imag6tg a scaie, = a camera processor means for prooessiog said image scene in aocordance with a predetermined scene transfonnation requirement, a printer for printing out said processed image sceae on print media said prv-ter, print media and printing ink stored in a single dotachable moduk inside said cameca systtm, said carneta system comprising a pottable hand held unit for the imaging of scenes by said area image sensor and p-inting said scenes directly out of said camera system via said prilger T'refaablY the camaa system includes a print roU for the storage of print media and printing ink for utt7isatiot- by the ptinter, s the aid print roll being detachable from the camera systan. i=lather, the print roU can include an authentication chip containing autheatication information and the camera processing means is adapted to 'nftn 8aft the authentcafion chip so as to detamine the authenticity of said print roll when iaserted within said camera system.
Further, the printer can include a drop on demand ink printer and guillotine means for the separa<ion of psu-ted photographs.
In aesowdance with a further aspect of the invention there is provided the camera system comprnsing:
at least one area inune sensor for imaging a scene;
a camera processor means for processing said imaged scene in accordance with a predetetmined scene ttmsformation requimnent;
a printer for printing out said processed image scene on print media said printer, a detachable moduk for storing said print media and printing ink for said printer, said camera system comprising a portable hand held unit for the imaging of scenes by said area iinage sensor and printing said scenes directly out of said camera system via said printer.
In accordance with a further aspect of the present invention, there is provided a camera system cotnprising a sensor means for sensing an image; a processing means for processing the sensed image in accordance with a predetermined processing requirement, if any; audio recording means for according an audio signal to be associated with the sensed image; printer means for printing the processed sensed image on a first area of a print media supplied with the camaa system, in addition to printing an encoded version of the audio signal on a second area of the print media. Preferably the sensed image is printed on a first surface of the print media and the encoded version of the audio signal is printed on a second surface of the print media.
In accordance with the present invention thete is provided a camera system having:
an area image sensor means for sensing an image;
an image storage means for storing the sense image;
an orientation means for sensing the cameta's orientation when sensing the image; and a processing means for processing said sensed image utilising said sensed cxmera orientation.
In accordance with the present invention thene is provided a camera systean having:
an area image sensor means for sensing an image;
an image storaga means for storing the sense image;
an orientation means for sensing the cameta's ocientation when sensing the image; and a prooessing means for processing said sensed image utilising said sensed camera orleattation.
In accordance with a further aspect of the present invention there is provided a method of processing a digital image comprising:
captnring the image utilising an adjustable focusing technique;
utilising the focusing settings as an indicator of the position of strucnu-es within the image;
processing the image, utilising the said focus settings to produce effeets specific to said focus settings; and printing out the itnage.
Pttiferably the image can be eapturzd utilising a zooming technique; and the z,ooming settings can be used in a hearistic manner so as to process portions of said image.
A number of creative judgements are made when any garment is created. Firstly, there is the shape and styling of the garment and additionally, there is the fabric colours and style. Often, a fashion designer will try many different altematives and may even attempt to draw the final fashion product before creating the fmished garment.
Such a process is generally unsatisfactory in providing a rapid and flexible tum around of the garments and also providing rapid opportunities judgement of the final appearance of a fashion product on a person.
A number of creative judgements are made when any garment is created. Firstly, there is the shape and styling of the garment and additionally, there is the fabric colours and style. Often, a fashion designer will try many different alternatives and may even attempt to draw the fmal fashion product before creating the finished garment.
Such a process is generally unsatisfactory in providing a rapid and flexible turn around of the garments and also providing rapid judgement of the final appearance of a fashion product on a person.
Binocular and telescope devices are well known. In particular, taking the example of a binocular device, the device provides for telescopic magnification of a scene so as to enhance the user's visual capabilities_ Further, devices such as night glasses etc. also operate to enhance the user's visual system. Unfortunately, these systems tend to rely upon real time analog optical components and a permanent record of the viewed scene is difficult to achieve. One methodology perhaps suitable for recording a permanent copy of a scene is to attach a sensor device such as a CCD or the like so as to catch the scene and store it on a storage device for later printing out.
Unfortunately, such an arrangement can be unduly cumbersome especially where it is desired to utilize the binocular system in the field in a highly portable manner.
Many forms of condensed information storage are well known. For example, in the field of computer devices, it is common to utilize magnetic disc drives which can be of a fixed or portable nature. In respect of portable discs, "Floppy Discs", "Zip Dises", and other fotms of portable magnetic storage media have to achieve to date a large degree of acceptance in the market place. Another form of portable storage is the compact disc "CD" which utilizes a series of elongated pits along a spiral track which is read by a laser beam device. The utilization of CD's provides for an extremely low cost form of storage.
However, the technologies involved are quite complex and the use of rewritable CD type devices is extremely limited Other forms of storage include magnetic cards, oRen utilized for credit cards or the like. These cards normally have a magnetic strip on the back for recording information which is of relevance to the card user.
Recently, the convenience of magnetic cards has been extended in the form of SmartCard technology which includes incotponition of integrated circuit type devices on to the card.
Unfortunately, the cost of such devices is often high and the ootnplexity of the technology utilized can also be sigaificant Traditionalty silver halide camera processing systems have given rise to the well known utilisation of a "negative" for the production of multiple prints. The negative normally fotnis the source of the production prints and the pntctice has grown up for the independent care and ptotection of negatives for their subsequent continual utilisation.
With any form of encoding system which is to be sawed in a fault tolerant manner, there is the significant question of how best to encode the data so that it can be effoctively and efficiently decoded- It is the.refore desirable to provide for an effective encoding sysiein.
Summary of the Invention A user interface for operating a device, said user interface comprising a card which is inserted in a machine and on the face of the card is contained a visual representation of the effect the card will have on the output of the machine.
Further aspects disclosed herein include:
An alternative form of camera system which includes a digital camera with an integral color printer. Additionally, the camera provides hardware and software for the increasing of the apparent resolution of the image sensing system and the conversion of the image to a wide range of "artistic styles"
and a graphic enhancement.
In acondance with afinthQ of the asped presatt invention, there is provided a catnera system canprising at least one area itoage sensor for imaging a soene, acunem processor means for processing said imaged scene in accordance with a predetermined scene transformation requitnment, a printer for priating out said processed image sceue on print medis, print media and printing ink stored in a single detachable module inside said catneta system, said camera system comprising a portable hand held unit for the imaging of scenes by said area image sensor aag prklttng said soenes dneWy out of said camera system via said printa.
Preferably the camera system ineludes a print roll for the storage of print media and priniing ink for utilization by the printer, the print roll being detachabie from the camera system. Further, the print noU can inchtde an authentication chip containing authentication infonnation and the camera processing meaas is adapted to interrogate the authentication chip so as to detenmine the authenticity of said print roU
when insarted wititin said camera system_ Further, the , printu can include a drop on demand ink printa and guittotitm means for the separation of Irinted Pltotogniphs.
In accordance with a first aspect of the present invention, there is provided a camnera system comprising at lad one atea image sensor for imag6tg a scaie, = a camera processor means for prooessiog said image scene in aocordance with a predetermined scene transfonnation requirement, a printer for printing out said processed image sceae on print media said prv-ter, print media and printing ink stored in a single dotachable moduk inside said cameca systtm, said carneta system comprising a pottable hand held unit for the imaging of scenes by said area image sensor and p-inting said scenes directly out of said camera system via said prilger T'refaablY the camaa system includes a print roU for the storage of print media and printing ink for utt7isatiot- by the ptinter, s the aid print roll being detachable from the camera systan. i=lather, the print roU can include an authentication chip containing autheatication information and the camera processing means is adapted to 'nftn 8aft the authentcafion chip so as to detamine the authenticity of said print roll when iaserted within said camera system.
Further, the printer can include a drop on demand ink printer and guillotine means for the separa<ion of psu-ted photographs.
In aesowdance with a further aspect of the invention there is provided the camera system comprnsing:
at least one area inune sensor for imaging a scene;
a camera processor means for processing said imaged scene in accordance with a predetetmined scene ttmsformation requimnent;
a printer for printing out said processed image scene on print media said printer, a detachable moduk for storing said print media and printing ink for said printer, said camera system comprising a portable hand held unit for the imaging of scenes by said area iinage sensor and printing said scenes directly out of said camera system via said printer.
In accordance with a further aspect of the present invention, there is provided a camera system cotnprising a sensor means for sensing an image; a processing means for processing the sensed image in accordance with a predetermined processing requirement, if any; audio recording means for according an audio signal to be associated with the sensed image; printer means for printing the processed sensed image on a first area of a print media supplied with the camaa system, in addition to printing an encoded version of the audio signal on a second area of the print media. Preferably the sensed image is printed on a first surface of the print media and the encoded version of the audio signal is printed on a second surface of the print media.
In accordance with the present invention thete is provided a camera system having:
an area image sensor means for sensing an image;
an image storage means for storing the sense image;
an orientation means for sensing the cameta's orientation when sensing the image; and a processing means for processing said sensed image utilising said sensed cxmera orientation.
In accordance with the present invention thene is provided a camera systean having:
an area image sensor means for sensing an image;
an image storaga means for storing the sense image;
an orientation means for sensing the cameta's ocientation when sensing the image; and a prooessing means for processing said sensed image utilising said sensed camera orleattation.
In accordance with a further aspect of the present invention there is provided a method of processing a digital image comprising:
captnring the image utilising an adjustable focusing technique;
utilising the focusing settings as an indicator of the position of strucnu-es within the image;
processing the image, utilising the said focus settings to produce effeets specific to said focus settings; and printing out the itnage.
Pttiferably the image can be eapturzd utilising a zooming technique; and the z,ooming settings can be used in a hearistic manner so as to process portions of said image.
In accordance with a further aspect of the invention there is provided a method of processing an image taken with a digital camera including an eye position sensing means said method comprising the step of utilizing the eye position information within the sensed image to process the image in a spatially varying sense, depending upon said location information.
The utilizing step can comprise utilizing the eye position information to locate an area of interest within said sensed image. The processing can includes the placement of speech bubbles within said image or applying a region specific warp to said image. Aitetttatively the processing can include appiying a brush stroke filter to the image having greater detail in the area of said eye position information.
Ideally the camera is able to substantially immediately print out the rosulu of the processing.
In accordance with a further aspect of the invention there is provided a method of processing an image taken with a digital camera including an auto exposure setting, said method comprising the step of utilising said information to process a sensed image.
The utilising step can comprise utilising the auto exposure setting to determine an advantageous rermapping of colours within the image so as to produce an amended image having colours within an image iransformed to account of the auto exposure setting. The processing can comprise re-mapping image colours so they appear deeper and richer when the exposure setting indicates low light conditions and re-mapping image colours to be brighter and more saturated when the auto exposure setting indicates bright light conditions.
The utilising step includes adding exposure specific graphics or manipulations to the image.
Recently, digital cameras have become inaeasingly popular. Ihese cameras normally operate by means of imaging a desired image utilising a charge coupled device (CCD) array and storing the imaged scene on an electronic stonige medium for later down loading onto a computer system for subsequent manipulation and printing out.
Normally, when utilising a computer system to print out an image, sophisticated software may available to manipulate the image in accordance with requiremems.
Utifortunately such systems require significant post processing of a captured image and normally present the image in an orientation to which is was taken, relying on the post processing process to perform any necessary or required modifications of the captured image. Further, much of the environmental information available when the picdue was taken is lost.
Recently, digital c.ameras have become increasingly popular. These catneras normally operate by means of imaging a desired image utilising a charge coupled device (CCD) atray and storing the imaged scene on an elecironic storage medium for later down loading onto a computer system for subsequent manipulation and printing out.
Normally, when utilising a computer system to print out an image, sophisticated software may available to manipulate the image in accordanoe with requ'veinents.
Unfortunately such systems tr,quire signifioant post processing of a capturad image and nomtally present the image in an orient,ation to which is was taken, relying on the post processing pnooess to perform any necessary or required modifications of the captured image. Further, much of the enviraunental information available when the pieture was taken is lost.
In accordance with a 5uther aspect of the present invention there is provided a method of processing an image captured utilising a digital camera and a flash said method comprising the steps of :
The utilizing step can comprise utilizing the eye position information to locate an area of interest within said sensed image. The processing can includes the placement of speech bubbles within said image or applying a region specific warp to said image. Aitetttatively the processing can include appiying a brush stroke filter to the image having greater detail in the area of said eye position information.
Ideally the camera is able to substantially immediately print out the rosulu of the processing.
In accordance with a further aspect of the invention there is provided a method of processing an image taken with a digital camera including an auto exposure setting, said method comprising the step of utilising said information to process a sensed image.
The utilising step can comprise utilising the auto exposure setting to determine an advantageous rermapping of colours within the image so as to produce an amended image having colours within an image iransformed to account of the auto exposure setting. The processing can comprise re-mapping image colours so they appear deeper and richer when the exposure setting indicates low light conditions and re-mapping image colours to be brighter and more saturated when the auto exposure setting indicates bright light conditions.
The utilising step includes adding exposure specific graphics or manipulations to the image.
Recently, digital cameras have become inaeasingly popular. Ihese cameras normally operate by means of imaging a desired image utilising a charge coupled device (CCD) array and storing the imaged scene on an electronic stonige medium for later down loading onto a computer system for subsequent manipulation and printing out.
Normally, when utilising a computer system to print out an image, sophisticated software may available to manipulate the image in accordance with requiremems.
Utifortunately such systems require significant post processing of a captured image and normally present the image in an orientation to which is was taken, relying on the post processing process to perform any necessary or required modifications of the captured image. Further, much of the environmental information available when the picdue was taken is lost.
Recently, digital c.ameras have become increasingly popular. These catneras normally operate by means of imaging a desired image utilising a charge coupled device (CCD) atray and storing the imaged scene on an elecironic storage medium for later down loading onto a computer system for subsequent manipulation and printing out.
Normally, when utilising a computer system to print out an image, sophisticated software may available to manipulate the image in accordanoe with requ'veinents.
Unfortunately such systems tr,quire signifioant post processing of a capturad image and nomtally present the image in an orient,ation to which is was taken, relying on the post processing pnooess to perform any necessary or required modifications of the captured image. Further, much of the enviraunental information available when the pieture was taken is lost.
In accordance with a 5uther aspect of the present invention there is provided a method of processing an image captured utilising a digital camera and a flash said method comprising the steps of :
a) locating distortions of said caphued image due to the utilisation of said flash;
b) retouching said image so as to locally reduce the effect of said distortions.
In accordance with the second aspect of the present invention there is provided a digital camera having reduced flash distortion effects on captured images comprising;
(a) a digital means capturing image for the capture of images;
(b) a distortion location means for locating flash induced colour distortions in the captured image; and (c) image inversed distortion means connected to said distortion location means and said digital image capture means and adapted to process said captured image to reduce the effects of said distortions;
(d) display means connected to said distortion for displaying.
In accordance with a further aspect of the present invention there is provided a method of creating a stereoscopic photographic image comprising:
(a) utilising a camera device to image a scene stereographicaily;
(b) printing said stereographic image as an integrally formed image at predetermined positions on a first surface portion of a transparent printing media, said transparent printing media having a second surface including a lensing system so as to stereographically image said scene to the left and right eye of a viewer of said printed stereographic image.
In accordance with a further aspect of the present invention there is provided a print media and ink supply means adapted to supply a printing mechanism with ink and printing media upon which the ink is to be deposited, said media and ink supply means including a roll of media rolled upon a media former within said media and ink suppiy means and at least one ink reservoir integrally formed within said media and ink supply means and adapted to be connected to said printing mechanism for the supply of ink and printing media to said printing mechanism.
In accordance with a further aspect of the present invention there is provided a print media and ink supply means adapted to supply a printing mechanism with ink and printing media upon which the ink is to be deposited, said media and ink supply means including a roll of media rolled upon a media fom-er within said media and ink supply means and at least one ink reservoir integrally formed within said media and ink supply means and adapted to be connected to said printing mechanism for the supply of ink and printing media to said printing mechanism.
In accordance with a further aspect of the present invention then: is provided a print roll for use in a camera imagirtg system said priat roll having a backing surface having a plurality of formatted postcard infonnation printed at pre-determined intervals.
In accordance with the second aspect of the present invention there is provided a method of creating customised postcards comprising the steps oF utilising a camera device having a print roll having a backing surface including a pluraiity of formatted postcard infonmation sections at pre-determined positions on said backing surface;
imaging a customised image on a corresponding intaging surface of said print roll; and utilising said print roll to produce postcards via said camera device.
In accordance with the third aspect of the present invention there is provided a method of sending postcards comprising cxmera images through the postal system said method comprising steps of setting a print roll having prepaid postage contained within the print roll;
b) retouching said image so as to locally reduce the effect of said distortions.
In accordance with the second aspect of the present invention there is provided a digital camera having reduced flash distortion effects on captured images comprising;
(a) a digital means capturing image for the capture of images;
(b) a distortion location means for locating flash induced colour distortions in the captured image; and (c) image inversed distortion means connected to said distortion location means and said digital image capture means and adapted to process said captured image to reduce the effects of said distortions;
(d) display means connected to said distortion for displaying.
In accordance with a further aspect of the present invention there is provided a method of creating a stereoscopic photographic image comprising:
(a) utilising a camera device to image a scene stereographicaily;
(b) printing said stereographic image as an integrally formed image at predetermined positions on a first surface portion of a transparent printing media, said transparent printing media having a second surface including a lensing system so as to stereographically image said scene to the left and right eye of a viewer of said printed stereographic image.
In accordance with a further aspect of the present invention there is provided a print media and ink supply means adapted to supply a printing mechanism with ink and printing media upon which the ink is to be deposited, said media and ink supply means including a roll of media rolled upon a media former within said media and ink suppiy means and at least one ink reservoir integrally formed within said media and ink supply means and adapted to be connected to said printing mechanism for the supply of ink and printing media to said printing mechanism.
In accordance with a further aspect of the present invention there is provided a print media and ink supply means adapted to supply a printing mechanism with ink and printing media upon which the ink is to be deposited, said media and ink supply means including a roll of media rolled upon a media fom-er within said media and ink supply means and at least one ink reservoir integrally formed within said media and ink supply means and adapted to be connected to said printing mechanism for the supply of ink and printing media to said printing mechanism.
In accordance with a further aspect of the present invention then: is provided a print roll for use in a camera imagirtg system said priat roll having a backing surface having a plurality of formatted postcard infonnation printed at pre-determined intervals.
In accordance with the second aspect of the present invention there is provided a method of creating customised postcards comprising the steps oF utilising a camera device having a print roll having a backing surface including a pluraiity of formatted postcard infonmation sections at pre-determined positions on said backing surface;
imaging a customised image on a corresponding intaging surface of said print roll; and utilising said print roll to produce postcards via said camera device.
In accordance with the third aspect of the present invention there is provided a method of sending postcards comprising cxmera images through the postal system said method comprising steps of setting a print roll having prepaid postage contained within the print roll;
utilising the print roll in a camera unaging system to produce postcards having prepaid postage; and sending said prepaid postcards through the mail.
The present invention is further directed to a caaznera system with an integral printer type device. The print media being detachable from the camera system and including a means for the storage of significant infonnation in respect of the print media.
Ilie present invention is further directed to a camera system with an integral printer type device. The print media being detachable from the camera system and including means for providing an authentication access to the print media.
In accordance with a further aspect of the present invention there is provided a plane print media having a reduced degree of curling in use, said print media having anisotropic stifihess in the direction of said planes.
In accordance with the second aspect of the present invention there is provided a method of reducing the curl in an image printed on plane print media having an anisotropic stiffness said method comprising applying a localised pressure to a portion of said print media.
The present invention is further directed to a camera system with an integral printer type device. The camera systetn including an indicator for the number of images left in the printer, with the indicator able to display the number of prints left in a number of different modes.
In accordance with a further aspect of the present invention there is provided a method of automatically processing an image comprising locating within the image features having a high spatial variance and stroking the image with a series of brush strokes emanating from those areas having high spatial variance. Preferably, the bnLsh strokes have decreasing sizes near impottant features of the image.
Additionally, the position of a predetermined portion of brust strokes can undergo random jitterittg.
In accordance with a further aspect of the invention there is provided a method of warping of producing a warped image from an input image, said method comprising the steps of:
inputting a warp map for an arbitrary output image having predetennined dimensions A x B, each element of said warp map mapping a corresponding region in a theoretical input image to a pixel location of said arbitrary output image corrcsponding to the co-ordinate location of said element within said warp map;
soaling said warp map to the ditnensioas of said warped image so as to produce a scaled warp map;
for substantially each element in said sealed warp map, calcalating a contribution region in said input image through utiliztion of said element value and adjacent element values; and determining an output image colour for a pixel of said warped image corresponding to said element &om said contribution region.
In accordatnce with a further aspect of the present invention, there is provided a method of increasing the resilience of data stored on a medium for reading by a sensor device pricing the steps of (a) modulating the stored data in a recoverable fashion with the modulating signal having a high frequency component.
(b) storing the data on said medium in a modulated form;
(c) sensing the modulated stored data by said sensor device;
(d) neutralising the modulation of the modulated stoned data to track the spread of location of said modulated stored data on said medium; and (e) recovering the unmodulated stored data from the modulated stored data.
The preferred embodiment of the present invention will be described with reference to a card reading system for reading data via a CCD type device into a camera system for subsequent decoding. Further, the discussion of the preferred embodiment relies heavily upon the field of error control systems.
Hence, the person to which this specification is directed should be an expert in error of control systems and in particular, be fvmly familiar with such standard texts such as "Error control systems for Digital Communication and Storage" by Stephen B Wicker published 1995 by Prentice - Hall Inc. and in particular, the discussion of Reed - Solomon codes contained therein and in other standard text.
It is an object of the present invention to provide for a method of converting a scanned image comprising scanned pixels to a coiresponding bitmap image, said method comprising the steps of, for each bit in the bitmap image;
a. determining an expected location in said scanned image of a current bit from the location of surrounding bits in said scamied image;
b. detennining a likely value of said bit from the values at the locations of expected corresponding pixels in said scanned image;
c. determining a centroid measures of the centre of the centre of the expected intensity at the said expected location;
d. determining similar centroid measures for adjacent pixels surrounding said current bit in said scanned image and;
e. where said centroid measure is improved relative to said expected location, adjusting said expected location to be an adjacent pixel having an improved centroid measure.
In accordance with a further aspect of the present invention there is provided an apparatus for text editing an image comprising a digital camera device able to sense an image; a manipulation data entry card adapted to be inserted into said digital camera device and to provide manipulation instructions to said digital camera device for manipulating said image, said manipulation instructions including the addition of text to said image; a text entry device connected to said digital camera device for the entry of said text for addition to said image wherein said text entry device includes a series of non-roman font characters utilised by said digital camera device in conjunction with said manipulation instructions so as to create new text characters for addition to said image.
Preferably, the font characters are transmitted to said digital camera device when required and rendered by said apparatus in accordance with said manipulation instructions so as to create said new text characters. The manipulation data entry card can include a rendered roman font character set and the non-roman characters include at least one of Hebrew, Cyrillic, Arabic, Kanji or Chinese characters.
In accordance with a further aspect of the present invention there is provided an apparatus for text editing an image comprising a digital camera device able to sense an image; a manipulation data entry card adapted to be inserted into said digital camera device and to provide manipulation instructions to said digital camera device for manipulating said image, said manipulation instructions including the addition of text to said image; a text entry device connected to said digital camera device for the entry of said text for addition to said image wherein said text entry device includes a series of non-roman font characters utilised by said digital camera device in conjunction with said manipulation instructions so as to create new text characters for addition to said image.
Preferably, the font characters are transmitted to said digital camera device when required and rendered by said apparatus in accordance with said manipuiation instructions so as to create said new text characters. The manipulation data entry card can include a rendered roman font character set and the non-roman characters include at least one of Hebrew, Cyrillic, Arabic, Kanji or Chinese eharacters.
It is an object of the present invention to provide a systern which readily is able to take advantage of updated technologies in a addition to taking advantage of new filters being ctrated and, in addition, providing a readily adaptable form of image processing of digitally captured images for printing aut. _.-In accordance with a further aspect of the present invention, there is provided an image copying device for reproduction of an input image which comprises a series of ink dots, said device comprising:
(a) imaging array means for imaging said input image at a sampling rate higher than the frequency of said dots so as to produce a corresponding sampled image;
(b) processing means for processing said image so as to determine the location of said print dots in said sample image;
(c) print means for printing ink dots on print media at locations corresponding to the locations of said print dots.
2. An image copying device as claimed in claim 1 wherein said copying device prints a full color copies of said input image.
In accordance with a further aspect of the present invention there is provided a camera system for outputting deblurred images, said system comprising;
an image sensor for sensing an image; a velocity detection means for determining any motion of said image relative to an externai environment and to produce a velocity output indicative thereof; a processor means interconnected to said image sensor and said velocity detection means and adapted to process said sensed image utilising the velocity output so as to deblurr said image and to output said deblurred image.
Preferably, the camera system is connected to a printer means for immediate output of said deblurred image and is a portable handheld unit. The velocity detection means can comprise an accelerometer such as a micro-electro mechanical(IvEMS) device.
In accordance with a fiulher aspect of the present invention, there is provided a photosensor reader preform oomprising:
(a) a series of light emitter recesses for the insettion of light emitted devices;
(b) light emitter focusing means for focusing light emitted from the series of light emitter devices onto the surface of an object to be intaged as it traverses the surface of said pn;fornn;
(c) a photosensor recess for the inseition of a linear photosensor array; and (d) focussing means for focussing light reflected frotn said object to be unaged onto a distinct portion of said CCD array.
In accordance with an aspect of the present invention, there is provided a printer device for interconnection with a computer system comprising a printer head unit including an ink jet print head for printing _ 11_ images on print media and further having a cavity therein for insertion of a consumable print roll unit and a print roll unit containing a consumable print media and ink for insertion into said cavity, said ink being utilised by said ink jet print head for printing images on said print media.
In accordance with a further aspect of the present invention, there is provided a digital camera system comprising a sensing means for sensing an image; modification means for modifying the sensed image in accordance with modification instructions input into the camera; and an output means for outputting the modified image; wherein the modification means includes a series of processing elements arranged around a central crossbar switch. Preferably, the processing elements include an Arithmetic Logic Unit (ALU) acting under the control of a microcode store wherein the microcode store comprises a writeable control store. The processing elements can include an internal input and output FIFO for storing pixel data utilized by the processing elements and the modification means is interconnected to a read and write FIFO for reading and writing pixel data of images to the modification means.
Each of the processing elements can be arranged in a ring and each element is also separately connected to its nearest neighbours. The ALU accepts a series of inputs interconnected via an internal crossbar switch to a series of core processing units within the ALU and includes a number of internal registers for the storage of temporary data. The core processing units can include at least one one of a muttiplier, an adder and a barrel shifter. .
The processing elements are further connected to a common data bus for the transfer of pixel data to the processing elements and the data bus is interconnected to a data cache which acts as an intennediate cache between the processing elements and a memory store for storing the images.
In accordance with a further aspect of the present invention there is provided a method of rapidiy decoding, in real time, sensed image data stored at a high pitch rate on a card, said method comprising the steps of;
detecting the initial position of said image data;
decoding the image data so as to determine a corresponding bit pattern of said image data.
In accordance with a further aspect of the present invention there is provided a method of rapidly decoding sensed image data in a fault tolerant manner, said data stored at a high pitch rate oti a card and subject to rotations, warping and marking, said mehtod comprising the steps of:
detennining an initial location ofa start of said image data;
sensing said image data at a sampling rate greater than said pitch rate;
processing said sensed image data in a column by column process, keeping an expected location of the center of each dot (centroid) of a next cohunn and utilising fme adjustments of said centroid when processing each column so as to update the location of an expected next cetttroid.
In accordance with a further aspect of the present invention there is provided a method of accurately detecting the value of a dot of sensed image data, said image data comprising an array of dots and said sensed image data comprising a sampling of said image data at a rato greater dian the pitch fieqttency of said array of dots so as to producx an atray of pixeLs, said method cotnprising the steps of determining an expected middle pixel of said array of pixels, said middle pixel corresponding to an expected central location of a corresponding dot;
utilising the sensed value of said middle pixel and the sensed value of a number of adjacent pixels as an index to a lookup table having an output corresponding to the value of a dot centred around the corresponding location of said pixel.
In accordance with a further aspect of the present invention there is provided a method of accurately determining the location of dots of sensed image data amongst an array of dots of image data in a fault tolerant manner, said data stored at a high pitch rate on a card and subject to rotations, warping and marking effects, said method comprising the steps of:
prooessing the image data in a column by column format;
recording the dot pattern of previously processed columns of pixels;
genetating an expected dot pattern at a cutrent column position from the recorded dot pattern of previously processed pixels;
comparing the expected dot pattern with an actual dot pattem of sensed image data at said current column position;
if said comparison produces a match within a predetermined error, utilising said current column position as an aciual dot position otherwise altering said current column position to produce a better fit to said expected dot pattern to thereby produce new aetuai dot position, and utilising said actual dot position of the dot at a cun~ent column position in the detamining of dot location of dots of subsequent columns.
In accordance with a further aspect of the present invention there is provided a method of combining image bump maps to simulate the effect of painting on an image, the method comprising:
defming an image canvas bump map approximating the surface to be painted on;
deftning a painting bump map of a painting object to be painted on said surface;
combining said image canvas bump map and said painting bump map to produce a final composited bump map utilising a stiffness factor, said stiffness factor determining the degree of modulation of said painting bump map by said image canvas bump map.
In accordance with a fitrther aspect of the present invention there is provided =a method of automatically manipulating an input image to produce an artistic effect comprising:
predetermining a mapping of an input gamut to a desired output gamut so as to produce a desired artistic effect;
utilising said mapping to map said input image to an output image having a predetermined output gamut;
Preferably, the method further comprises the step of post processing the output image utilising a brush stroke filter.
Further, preferably the output gamut is formed from mapping a predetemtined number of input gamut values to corresponding output colour gamut values and interpolating the remaining mapping of input gamut values to output colour gamut values. The intetpolation process can include utilising a weighted sum ofsaid mapping of a predetermined number of input gamut values to corresponding output colour gamut values.
In accordance with the second aspect of the presettt invention there is provided a method of compressing an input colour gamut to be within an output colour gamut, said method comprising the steps of:
determining a zero chrominance value point at a current input colour intensity;
determining a source distance being the distance from said zero chrominance value to the edge of said input colour gamut;
determining a suitable edge of said output colour gamut;
determining a target distance being the distance from said zero chrominance value to the edge of said output colour gamut; and scaling the current input colour intensity by a factor derived from the ratio of source distance to target distance;
Preferably said current input colour intensity is further scaled by a factor dependent on the distance for said current input colour from said zero chrominance value point.
In accordance with a futtlter aspect of the present invention, there is provided a handheld camera for the output of an image sensed by the camera, with the camera including:
sensing means for sensing an image;
tiling means for adding tiling effects to the sensed image to produce a tiled image; and display means for displaying the tiled image.
In accordance with a fnrther aspect of the present invention, there is provided a handheld camera for the output of an image sensed by the camera, with the camera including:
sensing means for sensing an image;
texture mapping means for adding texturing effects to the sensed image to produce a texttu-ed image; and display means for displaying the textured image.
In xcordance with a further aspect of the present invention, there is provided a handheld camera for the output of an image sensed by the camera, with the camera including:
sensing means for sensing an image;
lighting means for adding lighting to the sensed itnage to produce an illuminated image which simulates the effect of light sources projected at the sensed image; and display means for displaying the i[luminated image.
In accordance with a further aspect of the present invention there is provided a garment creation system comprising:
a series of input tokens for inputting to a camera device for manipulation of a sensed image for outputting on a display device depicting a gannent constructed of fabric having characteristics of said sensed image;
a camera device adapted to read said input tokens and sense an image and manipulate said image in accordance with a read input token so as to produce said output image; and a display device adapted to display said output image In accordance with a further aspect of the present invention there is provided A garment creation system comprising:
an expected image creation system including an image sensor device and an image display device, said image creation system mapping portions of an arbitrary image sensed by said image sensor device onto a garment and outputting on said display device a depiction of said garment;
a garment fabric printer adapted to be interconnected to said image creation system for printing out corresponding pieces of said garment including said mapped portions..
In accordance with a further aspect of the present invention as provided a method of creating a manipulated image comprising interconnecting a series of camera manipulation units, each of said camera manipulation unit applying an image manipulation to an inputted image so as to produce a manipulated output image, an initial one of said camera manipulation units sensing an image from an environment and at least a final one of said camera manipulation units producing a permanent output image.
In accordance with a further aspect of the present invention there is provided a portable imaging system for viewing distant objects comprising an optical lensing system for magnifying a viewed distant object; a sensing system for simultaneously sensing said viewed distant object; a processor means interconnected to said sensing system for processing said sensed image and forwarding it to a printer mechanism; and a printer mechanism connected to said processor means for printing out on print media said sensed image on demand by said portable imaging system.
Preferably the system further comprisos a detachable print media supply means provided in a detachable module for interconnection with said printer mechanism for the supply of a roll of print media and ink to said printer mechanism.
The printer mechanism can comprise an ink jet printing mechanism providing a full color printer for the output of sensed images.
Further, the prefemed embodiment is implemented as a system of binoculars with a beam splitting device which projects said distant object onto said sensing system.
In accordance with a fiuther aspect of the present invention, there is provided a system for playing prerecorded audio encoded in a fault tolerant manner as a series of dots printed on a card, the system comprising an optical scanner means for scanning the visual form of the prerecorded audio; a processor means interconnected to the optical scanner means for decoding the scanned audio encoding to produce a corresponding audio signal;
and audio emitter means inter+connected to the processor means for emitting or playing the corresponding audio signal on demand.
The encoding can include Reed-Solomon encoding of the pm.recorded audio and can comprise an array of ink dots which are high frequency modulated to aid scanning.
The system can include a wand-like arm having a slot through which is inserted the car.d.
In accordance with a further aspect of the present invention, there is provided a method of information distribution on printed cards, the method comprising the steps of dividing the surface of the card into a number of predetennined areas; printing a first collection of data to be stored in a first one of the predetermined areas;
utilising the printed fust predetermined area when reading information stored on the card; and, when the informadon stored on the card is to be updated, dotermining a second one of the predetennined areas to print further information stored on the card, the second area not having being previously utilized to print data.
Preferably, the areas are selected in a predetermined order and the printing utilizes a high resolution ink dot printer for printing data having a degree of fault tolerance with the fault tolerance, for example, coming from Reed-Solomon encoding of the data. Printed border regions delineating the border of the area can be provided, in addition to a number of border target markers to assist in indicating the location of the regions. The border targets can comprise a large area of a first colour with a small region of a second colour located centrally in the first area.
Preferably, the data is printed utilising a high frequency modulating signal such as a checkerboard pattern. The printing can be an array of dots having a resolution of greater then substantially 1200 dots per inch and preferably at least 1600 dots per inch. The predetermined areas can be arranged in a regular array on the surface of the card and the card can be of a generally rectangular credit card sized shape.
In accordance with a further aspect of the present invention, there is provided a method of creating a set of instructions for the manipulation of an image, the method comprising the steps of displaying an initial array of sample images for a user to select from; accepting a user's selection of at least one of the sample images; utilizing attributes of the images selected to produce a further array of sample images;
iteratively applying the previous steps until such time as the user selects at least one final suitable image;
utilising the steps used in the creation of the sample image as the set of instructions; outputting the set of instructions.
The method can further include scanning a user's photograph and utilising the scanned photograph as an initial image in the creation of each of the sample images. The instructions can be printed out in an encoded form on one surface of a card in addition to printing out a visual representation of the instructions on a second surface of the card. Additionally, the manipulated image can itself be printed out.
Various techniques can be used in the creation of images including genetic algorithm or genetic programming techniques to create the array. Further, 'best so far' images can be saved for use in the creation of further images.
The method is preferably implemented in the form of a computer system incorporated into a vending machine for dispensing cards and photos.
In accordance with a further aspect of the present invention, there is provided an information storage apparatus for storing information on inserted cards the apparatus comprising a sensing means for sensing printed patterns on the surface stored on the card, the pattecns anmnged in a predetermined number of possible active areas of the card; a decoding means for decoding the sensed printed pattems into corresponding data; a printing means for printing dot patterns on the card in at least one of the active areas; a positioning means for positioning the sensed card at known locations relative to the sensing means and the printing means; wherein the sensing means is adaPted to sense the printed patterns in a current active printed area of the card, the decoding means is adapted to decode the sensed printed patterns into conesponding current data and, when the current data requires updating, the printing means is adapted to print the updated current data at a new one of the active areas after activation of the positioning means for correctly position the card.
Preferably, the printing means comprises an ink jet printer device having a card width print head able to print a line width of the card at a time. The positioning means can comprise a series of pinch rollers to pinch the card and control the movement of the card. The printed patterns can be laid out in a fault tolerant manner, for example, using Reed - Solomon decoding, and the decoding means includes a suitable decoder for the fault tolerant pattern.
In accordance with a furtlter aspect of the present invention, there is provided a digital camera system comprising an image sensor for sensing an image; storage means for storing the sensed image and associated system structures; data input means for the insertion of an image modification data module for modification of the sensed image; processor means interconnected to the image sensor, the storage means and the data input means for the control of the camera system in addition to the manipulation of the sensed image; printer means for printing out the sensed image on demand on print media supplied to the printer means;
and a method of providing an image modification data module adapted to cause the processor means to modify the operation of the digital camera system upon the insertion of further image modification modules.
Preferably, the image modification data module comprises a card having the data encoded on the surface thereof and the data encoding is in the fotm of printing and the data input means includes an optical scanner for scanning a surface of the card. 'fhe modification of operation can include applying each image modification in tum of a series of inserted image modification modules to the same image in a repetitive manner.
In accordance with a further aspect of the present invention, there is provided a digital camera system comprising an image sensor for sensing an image; storage means for storing the sensed image and associated system structures; data input means for the insertion of an image modification data module for modification of the sensed image; processor means interconnected to the image sensor, the storage means and the data input means for the control of the camera system in addition to the manipulation of the sensed image; printer means for printing out the sensed image on demand on print media supplied to the printer means;
including providing an image modification data module adapted to cause the processor means to perform a series of diagnostic tests on the digital camera system and to print out the results via the printer means.
Preferably, the image modification module can comprise a card having instruction data encoded on one surface thereof and the processor means includes means for interpreting the instruction data encoded on the card.
The diagnostic tests can include a cleaning cycle for the printer means so as to improve the operation of the printer means such as by printing a continuous all black strip. Alternatively, the diagnostic tests can include modulating the operation of the nozzles so as to improve the operation of the ink jet printer. Additionally, various internal operational parameters of the camera system can be printed out. Where the camera system is equipped with a gtavitadonal shock sensor, the diagnostic tests can include printing out an extreme value of the sensor.
In accordance with a further aspect of the present invention, there is provided a camera system for the creation of images, the camera system comprising a sensor for sensing an image; a processing means for processing the sensed image in accordance with any predetermined processing requirements; a printer means for printing the sensed image on the surface of print media, the print media including a magnetically sensitive surface;
a magnetic recording means for recording associated infonmation on the magnetically sensitive surface.
The associated information can comprises audio information associated with the sensed image and the printer means preferably prints the sensed image on a first surface of the print media and the magnetic recording means records the associated information on a second surface of the print media. The print media can be stored on an intemal detachable roll in the camera system. In one embodiment, the magnetic sensitive surface can comprise a strip affixed to the back surface of the print media.
In accordance with a further aspect of the present invention, there is provided a method of creating a permanent copy of an image captured on an image sensor of a handheld camera device having an interconnected integral computer device and an integral printer means for printing out on print media stored with the camera device, the method comprising the steps of sensing an image on the image sensor; converting the image to an encoded form of the image, the encoded form having fault tolerant encoding properties; printing out the encoded foitn of the image as a permanent record of the image utilizing the integral printer means.
Preferably, the integral printer means includes means for printing on a first and second surface of the print media and the sensed image or a visual manipulation thereof is printed on the first surface thereof and the encoded form is printed on the second surface thereof. A thumbnail of the sensed image can be printed alongside the encoded form of the image and the fault tolerant encoding can include forming a Reed-Solomon encoded version of the image in addition to applying a high frequency modulation signal such as a checkerboard pattem to the encoded form such that the permanent record includes repeatable high frequency spectral components. The print media can be supplied in a print roll means which is detachable from the camera device.
In accordance with a first aspect of the present invention, there is provided a distribution system for the distribution of image manipulation cards for utilization in camera devices having a card manipulation interface for the insertion of the image manipulation cards for the manipulation of images within the camera devices, the distribution system including a plurality of printer devices for outputting the image manipulation cards; each of the printer devices being interconnected to a corresponding computer system for the storage of a series of image manipulation card data necessary for the construction of the image manipulation cards; the computer systems being interconnected via a computer network to a card distribution computer responsible for the distribution of card lists to the computer systems for printing out corresponding cards by the printer systems.
Preferably the computer systems store the series of image manipulation card data in a cached manner over the computer network and card distribution computer is also responsible, for the distribution of new image manipulation cards to the computer systems.
'I'he present invention has particular application when the image manipulation cards include seasonal event cards which are distributed to the computer systems for the printing out of cards for utilization in respect of seasonal events.
In accordance with a further aspect of the present invention, there is provided a data structure encoded on the surface of an object comprising a series of block data regions with each of the block data regions including: an encoded data region containing data to be decoded in an encoded form; a series of clock marks structures located around a first peripheral portion of the encoded data region; and a series of easily identifiable target structures located around a second peripheral portion of the encoded data region.
The block data regions can further include an orientation data structure located round a third peripheral portion of the encoded data region. The orientation data structure can comprises a line of equal data points along an edge of the peripheral portion.
The clock marks structures can include a fust line of equal data points in addition to a substantially adjacent second line of altemating data points located along an edge of the encoded data region. The clock mark structures can be located on mutually opposite sides of the encoded data region.
The target structures can comprise a series of spaced apart block sets of data points having a substantially constant value of a first magnitude except for a core portion of a substantially opposite magnitude to the fust magnitude. The block sets can further includes a target nuwnber indicator strucu-re comprising a contiguous group of the values of the substantially opposite magnitude.
The data structure is ideally utilized in a series of printed dots on a substrate surface.
In accordance with a second aspect of the present invention, there is provided a method of decoding a data structure encoded on the surface of an object, the data structure comprising a serles of block data regions with each of the block data regions including: an encoded data region containing data to be decoded in an encoded form; a series of clock marks strucxures located around a first peaipheral portion of the encoded data region; a series of easily identifiable target sttucthues located around a second peripheral portion of the encoded data region; the method comprising the steps oF (a) scanning the data structure; (b) locating the start of the data structura; (c) locating the target structures including determining a current orientation of the target strucwres; (d) locating the clock mark structures from the position of the target structures; (e) utilizing the clock mark structures to determine an expected location of bit data of the encoded data region; and (f) determining an expected data value for each of the bit data.
The clock marks structures can include a first line of equal data points in addition to a substantially adjacent second line of aioemating data points located along an edge of the encoded data region and the utilising step (e) can comprise running along the second line of alternating data points utilizing a pseudo phase locked loop type algorithm so as to maintain a current location within the clock mark stn-dures.
Further, the determining step (t) can comprise dividing a sensed bit value into three contiguous regions comprising a niiddle region and a fnst lower and a second upper extreme regions, and with those values within a first lower region, detennining the conespondtmg bit value to be a first lower value; with those values within a second upper region, determining the corresponding bit value to be a second upper value; and with those values in the middle regions, utilising the spatially surrounding values to determine whether the value is of a first lower value or a second upper value.
In accordance with a fiuther aspect of the present invention, there is provided a method of determining an output data value of sensed data comprising: (a) dividing a sensed data value into three contiguous regions comprising a middle region and a fust lower and a second upper extrr.ine regions, and, with those values within a first lower region, detennining the cortrsponding bit value to be a first lower value; with those values within a second upper region, determining the oorresponding bit value to be a second upper value; and with those values in the middle regions, utilising the spatially surrounding values to detetmine whether the value is of a first lower value or a second upper value.
In accordance with a further aspect of the present invention, there is provided a fluid supply means for supplying a plurality of differeatt fluids to a plurality of difl'erent supply slots, whenein the supply slots are being spaced apart at periodic intervals in an interleaved manner, the fluid supply means comprising a fluid inlet means for each of the phuality of diffenent fluids, a main channel flow means for each of the diffemt fluids, cotmected to said fluid inlet means and running past each of the supply slots, and sub-channel flow means connecting each of the supply slots to a corresponding main channel flow means. The number of fluids is greater than 2 and at least two of the main channel flow means run along the fust surface of a moulded flow supply unit and another of the main channel flow means runs along the top surface of the moulded piece with the subchannel flow means being interconnected with the slots by means of through-holes through the surface of the nwukled piece.
Preferably, the supply means is plastic injection moulded and the pitch rate of the slots is substantially less than, or equal to 1,000 slots per inch. Further the collection of slots runs substantially the width of a photograph.
Prefecably, the fluid supply means further comprises a plurality of roller slot means for the rcception of one or more pinch rollers and the fluid comprises ink and the rollers are utilised to control the passage of a print media across a print-head interconnected to the slots. The slots are divided into corrosponding colour slots with each series of colour slots being arranged in columns.
Preferably, at least one of the channels of the fluid supply means is exposed when fabricated and is sealed by means of utilising sealing tape to seal the exposed surface of the channel.
Advantageously, the fluid supply means is further provided with a TAB slot for the reception of tape automated bonded (TAB) wires.
In accordance with a further aspect of the present invention, there is provided a fluid supply means for supplying a plurality of different fluids to a plurality of different supply slots, wherein the supply slots are being spaced apart at periodic intervals in an interleaved manner, the fluid supply means comprising a fluid inlet means for each of the plurality of different fluids, a main channel flow means for each of the different fluids, connected to said fluid inlet means and running past each of the supply slots, and sub-channel flow means connecting each of the supply slots to a corresponding main channel flow means. The number of fluids is greater than 2 and at least two of the main channel flow ineans run along the fitst surface of a moulded flow supply unit and another of the main channel flow means runs along the top surface of the moulded piece with the subchannel flow means being interconnected with the slots by means of through-holes through the surface of the moulded piece.
Preferably, the supply means is plactic injection moulded and the pitch rate of the slots is substantially less than, or equal to 1,000 slots per inch. Further the collection of slots nms substantially the width of a photograph.
Preferably, the fluid supply means forther comprises a plurality of roller slot means for the reception of one or more pinch rollers and the fluid comprises ink and the rollers are utilised to control the passage of a print media across a print-head interconnected to the slots. The slots are divided into corresponding colour slots with each series of colour slots being arranged in columns.
Preferably, at least one of the channels of the fluid supply means is exposed when fabricated and is sealed by means of utilising sealing tape to seal the exposed surface of the channel.
Advantageously, the fluid supply means is further provided with a TAB slot for the rmeption of tape automated bonded (TAB) wires.
In accordance with a further aspect of the present invention, there is provided a printer mechanism for printing images utilizing at least one ink ejection mechanism supplied through an ink supply channel, the mechanism comprising a series of ink supply portals at least one per output color, adapted to engage a corresponding ink supply mechanism for the supply of ink to the printer, a series of conductive connector pads along an extemal surface of the printer mechanism; a page width print head having a series of ink ejection mechanisms for the ejection of ink; an ink distribution system for distribution of ink from the ink supply portals to the ink ejection mechanisms of the page width print head; a plurality of interconnect control wires interconnecting the page width print head to the conductive connector pads; wherein the printer meehanism is adapted to be detachably inserted in a housing mechanism containing interconnection portions for interconnecting to the conductive connector pads and the ink supply coanecior of interconnection to the ink supply portals for the supply of ink by the ink supply mechanism.
Preferably, the plurality of interconnect control wires form a tape automated bonded sheet which wraps around an extetaal surface of the printer mechanism and which is interconnected to the conductive connector pads. The interconnect control wires can comprise a fust set of wires interconnecting the conductive connector pads and running along the length of the print head, substantially parallel to one another and a second set of wires tunning substantially parallel to one another from the surface of the print head, each of the fitst set of wires being interconnected to a number of the second set of wires. The ink supply portals can include a thin diaphragm portion which is pierced by the ink supply connector upon insertion into the housing mechanism.
77u page width print head can inchides a number of substantially identical repeatable units each containing a predetermined number of ink ejection mechanisms, each of the repeatable units including a standard interface mechanism containing a predetermined number of interconnect wires, each of the standard interface mechanism interconnecting as a group with the conductive connector pads. The print head itself can be conducted from a silicon wafer, separated into page width wide strips.
In accordance with a further aspect of the present invention there is provided a method of providing for resistance to monitoring of an integrated circuit by means of monitoring cucrent changes, said method comprising the step of including a spurious noise generation circuit as part of said integrated circ.uit.
The noise generation circuit can comprises a random number generator such as a LFSR (Linear Feedback Shift Register).
In accordance with a further aspect of the present invention there is provided a CMOS circuit having a low power eonsumption, said circuit including a p-type tiansistor having a gate eonnocted to a first clock and to an input and an n-type transistor connected to a second clock and said input and wherein said CMOS circuit is operated by transitioning said first and second clocks wherein said transitions occur in a non-overlapping manner.
The citr,uit can be positioned substantially adjacent a socond circuit having high power switching characteristics. The second circuit can comprise a noise generation circuit.
In accordance with a fiuther aspect of the present invention, there is provided a method of providing for resistance to monitoring of an memory circuit having multiple level states corresponding to diffenent output states, said method comprising utilizing the intermediate states only for valid output state. The memory can comprise flash memory and can further include one or more parity bits_ In accordance with a further aspect of the present invention, there is provided a method of providing for resistance to tampering of an integrated circuit comprising utilizing a circuit path attached to a tandom noise generator to monitor attentpts at tampering with the integrated circuit The circuit path can include a first path and a second path which are substantially inverses of one another and which are further connected to various test cirouitty and which are exclusive ORed togetber to produce a reset output signal. The circuit paths can substantially cover the tandom noise generator.
In accordance with a second aspect of the present invention, there is provided a tamper detection line connected at one end to a large resistance attached to ground and at a second end to a second large resistor attac.hed to a power supply, the tamper detection line further being interconnected to a comparator that compares against the expected voltage to within a predetermined tolerance, further in between the resistance are interconnected a series of test, each outputting a large resistattce such that if tampering is detected by one of the tests the comparator is caused to output a reset signal.
In accordance with a fucther aspect of the present invention there is provided an authentication system for determining the validity of an attached unit to be authenticated comprising: a central system unit for interrogation of fiist and second secure key holding units; first and second secure key holding objects attached to the central system unit, wherein the second key holding object is further permanently attached to the attached unit; wherein the central system unit is adapted to interrogate the first secure key holding object so as to deterrnine a fust response and to utilize the fust response to intemogate the second secure key holding object to determine a second response, and to fiuther compare the first and second response to determine whether the second secure key holding object is attached to a valid attached unit.
The second seeure key holding object can further include a response having an effectively monotonically decreasing magnitude factor such that, after a predetermined utilization of the attached unit, the attached unit ceases to function.
Hence the attached unit can comprises a consumable prodact Further, the the central system unit can interrogate the fust secure key holding object with a substantially random number to receives the first response, the central system then utilizes the ficst response in the interrogation of the second secure key holding object to determine the second response, the central system unit then utilizes the second response to interrogate the first secxue key holding unit to dexermine a validity measure of the second response.
The system is ideally utilized to authenticate a consumable for a printer such as ink for an mk jet printer.
Indeed the prefened embodiment will specifically be discussed with reference to the consumable of ink in a camera system having an internal ink jet printer although the presettt invention is not limited thereto.
Brief Description of the Drawings Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Fig. I illustrates an Artcam device constructed in accordance with the preferred embodiment Fig. 2 is a schematic block diagram of the main Artcam electronic components.
Fig. 3 is a schematic block diagram of the Artcam Central Processor.
Fig. 3(a) illustrate,c the VLIW Vector Processor in more ddail.
Fig. 4 illustrates the Processing Unit in more detail.
Fig. 5 illustrates the ALU 188 in more detail.
Fig. 6 illustrates the In block in more detail.
Fig. 7 illustrates the Out block in more detail.
Fig. 8 illustrates the Registers block in more detail.
Fig. 9 illustrates the Crossbarl in more detail.
Fig. 10 illuserates the Crossbar2 in more detail.
Fig. 11 illustrates the read process block in more detail.
Fig. 12 illustrates the read process block in more detail.
Fig. 13 illustrates the barrel shifter block in more detaiL
Fig. 14 illustrates the adder/togic block in more detail.
Fig. 15 illustrates the multiply block in more detail.
Fig. 16 illustrates the 1/0 address generator block in more detail.
Fig. 17 illustrates a pixel storage fotntat.
Fig. 18 illustrates a sequential read iterator proccss.
Fig. 19 illustrates a box read iterator process.
Fig. 20 illustrates a box write iterator process.
Fig. 21 iliustrates the vertical strip read/write iterator process.
Fig. 22 illustrates the vertical strip read/write iterator process.
Fig. 23 illustrates the generate sequential process.
Fig. 24 illustrates the generate sequex-tial process.
Fig. 25 iHustrate.s the generate vertical strip process.
Fig. 26 illusaates the generate vertical strip process.
Fig. 27 illustrates a pixel data configuration.
Fig. 28 iliustrates a pixel processing process.
Fig. 29 illustrates a schematic block diagram of the display controller.
Fig. 30 illustrates the CCD image organization.
Fig. 31 illustrates the storage format for a logical image.
Fig. 32 illustrates the interoal image memory storage fortnat.
Fig. 33 illustrates the image pyramid storage format.
Fig. 34 illustrates a time line of the process of sampling an Artcard.
Fig. 35 illustrate,s the super sampling process.
Fig. 36 illustrates the process of reading a rotated Artcard.
Fig. 37 illustrates a flow chart of the steps necessary to decode an Artcard.
Fig. 38 illustrates an enlargement of the left hand comer of a single Artcard.
Fig. 39 illustrates a single target for detection.
Fig. 40 illustrates the method utilised to detect targets.
Fig. 41 illustrates the method of calculating the distance between two targets.
Fig. 42 illusirates the process of centroid dri8.
Fig. 43 shows one form of centroid lookup table.
Fig. 44 illustrates the centroid updating process.
Fig. 45 illustrat.es a delta processing lookup table utilised in the prefecred embodiment.
Fig. 46 illustrates the process of unscrambling Artcard data.
Fig. 47 iUustrates a magnified view of a series of dots.
Fig. 48 illustrates the data surface of a dot card.
Fig. 49 illustrates schematically the layout of a single datablock.
Fig. 50 illustrates a single datablock.
Fig. 51 and Fig. 52 illustrate magnified views of portions ofthe datablock of Fig. 50.
Fig. 53 illustrates a single target shucture.
Fig. 54 iilustrat,es the target structure of a datablock.
Fig. 55 illushates the positional relationship of targets relative to border clocking regions of a data region.
Fig. 56 illustrates the orientation cohunns of a datablock.
Fig. 57 illustrates the array of dots of a datablock.
Fig. 58 illustrates schematically the structure of data for Reed-Solomon encoding.
Fig. 59 illustrates an example Reed-Solomon encoding.
Fig. 60 illustrates the Reed-Soiomon encoding process.
Fig. 61 illustrates the layout of encoded data within a datablock.
Fig. 62 illustrates the sampling process in sampling an alternative Artcard.
Fig. 63 illustrates, in exaggerated fomi, an example of sampling a rotated altemative Artcard.
Fig. 64 illustrates the scanning process.
Fig. 65 iilustrates the IOcely scanning distribution of the scanning process.
Fig. 66 illustsates the reiationship between probability of symbol errors and Reed-Solomon block errors.
Fig. 67 illusttates a flow chart of the decoding process.
Fig. 68 illustrates a process utilization diagtam of the decoding process.
Fig. 69 illustrates the dataflow steps in decoding.
Fig. 70 illustrates the reading process in more detail.
Fig. 71 illustrates the process of detection of the start of an aitemat'rve Artcard in more detail.
Fig. 72 illust<ates the extraction of bit data prooess in more detaiL
Fig. 73 ilhutrates the segmentation process utilized in the decoding procxss_ Fig. 74 illusbates the decoding proce.ss of finding targets in more detail.
Fig. 75 illustrates the data sttuctures utilized in locating targets.
Fig. 76 illusirates the Lancos 3 function structure.
Fig. 77 illustrates an enlarged portion of a datablock illustcating the clockmark and border region.
Fig. 78 illustrates the processing steps in decoding a bit image.
Fig. 79 illustrates the dataflow steps in decoding a bit image.
S Fig. 80 illustrates the descrambling process of the preferred embodiment.
Fig. 81 illusttates one form of implementation of the convolver.
Fig. 82 illustrates a convolution process.
Fig. 83 illustrates the compositing process.
Fig. 84 illustrates the regular compositing process in more detail.
Fig. 85 illustrates the process of warping using a wacp map.
Fig. 86 illustrates the warping bi-linear interpolation proccss.
Fig. 87 illustrates the process of span calculation.
Fig. 88 illustrates the basic span calculation process_ Fig. 89 illustrates one form of detail implementation of the span calculation process.
Fig. 90 illustrates the process of reading image pyramid levels.
Fig. 91 illustrates using the pyramid table for blinear inteapolation.
Fig. 92 illustrates the histogram collection process.
Fig. 93 illustrates the color transform process.
Fig. 94 illustrates the color conversion process.
Fig. 95 illustrates the color space conversion process in more detail.
Fig. 96 iliustrates the process of calculating an idput coordinate.
Fig. 97 illustrates the process of compositing with feedback.
Fig. 98 illustrates the generalized scaling process.
Fig. 99 illustrates the scale in X scaling process.
Fig. 100 illustrates the scale in Y scaling process.
Fig. 101 illustrates the tessellation process.
Fig. 102 illusimts the sub-pixel translation process.
Fig. 103 illusatates the compositing process.
Fig. 104 ilhistrates the process of compositing with feedback.
Fig. 105 illustrates the process of tiling with color from the input image.
Fig. 106 illustrates the process of tiling with feedback Fig. 107 illuspates the process of til"mg with texture replacement.
Fig. 108 illustrate.c the process of tiling with color from the input image.
Fig. 109 illustrates the process of applying a texture without feedback.
Fig. 110 illustrates the process of applying a texture with feedback.
Fig. I 11 illustrates the process of rotation of CCD pixels.
Fig. 112 itlustrates the process of interpolation of Green subpixels.
Fig. 113 ilhutiate.s the process of interpolation of Blue subpixels.
Fig. 114 illustrates the process of interpolation of Red subpixels.
Fig. 115 illustrates the process of CCD pixel interpolation with 0 degree rotation for odd pixel lines_ Fig. 116 illustrates the process of CCD pixel interpolation with 0 degree rotation for even pixel lines.
Fig. 117 illustrates the process of color conversion to Lab color space.
Fig. 118 illustrates the process of calculation of INJ{.
Fig. 119 illustrates the implementation of the calculation of 1hfX in more detail.
Fig. 120 illustrates the process of Nonnal calculation with a bump map.
Fig. 121 illustrates the process of illumination caicvlation with a bump map.
Fig. 122 illustrates the process of illumination calculation with a bump map in more detail.
Fig. 123 illustrates the process of calculation of L using a directional light.
Fig. 124 illustrates the process of calculation of L using a Omni Gghts and spotlights.
Fig. 125 illustrates one form of implementation of calculation of L using a Omni lights and spotlights.
Fig. 126 iliustrates the process of calculating the N.L dot product.
Fig. 127 illustrates the process of calculating the N.L dot product in more detail.
Fig. 128 illustrates the process of calculating the R.V dot product.
Fig. 129 illustrates the process of caiculating the RV dot product in more detail.
Fig. 130 illustrates the attenuation calculation inputs and outputs.
Fig. 131 illustrates an actual implementation of attenuation calculation.
Fig. 132 illustrates an graph of the cone factor.
Fig. 133 illustrates the process of penumbra calculation.
Fig. 134 illustrates the angles utilised in penumbra calculation.
Fig. 135 illusttabes the inputs and outputs to penumbra caiculation.
Fig. 136 illustrates an actual implementation of penumbra calculation.
Fig. 137 illustrates the inputs and outputs to ambient calculation.
Fig. 138 illushates an actual intplementation of ambient calcuiation.
Fig. 139 illustrates an actual implementation ofdiffuse calculation.
Fig. 140 illustrates the inputs and outputs to a diffuse calculation.
Fig. 141 illustrates an actaal implementation of a diffuse calculation.
Fig. 142 illustrates the inputs and outputs to a specular calculation.
Fig. 143 iliusfttes an actual itnpiementation of a specular calculation.
Fig. 144 illustrates the inputs and outputs to a specular calculation.
Fig. 145 illustrates an actual implementation of a specular calculation.
Fig. 146 iliustrates an actual mnplemattation of a ambient only calcuiation.
Fig. 147 iilustrates the process overview of light calculation.
Fig. 148 illustrates an example illumittation calculation for a single infmite light source.
Fig. 149 illustrates an example illumination calculation for a Omni ligfit source without a bump map.
Fig. 150 illustrates an example ilhunination calculation for a Omni light source with a bump map.
Fig. 151 illustrates an example illumination caiculation for a Spotlight light source without a bump map.
Fig. 152 illustrates the process of applying a single Spodight onto an image with an associated bump-map.
Fig. 153 illustrates the logical layout of a single printhead.
Fig. 154 illustrates the strueture of the printhead interface.
Fig. 155 illustrates the process of rotation of a Lab image.
Fig. 156 illustrates the format of a pixel of the printed image.
Fig. 157 illustrates the dithering process.
Fig. 158 illustrates the process of generating an 8 bit dot output.
Fig. 159 illustrates a perspective view of the card reader.
Fig. 160 illustrates an exploded perspective of a card reader.
Fig. 161 illustratcs a close up view of the Artcard reader.
Fig. 162 illustrates a perspective view of the print roll and print head.
Fig. 163 illustrates a first expioded perspective view of the print roll.
Fig. 164 illustrates a second exploded perspective view of the print roll.
Fig. 165 ilhistrates the print roll authentication chip.
Fig. 166 iilustrates an enlarged view of the print roll authentication chip.
Fig. 167 illustrates a single authentication chip data protocol.
Fig. 168 illustrates a dual authentication chip data protocol.
Fig. 169 illustrates a first presence only protocoL
Fig. 170 illustrates a second presence only protocol.
Fig. 171 IIlustrates a third data protocol.
Fig. 172 illustrates a fourth data protocol.
Fig. 173 is a schematic block diagram of a maximal period LFSR.
Fig. 174 is a schematic block diagram of a clock limiting filter.
Fig. 175 is a sdtematic block diagram of the tamper detection lines.
Fig. 176 illustrates an oversized nMOS transistor.
Fig. 177 illustrates the taking of multiple XORs from the Tamper Detect Line Fig. 178 illustrate how the Tamper Lines cover the noise generator circuitry.
Fig. 179 illustrates the normal form of FET implementation.
Fig. I SO illusirates the modified form of FET implementation of the prefen-ed embodiment.
Fig. 181 ilh-sttates a schematic block diagram of the authentication chip.
Fig. 182 illustrates an example memory map.
Fig. 183 ilhistrates an example of the constants memory map.
Fig.184 illustrates an example ofthe RAM memory map.
Fig. 185 illustrates an example of the Flash memory variables memory map.
Fig. 186 illustrates an example of the Flash memory program memory map.
Fig. 187 shows the data flow and relationship between components of the State Machine.
Fig. 188 ahows the data flow and relationship between components of the I/O
UniL
Fig. 189 illustratas a schematic block diagtam of the Arithmetic Logic Unit Fig. 190 illustrates a schematic block diagram of the RPL unit.
Fig. 191 illustrates a schematic block diagram of the ROR block of the ALU.
Fig. 192 is a block diagram of the Program Counter Unit.
Fig. 193 is a block diagram of the Memory UniL
Fig. 194 shows a schematic block diagram for the Address Generator Unit.
Fig. 195 shows a schematic block diagram for the JSIGEN Unit.
Fig. 196 shows a schematic block diagram for the JSRGEN Unit_ Fig. 197 shows a schematic block diagram for the DBRGEN Unit.
Fig. 198 shows a schematic block diagram for the LDKGEN Unit.
Fig. 199 shows a schematic block diagram for the RPLGEN Unit Fig. 200 shows a schematic block diagram for the VARGEN UniL
Fig. 201 shows a schematic block diagram for the CLRGEN Unit.
Fig. 202 shows a schematic block diagram for the BITGEN Unit.
Fig. 203 sets out the infotmation stored on the print roll authentication chip.
Fig. 204 illusttates tfie data stored within the Artcam authorization chip.
Fig. 205 illustrates the process of print head pulse characterization.
Fig. 206 is an exploded perspective, in section, of the print head ink supply mechanism.
Fig. 207 is a bottom perspective of the ink head supply unit.
Fig. 208 is a bottom side sectional view of the ink head supply unit.
Fig. 209 is a top perspective of the ink head supply unit.
Fig. 210 is a top side sectional view of the ink head supply unit.
Fig. 211 illustrates a perspective view of a small portion of the print head.
Fig. 212 itlustztes is an exploded perspective of the print head unit Fig. 213 illustrates a top side perspective view of the internal portions of an Artcam camera, showing the parts flattened ouL
Fig. 214 ilhutrates a bottom side perspective view of the intemal portions of an Artcatn camera, showing the parts flattened out Fig. 215 illustrates a fust top side perspective view of the intemal portions of an Artcam camera, showing the parts as encased in an Artcam.
Fig. 216 illustates a second top side perspecdve view of the internal portions of an Artcartt camera, showing the parts as encased in an Artcam.
Fig. 217 illustues a second top side perspective view of the internal portions of an Arteam camera, sbowing the parts as encased in an Artcam.
Fig. 218 illustrates the backing portion of a postcard print roll.
Fig. 219 iAustrates the corresponding front image on the postcard print roll after printing out images.
Fig. 220 illusttates a form of print roll ready for purchase by a consumer.
Fig. 221 illustrates a layout of the softwarr.Jltardware modules of the overall Artcam application.
Fig. 222 illustrates a layout of the softwarelhardware modules of the Camera Manager.
Fig. 223 illustrates a layout of the software/hardware modules of the Image Processing Manager.
Fig. 224 illustrates a layout of the software/hardware modules of the Printer Manager.
Fig. 225 illusirates a layout of the software/hardware modules of the Image Processing Manager.
Fig. 226 illustrates a layout of the software/hardware modules of the File Manager.
-28_ Fig. 227 illustrates a perspective view, partly in section, of an ahernative form of printroll.
Fig. 228 is a left side exploded perspective view of the print roll of Fig.
227.
Fig. 229 is a right side exploded perspective view of a single printroll.
Fig. 230 is an exploded pecspective view, partly in section, of the core portion of the printroll.
Fig. 231 is a second exploded perspective view of the core portion of the printroll.
Fig. 232 illustnrtes a front view of a'Bizcard'.
Fig. 233 illustrates schematically the camera system constructed in accordance to a further refinement.
Fig. 234 illustrates schematically a printer mechanism for printing on the front and back of output media.
Fig. 235 illustrates a format of the output data on the back of the photo.
Fig. 236 illustrates an enlarged portion of the output media.
Fig. 237 illustrates a reader device utilized to read data from the back of a photograph.
Fig. 238 illustrates the utilization of an apparatus of a further refinement.
Fig. 239 illustrates a schematic example of image orientation specific processing.
Fig. 240 illustrates a method of producing an image specific effect when utilizing a camera as constructed in accordance with a further refinement.
Fig. 241 illustrates a print roll in accordance with a further refinement Fig. 242 illustrates the method of a fiuther rofined embadiment.
Fig. 243 illustrates the method of operation of a further refinement.
Fig. 244 illustrates one form of image processing in accordance with a further refinement.
Fig. 245 illustrates the method of operation of a further refinement.
Fig. 246 illustraLes the process of capturing and outputting an image.
Fig. 247 illustrates the process of red-eye removal.
Fig. 248 illustrates a photo printing arrangement as constructed in accordance with a standard artcam device.
Fig. 249 illustrates a dual print-head arrangement as constructed in accordance with a further refinement.
Fig. 250 illustrates the de-curling mechanism of a further refinement.
Fig. 251 illustrates the process of viewing a stereo photographic image.
Fig. 252 illustrates the rectilinear system of a futther refatetnents designed to produce a stereo photographic effecx.
Fig. 253 is a pattial peispective view illustrating the ccr,adion of a ste.reo photographic image.
Fig. 254 illustraDes an apparatus for producing stereo photogtaphic images in accordanee with a further tefinennents.
Fig. 255 illustrates the positioning unit of Fig. 254 in more detail.
Fig. 256 illustrates a catnera device suitable for production of stereo photographic images.
Fig. 257 illustrates the proeess of using an opaque backing to improve the stereo photographic effect.
Fig. 258 illustrates schematically a method of creation of images on print media.
Fig. 259 and Fig. illustrate the structure of the printing media constructed in accordance with the present invention.
Fig. 260 illustnttes utilization of the print media conshncted in accordance with a fiuther refinement.
Fig. 261 illustrates a fust form of construction of print media in accordance with a fiuther refinement.
Fig. 262 illustrates a further form of conshuction of print media in accordance with the present invention.
Fig. 263 and Fig. 264 illustrate schematic cross-sectional views of a fiudier fortn of construction of print media in acoordance with the present invention.
Fig. 265 illusuatos one form of manufacture of the print media construction in accordance with Fig. 263 and 7.
Fig. 266 illustrates an alternative form of manufacture by extruding fibrous material for utilization with the an-angement of Fig. 265.
Fig. 267 illustrates the major steps in a further refinement.
Fig. 268 illustrates the Sobel fiiber co-efficients utilized within a further refinement Fig. 269 and Fig. 270 illustrate the process of offsetting curves utilized in a further refinements.
Fig. 271 illustrates a standard image including a face to be recognised.
Fig. 272 illustrates a fist flowchart for determining a region of interest.
Fig. 273 iilustrates a second flowchart for determining a region of interest.
Fig. 274 illustrates an initial process of tiling an image.
Fig. 275 illustrates an ahernative tile pattern for tiling an image.
Fig. 276 illustrates a tile opacity mask Fig. 277 and Fig. 278 illusarate a corresponding surface texttu+e height field for the tile of Fig. 276.
Fig. 279 illustrates the process of using a global opacity to modify the image.
Fig. 280 illustrates the process of modifying the stroking effect so as to simulate the effect of combining real paints.
Fig. 281 illustrates the process of brush stroke table creation.
Fig. 282 illustnites the process of creating stroke color palettes.
Fig. 283 illustrates the consequential painting process.
Fig. 284 illustrates a flow chart of the steps in a further embodiment in compositing brush strokes.
Fig. 285 illustrates the process conversion of Bezier curves to piecewise line segments.
Fig. 286 illustrates the brush stroking process.
Fig. 287 illustrates suitable brush stamps for use by a further embodiment.
Fig. 288 illustrates a first atrangement of a further refinement.
Fig. 289 illustrates a flow chart of the operation of a further refinement.
Fig. 290 illuustrates the structure of a high nsoludon printed image.
Fig. 291 illustrates an apparatus for process the image of Fig. 290 so as to produce a copy.
Fig. 292 illustrates the centroid processing steps.
Fig. 293 illustrates a series of likely sensed pattern.
Fig. 294 illustrates a schematic implementation of a further refutemeni.
Fig. 295 illustrates a further refinement Fig. 296 illustrates the card reading arrangement of a further embodiment.
Fig. 297 and Fig. 298 illustrate a bntsh bump map.
Fig. 299 and Fig. 300 illush-ate a background canvas bump map.
Fig. 301 and Fig. 302 illustrate the process of combining bump maps.
Fig. 303 illustrates a background of the map.
Fig. 304 and Fig. 305 illustrate the process of combining bump maps in accordance with a further refinement.
Fig. 306 illustrates the steps in the method of a further refinement in production of an artistic image.
Fig. 307 illustrates the process of mapping one gamut to a second gamut.
Fig. 308 illustrates one form of implementation of a further refinement.
Fig. 309 illustrates the preferred fotm of gamut remapping.
Fig. 310 illustrates one form of gamut morphing as utilized in a further refinement.
Fig. 311 illustrates the basic operation of an Arteam device.
Fig. 312 illustrates a series of Artcards for use with a further refinement.
Fig. 313 is a flow diagram of the algorithm utilized by a further refinement.
Fig. 314 is a schematic illustration of the outputting of printed fabrics produced in accordance with the present invention.
Fig. 315 illustrates the form of interconnection of a fwther refinement.
Fig. 316 illustrates a perspective view, partly in section of a further refinement.
Fig. 317 illustrates a card having an array of written data areas.
Fig. 318 illustrates a card having only a limited number of written data areas.
Fig. 319 illustrates the structure of a data area.
Fig. 320 iliustrates the structure of a target.
Fig. 321 illustrates an apparatus of a further refinement.
Fig. 322 illustrates a closer view of Fig. 321.
Fig. 323 illustrates the process of inserting a card into a reader device.
Fig. 324 illustrates the process of ejecting a card.
Fig. 325 illustrates the process of writing a data area on a card.
Fig. 326 is a schematic of the architecture of a card reader.
Fig. 327 is a schematic arrangement of a further refinement.
Fig. 328 illustrates an example interface of a further refinement.
Fig. 329 illustrates one form of arrangement of software modules within a further refutement.
Fig. 330 is a schematic of the operation of an Artcam system.
Fig. 331 illustrates a first example modified operation of a Artcam system.
Fig. 332 illustrates a repetition card which modifies the operation of that Artcam device.
Fig. 333 illustrates a Artcard test card for modification of the operation of an Artcam device.
Fig. 334 illustrates the output test results of an Artcam device.
Fig. 335 illustrates schematically the camera system constructed in accordance to a further refinement.
Fig. 336 illustrates schematically a printer mechanism and recording mechanism of a further refinement.
Fig. 337 illustrates a format of the magnetic strip on the back of the photo.
Fig. 338 illustrates a reader device utilized to read data recorded on the back of a photograph.
Fig. 339 illustrates the utilization of an apparatus of a further refinement.
Fig. 340 illustrates a schematic of the functional portions an Artcam device.
Fig. 341 illustrates the steps utilizing a further refinement.
Fig. 342 illustrates the operation of an Artcam device in accordance with a further refinement.
Fig. 343 illustrates an alternative embodiment of printing out on the back surface of an output "photo".
Fig. 344 illustrates the intemal portions of a printer device constructed in accordance with a fiuther embodiment.
Fig. 345 illustrates a network distribution system as constructed in accordance with a further embodiment.
Fig. 346 illustrates schematically the operation of a printer computer of Fig.
345.
DSSCI7Dtion of Preferred and Other Embodiments The digital image processing camera system constructed in accordance with the preferred embodiment is as illustrated in Fig. 1. The camera unit 1 includes means for the insertion of an integral print roll (not shown). The camera unit 1 can include an area image sensor 2 which sensors an image 3 for captured by the camera Optionally, the second area image sensor can be provided to also image the scene 3 and to optionally provide for the production of stereographic output effects.
The camera I can include an optional color display 5 for the display of the image being sensed by the sensor 2. When a simpie image is being displayed on the display 5, the button 6 can be deptrsscd resulting in the printed image 8 being output by the camera unit 1. A series of cards, herein after known as Artcards' 9 contain, on one surface encoded information and on the othcr surface, contain an image distorted by the particular effect produced by the Artcard 9. The Artcard 9 is inserted in an Artcard reader 10 in the side of camera I and, upon insertion, results in output image 8 being distorted in the same manner as the distortion appearing on the surface of Artcard 9. Hence, by means of this simple user interface a user wishing to produce a particular effect can insert one of many Artcands 9 into the Artcard reader 10 and utilize button 19 to take a picture of the image 3 resulting in a corresponding distorted output image 8.
The camera unit I can also include a number of other control button 13, 14 in addition to a simple LCD output display 15 for the display of infortnative information including the number of printouts left on the internal print roll on the camera unit. Additionally, different output formats can be controlled by CHP switch 17.
Turning now to Fig. 2, there is illustrated a schematic view of the intemal hardware of the camera unit 1. The intemal hardware is based around an Artcam central processor unit (ACP) 31.
Artcam Central Processor 31 The Artcam central processor 31 provides many functions which form the 'heart' of the system. The ACP 31 is preferably implemented as a complex, high speed, CMOS system on-a-chip.
Utilising standard cell design with sonx full custom regions is recommended. Fabrication on a 0.25 CMOS process will provide the density and speod required, along with a reasonably small die area.
The functions provided by the ACP 31 include:
1. Control and digitization of the area image sensor 2. A 3D stereoscopic version of the ACP requires two area image sensor interfaces with a second optional image sensor 4 being provided for stereoscopic effects.
2. Area image sensor cotnpensation, reformatting, and image enhancement.
3. Memory interface and management to a memory store 33.
4. Interface, control, and analog to digital conversion of an Artcard reader linear image sensor 34 which is provided for the re,ading of data from the Artcards 9.
5. Extraction of the raw Artcard data from the digitized and encoded Artcard image.
6. Reed-Solomon error detection and coffwtion of the Artcard encoded data. The encoded surface of the Artcand 9 includes information on how to process an image to produce the effects displayed on the image distorted stgface of the Artcard 9. This information is in the form of a script, hereinafter known as a "Vark scxipt". The Vark script is utilised by an interpreter running within the ACP 31 to produce the desired effect.
7. Interpretation of the Vark script on the Artcatd 9.
8. Performing image processing operations as specified by the Vark script.
9. Controlling various motors for the paper ttansport 36, zoom lens 38.
autofocus 39 and Artcard driver 37.
10. Controlling a guillotine actuator 40 for the operation of a guillotine 41 for the cutting of photographs 8 from print roll 42.
The present invention is further directed to a caaznera system with an integral printer type device. The print media being detachable from the camera system and including a means for the storage of significant infonnation in respect of the print media.
Ilie present invention is further directed to a camera system with an integral printer type device. The print media being detachable from the camera system and including means for providing an authentication access to the print media.
In accordance with a further aspect of the present invention there is provided a plane print media having a reduced degree of curling in use, said print media having anisotropic stifihess in the direction of said planes.
In accordance with the second aspect of the present invention there is provided a method of reducing the curl in an image printed on plane print media having an anisotropic stiffness said method comprising applying a localised pressure to a portion of said print media.
The present invention is further directed to a camera system with an integral printer type device. The camera systetn including an indicator for the number of images left in the printer, with the indicator able to display the number of prints left in a number of different modes.
In accordance with a further aspect of the present invention there is provided a method of automatically processing an image comprising locating within the image features having a high spatial variance and stroking the image with a series of brush strokes emanating from those areas having high spatial variance. Preferably, the bnLsh strokes have decreasing sizes near impottant features of the image.
Additionally, the position of a predetermined portion of brust strokes can undergo random jitterittg.
In accordance with a further aspect of the invention there is provided a method of warping of producing a warped image from an input image, said method comprising the steps of:
inputting a warp map for an arbitrary output image having predetennined dimensions A x B, each element of said warp map mapping a corresponding region in a theoretical input image to a pixel location of said arbitrary output image corrcsponding to the co-ordinate location of said element within said warp map;
soaling said warp map to the ditnensioas of said warped image so as to produce a scaled warp map;
for substantially each element in said sealed warp map, calcalating a contribution region in said input image through utiliztion of said element value and adjacent element values; and determining an output image colour for a pixel of said warped image corresponding to said element &om said contribution region.
In accordatnce with a further aspect of the present invention, there is provided a method of increasing the resilience of data stored on a medium for reading by a sensor device pricing the steps of (a) modulating the stored data in a recoverable fashion with the modulating signal having a high frequency component.
(b) storing the data on said medium in a modulated form;
(c) sensing the modulated stored data by said sensor device;
(d) neutralising the modulation of the modulated stoned data to track the spread of location of said modulated stored data on said medium; and (e) recovering the unmodulated stored data from the modulated stored data.
The preferred embodiment of the present invention will be described with reference to a card reading system for reading data via a CCD type device into a camera system for subsequent decoding. Further, the discussion of the preferred embodiment relies heavily upon the field of error control systems.
Hence, the person to which this specification is directed should be an expert in error of control systems and in particular, be fvmly familiar with such standard texts such as "Error control systems for Digital Communication and Storage" by Stephen B Wicker published 1995 by Prentice - Hall Inc. and in particular, the discussion of Reed - Solomon codes contained therein and in other standard text.
It is an object of the present invention to provide for a method of converting a scanned image comprising scanned pixels to a coiresponding bitmap image, said method comprising the steps of, for each bit in the bitmap image;
a. determining an expected location in said scanned image of a current bit from the location of surrounding bits in said scamied image;
b. detennining a likely value of said bit from the values at the locations of expected corresponding pixels in said scanned image;
c. determining a centroid measures of the centre of the centre of the expected intensity at the said expected location;
d. determining similar centroid measures for adjacent pixels surrounding said current bit in said scanned image and;
e. where said centroid measure is improved relative to said expected location, adjusting said expected location to be an adjacent pixel having an improved centroid measure.
In accordance with a further aspect of the present invention there is provided an apparatus for text editing an image comprising a digital camera device able to sense an image; a manipulation data entry card adapted to be inserted into said digital camera device and to provide manipulation instructions to said digital camera device for manipulating said image, said manipulation instructions including the addition of text to said image; a text entry device connected to said digital camera device for the entry of said text for addition to said image wherein said text entry device includes a series of non-roman font characters utilised by said digital camera device in conjunction with said manipulation instructions so as to create new text characters for addition to said image.
Preferably, the font characters are transmitted to said digital camera device when required and rendered by said apparatus in accordance with said manipulation instructions so as to create said new text characters. The manipulation data entry card can include a rendered roman font character set and the non-roman characters include at least one of Hebrew, Cyrillic, Arabic, Kanji or Chinese characters.
In accordance with a further aspect of the present invention there is provided an apparatus for text editing an image comprising a digital camera device able to sense an image; a manipulation data entry card adapted to be inserted into said digital camera device and to provide manipulation instructions to said digital camera device for manipulating said image, said manipulation instructions including the addition of text to said image; a text entry device connected to said digital camera device for the entry of said text for addition to said image wherein said text entry device includes a series of non-roman font characters utilised by said digital camera device in conjunction with said manipulation instructions so as to create new text characters for addition to said image.
Preferably, the font characters are transmitted to said digital camera device when required and rendered by said apparatus in accordance with said manipuiation instructions so as to create said new text characters. The manipulation data entry card can include a rendered roman font character set and the non-roman characters include at least one of Hebrew, Cyrillic, Arabic, Kanji or Chinese eharacters.
It is an object of the present invention to provide a systern which readily is able to take advantage of updated technologies in a addition to taking advantage of new filters being ctrated and, in addition, providing a readily adaptable form of image processing of digitally captured images for printing aut. _.-In accordance with a further aspect of the present invention, there is provided an image copying device for reproduction of an input image which comprises a series of ink dots, said device comprising:
(a) imaging array means for imaging said input image at a sampling rate higher than the frequency of said dots so as to produce a corresponding sampled image;
(b) processing means for processing said image so as to determine the location of said print dots in said sample image;
(c) print means for printing ink dots on print media at locations corresponding to the locations of said print dots.
2. An image copying device as claimed in claim 1 wherein said copying device prints a full color copies of said input image.
In accordance with a further aspect of the present invention there is provided a camera system for outputting deblurred images, said system comprising;
an image sensor for sensing an image; a velocity detection means for determining any motion of said image relative to an externai environment and to produce a velocity output indicative thereof; a processor means interconnected to said image sensor and said velocity detection means and adapted to process said sensed image utilising the velocity output so as to deblurr said image and to output said deblurred image.
Preferably, the camera system is connected to a printer means for immediate output of said deblurred image and is a portable handheld unit. The velocity detection means can comprise an accelerometer such as a micro-electro mechanical(IvEMS) device.
In accordance with a fiulher aspect of the present invention, there is provided a photosensor reader preform oomprising:
(a) a series of light emitter recesses for the insettion of light emitted devices;
(b) light emitter focusing means for focusing light emitted from the series of light emitter devices onto the surface of an object to be intaged as it traverses the surface of said pn;fornn;
(c) a photosensor recess for the inseition of a linear photosensor array; and (d) focussing means for focussing light reflected frotn said object to be unaged onto a distinct portion of said CCD array.
In accordance with an aspect of the present invention, there is provided a printer device for interconnection with a computer system comprising a printer head unit including an ink jet print head for printing _ 11_ images on print media and further having a cavity therein for insertion of a consumable print roll unit and a print roll unit containing a consumable print media and ink for insertion into said cavity, said ink being utilised by said ink jet print head for printing images on said print media.
In accordance with a further aspect of the present invention, there is provided a digital camera system comprising a sensing means for sensing an image; modification means for modifying the sensed image in accordance with modification instructions input into the camera; and an output means for outputting the modified image; wherein the modification means includes a series of processing elements arranged around a central crossbar switch. Preferably, the processing elements include an Arithmetic Logic Unit (ALU) acting under the control of a microcode store wherein the microcode store comprises a writeable control store. The processing elements can include an internal input and output FIFO for storing pixel data utilized by the processing elements and the modification means is interconnected to a read and write FIFO for reading and writing pixel data of images to the modification means.
Each of the processing elements can be arranged in a ring and each element is also separately connected to its nearest neighbours. The ALU accepts a series of inputs interconnected via an internal crossbar switch to a series of core processing units within the ALU and includes a number of internal registers for the storage of temporary data. The core processing units can include at least one one of a muttiplier, an adder and a barrel shifter. .
The processing elements are further connected to a common data bus for the transfer of pixel data to the processing elements and the data bus is interconnected to a data cache which acts as an intennediate cache between the processing elements and a memory store for storing the images.
In accordance with a further aspect of the present invention there is provided a method of rapidiy decoding, in real time, sensed image data stored at a high pitch rate on a card, said method comprising the steps of;
detecting the initial position of said image data;
decoding the image data so as to determine a corresponding bit pattern of said image data.
In accordance with a further aspect of the present invention there is provided a method of rapidly decoding sensed image data in a fault tolerant manner, said data stored at a high pitch rate oti a card and subject to rotations, warping and marking, said mehtod comprising the steps of:
detennining an initial location ofa start of said image data;
sensing said image data at a sampling rate greater than said pitch rate;
processing said sensed image data in a column by column process, keeping an expected location of the center of each dot (centroid) of a next cohunn and utilising fme adjustments of said centroid when processing each column so as to update the location of an expected next cetttroid.
In accordance with a further aspect of the present invention there is provided a method of accurately detecting the value of a dot of sensed image data, said image data comprising an array of dots and said sensed image data comprising a sampling of said image data at a rato greater dian the pitch fieqttency of said array of dots so as to producx an atray of pixeLs, said method cotnprising the steps of determining an expected middle pixel of said array of pixels, said middle pixel corresponding to an expected central location of a corresponding dot;
utilising the sensed value of said middle pixel and the sensed value of a number of adjacent pixels as an index to a lookup table having an output corresponding to the value of a dot centred around the corresponding location of said pixel.
In accordance with a further aspect of the present invention there is provided a method of accurately determining the location of dots of sensed image data amongst an array of dots of image data in a fault tolerant manner, said data stored at a high pitch rate on a card and subject to rotations, warping and marking effects, said method comprising the steps of:
prooessing the image data in a column by column format;
recording the dot pattern of previously processed columns of pixels;
genetating an expected dot pattern at a cutrent column position from the recorded dot pattern of previously processed pixels;
comparing the expected dot pattern with an actual dot pattem of sensed image data at said current column position;
if said comparison produces a match within a predetermined error, utilising said current column position as an aciual dot position otherwise altering said current column position to produce a better fit to said expected dot pattern to thereby produce new aetuai dot position, and utilising said actual dot position of the dot at a cun~ent column position in the detamining of dot location of dots of subsequent columns.
In accordance with a further aspect of the present invention there is provided a method of combining image bump maps to simulate the effect of painting on an image, the method comprising:
defming an image canvas bump map approximating the surface to be painted on;
deftning a painting bump map of a painting object to be painted on said surface;
combining said image canvas bump map and said painting bump map to produce a final composited bump map utilising a stiffness factor, said stiffness factor determining the degree of modulation of said painting bump map by said image canvas bump map.
In accordance with a fitrther aspect of the present invention there is provided =a method of automatically manipulating an input image to produce an artistic effect comprising:
predetermining a mapping of an input gamut to a desired output gamut so as to produce a desired artistic effect;
utilising said mapping to map said input image to an output image having a predetermined output gamut;
Preferably, the method further comprises the step of post processing the output image utilising a brush stroke filter.
Further, preferably the output gamut is formed from mapping a predetemtined number of input gamut values to corresponding output colour gamut values and interpolating the remaining mapping of input gamut values to output colour gamut values. The intetpolation process can include utilising a weighted sum ofsaid mapping of a predetermined number of input gamut values to corresponding output colour gamut values.
In accordance with the second aspect of the presettt invention there is provided a method of compressing an input colour gamut to be within an output colour gamut, said method comprising the steps of:
determining a zero chrominance value point at a current input colour intensity;
determining a source distance being the distance from said zero chrominance value to the edge of said input colour gamut;
determining a suitable edge of said output colour gamut;
determining a target distance being the distance from said zero chrominance value to the edge of said output colour gamut; and scaling the current input colour intensity by a factor derived from the ratio of source distance to target distance;
Preferably said current input colour intensity is further scaled by a factor dependent on the distance for said current input colour from said zero chrominance value point.
In accordance with a futtlter aspect of the present invention, there is provided a handheld camera for the output of an image sensed by the camera, with the camera including:
sensing means for sensing an image;
tiling means for adding tiling effects to the sensed image to produce a tiled image; and display means for displaying the tiled image.
In accordance with a fnrther aspect of the present invention, there is provided a handheld camera for the output of an image sensed by the camera, with the camera including:
sensing means for sensing an image;
texture mapping means for adding texturing effects to the sensed image to produce a texttu-ed image; and display means for displaying the textured image.
In xcordance with a further aspect of the present invention, there is provided a handheld camera for the output of an image sensed by the camera, with the camera including:
sensing means for sensing an image;
lighting means for adding lighting to the sensed itnage to produce an illuminated image which simulates the effect of light sources projected at the sensed image; and display means for displaying the i[luminated image.
In accordance with a further aspect of the present invention there is provided a garment creation system comprising:
a series of input tokens for inputting to a camera device for manipulation of a sensed image for outputting on a display device depicting a gannent constructed of fabric having characteristics of said sensed image;
a camera device adapted to read said input tokens and sense an image and manipulate said image in accordance with a read input token so as to produce said output image; and a display device adapted to display said output image In accordance with a further aspect of the present invention there is provided A garment creation system comprising:
an expected image creation system including an image sensor device and an image display device, said image creation system mapping portions of an arbitrary image sensed by said image sensor device onto a garment and outputting on said display device a depiction of said garment;
a garment fabric printer adapted to be interconnected to said image creation system for printing out corresponding pieces of said garment including said mapped portions..
In accordance with a further aspect of the present invention as provided a method of creating a manipulated image comprising interconnecting a series of camera manipulation units, each of said camera manipulation unit applying an image manipulation to an inputted image so as to produce a manipulated output image, an initial one of said camera manipulation units sensing an image from an environment and at least a final one of said camera manipulation units producing a permanent output image.
In accordance with a further aspect of the present invention there is provided a portable imaging system for viewing distant objects comprising an optical lensing system for magnifying a viewed distant object; a sensing system for simultaneously sensing said viewed distant object; a processor means interconnected to said sensing system for processing said sensed image and forwarding it to a printer mechanism; and a printer mechanism connected to said processor means for printing out on print media said sensed image on demand by said portable imaging system.
Preferably the system further comprisos a detachable print media supply means provided in a detachable module for interconnection with said printer mechanism for the supply of a roll of print media and ink to said printer mechanism.
The printer mechanism can comprise an ink jet printing mechanism providing a full color printer for the output of sensed images.
Further, the prefemed embodiment is implemented as a system of binoculars with a beam splitting device which projects said distant object onto said sensing system.
In accordance with a fiuther aspect of the present invention, there is provided a system for playing prerecorded audio encoded in a fault tolerant manner as a series of dots printed on a card, the system comprising an optical scanner means for scanning the visual form of the prerecorded audio; a processor means interconnected to the optical scanner means for decoding the scanned audio encoding to produce a corresponding audio signal;
and audio emitter means inter+connected to the processor means for emitting or playing the corresponding audio signal on demand.
The encoding can include Reed-Solomon encoding of the pm.recorded audio and can comprise an array of ink dots which are high frequency modulated to aid scanning.
The system can include a wand-like arm having a slot through which is inserted the car.d.
In accordance with a further aspect of the present invention, there is provided a method of information distribution on printed cards, the method comprising the steps of dividing the surface of the card into a number of predetennined areas; printing a first collection of data to be stored in a first one of the predetermined areas;
utilising the printed fust predetermined area when reading information stored on the card; and, when the informadon stored on the card is to be updated, dotermining a second one of the predetennined areas to print further information stored on the card, the second area not having being previously utilized to print data.
Preferably, the areas are selected in a predetermined order and the printing utilizes a high resolution ink dot printer for printing data having a degree of fault tolerance with the fault tolerance, for example, coming from Reed-Solomon encoding of the data. Printed border regions delineating the border of the area can be provided, in addition to a number of border target markers to assist in indicating the location of the regions. The border targets can comprise a large area of a first colour with a small region of a second colour located centrally in the first area.
Preferably, the data is printed utilising a high frequency modulating signal such as a checkerboard pattern. The printing can be an array of dots having a resolution of greater then substantially 1200 dots per inch and preferably at least 1600 dots per inch. The predetermined areas can be arranged in a regular array on the surface of the card and the card can be of a generally rectangular credit card sized shape.
In accordance with a further aspect of the present invention, there is provided a method of creating a set of instructions for the manipulation of an image, the method comprising the steps of displaying an initial array of sample images for a user to select from; accepting a user's selection of at least one of the sample images; utilizing attributes of the images selected to produce a further array of sample images;
iteratively applying the previous steps until such time as the user selects at least one final suitable image;
utilising the steps used in the creation of the sample image as the set of instructions; outputting the set of instructions.
The method can further include scanning a user's photograph and utilising the scanned photograph as an initial image in the creation of each of the sample images. The instructions can be printed out in an encoded form on one surface of a card in addition to printing out a visual representation of the instructions on a second surface of the card. Additionally, the manipulated image can itself be printed out.
Various techniques can be used in the creation of images including genetic algorithm or genetic programming techniques to create the array. Further, 'best so far' images can be saved for use in the creation of further images.
The method is preferably implemented in the form of a computer system incorporated into a vending machine for dispensing cards and photos.
In accordance with a further aspect of the present invention, there is provided an information storage apparatus for storing information on inserted cards the apparatus comprising a sensing means for sensing printed patterns on the surface stored on the card, the pattecns anmnged in a predetermined number of possible active areas of the card; a decoding means for decoding the sensed printed pattems into corresponding data; a printing means for printing dot patterns on the card in at least one of the active areas; a positioning means for positioning the sensed card at known locations relative to the sensing means and the printing means; wherein the sensing means is adaPted to sense the printed patterns in a current active printed area of the card, the decoding means is adapted to decode the sensed printed patterns into conesponding current data and, when the current data requires updating, the printing means is adapted to print the updated current data at a new one of the active areas after activation of the positioning means for correctly position the card.
Preferably, the printing means comprises an ink jet printer device having a card width print head able to print a line width of the card at a time. The positioning means can comprise a series of pinch rollers to pinch the card and control the movement of the card. The printed patterns can be laid out in a fault tolerant manner, for example, using Reed - Solomon decoding, and the decoding means includes a suitable decoder for the fault tolerant pattern.
In accordance with a furtlter aspect of the present invention, there is provided a digital camera system comprising an image sensor for sensing an image; storage means for storing the sensed image and associated system structures; data input means for the insertion of an image modification data module for modification of the sensed image; processor means interconnected to the image sensor, the storage means and the data input means for the control of the camera system in addition to the manipulation of the sensed image; printer means for printing out the sensed image on demand on print media supplied to the printer means;
and a method of providing an image modification data module adapted to cause the processor means to modify the operation of the digital camera system upon the insertion of further image modification modules.
Preferably, the image modification data module comprises a card having the data encoded on the surface thereof and the data encoding is in the fotm of printing and the data input means includes an optical scanner for scanning a surface of the card. 'fhe modification of operation can include applying each image modification in tum of a series of inserted image modification modules to the same image in a repetitive manner.
In accordance with a further aspect of the present invention, there is provided a digital camera system comprising an image sensor for sensing an image; storage means for storing the sensed image and associated system structures; data input means for the insertion of an image modification data module for modification of the sensed image; processor means interconnected to the image sensor, the storage means and the data input means for the control of the camera system in addition to the manipulation of the sensed image; printer means for printing out the sensed image on demand on print media supplied to the printer means;
including providing an image modification data module adapted to cause the processor means to perform a series of diagnostic tests on the digital camera system and to print out the results via the printer means.
Preferably, the image modification module can comprise a card having instruction data encoded on one surface thereof and the processor means includes means for interpreting the instruction data encoded on the card.
The diagnostic tests can include a cleaning cycle for the printer means so as to improve the operation of the printer means such as by printing a continuous all black strip. Alternatively, the diagnostic tests can include modulating the operation of the nozzles so as to improve the operation of the ink jet printer. Additionally, various internal operational parameters of the camera system can be printed out. Where the camera system is equipped with a gtavitadonal shock sensor, the diagnostic tests can include printing out an extreme value of the sensor.
In accordance with a further aspect of the present invention, there is provided a camera system for the creation of images, the camera system comprising a sensor for sensing an image; a processing means for processing the sensed image in accordance with any predetermined processing requirements; a printer means for printing the sensed image on the surface of print media, the print media including a magnetically sensitive surface;
a magnetic recording means for recording associated infonmation on the magnetically sensitive surface.
The associated information can comprises audio information associated with the sensed image and the printer means preferably prints the sensed image on a first surface of the print media and the magnetic recording means records the associated information on a second surface of the print media. The print media can be stored on an intemal detachable roll in the camera system. In one embodiment, the magnetic sensitive surface can comprise a strip affixed to the back surface of the print media.
In accordance with a further aspect of the present invention, there is provided a method of creating a permanent copy of an image captured on an image sensor of a handheld camera device having an interconnected integral computer device and an integral printer means for printing out on print media stored with the camera device, the method comprising the steps of sensing an image on the image sensor; converting the image to an encoded form of the image, the encoded form having fault tolerant encoding properties; printing out the encoded foitn of the image as a permanent record of the image utilizing the integral printer means.
Preferably, the integral printer means includes means for printing on a first and second surface of the print media and the sensed image or a visual manipulation thereof is printed on the first surface thereof and the encoded form is printed on the second surface thereof. A thumbnail of the sensed image can be printed alongside the encoded form of the image and the fault tolerant encoding can include forming a Reed-Solomon encoded version of the image in addition to applying a high frequency modulation signal such as a checkerboard pattem to the encoded form such that the permanent record includes repeatable high frequency spectral components. The print media can be supplied in a print roll means which is detachable from the camera device.
In accordance with a first aspect of the present invention, there is provided a distribution system for the distribution of image manipulation cards for utilization in camera devices having a card manipulation interface for the insertion of the image manipulation cards for the manipulation of images within the camera devices, the distribution system including a plurality of printer devices for outputting the image manipulation cards; each of the printer devices being interconnected to a corresponding computer system for the storage of a series of image manipulation card data necessary for the construction of the image manipulation cards; the computer systems being interconnected via a computer network to a card distribution computer responsible for the distribution of card lists to the computer systems for printing out corresponding cards by the printer systems.
Preferably the computer systems store the series of image manipulation card data in a cached manner over the computer network and card distribution computer is also responsible, for the distribution of new image manipulation cards to the computer systems.
'I'he present invention has particular application when the image manipulation cards include seasonal event cards which are distributed to the computer systems for the printing out of cards for utilization in respect of seasonal events.
In accordance with a further aspect of the present invention, there is provided a data structure encoded on the surface of an object comprising a series of block data regions with each of the block data regions including: an encoded data region containing data to be decoded in an encoded form; a series of clock marks structures located around a first peripheral portion of the encoded data region; and a series of easily identifiable target structures located around a second peripheral portion of the encoded data region.
The block data regions can further include an orientation data structure located round a third peripheral portion of the encoded data region. The orientation data structure can comprises a line of equal data points along an edge of the peripheral portion.
The clock marks structures can include a fust line of equal data points in addition to a substantially adjacent second line of altemating data points located along an edge of the encoded data region. The clock mark structures can be located on mutually opposite sides of the encoded data region.
The target structures can comprise a series of spaced apart block sets of data points having a substantially constant value of a first magnitude except for a core portion of a substantially opposite magnitude to the fust magnitude. The block sets can further includes a target nuwnber indicator strucu-re comprising a contiguous group of the values of the substantially opposite magnitude.
The data structure is ideally utilized in a series of printed dots on a substrate surface.
In accordance with a second aspect of the present invention, there is provided a method of decoding a data structure encoded on the surface of an object, the data structure comprising a serles of block data regions with each of the block data regions including: an encoded data region containing data to be decoded in an encoded form; a series of clock marks strucxures located around a first peaipheral portion of the encoded data region; a series of easily identifiable target sttucthues located around a second peripheral portion of the encoded data region; the method comprising the steps oF (a) scanning the data structure; (b) locating the start of the data structura; (c) locating the target structures including determining a current orientation of the target strucwres; (d) locating the clock mark structures from the position of the target structures; (e) utilizing the clock mark structures to determine an expected location of bit data of the encoded data region; and (f) determining an expected data value for each of the bit data.
The clock marks structures can include a first line of equal data points in addition to a substantially adjacent second line of aioemating data points located along an edge of the encoded data region and the utilising step (e) can comprise running along the second line of alternating data points utilizing a pseudo phase locked loop type algorithm so as to maintain a current location within the clock mark stn-dures.
Further, the determining step (t) can comprise dividing a sensed bit value into three contiguous regions comprising a niiddle region and a fnst lower and a second upper extreme regions, and with those values within a first lower region, detennining the conespondtmg bit value to be a first lower value; with those values within a second upper region, determining the corresponding bit value to be a second upper value; and with those values in the middle regions, utilising the spatially surrounding values to determine whether the value is of a first lower value or a second upper value.
In accordance with a fiuther aspect of the present invention, there is provided a method of determining an output data value of sensed data comprising: (a) dividing a sensed data value into three contiguous regions comprising a middle region and a fust lower and a second upper extrr.ine regions, and, with those values within a first lower region, detennining the cortrsponding bit value to be a first lower value; with those values within a second upper region, determining the oorresponding bit value to be a second upper value; and with those values in the middle regions, utilising the spatially surrounding values to detetmine whether the value is of a first lower value or a second upper value.
In accordance with a further aspect of the present invention, there is provided a fluid supply means for supplying a plurality of differeatt fluids to a plurality of difl'erent supply slots, whenein the supply slots are being spaced apart at periodic intervals in an interleaved manner, the fluid supply means comprising a fluid inlet means for each of the phuality of diffenent fluids, a main channel flow means for each of the diffemt fluids, cotmected to said fluid inlet means and running past each of the supply slots, and sub-channel flow means connecting each of the supply slots to a corresponding main channel flow means. The number of fluids is greater than 2 and at least two of the main channel flow means run along the fust surface of a moulded flow supply unit and another of the main channel flow means runs along the top surface of the moulded piece with the subchannel flow means being interconnected with the slots by means of through-holes through the surface of the nwukled piece.
Preferably, the supply means is plastic injection moulded and the pitch rate of the slots is substantially less than, or equal to 1,000 slots per inch. Further the collection of slots runs substantially the width of a photograph.
Prefecably, the fluid supply means further comprises a plurality of roller slot means for the rcception of one or more pinch rollers and the fluid comprises ink and the rollers are utilised to control the passage of a print media across a print-head interconnected to the slots. The slots are divided into corrosponding colour slots with each series of colour slots being arranged in columns.
Preferably, at least one of the channels of the fluid supply means is exposed when fabricated and is sealed by means of utilising sealing tape to seal the exposed surface of the channel.
Advantageously, the fluid supply means is further provided with a TAB slot for the reception of tape automated bonded (TAB) wires.
In accordance with a further aspect of the present invention, there is provided a fluid supply means for supplying a plurality of different fluids to a plurality of different supply slots, wherein the supply slots are being spaced apart at periodic intervals in an interleaved manner, the fluid supply means comprising a fluid inlet means for each of the plurality of different fluids, a main channel flow means for each of the different fluids, connected to said fluid inlet means and running past each of the supply slots, and sub-channel flow means connecting each of the supply slots to a corresponding main channel flow means. The number of fluids is greater than 2 and at least two of the main channel flow ineans run along the fitst surface of a moulded flow supply unit and another of the main channel flow means runs along the top surface of the moulded piece with the subchannel flow means being interconnected with the slots by means of through-holes through the surface of the moulded piece.
Preferably, the supply means is plactic injection moulded and the pitch rate of the slots is substantially less than, or equal to 1,000 slots per inch. Further the collection of slots nms substantially the width of a photograph.
Preferably, the fluid supply means forther comprises a plurality of roller slot means for the reception of one or more pinch rollers and the fluid comprises ink and the rollers are utilised to control the passage of a print media across a print-head interconnected to the slots. The slots are divided into corresponding colour slots with each series of colour slots being arranged in columns.
Preferably, at least one of the channels of the fluid supply means is exposed when fabricated and is sealed by means of utilising sealing tape to seal the exposed surface of the channel.
Advantageously, the fluid supply means is further provided with a TAB slot for the rmeption of tape automated bonded (TAB) wires.
In accordance with a further aspect of the present invention, there is provided a printer mechanism for printing images utilizing at least one ink ejection mechanism supplied through an ink supply channel, the mechanism comprising a series of ink supply portals at least one per output color, adapted to engage a corresponding ink supply mechanism for the supply of ink to the printer, a series of conductive connector pads along an extemal surface of the printer mechanism; a page width print head having a series of ink ejection mechanisms for the ejection of ink; an ink distribution system for distribution of ink from the ink supply portals to the ink ejection mechanisms of the page width print head; a plurality of interconnect control wires interconnecting the page width print head to the conductive connector pads; wherein the printer meehanism is adapted to be detachably inserted in a housing mechanism containing interconnection portions for interconnecting to the conductive connector pads and the ink supply coanecior of interconnection to the ink supply portals for the supply of ink by the ink supply mechanism.
Preferably, the plurality of interconnect control wires form a tape automated bonded sheet which wraps around an extetaal surface of the printer mechanism and which is interconnected to the conductive connector pads. The interconnect control wires can comprise a fust set of wires interconnecting the conductive connector pads and running along the length of the print head, substantially parallel to one another and a second set of wires tunning substantially parallel to one another from the surface of the print head, each of the fitst set of wires being interconnected to a number of the second set of wires. The ink supply portals can include a thin diaphragm portion which is pierced by the ink supply connector upon insertion into the housing mechanism.
77u page width print head can inchides a number of substantially identical repeatable units each containing a predetermined number of ink ejection mechanisms, each of the repeatable units including a standard interface mechanism containing a predetermined number of interconnect wires, each of the standard interface mechanism interconnecting as a group with the conductive connector pads. The print head itself can be conducted from a silicon wafer, separated into page width wide strips.
In accordance with a further aspect of the present invention there is provided a method of providing for resistance to monitoring of an integrated circuit by means of monitoring cucrent changes, said method comprising the step of including a spurious noise generation circuit as part of said integrated circ.uit.
The noise generation circuit can comprises a random number generator such as a LFSR (Linear Feedback Shift Register).
In accordance with a further aspect of the present invention there is provided a CMOS circuit having a low power eonsumption, said circuit including a p-type tiansistor having a gate eonnocted to a first clock and to an input and an n-type transistor connected to a second clock and said input and wherein said CMOS circuit is operated by transitioning said first and second clocks wherein said transitions occur in a non-overlapping manner.
The citr,uit can be positioned substantially adjacent a socond circuit having high power switching characteristics. The second circuit can comprise a noise generation circuit.
In accordance with a fiuther aspect of the present invention, there is provided a method of providing for resistance to monitoring of an memory circuit having multiple level states corresponding to diffenent output states, said method comprising utilizing the intermediate states only for valid output state. The memory can comprise flash memory and can further include one or more parity bits_ In accordance with a further aspect of the present invention, there is provided a method of providing for resistance to tampering of an integrated circuit comprising utilizing a circuit path attached to a tandom noise generator to monitor attentpts at tampering with the integrated circuit The circuit path can include a first path and a second path which are substantially inverses of one another and which are further connected to various test cirouitty and which are exclusive ORed togetber to produce a reset output signal. The circuit paths can substantially cover the tandom noise generator.
In accordance with a second aspect of the present invention, there is provided a tamper detection line connected at one end to a large resistance attached to ground and at a second end to a second large resistor attac.hed to a power supply, the tamper detection line further being interconnected to a comparator that compares against the expected voltage to within a predetermined tolerance, further in between the resistance are interconnected a series of test, each outputting a large resistattce such that if tampering is detected by one of the tests the comparator is caused to output a reset signal.
In accordance with a fucther aspect of the present invention there is provided an authentication system for determining the validity of an attached unit to be authenticated comprising: a central system unit for interrogation of fiist and second secure key holding units; first and second secure key holding objects attached to the central system unit, wherein the second key holding object is further permanently attached to the attached unit; wherein the central system unit is adapted to interrogate the first secure key holding object so as to deterrnine a fust response and to utilize the fust response to intemogate the second secure key holding object to determine a second response, and to fiuther compare the first and second response to determine whether the second secure key holding object is attached to a valid attached unit.
The second seeure key holding object can further include a response having an effectively monotonically decreasing magnitude factor such that, after a predetermined utilization of the attached unit, the attached unit ceases to function.
Hence the attached unit can comprises a consumable prodact Further, the the central system unit can interrogate the fust secure key holding object with a substantially random number to receives the first response, the central system then utilizes the ficst response in the interrogation of the second secure key holding object to determine the second response, the central system unit then utilizes the second response to interrogate the first secxue key holding unit to dexermine a validity measure of the second response.
The system is ideally utilized to authenticate a consumable for a printer such as ink for an mk jet printer.
Indeed the prefened embodiment will specifically be discussed with reference to the consumable of ink in a camera system having an internal ink jet printer although the presettt invention is not limited thereto.
Brief Description of the Drawings Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Fig. I illustrates an Artcam device constructed in accordance with the preferred embodiment Fig. 2 is a schematic block diagram of the main Artcam electronic components.
Fig. 3 is a schematic block diagram of the Artcam Central Processor.
Fig. 3(a) illustrate,c the VLIW Vector Processor in more ddail.
Fig. 4 illustrates the Processing Unit in more detail.
Fig. 5 illustrates the ALU 188 in more detail.
Fig. 6 illustrates the In block in more detail.
Fig. 7 illustrates the Out block in more detail.
Fig. 8 illustrates the Registers block in more detail.
Fig. 9 illustrates the Crossbarl in more detail.
Fig. 10 illuserates the Crossbar2 in more detail.
Fig. 11 illustrates the read process block in more detail.
Fig. 12 illustrates the read process block in more detail.
Fig. 13 illustrates the barrel shifter block in more detaiL
Fig. 14 illustrates the adder/togic block in more detail.
Fig. 15 illustrates the multiply block in more detail.
Fig. 16 illustrates the 1/0 address generator block in more detail.
Fig. 17 illustrates a pixel storage fotntat.
Fig. 18 illustrates a sequential read iterator proccss.
Fig. 19 illustrates a box read iterator process.
Fig. 20 illustrates a box write iterator process.
Fig. 21 iliustrates the vertical strip read/write iterator process.
Fig. 22 illustrates the vertical strip read/write iterator process.
Fig. 23 illustrates the generate sequential process.
Fig. 24 illustrates the generate sequex-tial process.
Fig. 25 iHustrate.s the generate vertical strip process.
Fig. 26 illusaates the generate vertical strip process.
Fig. 27 illustrates a pixel data configuration.
Fig. 28 iliustrates a pixel processing process.
Fig. 29 illustrates a schematic block diagram of the display controller.
Fig. 30 illustrates the CCD image organization.
Fig. 31 illustrates the storage format for a logical image.
Fig. 32 illustrates the interoal image memory storage fortnat.
Fig. 33 illustrates the image pyramid storage format.
Fig. 34 illustrates a time line of the process of sampling an Artcard.
Fig. 35 illustrate,s the super sampling process.
Fig. 36 illustrates the process of reading a rotated Artcard.
Fig. 37 illustrates a flow chart of the steps necessary to decode an Artcard.
Fig. 38 illustrates an enlargement of the left hand comer of a single Artcard.
Fig. 39 illustrates a single target for detection.
Fig. 40 illustrates the method utilised to detect targets.
Fig. 41 illustrates the method of calculating the distance between two targets.
Fig. 42 illusirates the process of centroid dri8.
Fig. 43 shows one form of centroid lookup table.
Fig. 44 illustrates the centroid updating process.
Fig. 45 illustrat.es a delta processing lookup table utilised in the prefecred embodiment.
Fig. 46 illustrates the process of unscrambling Artcard data.
Fig. 47 iUustrates a magnified view of a series of dots.
Fig. 48 illustrates the data surface of a dot card.
Fig. 49 illustrates schematically the layout of a single datablock.
Fig. 50 illustrates a single datablock.
Fig. 51 and Fig. 52 illustrate magnified views of portions ofthe datablock of Fig. 50.
Fig. 53 illustrates a single target shucture.
Fig. 54 iilustrat,es the target structure of a datablock.
Fig. 55 illushates the positional relationship of targets relative to border clocking regions of a data region.
Fig. 56 illustrates the orientation cohunns of a datablock.
Fig. 57 illustrates the array of dots of a datablock.
Fig. 58 illustrates schematically the structure of data for Reed-Solomon encoding.
Fig. 59 illustrates an example Reed-Solomon encoding.
Fig. 60 illustrates the Reed-Soiomon encoding process.
Fig. 61 illustrates the layout of encoded data within a datablock.
Fig. 62 illustrates the sampling process in sampling an alternative Artcard.
Fig. 63 illustrates, in exaggerated fomi, an example of sampling a rotated altemative Artcard.
Fig. 64 illustrates the scanning process.
Fig. 65 iilustrates the IOcely scanning distribution of the scanning process.
Fig. 66 illustsates the reiationship between probability of symbol errors and Reed-Solomon block errors.
Fig. 67 illusttates a flow chart of the decoding process.
Fig. 68 illustrates a process utilization diagtam of the decoding process.
Fig. 69 illustrates the dataflow steps in decoding.
Fig. 70 illustrates the reading process in more detail.
Fig. 71 illustrates the process of detection of the start of an aitemat'rve Artcard in more detail.
Fig. 72 illust<ates the extraction of bit data prooess in more detaiL
Fig. 73 ilhutrates the segmentation process utilized in the decoding procxss_ Fig. 74 illusbates the decoding proce.ss of finding targets in more detail.
Fig. 75 illustrates the data sttuctures utilized in locating targets.
Fig. 76 illusirates the Lancos 3 function structure.
Fig. 77 illustrates an enlarged portion of a datablock illustcating the clockmark and border region.
Fig. 78 illustrates the processing steps in decoding a bit image.
Fig. 79 illustrates the dataflow steps in decoding a bit image.
S Fig. 80 illustrates the descrambling process of the preferred embodiment.
Fig. 81 illusttates one form of implementation of the convolver.
Fig. 82 illustrates a convolution process.
Fig. 83 illustrates the compositing process.
Fig. 84 illustrates the regular compositing process in more detail.
Fig. 85 illustrates the process of warping using a wacp map.
Fig. 86 illustrates the warping bi-linear interpolation proccss.
Fig. 87 illustrates the process of span calculation.
Fig. 88 illustrates the basic span calculation process_ Fig. 89 illustrates one form of detail implementation of the span calculation process.
Fig. 90 illustrates the process of reading image pyramid levels.
Fig. 91 illustrates using the pyramid table for blinear inteapolation.
Fig. 92 illustrates the histogram collection process.
Fig. 93 illustrates the color transform process.
Fig. 94 illustrates the color conversion process.
Fig. 95 illustrates the color space conversion process in more detail.
Fig. 96 iliustrates the process of calculating an idput coordinate.
Fig. 97 illustrates the process of compositing with feedback.
Fig. 98 illustrates the generalized scaling process.
Fig. 99 illustrates the scale in X scaling process.
Fig. 100 illustrates the scale in Y scaling process.
Fig. 101 illustrates the tessellation process.
Fig. 102 illusimts the sub-pixel translation process.
Fig. 103 illusatates the compositing process.
Fig. 104 ilhistrates the process of compositing with feedback.
Fig. 105 illustrates the process of tiling with color from the input image.
Fig. 106 illustrates the process of tiling with feedback Fig. 107 illuspates the process of til"mg with texture replacement.
Fig. 108 illustrate.c the process of tiling with color from the input image.
Fig. 109 illustrates the process of applying a texture without feedback.
Fig. 110 illustrates the process of applying a texture with feedback.
Fig. I 11 illustrates the process of rotation of CCD pixels.
Fig. 112 itlustrates the process of interpolation of Green subpixels.
Fig. 113 ilhutiate.s the process of interpolation of Blue subpixels.
Fig. 114 illustrates the process of interpolation of Red subpixels.
Fig. 115 illustrates the process of CCD pixel interpolation with 0 degree rotation for odd pixel lines_ Fig. 116 illustrates the process of CCD pixel interpolation with 0 degree rotation for even pixel lines.
Fig. 117 illustrates the process of color conversion to Lab color space.
Fig. 118 illustrates the process of calculation of INJ{.
Fig. 119 illustrates the implementation of the calculation of 1hfX in more detail.
Fig. 120 illustrates the process of Nonnal calculation with a bump map.
Fig. 121 illustrates the process of illumination caicvlation with a bump map.
Fig. 122 illustrates the process of illumination calculation with a bump map in more detail.
Fig. 123 illustrates the process of calculation of L using a directional light.
Fig. 124 illustrates the process of calculation of L using a Omni Gghts and spotlights.
Fig. 125 illustrates one form of implementation of calculation of L using a Omni lights and spotlights.
Fig. 126 iliustrates the process of calculating the N.L dot product.
Fig. 127 illustrates the process of calculating the N.L dot product in more detail.
Fig. 128 illustrates the process of calculating the R.V dot product.
Fig. 129 illustrates the process of caiculating the RV dot product in more detail.
Fig. 130 illustrates the attenuation calculation inputs and outputs.
Fig. 131 illustrates an actual implementation of attenuation calculation.
Fig. 132 illustrates an graph of the cone factor.
Fig. 133 illustrates the process of penumbra calculation.
Fig. 134 illustrates the angles utilised in penumbra calculation.
Fig. 135 illusttabes the inputs and outputs to penumbra caiculation.
Fig. 136 illustrates an actual implementation of penumbra calculation.
Fig. 137 illustrates the inputs and outputs to ambient calculation.
Fig. 138 illushates an actual intplementation of ambient calcuiation.
Fig. 139 illustrates an actual implementation ofdiffuse calculation.
Fig. 140 illustrates the inputs and outputs to a diffuse calculation.
Fig. 141 illustrates an actaal implementation of a diffuse calculation.
Fig. 142 illustrates the inputs and outputs to a specular calculation.
Fig. 143 iliusfttes an actual itnpiementation of a specular calculation.
Fig. 144 illustrates the inputs and outputs to a specular calculation.
Fig. 145 illustrates an actual implementation of a specular calculation.
Fig. 146 iliustrates an actual mnplemattation of a ambient only calcuiation.
Fig. 147 iilustrates the process overview of light calculation.
Fig. 148 illustrates an example illumittation calculation for a single infmite light source.
Fig. 149 illustrates an example illumination calculation for a Omni ligfit source without a bump map.
Fig. 150 illustrates an example ilhunination calculation for a Omni light source with a bump map.
Fig. 151 illustrates an example illumination caiculation for a Spotlight light source without a bump map.
Fig. 152 illustrates the process of applying a single Spodight onto an image with an associated bump-map.
Fig. 153 illustrates the logical layout of a single printhead.
Fig. 154 illustrates the strueture of the printhead interface.
Fig. 155 illustrates the process of rotation of a Lab image.
Fig. 156 illustrates the format of a pixel of the printed image.
Fig. 157 illustrates the dithering process.
Fig. 158 illustrates the process of generating an 8 bit dot output.
Fig. 159 illustrates a perspective view of the card reader.
Fig. 160 illustrates an exploded perspective of a card reader.
Fig. 161 illustratcs a close up view of the Artcard reader.
Fig. 162 illustrates a perspective view of the print roll and print head.
Fig. 163 illustrates a first expioded perspective view of the print roll.
Fig. 164 illustrates a second exploded perspective view of the print roll.
Fig. 165 ilhistrates the print roll authentication chip.
Fig. 166 iilustrates an enlarged view of the print roll authentication chip.
Fig. 167 illustrates a single authentication chip data protocol.
Fig. 168 illustrates a dual authentication chip data protocol.
Fig. 169 illustrates a first presence only protocoL
Fig. 170 illustrates a second presence only protocol.
Fig. 171 IIlustrates a third data protocol.
Fig. 172 illustrates a fourth data protocol.
Fig. 173 is a schematic block diagram of a maximal period LFSR.
Fig. 174 is a schematic block diagram of a clock limiting filter.
Fig. 175 is a sdtematic block diagram of the tamper detection lines.
Fig. 176 illustrates an oversized nMOS transistor.
Fig. 177 illustrates the taking of multiple XORs from the Tamper Detect Line Fig. 178 illustrate how the Tamper Lines cover the noise generator circuitry.
Fig. 179 illustrates the normal form of FET implementation.
Fig. I SO illusirates the modified form of FET implementation of the prefen-ed embodiment.
Fig. 181 ilh-sttates a schematic block diagram of the authentication chip.
Fig. 182 illustrates an example memory map.
Fig. 183 ilhistrates an example of the constants memory map.
Fig.184 illustrates an example ofthe RAM memory map.
Fig. 185 illustrates an example of the Flash memory variables memory map.
Fig. 186 illustrates an example of the Flash memory program memory map.
Fig. 187 shows the data flow and relationship between components of the State Machine.
Fig. 188 ahows the data flow and relationship between components of the I/O
UniL
Fig. 189 illustratas a schematic block diagtam of the Arithmetic Logic Unit Fig. 190 illustrates a schematic block diagram of the RPL unit.
Fig. 191 illustrates a schematic block diagram of the ROR block of the ALU.
Fig. 192 is a block diagram of the Program Counter Unit.
Fig. 193 is a block diagram of the Memory UniL
Fig. 194 shows a schematic block diagram for the Address Generator Unit.
Fig. 195 shows a schematic block diagram for the JSIGEN Unit.
Fig. 196 shows a schematic block diagram for the JSRGEN Unit_ Fig. 197 shows a schematic block diagram for the DBRGEN Unit.
Fig. 198 shows a schematic block diagram for the LDKGEN Unit.
Fig. 199 shows a schematic block diagram for the RPLGEN Unit Fig. 200 shows a schematic block diagram for the VARGEN UniL
Fig. 201 shows a schematic block diagram for the CLRGEN Unit.
Fig. 202 shows a schematic block diagram for the BITGEN Unit.
Fig. 203 sets out the infotmation stored on the print roll authentication chip.
Fig. 204 illusttates tfie data stored within the Artcam authorization chip.
Fig. 205 illustrates the process of print head pulse characterization.
Fig. 206 is an exploded perspective, in section, of the print head ink supply mechanism.
Fig. 207 is a bottom perspective of the ink head supply unit.
Fig. 208 is a bottom side sectional view of the ink head supply unit.
Fig. 209 is a top perspective of the ink head supply unit.
Fig. 210 is a top side sectional view of the ink head supply unit.
Fig. 211 illustrates a perspective view of a small portion of the print head.
Fig. 212 itlustztes is an exploded perspective of the print head unit Fig. 213 illustrates a top side perspective view of the internal portions of an Artcam camera, showing the parts flattened ouL
Fig. 214 ilhutrates a bottom side perspective view of the intemal portions of an Artcatn camera, showing the parts flattened out Fig. 215 illustrates a fust top side perspective view of the intemal portions of an Artcam camera, showing the parts as encased in an Artcam.
Fig. 216 illustates a second top side perspecdve view of the internal portions of an Artcartt camera, showing the parts as encased in an Artcam.
Fig. 217 illustues a second top side perspective view of the internal portions of an Arteam camera, sbowing the parts as encased in an Artcam.
Fig. 218 illustrates the backing portion of a postcard print roll.
Fig. 219 iAustrates the corresponding front image on the postcard print roll after printing out images.
Fig. 220 illusttates a form of print roll ready for purchase by a consumer.
Fig. 221 illustrates a layout of the softwarr.Jltardware modules of the overall Artcam application.
Fig. 222 illustrates a layout of the softwarelhardware modules of the Camera Manager.
Fig. 223 illustrates a layout of the software/hardware modules of the Image Processing Manager.
Fig. 224 illustrates a layout of the software/hardware modules of the Printer Manager.
Fig. 225 illusirates a layout of the software/hardware modules of the Image Processing Manager.
Fig. 226 illustrates a layout of the software/hardware modules of the File Manager.
-28_ Fig. 227 illustrates a perspective view, partly in section, of an ahernative form of printroll.
Fig. 228 is a left side exploded perspective view of the print roll of Fig.
227.
Fig. 229 is a right side exploded perspective view of a single printroll.
Fig. 230 is an exploded pecspective view, partly in section, of the core portion of the printroll.
Fig. 231 is a second exploded perspective view of the core portion of the printroll.
Fig. 232 illustnrtes a front view of a'Bizcard'.
Fig. 233 illustrates schematically the camera system constructed in accordance to a further refinement.
Fig. 234 illustrates schematically a printer mechanism for printing on the front and back of output media.
Fig. 235 illustrates a format of the output data on the back of the photo.
Fig. 236 illustrates an enlarged portion of the output media.
Fig. 237 illustrates a reader device utilized to read data from the back of a photograph.
Fig. 238 illustrates the utilization of an apparatus of a further refinement.
Fig. 239 illustrates a schematic example of image orientation specific processing.
Fig. 240 illustrates a method of producing an image specific effect when utilizing a camera as constructed in accordance with a further refinement.
Fig. 241 illustrates a print roll in accordance with a further refinement Fig. 242 illustrates the method of a fiuther rofined embadiment.
Fig. 243 illustrates the method of operation of a further refinement.
Fig. 244 illustrates one form of image processing in accordance with a further refinement.
Fig. 245 illustrates the method of operation of a further refinement.
Fig. 246 illustraLes the process of capturing and outputting an image.
Fig. 247 illustrates the process of red-eye removal.
Fig. 248 illustrates a photo printing arrangement as constructed in accordance with a standard artcam device.
Fig. 249 illustrates a dual print-head arrangement as constructed in accordance with a further refinement.
Fig. 250 illustrates the de-curling mechanism of a further refinement.
Fig. 251 illustrates the process of viewing a stereo photographic image.
Fig. 252 illustrates the rectilinear system of a futther refatetnents designed to produce a stereo photographic effecx.
Fig. 253 is a pattial peispective view illustrating the ccr,adion of a ste.reo photographic image.
Fig. 254 illustraDes an apparatus for producing stereo photogtaphic images in accordanee with a further tefinennents.
Fig. 255 illustrates the positioning unit of Fig. 254 in more detail.
Fig. 256 illustrates a catnera device suitable for production of stereo photographic images.
Fig. 257 illustrates the proeess of using an opaque backing to improve the stereo photographic effect.
Fig. 258 illustrates schematically a method of creation of images on print media.
Fig. 259 and Fig. illustrate the structure of the printing media constructed in accordance with the present invention.
Fig. 260 illustnttes utilization of the print media conshncted in accordance with a fiuther refinement.
Fig. 261 illustrates a fust form of construction of print media in accordance with a fiuther refinement.
Fig. 262 illustrates a further form of conshuction of print media in accordance with the present invention.
Fig. 263 and Fig. 264 illustrate schematic cross-sectional views of a fiudier fortn of construction of print media in acoordance with the present invention.
Fig. 265 illusuatos one form of manufacture of the print media construction in accordance with Fig. 263 and 7.
Fig. 266 illustrates an alternative form of manufacture by extruding fibrous material for utilization with the an-angement of Fig. 265.
Fig. 267 illustrates the major steps in a further refinement.
Fig. 268 illustrates the Sobel fiiber co-efficients utilized within a further refinement Fig. 269 and Fig. 270 illustrate the process of offsetting curves utilized in a further refinements.
Fig. 271 illustrates a standard image including a face to be recognised.
Fig. 272 illustrates a fist flowchart for determining a region of interest.
Fig. 273 iilustrates a second flowchart for determining a region of interest.
Fig. 274 illustrates an initial process of tiling an image.
Fig. 275 illustrates an ahernative tile pattern for tiling an image.
Fig. 276 illustrates a tile opacity mask Fig. 277 and Fig. 278 illusarate a corresponding surface texttu+e height field for the tile of Fig. 276.
Fig. 279 illustrates the process of using a global opacity to modify the image.
Fig. 280 illustrates the process of modifying the stroking effect so as to simulate the effect of combining real paints.
Fig. 281 illustrates the process of brush stroke table creation.
Fig. 282 illustnites the process of creating stroke color palettes.
Fig. 283 illustrates the consequential painting process.
Fig. 284 illustrates a flow chart of the steps in a further embodiment in compositing brush strokes.
Fig. 285 illustrates the process conversion of Bezier curves to piecewise line segments.
Fig. 286 illustrates the brush stroking process.
Fig. 287 illustrates suitable brush stamps for use by a further embodiment.
Fig. 288 illustrates a first atrangement of a further refinement.
Fig. 289 illustrates a flow chart of the operation of a further refinement.
Fig. 290 illuustrates the structure of a high nsoludon printed image.
Fig. 291 illustrates an apparatus for process the image of Fig. 290 so as to produce a copy.
Fig. 292 illustrates the centroid processing steps.
Fig. 293 illustrates a series of likely sensed pattern.
Fig. 294 illustrates a schematic implementation of a further refutemeni.
Fig. 295 illustrates a further refinement Fig. 296 illustrates the card reading arrangement of a further embodiment.
Fig. 297 and Fig. 298 illustrate a bntsh bump map.
Fig. 299 and Fig. 300 illush-ate a background canvas bump map.
Fig. 301 and Fig. 302 illustrate the process of combining bump maps.
Fig. 303 illustrates a background of the map.
Fig. 304 and Fig. 305 illustrate the process of combining bump maps in accordance with a further refinement.
Fig. 306 illustrates the steps in the method of a further refinement in production of an artistic image.
Fig. 307 illustrates the process of mapping one gamut to a second gamut.
Fig. 308 illustrates one form of implementation of a further refinement.
Fig. 309 illustrates the preferred fotm of gamut remapping.
Fig. 310 illustrates one form of gamut morphing as utilized in a further refinement.
Fig. 311 illustrates the basic operation of an Arteam device.
Fig. 312 illustrates a series of Artcards for use with a further refinement.
Fig. 313 is a flow diagram of the algorithm utilized by a further refinement.
Fig. 314 is a schematic illustration of the outputting of printed fabrics produced in accordance with the present invention.
Fig. 315 illustrates the form of interconnection of a fwther refinement.
Fig. 316 illustrates a perspective view, partly in section of a further refinement.
Fig. 317 illustrates a card having an array of written data areas.
Fig. 318 illustrates a card having only a limited number of written data areas.
Fig. 319 illustrates the structure of a data area.
Fig. 320 iliustrates the structure of a target.
Fig. 321 illustrates an apparatus of a further refinement.
Fig. 322 illustrates a closer view of Fig. 321.
Fig. 323 illustrates the process of inserting a card into a reader device.
Fig. 324 illustrates the process of ejecting a card.
Fig. 325 illustrates the process of writing a data area on a card.
Fig. 326 is a schematic of the architecture of a card reader.
Fig. 327 is a schematic arrangement of a further refinement.
Fig. 328 illustrates an example interface of a further refinement.
Fig. 329 illustrates one form of arrangement of software modules within a further refutement.
Fig. 330 is a schematic of the operation of an Artcam system.
Fig. 331 illustrates a first example modified operation of a Artcam system.
Fig. 332 illustrates a repetition card which modifies the operation of that Artcam device.
Fig. 333 illustrates a Artcard test card for modification of the operation of an Artcam device.
Fig. 334 illustrates the output test results of an Artcam device.
Fig. 335 illustrates schematically the camera system constructed in accordance to a further refinement.
Fig. 336 illustrates schematically a printer mechanism and recording mechanism of a further refinement.
Fig. 337 illustrates a format of the magnetic strip on the back of the photo.
Fig. 338 illustrates a reader device utilized to read data recorded on the back of a photograph.
Fig. 339 illustrates the utilization of an apparatus of a further refinement.
Fig. 340 illustrates a schematic of the functional portions an Artcam device.
Fig. 341 illustrates the steps utilizing a further refinement.
Fig. 342 illustrates the operation of an Artcam device in accordance with a further refinement.
Fig. 343 illustrates an alternative embodiment of printing out on the back surface of an output "photo".
Fig. 344 illustrates the intemal portions of a printer device constructed in accordance with a fiuther embodiment.
Fig. 345 illustrates a network distribution system as constructed in accordance with a further embodiment.
Fig. 346 illustrates schematically the operation of a printer computer of Fig.
345.
DSSCI7Dtion of Preferred and Other Embodiments The digital image processing camera system constructed in accordance with the preferred embodiment is as illustrated in Fig. 1. The camera unit 1 includes means for the insertion of an integral print roll (not shown). The camera unit 1 can include an area image sensor 2 which sensors an image 3 for captured by the camera Optionally, the second area image sensor can be provided to also image the scene 3 and to optionally provide for the production of stereographic output effects.
The camera I can include an optional color display 5 for the display of the image being sensed by the sensor 2. When a simpie image is being displayed on the display 5, the button 6 can be deptrsscd resulting in the printed image 8 being output by the camera unit 1. A series of cards, herein after known as Artcards' 9 contain, on one surface encoded information and on the othcr surface, contain an image distorted by the particular effect produced by the Artcard 9. The Artcard 9 is inserted in an Artcard reader 10 in the side of camera I and, upon insertion, results in output image 8 being distorted in the same manner as the distortion appearing on the surface of Artcard 9. Hence, by means of this simple user interface a user wishing to produce a particular effect can insert one of many Artcands 9 into the Artcard reader 10 and utilize button 19 to take a picture of the image 3 resulting in a corresponding distorted output image 8.
The camera unit I can also include a number of other control button 13, 14 in addition to a simple LCD output display 15 for the display of infortnative information including the number of printouts left on the internal print roll on the camera unit. Additionally, different output formats can be controlled by CHP switch 17.
Turning now to Fig. 2, there is illustrated a schematic view of the intemal hardware of the camera unit 1. The intemal hardware is based around an Artcam central processor unit (ACP) 31.
Artcam Central Processor 31 The Artcam central processor 31 provides many functions which form the 'heart' of the system. The ACP 31 is preferably implemented as a complex, high speed, CMOS system on-a-chip.
Utilising standard cell design with sonx full custom regions is recommended. Fabrication on a 0.25 CMOS process will provide the density and speod required, along with a reasonably small die area.
The functions provided by the ACP 31 include:
1. Control and digitization of the area image sensor 2. A 3D stereoscopic version of the ACP requires two area image sensor interfaces with a second optional image sensor 4 being provided for stereoscopic effects.
2. Area image sensor cotnpensation, reformatting, and image enhancement.
3. Memory interface and management to a memory store 33.
4. Interface, control, and analog to digital conversion of an Artcard reader linear image sensor 34 which is provided for the re,ading of data from the Artcards 9.
5. Extraction of the raw Artcard data from the digitized and encoded Artcard image.
6. Reed-Solomon error detection and coffwtion of the Artcard encoded data. The encoded surface of the Artcand 9 includes information on how to process an image to produce the effects displayed on the image distorted stgface of the Artcard 9. This information is in the form of a script, hereinafter known as a "Vark scxipt". The Vark script is utilised by an interpreter running within the ACP 31 to produce the desired effect.
7. Interpretation of the Vark script on the Artcatd 9.
8. Performing image processing operations as specified by the Vark script.
9. Controlling various motors for the paper ttansport 36, zoom lens 38.
autofocus 39 and Artcard driver 37.
10. Controlling a guillotine actuator 40 for the operation of a guillotine 41 for the cutting of photographs 8 from print roll 42.
11. Half-toning of the image data for printing.
12. Providing the print data to a print-head 44 at the appropriate times.
13. Controlling the print head 44.
14. Controlling the ink pressure feed to print-head 44.
15. Controlling optional flash unit 56.
16. Reading and acting on various sensors in the camera, including camera orientation sensor 46.
autofocus 47 and Artcard insertion sensor 49.
autofocus 47 and Artcard insertion sensor 49.
17. Reading and acting on the user interface buttons 6, 13, 14.
18. Controlling the status display 15.
19. Providing viewfinder and preview images to the color display 5.
20. Control of the system power consumption, including the ACP power consumption via power management circuit 51 .
21. Providing extemal communications 52 to general purpose computers (using part USB).
22. Reading and storing information in a printing roll authentication chip 53.
23. Reading and storing information in a camera authentication chip 54.
24. Communicating with an optional mini-keyboard 57 for text modification.
Ouartz crystal 58 A quartz crysta158 is used as a frequency reference for the system clock. As the system clock is very high, the ACP 31 includes a phase locked loop clock circuit to increase the frequency derived from the crysta158.
ImaQe Sensine Area image sensor 2 The area image sensor 2 convetts an image through its lens into an elecarical signal. It can either be a charge coupled device (CCD) or an active pixel sensor (APS)CMOS image sector. At present, available CCD's nonmally have a higher image quality, however, there is cutrently much development occurring in CMOS imagers. CMOS
imagers arc eventually expected to be substantially cheaper than CCD's have smaUer pixel areas, and be able to incorporate drive circuitry and signal processing. They can also be made in CMOS fabs, which are transitioning to 12"
wafers. CCD's are usually built in 6" wafer fabs, and economics may not allow a conversion to 12" fabs. T7herefore, the diffaeme in fabrication cost between CCD's and CMOS imagers is likely to increase, prognessively favoring CMOS imagers. However, at present, a CCD is probably the best option.
The Artcam unit will produce suitable results with a 1,500 x 1,000 area image sensor. However, smaller sensors, such as 750 x 500, will be adequate for many markets. The Artcam is less sensitive to image sensor resolution than are conventional digital cameras. This is because many of the styles contained on Artcards 9 process the image in such a way as to obscure the lack of resolution. For example, if the image is distorted to simulate the effect of being converted to an itttpressionistic painting, low source intage resolution can be used with minimal effect. Ftmher examples for which low resolution input images will typically not be noticed include image warps which produce high distorted images, multiple miniature copies of the of the image (eg. passport photos), textural processing such as bump mapping for a base relief metal look, and photo-compositing into structured scenes.
This tolerance of low resolution image sensors may be a significant factor in reducing the manufacturing cost of an Artcam unit I camera. An Artcam with a low cost 750 x 500 image sensor will often produce superior results to a conventional digital camera with a much more expensive 1,500 x 1,000 image sensor.
Qptional stereosconic 3D image sensor 4 The 3D versions of the Artcam unit 1 have an additional image sensor 4, for stereoscopic operation. This image sensor is identical to the main image sensor. The circuitry to drive the optional image sensor may be included as a standard part of the ACP chip 31 to reduce incremental design cost.
Alternatively, a separate 3D Art.cam ACP can be designed. This option will reduce the manufacturing cost of a mainstream single sensor Artcam.
Print roll authentication chip 53 A small chip 53 is included in each print roll 42. This chip replaced the functions of the bar code, optical sensor and wheel, and ISO/ASA sensor on other forms of camera film units such as Advanced Photo Systems film carQidges.
The authentication chip also provides other features:
i. The storage of data rather than that which is mechanically and optically sensed from APS rolls 2. A remaining media length indication, accurate to high resolution.
3. Authentication Information to prevent inferior clone print roll copies.
The authentication chip 53 contains 1024 bits of Flash memory, of which 128 bits is an authentication key, and 512 bits is the authentication information. Also included is an encryption circuit to ensure that the authentication key cannot be accessed directly.
Print-head 44 The Artcam unit I. can utilize any color print technology which is stnall enough, low enough power, fast enough, high onough quality, attd low enough cost, and is compatible with the print roll. Relevant printheads will be specifically discussed hereinafter.
The specifications of the ink jet head are:
Image type Bi-level, dithered Color CMY Process Color Resolution 1600 dpi Print head length 'Page-width' (]00mm) Print speed 2 seconds per photo Ontional ink m+essure Controller (not shown) The function of the ink pressure controller depends upon the type of ink jet print head 44 incorporated in the Artcam. For some types of ink jet, the use of an ink pressure controller can be eliminated, as the ink pressure is simply atmospheric pressure. Other types of print head require a regulated positive ink ptessure. In this case, the in pressure controller consists of a pump and pressure transducer.
Other print heads may require an ultrasonic transducer to cause regular oscillations in the ink pressure, typically at frequencies around 100KHz. In the case, the ACP 31 controls the frequency phase and amplitude of these oscillations.
Paocr tran_port motor 36 'Ilie paper transport motor 36 moves the paper from within the print roll 42 past the print head at a relatively constant rate. The motor 36 is a miniature motor geared down to an appropriate speed to drive rollers which move the paper. A high quality motor and mechanical gears are required to achieve high image quality, as mechanical rumble or other vibrations will affect the printed dot row spacing.
Pe,per transnort motor driver 60 The motor driver 60 is a smail circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor 36.
Paper Pull sensor A paper pull sensor 50 detects a user's attempt to pull a photo from the camera unit during the printing process. The APC 31 reads this sensor 50, and activates the guillotine 41 if the condition oocuts. The paper pull sensor 50 is incorporated to make the camera more 'foolproof in operation.
Were the user to pull the paper out forcefully during printing, the print mechanism 44 or print roll 42 may (in extreme cases) be damaged. Since it is acceptable to pull out the 'pod' from a Polaroid type cautera before it is fully ejected, the public has been 'trained' to do this. Therefore, they are unlikely to heed printed instructions not to pull the paper.
The Artcam preferably restaru the photo print process after the guillotine 41 has cut the paper after pull sensing.
The pull sensor can be implemented as a strain gauge sensor, or as an optical sensor detecting a small plastic flag which is deflected by the torque that occurs on the paper drive rollers when the paper is pulled. The latter impletwntation is rccoRUnendation for low cost.
Pgper tnxiilotine actuator 40 Tlta paper guillotitte actuator 40 is a small actuator which causes the guillotine 41 to cut the paper either at the end of a photograph, or when the paper pull sensor 50 is activated.
The guillotine actuator 40 is a small circuit which amplifies a guillotine control signal from the APC tot the level required by the actuator 41.
Artcwd 9 The Artcard 9 is a program storage medium for the Artcam unit. As noted previously, the programs are in the form of Vark scripts. Vark is a powerful image processing language especially developed for the Artcam unit. Each Artcard 9 contains one Vark script, and thereby defines one image processing style.
Preferably, the VARK languagc is highly image processing specific. By being highly image processing specific, the atrwunt of storage required to store the details on the card are substantially reduced. Further, the ease with which new programs can be created, including enhanced effects, is also substantially increased. Preferably, the language includes facilities for handling many image processing functions ittcluding image warping via a warp map, convolution, color lookup tables, posterizing an image, adding noise to an image, image enhancement filters, painting algorithms, brush jiuering and manipulation edge detection filters, tiling, iilumination via light sources, bump maps, text. face detection and object detection attributes, fonts, including three dimensional fonts, and arbitrary complexity pre-rendered icons. Further details of the operation of the Vark language interpreter are contained hereinafter.
Hence, by utilizing the language constructs as defined by the created language, new affects on arbitrary images can be created and constructed for inexpensive storage on Artcard and subsequent distribution to camera owners. Further, on one surface of the card can be provided an example illustrating the effect that a particular VARK
script, stored on t}he other surface of the card, will have on an arbitrary captured image.
By utilizing such a system, camera technology can be distributed without a great fear of obsolescence in that, provided a VARK interpreter is incorporated in the cantera device, a device independent scenario is provided whereby the underlying technology can be completely varied over time. Further, the VARK scripts can be updated as new filters are created and distributed in an inexpensive manner, such as via simple cards for card reading.
The Artcard 9 is a piece of thin white plastic with the same format as a credit card (86mm long by 54mm wide). The Artcard is printed on both sides using a high resolution ink jet printer. The inkjet printer technology is assumed to be the same as that used in the Artcam, with 1600 dpi (63dpmm) resolution. A major feature of the Arteard 9 is low manufacturing cost. Artcards can be manufactured at high speeds as a wide web of plastic film. The plastic web is coated on both sides with a hydrophilic dye fixing layer. The web is printed simultaneously on both sides using a'pagewidth' color ink jet printer. The web is then cut and punched into individual cards. On one face of the card is printed a human readable representation of the effect the Artcard 9 will have on the sensed image. This can be simply a standard image which has been processed using the Vark script stored on the back face of the card.
On the back face of the card is printed an array of dots which can be decoded into the Vark script that defines the image processing sequence. The print area is 80mm x 50mm, giving a total of 15,876,000 dots. This array of dots could represent at least 1.89 Mbytes of data. To achieve high reliability, extensive error detection and correction is incorporated in the array of dots. This allows a substantial portion of the card to be defaced, worn, creased, or dirty with no effect on data integrity. The data coding used is Reed-Solomon coding, with half of the data devoted to error correction. This allows the storage of 967 Kbytes of error corrected data on each Artcard 9.
Linear image sensor 34 The Artcard linear sensor 34 converts the aforementioned Attcard data intage to electrical signals. As with the area image sensor 2,4, the linear image sensor can be fabricated using either CCD or APS CMOS technology. The active length of the image sensor 34 is 50mm, equal to the width of the data array on the Mcard 9. To satisfy Nyquist's sampling theorem, the resolution of the linear image sensor 34 must be at least twice the highest spatial frequency of the Artcard optical image reaching the image sensor. In practice, data detection is easier if the image sensor resolution is substantially above this. A resolution of 4800 dpi (189 dptnm) is chosen, giving a total of 9,450 pixels. This resolution requires a pixel sensor pitch of 5.3pm. This can readily be achieved by using four staggered rows of 20pm pixel sensors.
The linear image sensor is mounted in a special package which includes a LED
65 to illuminate the Artcard 9 via a Gght-pipe (not shown).
"I'he Ancard reader light-pipe can be a moided light-pipe which has several function:
1. It diflirses the light from the LED over the width of the card using total internal reflection facets.
2. It focuses the light onto a l6pm wide strip of the Artcard 9 using an integrated cylindrical lens.
3. It focuses light reflected from the Artcard onto the linear image sensor pixels using a molded array of microlenses.
The operation of the Artcard reader is explained further hereinafter.
Artcard reader motor 37 The Artcard reader motor propels the Artcard past the linear intage sensor 34 at a relatively constant rate. As it may not be cost effective to include extreme precision mechanical components in the Artcard reader, the motor 37 is a standard miniature motor geared down to an appropriate speed to drive a pair of rollets which move the Artcard 9.
The speed variations, rtunble, and other vibtations will affect the raw image data as circuitry within the APC 31 includes extensive compensation for these effects to reliably read the Artcard data.
The motor 37 is driven in reverse when the Artcard is to be ejected.
Artcar+d niotor driver 61 The Artcard motor driver 61 is a small circuit which amplifies the digital motor control signals from the APC
31 to levels suitable for driving the motor 37.
Card Insertion sensor 49 The card insertion sensor 49 is an optical sensor which detects the presence of a card as it is being inserted in the cani reader 34. Upon a signal from this sensor 49, the APC 31 initiates the card reading process, including the activation of the Artcard reader motor 37.
Card e1ect button 16 A card eject button 16 (Fig. 1) is used by the user to eject the current Artcard, so that another Artcard can be inserted. The APC 31 detects the pressing of the button, and reverses the Artcard reader motor 37 to eject the card.
Card status indicator 66 A card status indicator 66 is provided to signal the user as to the status of the Artcard reading process. This can be a standard bi-color (redlgreen) LED. When the card is successfully read, and data integrity has been verified, the LED lights up green continually. If the card is faulty, then the LED
lights up red.
If the camera is powered from a 1S V instead of 3V battery, then the power supply voltage is less than the forward voltage drop of the greed LED, and the LED will not light. In this case, red LEDs can be used, or the LED
can be powered from a voltage pump which also powers other circuits in the Artcam which require higher voltage.
64 Mbit DRAM 33 To perform the wide variety of image processing effects, the camera utilizes 8 Mbytes of tnemory 33. This can be provided by a single 64 Mbit memory chip. Of course, with changing memory technology increased Dram storage sizes may be substituted.
High speed access to the memory chip is required. This can be achieved by using a Rambus DRAM (burst access rat,e of 500 Mbytes per second) or chips using the new open standards such as double data rate (DDR) SDRAM
or Synclink DRAM.
Carnera authentication chiQ
The camera authentication chip 54 is identical to the print roll authentication chip 53, except that it has different information stored in it The camera authentication chip 54 has threo main purposes:
1. To provide a secure means of comparing authentication codes with the print roll authentication chip;
2. To provide storage for manufacturing infortttation, such as the serial number of the catnera;
3. To provide a small amount of non-volatile memory for storage of user information.
D~snlavs The Artcam includes an optional color display 5 and small status display 15.
Lowest cost consumer cameras may include a color image display, such as a small TFT LCD 5 similar to those found on some digital cameras and camcorders. The color display 5 is a major cost element of these versions of Artcam, and the display 5 plus back light are a major power consumption drain.
Status displav 15 The status display 15 is a small passive segment based LCD, sinular to those currently provided on silver halide and digital cameras. Its main function is to show the number of prints remaining in the print roll 42 and icons for various standard camera features, such as flash and bauery status.
Color disolav 5 Tlte color display 5 is a full motion image display which operates as a viewfinder, as a verification of the image to be printed, and as a user interface display. The cost of the display 5 is approximately proportional to its area, so large displays (say 4" diagonal) unit will be restricted to expensive versions of the Artcam unit. Smaller displays, such as color catncorder viewfinder'fFT's at around I", may be effective for mid-range Artcams.
Zoom lens (not shown) The Artcam can include a zoom lens. This can be a standard electronically controlled zoom lens, identical to one which would be used on a standard electronic camera, and similar to pocket camera zoom lenses. A referred version of the Artcazn unit may include standard interchangeable 35tnm SLR
lenses.
Autofocus motor 39 The autofocus motor 39 changes the focus of the zoom lens. The motor is a miniature motor geared down to an appropriate speed to drive the autofocus mechanism.
Autofocus motor driver 63 The autofocus motor driver 63 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor 39.
Zoom motor 38 The zoom motor 38 moves the zoom front lenses in and out. The motor is a miniature motor geared down to an appropriate speed to drive the zoom mechanism.
Zoom motor driver 62 The zoom motor driver 62 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor.
Communications The ACP 31 contains a universal serial bus (USB) interface 52 for communication with personal computers.
Not all Artcam models are intended to include the USB connector. However, the silicon area required for a USB
circuit 52 is smalt, so the interface can be included in the standard ACP.
4otional Keyboard 57 The Artcam unit may include an optional miniature keyboard 57 for customizing text specified by the Artcard. Any text appearing in an Artcard image may be editable, even if it is in a complex metallic 3D font. The miniature keyboatd includes a single line alphanumeric LCD to display the original text and editetl texL The keyboatd may be a standard accessory.
'Ihe ACP 31 contains a serial communications circuit for ttansferring data to and from the miniature keyboard.
Power Sunolv The Artcam unit uses a battery 48. Depending upon the Artcam options, this is either a 3V Lithium cell, 1.5 V AA alkaline cells, or other battery an-angement.
Power Managenient Unit 51 Power consumption is an important design constraint in the Artcam. It is desirable that either standard camera batteries (such as 3V lithium batters) or standard AA or AAA alkaline cells can be used. While the eleeunnic complexity of the Artcam unit is dramatically higher than 35mm photographic cameras, the power consumption need not be comrnensurately higher. Power in the Artcam can be carefully managed with all unit being turned off when not in use.
The most significant current drains are the ACP 31, the area image sensors 2,4, the printer 44 various motors, the flash unit 56, and the optional color display 5 dealing with each part separately:
1. ACP: If fabricated using 0.25 m CMOS, and running on 1.5V, the ACP power consumption can be quite low. Clocks to various parts of the ACP chip can be quite low. Clocks to various parts of the ACP chip can be turned off when not in use, virtually eliminating standby current consumption.
The ACP will only fully used for approximately 4 seconds for each photograph printed.
2. Area image sensor. power is only, supplied to the area image sensor when the user has their finger on the button.
3. 'Ihe printer power is only supplied to the printer when actually printing.
This is for around 2 seconds for each photograph. Even so, suitably lower power consumption printing shouid be used.
4. The motors required in the Artcam are all low power miniature motors, and are typically only activated for a few seconds per photo.
5. The flash unit 45 is only used for some photographs. Its power consumption can readily be provided by a 3V lithium battery for a reasonably battery life.
6. The optional color display 5 is a major current drain for two reasons: it must be on for the whole time that the camera is in use, and a backlight will be required if a liquid crystal display is used. Cameras which incorporate a color display will require a larger battery to achieve acceptable batter life.
F1ash unit 56 The flash unit 56 can be a standard miniature electronic flash for consumer cameras.
Overview of the ACP 31 Fig. 3 illustrates the Artcam Central Processor (ACP) 31 in more detail. The Artcam Central Prnoessor provides all of the processing power for Artcam. It is designed for a 0.25 micron CMOS
process, with approximately 1.5 million tt ansistors and an area of around 50 mm2. The ACP 31 is a complex design, but design effmt can be teduced by the use of datapath compilation techniques, macrocells, and IP cores. 'Ilte ACP 31 contains:
A RISC CPU core 72 A 4 way parallel VLIW Vector Processor 74 A Direct RAMbus interface 81 A CMOS image sensor interface 83 A CMOS linear image sensor interface 88 A USB serial interface 52 An infrared keyboard interface 55 A numeric LCD interface 84, and A color TFI' LCD interface 88 A 4Mbyte Flash tnemory 70 for program storage 70 The RISC CPU, Direct RAMbus interface 81, CMOS sensor interface 83 and USB
serial interface 52 can be vendor supplied cores. The ACP 31 is intended to run at a clock speed of 200 MHz on 3V externally and 1.5V internally to nrinimize power consumption. The CPU core needs only to run at 100 MHz. The following two block diagrams give two views of the ACP 3 1:
A view of tlte ACP 31 in isolation An example Artcam showing a high-level view of the ACP 31 connected to the rest of the Artcam hardware.
Access Image As stated previously, the DRAM Interface 81 is responsible for interfacing between other client portions of the ACP chip and the RAMBUS DRAM. In effect, each module within the DRAM
Interface is an address generator.
There are three logical types of images manipulated by the ACP. They are:
-CCD Itnage, which is the Input Inuige captured from the CCD.
-Internal Image format - the Image fomtat utilised intetnally by the Artcam device.
Print Image - the Output Image format printed by the Art,cam These images are typically different in color space, resolution, and the output & input color spaces which can vary from caniera to camera. For example, a CCD image on a low-end camera may be a different resolution, or have different color characteristics from that used in a high-end camera. However all internal image formats are the same format in tetms of color space across all cameras.
In addition, the three image types can vary with respect to which direction is 'up'_ The physical orientation of the camera causes the notion of a portrait or landscape itnage, and this must be maintained throughout processing. For this reason, the intemal image is always oriented correcdy, and rotation is performed on intages obtained from the CCD and during the print operation.
CPU Core (CPU) 71 The ACP 31 incorporates a 32 bit RISC CPU 72 to run the Vark image processing language interpreter and to perform Artcam's general operating system duties. A wide variety of CPU cores are suitable: it can be any processor core with sufScient processing power to perform the required core calculadons and control functions fast enough to met consumer expxtations. Examples of suitable cores are_ MIPS R4000 core from LSI
Logic, StrongARM core. There is no need to maintain instruction set continuity between different Artcam models. Artcard compatibility is maintained irrespective of future processor advances and changes, because the Vark interpreter is simply re-compiled for each new instruction set. The ACP 31 architecture is therefore also free to evolve.
Different ACP 31 chip designs may be fabricated by different manufacturers, without requiring to license or port the CPU core. This device independence avoids the chip vendor lock-in such as has occurred in the PC market with Intel. 'Ihe CPU operates at 1001vIHz, with a single cycle time of l0ns. It must be fast enough to run the Vark interpreter, although the VLIW Vector Processor 74 is responsible for most of the time-critical operations.
PtoSam cache 72 Although the program code is stored in on-chip Flash memory 70, it is unlikely that well packed Flash metnory 70 will be able to operate at the lOns cycle tinie required by the CPU. Consequently a smali cache is required for good perfotmance. 16 cache lines of 32 bytes each are sufficient, for a total of 512 bytes. The program cache 72 is defined in the chapter entitled Program cache 72.
Data cache 76 A small data cache 76 is required for good performance. This requirement is mostly due to the use of a RAMbus DRAM, which can provide high-speed data in bursts, but is inefficient for single byte accesses. The CPU has access to a memory caching system that allows flexible manipulation of CPU data cache 76 sizes. A minimum of 16 cache lines (5 12 bytes) is recommended for good perfortnance.
CPU Memory Model An Arteam's CPU memory model consists of a 32MB area. It consists of 8MB of physical RDRAM off-chip in the base model of Artcam, with provision for up to 16MB of off-chip memory. 'Ihcre is a 4MB Flash memory 70 on the ACP 31 for program st.orage, and finally a 4MB address space mapped to the various registers and controls of the ACP
31. The memory map then, for an Artcam is as follows:
Contents Size Base Artcam DRAM 8 MB
Extended DRAM 8 MB
Program memory (on ACP 31 in Flash memory 70) 4 MB
Reserved for extension of program memory 4 MB
ACP 31 registers and memory-mapped UO 4 MB
Resenied 4 MB
A straightforward way of decoding addresses is to use addwss bits 23-24:
If bit 24 is ckar, the address is in the lower 16-MB range, and =hence can be satisfied from DRAM and the Data cache 76. In most cases the DRAM will only be 8 MB, but 16 MB is allocated to cater for a higher memory model Artcams.
If bit 24 is set, and bit 23 is clear, then the address represents the Flash memory 70 4Mbyte range and is satisfied by the Pt+ogram cache 72.
If bit 24 = 1 and bit 23 = 1, the address is translated into an access over the low speed bus to the requested component in the AC by the CPU Memory Decoder 68.
Flash memory 70 The ACP 31 contains a 4Mbyte Plaslt memory 70 for storing the Artcam program.
It is envisaged that Flash memory 70 will have denser packing coefficients than masked ROM, and allows for greater flexibility for tesdng camera progratn code. The downside of the Flash memory 70 is the access time, which is unlikely to be fast enough for the 100 MHz operating speed (IOns cycle time) of the CPU. A fast Program Instruction cache 77 therefore acu as the interface between the CPU and the slower Flash memory 70.
Proeram cache 72 A small cache is required for good CPU performance. This requirement is due to the slow speed Flash memory 70 which stores the Progtam code. 16 cache lines of 32 bytes each are sufficient, for a total of 512 bytes. The PAogram cache 72 is a read only cache. The data used by CPU programs comes through the CPU Memory Decoder 68 and if the addttss is in DRAM, through the general Data cache 76. The separation allows the CPU to operate independently of the VLIW Vector Processor 74. If the data requirements are low for a given process, it can consequently operate completely out of cache.
Finally, the Program cache 72 can be read as data by the CPU rather than purely as program instructions. This allows tables, microcode for the VLIW etc to be loaded from the Flash memory 70.
Addresses with bit 24 set and bit 23 clear are satisfied from the Progtam cache 72.
CPU Memory Decoder 68 The CPU Memory Decoder 68 is a simple decoder for satisfying CPU data accesses. The Decoder translates data addresses into internal ACP register accesses over the internal low speed bus, and therefore allows for memory mappod 1/O of ACP registers. The CPU Memory Decoder 68 only interprets addresses that have bit 24 set and bit 23 clear. There is no caching in the CPU Memory Decoder 68.
DRAM interface81 The DRAM used by the Artcam is a single channel 64Mbit (8MB) RAMbus RDRAM
operating at 1.6GB/sec.
RDRAM accesses are by a single channel (16-bit data path) controller. The RDRAM also has several useful operating modes for low power operation. Although the Rambus specification describes a system with random 32 byte ttansfers as capable of achieving a greater than 95% efficiency, this is not true if only part of the 32 bytes are used. Two reads followed by two writes to the same device yields over 86% efficiency. The primary latency is required for bus turn-around going from a Write to a Read, and since there is a Delayed Write mechanism, efficiency can be further improved. With regards to writes, Write Masks allow specific subsets of bytes to be written to. These write masks would be set via intetnal cache "dirty bits". The upshot of the Rambus Direct RDRAM is a throughput of >1 GB/sec is easily achievable, and with multiple reads for every write (most processes) combined with intelligent algorithms making good use of 32 byte ttansfer knowledge, traasfer rates of >1.3 GB/sec ane expected. Every l Ons, 16 bytes can be ttansferred to or from the core.
DRAM Organization The DRAM organization for a base model (8MB RDRAM) Artcam is as follows:
Contents Size Program scratch RAM 0.50 MB
Artcard data 1.00 MB
Photo Image, captured from CMOS Sensor 0.50 MB
Print Image (compressed) 2.25 MB
I Channel of expanded Photo Image 1.50 MB
I Image Pyramid of single channel 1.00 MB
Intermediate Image Processing 1.25 MB
Notes:
the Print lmage requires 4.5MB (ISMB per channel). To accommodate other objects in the 8MB
model, the Print Image needs to be compressed. If the chrominance channel.s are compressed by 4:1 they require only 0.375MB each).
The memory model described here assumes a single 8 MB RDRAM. Other models of the Artcam niay have more memory, and thus not require compression of the Print Image. In addition, with more memory a larger part of the final image can be worlced on at once, potentially giving a speed improvement.
Note that ejecting or inserting an Artcard invalidates the 5.5MB area holding the Print Image, 1 channel of expanded phot.o image, and ihe image pyramid. This space may be safely used by the Artcard Interface for decoding the Artcard data.
Data cache 76 The ACP 31 contains a dedicated CPU instruction cache 77 and a general data cache 76. The Data cache 76 handles all DRAM requests (reads and writes of data) from the CPU, the Vi.IW Vector Processor 74, and the Display Controlkr 88. '17tese requests may have very different profiles in terms of inemory usage and algorithmic timing requiremonts.
For example, a VLIW process may be processing an image in linear mcmory, and lookup a value in a table for each value in the image. There is little need to cache much of the image, but it may be desirable to cache the entire lookup table so that no real memory access is required. Because of these differing requiretnents, the Data cache 76 allows for an intelligent definition of caching.
Although the Ranibus DRAM interface 81 is capable of very high-speed memory access (an avaage ihroughput of 32 bytes in 25ns), it is not efficient dealing with single byte requests. In order to reduce effective memory latency, the ACP 31 contains 128 cache lines. Each cache line is 32 bytes wide. Thus the total amount of data cache 76 is 4096 bytes (4KB). The 128 cache lines are configured into 16 progranunable-sized groups. Each of the 16 groups must be a contiguous set of cache lines. The CPU is responsible for determining how many cache lines to allocate to each group.
Within each group cache lines are filled according to a simple Least Recently Used algorithm. In tetms of CPU data requests, the Data cache 76 handles tnemory access requests that have address bit 24 clear. If bit 24 is clear, the address is in the lower 16 MB range, and hence can be satisfied from DRAM and the Data cache 76. In Tnost cases the DRAM
will only be 8 MB, but 16 MB is allocated to cater for a higher memory model Attcam If bit 24 is set, the address is ignored by the Data cache 76.
All CPU data requests are satisfied from Cache Group 0. A nanimum of 16 cache lines is recommended for good CPU
perfor,atance, although the CPU can assign any number of cache lines (except none) to Cache Group 0. The remaining Cache Groups (1 to 15) are allocated according to the curnent requirements.
This could mean allocation to a VLIW
Vector Processor 74 progtam or the Display Conttnller 88. For example, a 256 byte lookup table tecptired to be permanently available would require 8 cache lines. Writing out a sequential image would only require 2-4 cache lines (depending on the size of reoord being generated and whether write requests are being Write Delayed for a significant number of cycles). Associated with each cache line byte is a dirty bit, used for creating a Write Mask when writing memory to DRAM. Associated with each cache line is another dirty bit, which indicates whether any of the cache line bytes has been written to (and therefore the cache line must be written back to DRAM before it can be reused). Note that it is possible for two different Cache Groups to be accessing the same address in memory and to get out of sync.
The VLIW program writer is responsible to ensure that this is not an issue. It could be perfectly reasonable, for example, to have a Cache Group responsible for reading an image, and another Cache Group responsible for writing the changed image back to tnemory again. If the images are read or written sequentially there may be advantages in allocating cache iines in this manner. A total of 8 buses 182 connect the VL1W
Vector Processor 74 to the Data cache 76. Each bus is connected to an 1/O Address Generator. (There are 21/0 Address Generators 189, 190 per Processing Unit 178, and there are 4 Processing Units in the VLIW Vector Processor 74.
The total number of buses is therefore 8.) In any given cycle, in addition to a single 32 bit (4 byte) access to the CPU's cache group (Group 0), 4 simultaneous accesses of 16 byts (2 bytes) to remaining cache groups are petmitted on the 8 VLIW Vector Processor 74 buses. The Data cache 76 is responsible for fairly processing the requests. On a given cycle, no more than 1 request to a specific Cache Group will be processed. Given dtat there are 8 Address Generators 189, 190 in the VI.IW Vector Processor 74, each one of thesc has the potential to nafer to an individual Cache Group.
However it is possible and occasionally reasonable for 2 or more Address Generators 189, 190 to access the same Cache Group. The CPU is tesponsible for ensuring that the Cache Groups have been allocated the correct number of cache lines, and that the various Address Generators 189, 190 in the VLIW Vector Procassor 74 reference the specific Cache Groups eoerectly.
The Data cache 76 as descn'bed allows for the Display Controller 88 and VLIW
Vector Processor 74 to be active simultaueously. If the operation of these two components were deemed to never occur simultaneously, a total9 Cache Groups wottld suffice. Itie CPU would use Cache Group 0, and the VLIW Vector Processor 74 and the Display Controller 88 would share the mmaining 8 Cache Groups, requiring only 3 bits (tather than 4) to define which Cache Group would satisfy a particular request.
JTAG Intuface 85 A standard JTAG (Joint Test Action Group) Interface is included in the ACP 31 for testing purposes. Due to the con-plexity of the chip, a variety of testing techniques are required, including BIST (Built In Self Test) and functional block isolation. An overhead of 1096 in chip area is assumed for ovetall chip testing circuitry. The test circuitry is beyond the scope of this docament.
SerialInterfaces USB serial aort interface 52 This is a standard USB serial port, which is connected to the internal chip low speed bus, thereby allowing the CPU to control iL
Kevboard interface 65 This is a standard low-speed serial port, which is connected to the internal chip low speed bus, thereby allowing the CPU to control it. It is designed to be optionally connected to a keyboard to allow simple data input to customize prints.
Authentication chip serial interfaces 64 Those are 2 standard low-speed seriai porls, which are connected to the internal chip low speed bus, thereby allowing the CPU to control them. The reason for having 2 ports is to connect to both the on-camera Authentication chip, and to the print-roll Authentication chip using sepacate lines. Only using 1 line may make it possible for a clone print-roll manufacturer to design a chip which, instead of generating an authentication code, tricks the camera into using the code generated by the authentication chip in the camera.
Parallel Interface 67 The parallel interface connects the ACP 31 to individual static electrical signals. The CPU is able to control each of these connections as memory-mapped I/O via the low speed bus The following table is a list of connections to the parallel interface:
Connection Direction Pins Paper transpoct stepper motor Out 4 Artcard stepper motor Out 4 Zoom stepper motor Out 4 Guillotine motor Out 1 Flash trigger Out 1 Status LCD segment drivers Out 7 Status LCD common drivers Out 4 Artcard illumination LED Out 1 Artcard status LED (red/green) In 2 ~d sensor In I
Paper pull sensor In I
Orientation sensor In 2 Buttons In 4 VLIW Inout and Output FIFOs 78,79 The VLIW Input and Output FIFOs are 8 bit wide FIFOs used for communicating between processes and the VLIW
Vector Processor 74. Both FIFOs are under the control of the VLIW Vector Processor 74, but can be cleared and queried (e.g. for status) etc by the CPU.
VLIW n wt FII 0 78 A client writes 8-bit data to the VLIW Iwut FIFO 78 in order to have the data processed by the VLIW Vector Processor 74. Clients include the Image Sensor Interface, Artcard Interface, and CPU. Each of these processes is able to offload processing by simply writing the data to the FIFO, and letting the VLIW Vector Processor 74 do all the hard work. An example of the use of a client's use of the VLIW Input FIFO 78 is the Image Sensor Intetfaee (ISI 83). The ISI 83 takes data from the Image Sensor and writes it to the FIFO. A VLIW
process takes it from the FIFO, transforming it into the oorrect image data format, and writing it out to DRAM. The ISI 83 becomes much simpler as a result.
VLIW Output FIFO 79 The VLIW Vector Processor 74 writes 8-bit data to the VLIW Output FIFO 79 where clients can read it. Ciients include the Print Head Interface and the CPU. Both of these clients is able to offload processing by simply rrading the already processed data from the FiFO, and leaing the VLIW Vector Processor 74 do all the hard work. The CPU can also be intertupted whenever data is placed into the VLIW Output FIFO 79, allowing it to only process the data as it becomes available rather than polling the FIFO continuously. An example of the use of a client's use of the VLIW
Output FIFO 79 is the Print Head Interface (PHI 62). A VLIW proeGSS takes an image, rotates it to the cocrect orientation, color converts it, and dithers the resulting image according to the print head requirements. The PHI 62 reads the dithered fortnatted 8-bit data from the VLIW Output FIFO 79 and simply passes it on to the Print Head external to the ACP 31. The PHI 62 becomes much simpler as a result.
VLIW Vector Processor 74 To achieve the high processing requirements of Artcam, the ACP 31 contains a VLIW (Very Long Instntction Word) Vector Processor. The VLIW processor is a set of 4 identical Processing Units (PU e.g 178) working in parallel, connected by a crossbar switch 183. Each PU e.g 178 can perform four 8-bit multiplications, eight 8-bit additions, tlme 32-bit additions, UO processing, and various logical operations in each cycle. The PUs e.g 178 are niicrocoded, and each has two Address Generators 189, 190 to allow full use of available cycles for data processing. The four PUs e.g 178 are nomutly synchronized to provide a tightty interacting VLIW
processor. Clocldng at 200 MHz, the VLIW
Vector Processor 74 taas at 12 Gops (12 biliion operations per second).
Instructions are tuned for image processing functions such as warping, artistic brushing, complex synthetic illumination, color transfornts, image filtering, and compositing.lhese are accelerated by two orders of magnitude over desktop computers.
As shown in more detail in Fig. 3(a), the VLIW Vector Processor 74 is 4 PUs e.g 178 connected by a crossbar switch 183 such that each PU e.g 178 provides two inputs to, and takes two outputs from, the crossbar switch 183. Two comnton regisOers fotm a control and syncluonizadon mechanism for the PUs e.g 178. 8 Cache buses 182 allow connectivity to DRAM via the Data cache 76, with 2 buses going to each PU e.g 178 (1 bus per I/O Address Gettetator).
Each PU e.g 178 consists of an ALU 188 (containing a number of registers &
some arithmetic logic for processing data), some microcode RAM 196, and connections to the outside world (including other ALUs). A local PU state machine runs in microcode and is the means by which the PU e.g 178 is controlled. Each PU e.g 178 contains two 1/O
Address Generators 189, 190 controlling data flow between DRAM (via the Data cache 76) and the ALU 188 (via lnput FIFO and Output FIFO). The address genetator is able to read and write data (specifically iniages in a variety of formats) as well as tables and simulated FIFOs in DRAM. The formats are customizable under software control, but are not microcoded. Data taken from the Data cache 76 is iransferred to the ALU 188 via the 16-bit wide Input FIFO.
Output data is written to the 16-bit wide Output FIFO and from there to the Data cache 76. Finally, all PUs e.g 178 share a single 8-bit wide VLIW Input FIFO 78 and a single 8-bit wide VLIW
Output FIFO 79. The low speed data bus connection allows the CPU to read and write registers in the PU e.g 178, update mictocode, as well as the common registers shared by all PUs e.g 178 in the VLIW Vector Processor 74. Turning now to Fig. 4, a closer detail of the intetnals of a single PU e.g 178 can be seen, with components and control signals detailed in subsequent hereinafter:
Micxocade Each PU e.g 178 contains a microcode RAM 196 to hold the program for that particular PU e.g 178. Rather than have the microcode in ROM, the microcode is in RAM, with the CPU responsible for loading it up. For the same space on chip, this tradeoff reduces the maximum size of any one function to the size of the RAM, but allows an unlinated number of functions to be written in microcode. Functions implemented using microcode include Vark acceleration, ARcard reading, and Printing. The VLIW Vector Processor 74 scheme has several advantages for the case of the ACP
31:
Hardware design complexity is reduced Hardware risk is reduced due to reduction in complexity Hardware design tinte does not depend on all Vark functionality being implemented in dedicated silicon Space on chip is reduced overall (due to large number of processes able to be implemented as microcode) Functionality can be added to Vark (via microcode) with no impact on hardware design time Size and Content The CPU loaded microcode RAM 196 for controlling each PU e.g 178 is 128 words, with each word being 96 bits wide. A summary of the microcode size for control of various units of the PU
e.g 178 is listed in the following table:
Prucess Block Size (bits) Status Output 3 Branching (microcode control) 11 In 8 Out 6 Registers 7 Read 10 Write 6 Barrel Shifter 12 Adder/Logical 14 Multiply/Interpolate 19 With 128 instruction words, the total microcode RAM 196 per PU e.g 178 is 12,288 bits, or 1 SKB exactly. Since the VI.IW Vector Processor 74 consists of 4 identical PUs e.g 178 this equates to 6,144 bytes, exactly 6KB. Some of the bits in a microcode word ate directiy used as control bits, while others are decoded. See the various unit descriptions that detail the interpretation of each of the bits of the microcode word.
Svnchronization Between PUs e.,R 178 Each PU e.g 178.contains a 4 bit Synchronvation Register 197. It is a mask used to determine which PUs e.g 178 work together, and has one bit set for each of the cornsponding PUs e.g 178 that are functioning as a single process. For example, if all of the PUs e.g 178 were functioning as a single process, each of the 4 Synchronization Register 197s would have all 4 bits set. If there were two asynchronous processes of 2 PUs e.g 178 each, two of the PUs e.g 178 would have 2 bits set in their Synchronization Register 197s (corresponding to themselves), and the other two would have the other 2 bits set in their Synchronization Register 197s (corresponding to themselves).
The Synchronization Register 197 is used in two basic ways:
Stopping and starting a given process in synchrony Suspending execution within a process StoppinQ and Starting Processes The CPU is responsible for loading the microcode RAM 196 and loading the execution address for the first instruction (usually 0). When the CPU starts executing microcode, it begins at the specified address.
Fatectuion of niicrocode only occurs when all the bits of the Synchronization Register 197 are also set in the Common Synchronization Register 197. The CPU therefore sets up all the PUs e.g 178 and then starts or stops processes with a single write to the Common Synchronization Register 197.
This synchronization scheme. allows tnultiple processes to be running asynchronously on the PUs e.g 178, being stopped and started as processes rather than one PU e.g 178 at a time.
SuspQndjng Execution within a Process In a given eycle, a PU e.g 178 may need to read from or write to a FIFO (based on the opcode of the current microcode instruction). If the FIFO is empty on a read request, or full on a wtite request, the FIFO request cannot be completed.
The PU e.g 178 will therefore assert its SuspendProcess control signal 198.
The SuspendProcess signals from all PUs e.g 178 are fed back to all the PUs e.g 178. The Synchronization Register 197 is ANDed with the 4 SuspendProcess bits, and if the result is non-zero, none of the PU e.g 178's register WriteEnables or FIFO strobes will be seL
Consequently none of the PUs e.g 178 that form the same prooess group as the PU e.g 178 that was unable to complete its task will have their registers or FIFOs updated during that cycle. This simple technique keeps a given process group in syncitronization. Each subsequent cycle the PU e.g 178's state machine will attempt to re-execute the nucrocode instruction at the same address, and will continue to do so until successful.
Of course the Common Synchronization Register 197 can be written to by the CPU to stop the entire process if necessary. This synchronization scheme allows any combinations of PUs e.g 178 to work together, each group only affecting its co-workers with regards to suspension due to data not being ready for reading or writing.
Controi and Branchine During each cycle, each of the four basic input and calculation units within a PU e.g 178's ALU 188 (Read, Adder/Logic, Multiply/Interpolate, and Barrel Shifter) produces two status bits: a Zero flag and a Negative flag indicating whether the result of the operation during that cycle was 0 or negative. Each cycle one of those 4 status bits is chosen by nucrocode instructions to be output from the PU e.g 178. The 4 status bits (i per PU e.g 178's ALU 188) are combined into a 4 bit Convnon Status Register 200. During the next cycle, each PU e.g 178's niicrocode program can select one of the bits from the Conunon Status Register 200, and branch to another mlcrocode address dependant on the value of the status bit_ Status bit F.ach PU e.g 178's ALU 188 contains a number of input and calculation units.
Each unit produces 2 status bits - a negative flag and a zero flag. One of these status bits is output from the PU
e.g 178 when a particular unit asserts the value on the 1-bit tri-state status bit bus. The single status bit is output from the PU e.g 178, and then combined with the other PU e.g 178 status bits to update the Common Status Register 200. The microcode for determining the output status bit takes the following fotmv.
# Bits Description 2 Select unit whose status bit is to be output 00 = Adder unit 01 = Multiply/Logic unit = Barrel Shift unit 11 = Reader unit 1 0=Zeroflag i = Negative flag Within the ALU 188, the 2-bit Select Processor Block value is decoded into four 1-bit enable bits, with a different enable bit sent to each processor unit block. The status select bit (choosing Zero or Negative) is passed into all units to determine which bit is to be output onto the status bit bus.
Btanching Within Microcode Each PU e.g 178 contains a 7 bit Program Counter (PC) that holds the current microcode address being executed.
Normal program execution is linear, moving from address N in one cycle to address N+1 in the next cycle. Every cycle however, a microcode program has the ability to branch to a different location, or to test a status bit from the Common Status Register 200 and branch. The microcode for determining the next execution address takes the following form:
# Bits Description 2 00 = NOP (PC = PC+1) 01 = Branch always 10 = Branch if status bit clear II - Branch if status bit set 2 Select status bit from status word 7 Address to branch to (absolute address, 00-7F) Fig. 5 illustrates the ALU 188 in more detail. Inside the ALU 188 are a nttmber of specialized processing blocks, tmtrolled by a microcode ptngram. The specialized processing blocks include:
Read Block 202, for accepting data from the input FIFOs Write Block 203, for sending data out via the output FIFOs Adder/i..ogical block 204, for addition & subttaction, comparisons and logical operations Multiply/Interpolate block 205, for multiple types of interpolations and multiply/accumulates Barrel Shift block 206, for shifting data as required In block 207, for accepting data from the external crossbar switch 183 Out block 208, for sending data to the external crossbar switch 183 Registers block 215, for holding data in temporary storage Four specialized 32 bit registers hold the results of the 4 main processing blocks:
M register 209 holds the result of the Multiply/Interpolate biock L register 209 holds the result of the Adder/Logic block S register 209 holds the result of the Baael Shifter block R register 209 holds the result of the Read Block 202 In addition there are two internal crossbar switches 213m 214 for data transport. The various process blocks are further expanded in the following sections, together with the microcode definitions that pertain to each block. Note that the nticrocode is decoded within a block to provide the control signals to the vatious units within.
Data Transfers Between PUs e.g 178 Each PU e.g 178 is able to exchange data via the external crossbar. A PU e.g 178 takes two inputs and outputs two values to the external crossbar. In this way two operands for processing can be obtained in a single cycle, but cannot be actually used in an operation until the following cycle.
In 207 This block is illustrated in Fig. 6 and contains two registers, In, and In2 that accept data from the extemal crossbar. The registers can be loaded each cycle, or can remain unchanged. The selection bits for choosing from among the 8 inputs are output to the extemal crossbar switch 183. The microcode takes the following form:
# Bits Description 1 0 = NOP
1= Load In, from crossbar 3 Select Input 1 from external crossbar 1 0 = NOP
1= Load In2 from crossbar 3 Select Input 2 from external crossbar Out 208 Complementing In is Out 208. The Out block is illustrated in more detail in Fig. 7. Out contains two registers, Out, and Out2, both of which are output to the external crossbar each cycle for use by other PUs e.g 178. The Write unit is also able to write one of Out, or Out2 to one of the output FIFOs attached to the ALU 188. Finally, both registers are available as inputs to Crossbarl 213, which therefore makes the register values available as inputs to other units within the ALU 188. Each cycle either of the two registers can be updated according to microcode selection. The data loaded into the specified register can be one of Do - D3 (select,ed from Crossbarl 213) one of M, L, S, and R (selected from Crossbar2 214), one of 2 progratnmable constants, or the fixed values 0 or 1.
Tlte microcode for Out takes the following form:
# Bits Description 1 0 = NOP
I = Load Register I Select Register to load [Outt or Out2]
4 Select input [In1,In2,Outl,Outz,Da,D1,D2,D3,M,L,S,R,K1 ,KZ,0,1]
Local Registers and Data Transfers within ALU 188 As noted previously, the ALU 188 contains four specialized 32-bit registers to hold the results of the 4 main processing blocks:
M register 209 holds the result of the Multiply/Interpolate block L register 209 holds the result of the Adder/Logic block S register 209 holds the result of the Barrel Shifter block R register 209 holds the result of the Read Block 202 The CPU has direct access to these registers, and other units can select them as inputs via Crossbar2 214. Sometimes it is necessary to delay an operation for one or more cycles. The Registers block contains four 32-bit registers Da - D3 to hold temporary variables during processing. Each cycle one of the registers can be updated, while all the registers are output for other units to use via Crossbarl 213 (which also includes In,, In,, Out, and Out,). The CPU has direct access to these registers. The data loaded into the specified register can be one of Do - Di (selected from Crossbarl 213) one of M, L, S, and R (selected from Crossbar2 214), one of 2 programmable constants, or the fixed values 0 or 1. The Registers block 215 is illustrated in more detail in Fig. 8. The microcode for Registers takes the following form:
# Bits Description 1 0 = NOP
1 = Load Register 2 Select Register to load [Do - D3]
4 Select input [1n,,In2,Outt,Out2,Do,D,,D2,D3,M,L,S,R,K,,K2,0,1 ]
Crossbar] 213 Crossbarl 213 is illustrated in more detail in Fig. 9. Crossbarl 213 is used to select from inputs In,, In2, Outt, Out2, Do-I);. 7 outputs are generated from Crossbarl 213: 3 to the Multiply/Interpolate Unit, 2 to the Adder Unit, I to the Registers unit and 1 to the Out unit. The control signals for Crossbarl 213 come from the various units that use the Crossbar inputs. There is no specific microcode that is separate for Crossbarl 213.
Crossbar2 214 Crossbar2 214 is illustrated in more detail in Fig. 10.Crossbat2 214 is used to select from the general ALU 188 registers M, L, S and R. 6 outputs are generated from Crossbarl 213: 2 to the Multiply/Interpolate Unit, 2 to the Adder Unit, I to the Registers unit and I to the Out unit. The control signals for Crossbar2 214 come from the various units that use the Crossbar inputs. There is no specific microcode that is separate for Crossbar2 214.
Data Transfers Between PUs e.e 178 and DRAM or External Processes Returning to Fig. 4, PUs e.g 178 share data with each other directly via the external crossbar. They also transfer data to and from external processes as well as DRAM. Each PU e.g 178 has 2 UO Address Generators 189, 190 for transfetring data to and from DRAM. A PU e.g 178 can send data to DRAM via an I/O Address Generator's Output FIFO e.g. 186, or accept data from DRAM via an I/O Address Generator's Input FIFO 187. These F1FOs are local to the PU e.g 178. There is also a mechanism for transferring data to and from external processes in the form of a common VLIW Input FIFO 78 and a common VLIW Output FIFO 79, shared between all ALUs_ The VLIW Input and Output FIFOs are only 8 bits wide, and are used for printing, Artcard reading, transferring data to the CPU etc. The local Input and Output FIFOs are 16 bits wide.
Read The Read process block 202 of Fig. 5 is responsible for updating the ALU 188's R register 209, which represents the external input data to a VLIW microcoded process. Each cycle the Read Unit is able to read from either the common VLIW Input FIFO 78 (8 bits) or one of two local Input FIFOs (16 bits). A 32-bit value is generated, and then all or part of that data is transferred to the R register 209. The process can be seen in Fig. 11. The microcode for Read is described in the following table. Note that the interpretations of some bit patterns are deliberately chosen to aid decoding.
# Bits Description 2 00 = NOP
01 = Read from VL1W Input FIFO 78 = Read from Local FIFO I
I i= Read from Local FIFO 2 1 How many significant bits 0= 8 bits (pad with 0 or sign extend) 1= 16 bits (only valid for Local FIFO reads) 1 0 = Treat data as unsigned (pad with 0) 1= Treat data as signed (sign extend when reading from FIFO)r 2 How much to shift data left by:
00 = 0 bits (no change) 01 = 8 bits 10 = 16 bits 11=24bits 4 Which bytes of R to update (hi to lo order byte) Each of the 4 bits represents I byte WriteEnable on R
Write The Write process block is able to write to either the common VLIW Output FIFO
79 or one of the two local Output FIF.Os each cycle. Note that since only I FIFO is written to in a given cycle, only one 16-bit value is output to all FIFOs, with the low 8 bits going to the VLIW Output FIFO 79. The microcode controls which of the FIFOs gates in the value. The process of data selection can be seen in more detail in Fig.
12_ The source values Out, and Out-, come from the Out block. They are simply two registers. The nticrocode for Write takes the following form:
# Bits Description 2 00=NOP
01 = Write VLIW Output FIFO 79 = Write local Output FIFO I
11 = Write local Output FIFO 2 I. Select Output Value [Outt or Out2j 3 Select part of Output Value to write (32 bits = 4 bytes ABCD) 000=0D
001 = OD
010 = 0B
011 =0A
100=CD
101 = BC
110 = AB
I11=0 Cotnputational Biocks Each ALU 188 has two computational process blocks, namely an Addcr/Logic process block 204, and a Multiply/Interpolate process block 205. In addition there is a Barrel Shifter block to provide help to these cotnputational blocks. Registers from the Registers block 215 can be used for temporary storage during pipelined operations.
Batrel Shifter The Batrel Shifter process block 206 is shown in more detail in Fig. 13 and takes its input from the output of Adder/Logic or Multiply/Interpolate process blocks or the previous cycle's results from those blocks (ALU registers L
and M). The 32 bits selected are barrel shifted an arbitrary number of bits in either direction (with sign extension as necessary), and output to the ALU 188's S register 209. The tnicrocode for the Batrel Shift process block is described in the following table. Note that the intetpretations of some bit pattertu are deliberately chosen to aid decoding.
# Bits Description 3 000 = NOP
001 = Shift Left (unsigned) 010 = Reserved 011 = Shift Left (signed) 100 = Shift right (unsigned, no rounding) 101 = Shift right (unsigned, with rounding) I 10 = Shift right (signed, no rounding) 111 = Shift right (signed, with rounding) 2 Select Input to barrel shift:
00 = Multiply/Interpolate result 01 =M
= Adder/Logic result 11=L
5 # bits to shift 1 Ceiling of 255 1 Floor of 0 (signed data) Adder/Log'tc 204 The Adder/Logic process block is shown in more detail in Fig_ 14 and is designed for simple 32-bit addition/subtraction, comparisons, and logical operations. In a single cycle a single addition, comparison, or logical operation can be performed, with the result stored in the ALU 188's L register 209. There are two primary operands, A
and B, which are selected from either of the two crossbars or from the 4 constant registers. One crossbar selection allows the results of the previous cycle's arithmetic operation to be used while the second provides access to operands previously calculated by this or another ALU 188. The CPU is the only unit that has write access to the four constants (IKt-S4). In cases where an operation such as (A+B) x 4 is desired, the direct output from the adder can be used as input to the Barrel Shifter, and can thus be shifted left 2 places without needing to be latched into the L register 209 first. The output from the adder can also be made available to the multiply unit for a multiply-accumulate operation.
The microcode for the Adder/Logic process block is described in the following table. The interpretations of some bit pattertts are deliberately chosen to aid decoding. Microcode bit interpretation for Adder/Logic unit # Bits Description 4 0000=A+B (carry in=0) 0001 = A+B (carry in = carry out of previous operation) 0010 = A+B+1 (caey in = 1) 0011 = A+l (increments A) 0100 = A-B-1 (carry in = 0) 0101 = A-B (carry in = carry out of previous operation) 0110 = A-B (carry in = 1) 0111 = A-1 (decrements A) 1000=NOP
1001 = ABS(A-B) 1010 = MIN(A, B) 1011 = MAX(A, B) 1100 = A AND B (both A & B can be inverted, see below) 1101 = A OR B(both A& B can be inverted, see below) 1110 = A XOR B (both A & B can be inverted, see below) IIII = A (A can be inverted, see below) 1 If logical operation:
0 = A=A
1 = A=NOT(A) If Adder operation:
0 = A is unsigned 1 = A is signed If logical operation:
0=B=B
I = B=NOT(B) If Adder operation 0 = B is unsigned 1 = B is signed 4 Select A [In1,In2,Out1,Out2,Do,D,,D2,Dj,M,L,S,R,K1,KZ,K3,K4]
4 Select B [In,,In2,Out1,Out2,Do,D1 ,DZ,D3,M,L,S,R,K1,KZ,K3,K4]
Multiply/Interoolate 205 The Multiply/Interpolate process block is shown in more detail in Fig. 15 and is a set of four 8 x 8 interpolator units that are capable of performing four individual 8 x 8 interpolates per cycle, or can be combined to perform a single 16 x 16 multiply. This gives the possibility to perform up to 4 linear interpolations, a single bi-linear interpolation, or half of a tri-linear interpolation in a single cycle. The result of the interpolations or multiplication is stored in the ALU 188's M register 209. There are two primary operands, A and B. which are selected from any of the general registers in the ALU 188 or from four programmable constants internal to the Multiply/[nterpolate process block. Each interpolator block functions as a simple 8 bit interpolator [result = A+(B-A)f] or as a simple 8 x 8 multiply [result = A * B]. When the operation is interpolation, A and B are treated as four 8 bit numbers Aa thru A3 (Ao is the low order byte), and Bo thru B3. Agen, Bgen, and Fgen are responsible for ordering the inputs to the Interpolate units so that they match the operation being performed. For example, to perform bilinear interpolation, each of the 4 values must be multiplied by a different factor & the result summed, while a 16 x 16 bit multiplication requires the factors to be 0. The microcode for the Adder/Logic process block is described in the following table. Note that the interpretations of some bit patterns are deliberately chosen to aid decoding.
# Bits Description 4 0000=(A,o*B,o)+V
0001 =(AO * B0) +(A 1* B 1) + V
0010=(A,o*B,o)-V
0011=V-(A,o*B,o) 0100 = Interpolate Ao,Bo by fo 0101 = Interpolate Ao,Bo by fo, A,,B, by f, 0110 = Interpolate Ao,Bo by fo, A,,B, by f,, AZ,B, by f, 0111 = Interpolate Ao,Bo by fo, A,,B, by f,, A,,BZ by f,, A3,B3 by f3 1000 = Interpolate 16 bits stage 1[M = A,o * f,o]
1001 = Interpolate 16 bits stage 2 [M = M+(A,o * f,o)]
1010 = Tri-linear interpolate A by f stage I[M=Aofo+A, f,+A,f,+A3f3]
101 ]= Tri-linear interpolate A by f stage 2[M=M+Aafo+A,f,+A,f,+A3f3]
1100 = Bi-linear interpolate A by f stage 1[M=Aofo+A,f,]
1101 = B i-linear interpolate A by f stage 2[M=M+Aofo+A,f,]
1110 = Bi-linear interpolate A by f complete (M=Aofo+A,f,+AZf2+A3f3]
1111 =NOP
4 Select A [In1 ,In,,Out1 ,Out2,Do,D1,DZ,D3,M,L,S,R,Ki,K,,K3,K4]
4 Select B [In1 ,InZ,Out1,Out2,Do,D1,D,,D3,M,L,S,R,K1,K,,K3,K4]
If Mult:
4 Select V[In,,InZ,Out,,Out2,Do,D,,DZ,D3,K1,K,,K3,Ka,Adder result,M,O, I]
1 Treat A as signed 1 Treat B as signed 1 Treat V as signed If Interp:
4 Select basis for f(In,,In2,Out,,OutZ,Do,D,,D,,D3,K,,KZ,K3,Ka,X,X,X,X]
1 Select interpolation f generation from P, or P2 P. is interpreted as # fractional bits in f If Põ=0, f is range 0..255 representing 0..1 2 Reserved The same 4 bits are used for the selection of V and f, although the last 4 options for V don't generally make sense as f values. Interpolating with a factor of I or 0 is pointless, and the previous multiplication or current result is unlikely to be a meaningful value for f.
I/O Address GeneratorS 189. 190 The I/O Address Generators are shown in more detail in Fig. 16. A VLIW process does not access DRAM directly.
Access is via 2 1/0 Address Generators 189, 190, each with its own Input and Output FIFO. A PU e.g 178 reads data from one of two local Input FIFOs, and writes data to one of two local Output FIFOs. Each 1/0 Address Generator is responsible for reading data from DRAM and placing it into its Input FIFO, where it can be read by the PU e.g 178, and is responsible for taking the data from its Output FIFO (placed there by the PU e.g 178) and writing it to DRAM.
The I/O Address Generator is a state machine responsible for generating addresses and control for data retrieval and storage in DRAM via the Data cache 76. It is customizable under CPU software control, but cannot be microcoded.
The address generator produces addresses in two broad categories:
Image Iterators, used to iterate (reading, writing or both) through pixels of an image in a variety of ways Table 1/0, used to randomly access pixels in images, data in tables, and to simulate FIFOs in DRAM
Each of the 1/0 Address Generators 189, 190 has its own bus connection to the Data cache 76, making 2 bus connections per PU e.g 178, and a total of 8 buses over the entire VLIW Vector Processor 74. The Data cache 76 is able to service 4 of the maximum 8 requests from the 4 PUs e.g 178 each cycle_ The Input and Output FIFOs are 8 entry deep 16-bit wide FIFOs. The various types of address generation (Image Iterators and Table 1/0) are described in the subsequent sections.
e' e The I/O Address Generator has a set of registers for that are used to control address generation. The addressing mode also determines how the data is formatted and sent into the local Input FIFO, and how data is interpreted from the local Output FIFO. The CPU is able to access the registers of the I/O Address Generator via the low speed bus. The first set of registers define the housekeeping parameters for the 1/0 Generator:
Register Name # bits Description Reset 0 A write to this register halts any operations, and writes Os to all the data registers of the I/O Generator. The input and output FIFOs are not cleared.
Go 0 A write to this register restarts the counters according to the current setup. For example, if the 1/0 Generator is a Read Iterator, and the Iterator is currently halfway through the image, a write to Go will cause the reading to begin at the start of the image again. While the 1/0 Generator is performing, the Active bit of the Status register will be set.
Halt 0 A write to this register stops any current activity and clears the Active bit of the Status register. If the Active bit is already cleared, writing to this register has no effect.
Continue 0 A write to this register continues the 1/0 Generator from the current setup. Counters are not reset, and FIFOs are not cleared. A write to this register while the I/O Generator is active has no effect.
ClearFlFOsOnGo 1 0= Don't clear FIFOs on a write to the Go bit_ 1= Do clear FIFOs on a write to the Go bit.
Status 8 Status flags The Status register has the following values Register Name # bits Description Active 1 0= Currently inactive 1 = Currently active Reserved 7 -Cachine Several registers are used to control the caching mechanism, specifying which cache group to use for inputs, outputs etc. See the section on the Data cache 76 for more infotmation about cache groups.
Register Name # bits Description CacheGroupl 4 Defines cache group to read data from CacheGroup2 4 Defines which cache group to write data to, and in the case of the ImagePyramidLookup 1/0 mode, defines the cache to use for reading the Level Information Table.
Image Iterators = Seouential Automatic Access to pixels The primary image pixel access method for software and hardware algorithms is via Image Iterators. Image iterators perform all of the addressing and access to the caches of the pixels within an ima.ge channel and read, write or read &
write pixels for their client Read Iterators read pixels in a specific order for their clients, and Write Iterators write pixels in a specific order for their clients. Clients of Iterators read pixels from the local Input FIFO or write pixels via the local Output FIFO.
Read Image Iterators read through an image in a specific order, placing the pixel data into the local Input FIFO.
Every time a client reads a pixel from the Input FIFO, the Read Iterator places the next pixel from the image (via the Data cache 76) into the FIFO.
Write Iatage Iterators write pixels in a specific order to write out the entire image. Clients write pixels to the Output FIFO that is in turn read by the Write Image Iterator and written to DRAM via the Data cache 76.
Typically a VLIW process will have its input tied to a Read Iterator, and output tied to a corresponding Write Iterator.
From the PU e.g 178 microcode program's perspective, the FIFO is the effective interface to DRAM. The actual method of carrying out the storage (apart from the logical ordering of the data) is not of concern. Although the FIFO is perceived to be effectively unlimited in length, in practice the FIFO is of limited length, and there can be delays storing and retrieving data, especially if several niemory accesses are competing. A
variety of Image Iterators exist to cope with the most common addressing requirements of image processing algorithms.
In most cases there is a corresponding Write Iterator for each Read Iterator. The different Iterators are listed in the following table:
Read Iterators Write Iterators Sequential Read Sequential Write Box Read Vertical Strip Read Vertical Strip Write The 4 bit Address Mode Register is used to determine the Iterator type:
Bit # Address Mode 3 0= This addressing mode is an Iterator 2 to 0 Iterator Mode 001 = Sequential Iterator 010 = Box [read only]
100 = Vertical Strip remaining bit pattems are reserved The Access Specific registers are used as follows:
Register Name LocalName Description AccessSpecific, Flags Flags used for reading and writing AccessSpecificz XBoxSize Determines the size in X of Box Read. Valid values are 3. 5, and 7.
AccessSpecific3 YBoxSize Determines the size in Y of Box Read. Valid values are 3, 5, and 7.
AccessSpecific4 BoxOffset Offset between one pixel center and the next during a Box Read only.
Usual value is l, but other useful values include 2, 4, 8...
See Box Read for more details.
The Flags register (AccessSpecificl) contains a number of flags used to determine factors affecting the reading and writing of data. The Flags register has the following composition:
Label #bits Description ReadEnable I Read data from DRAM
WriteEnable 1 Write data to DRAM [not valid for Box model PassX 1 Pass X (pixel) ordinate back to Input FIFO
PassY I Pass Y (row) ordinate back to Input FIFO
Loop 1 0= Do not loop through data I = Loop through data Reserved 1 I Must be 0 Notes on ReadEnable and WriteEnable:
When ReadEnable is set, the 1/O Address Generator acts as a Read Iterator, and therefore reads the image in a particular order, placing the pixels into the Input FIFO.
When WriteEnable is set, the I/O Address Generator acts as a Write Iterator, and then:fore writes the image in a particular order, taking the pixels from the Output FIFO.
When both ReadEnable and WriteEnable are set, the 110 Address Generator acts as a Read Iterator and as a Write Iterator, reading pixels into the Input FIFO, and writing pixels from the Output FIFO. Pixels are only written after they have been read - i.e. the Write Iterator will never go faster than the Read Iterator. Whenever this mode is used, care should be taken to ensure balance between in and out processing by the VLIW microcode. Note that separate cache groups can be specified on reads and writes by loading different values in CacheGroupl and CacheGroup2.
Notes on PassX and PassY:
If PassX and PassY are both set, the Y ordinate is placed into the Input FIFO
before the X ordinate.
PassX and PassY are only intended to be set when the ReadEnable bit is clear.
Instead of passing the ordinates to the address generator, the ordinates are placed directly into the Input FIFO. The ordinates advance as they are removed from the FIFO.
If WriteEnable bit is set, the VLIW program must ensure that it balances reads of ordinates from the Input FIFO with writes to the Output FIFO, as writes will only occur up to the ordinates (see note on ReadEnable and WriteEnable above).
Notes on Looo-If the Loop bit is set, reads will recommence at [StartPixel, StartRowj once it has reached [EndPixet, EndRowl. This is ideal for processing a structure such a convolution kernel or a dither cell matrix, where the data must be read repeatedly.
Looping with ReadEnable and WriteEnable set can be useful in an environment keeping a single line history, but only where it is useful to have reading occur before writing. For a FIFO effect (where writing occurs before reading in a length constrained fashion), use an appropriate Table 1/0 addressing mode instead of an Intage Iterator.
Looping with only WriteEnable set creates a written window of the last N
pixels. This can be used with an asynchronous process that reads the data from the window. The Artcard Reading algorithm makes use of this mode.
Sequential Read and Write Iterators Fig. 17 illustrates the pixel data format. The simplest Image Iterators are the Sequential Read Iterator and corresponding Sequential Write Iterator. The Sequential Read Iterator presents the pixels from a channel one line at a time from top to bottom, and within a line, pixels are presented left to right. The padding bytes are not presented to the client. It is most useful for algorithtns that must perform some process on each pixel from an intage but don't care about the order of the pixels being processed, or want the data specifically in this order. Complementing the Sequential Read Iterator is the Sequential Write Iterator. Clients write pixels to the Output FIFO. A Sequential Write Iterator subsequently writes out a valid image using appropriate caching and appropriate padding bytes. Each Sequential Iterator requires access to 2 cache lines. When reading, while 32 pixels are presented from one cache line, the other cache line can be loaded from memory. When writing, while 32 pixels are being filled up in one cache line, the other can be being written to memory.
A process that perforins an operation on each pixel of an itnage independently would typically use a Sequential Read Itetator to obtain pixels, and a Sequential Write Iterator to write the new pixel values to their cotresponding locations within the destination image. Such a prooess is shown in Fig. 18.
In most cases, the source and destination images are different, and are represented by 2 1/0 Address Generators 189, 190. However it can be valid to have the source image and destination image to be the same, since a given input pixel is not read more than once. In that case, then the same Iterator can be used for both input and output, with both the ReadEnable and WriteEnable registers set appropriately. For maximum efficiency, 2 different cache groups should be used - one for reading and the other for writing. If data is being created by a VLIW process to be written via a Sequential Write Iterator, the PassX and PassY flags can be used to generate coordinates that are then passed down the Input FIFO. The VLIW process can use these coordinates and create the output data appropriately.
Box Read Iterator The Box Read Iterator is used to present pixels in an order most useful for perfortning operations such as general-purpose filters and convolve. The Iterator presents pixel values in a square box around the sequentially read pixels. The box is limited to being 1, 3, 5, or 7 pixels wide in X and Y (set XBoxSize and YBoxSize- they must be the same value or I in one dimension and 3, 5, or 7 in the other). The process is shown in Fig. 19:
BoxOffset: This special purpose register is used to determine a sub-sampling in terms of which input pixels will be used as the center of the box. The usual value is 1, which means that each pixel is used as the center of the box. The value "2" would be useful in scaling an image down by 4:1 as in the case of building an image pyramid. Using pixel addresses from the previous diagram, the box would be centered on pixel 0, then 2, 8, and 10. The Box Read Iterator requires access to a maximum of 14 (2 x 7) cache lines. While pixels are presented from one set of 7 lines, the other cache lines can be loaded from memory.
Box Write Iterator There is no corresponding Box Write Iterator, since the duplication of pixels is only required on input. A process that uses the Box Read Iterator for input would most likely use the Sequential Write Iterator for output since they are in sync. A good example is the convolver, where N input pixels are read to calculate I output pixel. The process flow is as illustrated in Fig. 20. The source and destination images should not occupy the same memory when using a Box Read Iterator, as subsequent lines of an image require the original (not newly calculated) values.
Vertical-Strip Read and Write Iterators In some instances it is necessary to write an image in output pixel order, but there is no knowledge about the direction of coherence in input pixels in relation to output pixels. An example of this is rotation. If an image is rotated 90 degrees, and we process the output pixels horizontally, there is a complete loss of cache coherence_ On the other hand, if we process the output image one cache line's width of pixels at a time and then advance to the next line (rather than advance to the next cache-line's worth of pixels on the same line), we will gain cache coherence for our input image pixels. It can also be the case that there is known 'block' coherence in the input pixels (such as color coherence), in which case the read governs the processing order, and the write, to be synchronized, must follow the same pixel order.
The order of pixels presented as input (Vertical-Strip Read), or expected for output (Vertical-Strip Write) is the same.
The order is pixels 0 to 31 from Iine 0, then pixels 0 to 31 of line I etc for all lines of the image, then pixels 32 to 63 of line 0, pixels 32 to 63 of line I etc. In the final vertical strip there may not be exactly 32 pixels wide. In this case only the actual pixels in the image are presented or expected as input. This process is illustrated in Fig. 21.
process that requires only a Vertical-Strip Write Iterator will typically have a way of mapping input pixel coordinates given an output pixel coordinate. It would access the input image pixels according to this mapping, and coherence is determined by having sufficient cache lines on the 'random-access' reader for the input image. The coordinates will typically be generated by setting the PassX and PassY flags on the VerticalStripWrite Iterator, as shown in the process overview illustrated in Fig. 22.
It is not meaningful to pair a Write Iterator with a Sequential Read Iterator or a Box read Iterator, but a Vertical-Strip Write Iterator does give significant improvements in performance when there is a non trivial mapping between input and output coordinates.
It can be meaningful to pair a Vertical Strip Read Iterator and Vertical Strip Write Iterator. In this case it is possible to assign both to a single ALU 188 if input and output images are the same. If coordinates are required, a further Iterator must be used with PassX and PassY flags set_ The Vertical Strip Read/Write Iterator presents pixels to the Input FIFO, and accepts output pixels from the Output FIFO. Appropriate padding bytes will be inserted on the write. Input and output require a minimum of 2 cache lines each for good performance.
Table UO Addressing Modes It is often necessary to lookup values in a table (sttch as an image). Table I/O addressing modes provide this functionality, requiring the client to place the index/es into the Output FIFO. The I/O Address Generator then processes the index/es, looks up the data appropriately, and rettutts the looked-up values in the Input FIFO for subsequent processing by the VLIW client.
ID, 2D and 3D tables are supported, with particular modes targeted at interpolation. To reduce complexity on the VLIW client side, the index values are treated as fixed-point numbers, with AccessSpecific registers defining the fixed point and therefore which bits should be treated as the integer portion of the index. Data formats are restricted forms of the general Image Characteristics in that the PixelOPfset register is ignored, the data is assumed to be contiguous within a row, and can only be 8 or 16 bits (I or 2 bytes) per data element.
The 4 bit Address Mode Register is used to detem-iine the 1/0 type:
Bit # Address Mode 3 1 = This addressing mode is Table I/O
2 to 0 000 = 1 D Direct Lookup 001 = 1D Interpolate (linear) 010=DRAMFIFO
011 = Reserved 100 = 2D Interpolate (bi-linear) 101 = Reserved 110 = 3D Interpolate (tri-linear) III = Image Pyramid Lookup The access specific registers are:
Register Name LocalName #bits Description -AccessSpecifict Flags 8 General flags for reading and writing.
See below for more information.
AccessSpecific2 FractX 8 Number of fractional bits in X index AccessSpecific3 FractY 8 Number of fractional bits in Y index AccessSpecific4 FractZ 8 Number of fractional bits in Z index (low 8 bits / next 12 or 24 ZOffset 12 or See below bits)) 24 FractX, FractY, and FractZ are used to generate addresses based on indexes, and interpret the format of the index in terms of significant bits and integer/fractional components. The various parameters are only defined as required by the number of dimensions in the table being indexed. A 1D table only needs FractX, a 2D table requires FractX and FractY. Each Fract value consists of the number of fractional bits in the corresponding index. For example, an X
index may be in the format 5:3. This would indicate 5 bits of integer, and 3 bits of fraction. FractX would therefore be set to 3. A simple 1 D lookup could have the format 8:0, i.e. no fractional component at all. FractX would therefore be 0. ZOffset is only required for 3D lookup and takes on two different interpretations. It is described more fully in the 3D-table lookup section. The Flags register (AccessSpecificl) contains a number of flags used to determine factors affecting the reading (and in one case, writing) of data. The F1ags register has the following composition:
Label #bits Description ReadEnable I Read data from DRAM
WriteEnable 1 Write data to DRAM [only valid for 1 D direct lookup]
DataSize 1 0 = 8 bit data 1 = 16 bit data Reserved 5 Must be 0 With the exception of the ID Direct Lookup and DRAM FIFO, all Table 1/O modes only supjort readinQ, and not writing- Therefore the ReadEnable bit will be set and the WriteEnable bit will be clear for all 1/0 modes other than these two modes. The 1 D Direct Lookup supports 3 modes:
Read only, where the ReadEnable bit is set and the WriteEnable bit is clear Write only, where the ReadEnable bit is clear and the WriteEnable bit is clear Read-Modify-Write, where both ReadEnable and the WriteEnable bits are set The different modes are described in the 1D Direct Lookup section below. The DRAM FIFO mode supports only I
mode:
Write-Read mode, where both ReadEnable and the WriteEnable bits are set This mode is described in the DRAM FIFO section below. The DataSize flag detenmines whether the size of each data elentents of the table is 8 or 16 bits. Only the two data sizes are supported. 32 bit elements can be created in either of 2 ways depending on the requiretnents of the process:
Reading from 2 16-bit tables simultaneously and combining the result. This is convenient if timing is an issue, but has the disadvantage of consuming 2 1/0 Address Generators 189, 190, and each 32-bit element is not readable by the CPU as a 32-bit entity.
Reading from a 16-bit table twice and combining the result. This is convenient since only I lookup is used, although different indexes must be generated and passed into the lookup.
I Dimensional Structures Direct Lookuo A direct lookup is a simple indexing into a 1 dimensional lookup table.
Clients can choose between 3 access modes by setting appropriate bits in the Flags register:
Read only Write only Read-Modify-Write Read Only A client passes the fixed-point index X into the Output FIFO, and the 8 or 16-bit value at Table[Int(X)] is returned in the Input FIFO. The fractional component of the index is completely ignored.
If the index is out of bounds, the DuplicateEdge flag determines whether the edge pixel or ConstantPixel is returned. The address generation is straightforward:
If DataSize indicates 8 bits, X is barrel-shifted right FractX bits, and the result is added to the table's base address ImageStart.
If DataSize indicates 16 bits, X is barrel-shifted right FractX bits, and the result shifted left I bit (bitO
becomes 0) is added to the table's base address limageStart.
The 8 or 16-bit data value at the resultant address is placed into the Input FIFO. Address generation takes I cycle, and transferring the requested data from the cache to the Output FIFO also takes I
cycle (assuming a cache hit)_ For example, assume we are looking up values in a 256-entry table, where each entry is 16 bits, and the index is a 12 bit fixed-point format of 8:4. FractX should be 4, and DataSize 1. When an index is passed to the lookup, we shift right 4 bits, then add the result shifted left I bit to ImageStatt.
Write Only A client passes the fixed-point index X into the Output FIFO followed by the 8 or 16-bit value that is to be written to the specified location in the table. A complete transfer takes a minimum of 2 cycles. I cycle for address generation, and I cycle to transfer the data from the FIFO to DRAM. There can be an arbitrary number of cycles between a VLIW
process placing the index into the FIFO and placing the value to be written into the FIFO. Address generation occurs in the same way as Read Only mode, but instead of the data being read from the address, the data from the Output FIFO
is written to the address. If the address is outside the table range, the data is removed from the FIFO but not written to DRAM.
Read-Modify-Write A client passes the fixed-point index X into the Output FIFO, and the 8 or 16-bit value at Table[Int(X)] is returned in the Input FIFO. The next value placed into the Output FIFO is then written to Table[Int(X)], replacing the value that had been returned earlier. The general processing loop then, is that a process reads from a location, modifies the value, and writes it back. The overall time is 4 cycles:
Getierate address from index Return value from table Modify value in some way Write it back to the table Tha+e is no specific read/write mode where a client passes in a flag saying "read from X" or "write to X". Clients can simulate a "read from X" by writing the original value, and a"write to X" by simply ignoring the returned value.
However such use of the mode is not encouraged since each action consumes a minimum of 3 cycles (the modify is not required) and 2 data accesses instead of I access as provided by the specific Read and Write modes_ Interpolate table This is the same as a Direct Lookup in Read mode except that two values are returned for a given fixed-point index X
instead of one. The values returned are Table[Int(X)], and Table[Int(X)+l ]_ If either index is out of bounds the DuplicateEdge flag detennines whether the edge pixel or ConstantPixel is retutned. Address generation is the same as Direct Lookup, with the exception that the second address is simply Addressl+ 1 or 2 depending on 8 or 16 bit data.
Transferring the requested data to the Output FIFO takes 2 cycles (assuming a cache hit), although two 8-bit values may actually be returned from the cache to the Address Generator in a single 16-bit fetch.
DRAM FIFO
A special case of a read/write 1D table is a DRAM FIFO. It is often necessary to have a simulated FIFO of a given length using DRAM and associated caches. With a DRAM FIFO, clients do not index explicitly into the table, but write to the Output FIFO as if it was one end of a FIFO and read from the Input FIFO as if it was the other end of the same logical FIFO. 2 counters keep track of input and output positions in the simulated FIFO, and cache to DRAM as needed. Clients need to set both ReadEnable and WriteEnable bits in the Flags register.
An example use of a DRAM FIFO is keeping a single line history of some value.
The initial history is written before processing begins. As the general process goes through a line, the previous line's value is retrieved from the FIFO, and this line's value is placed into the FIFO (this line will be the previous line when we process the next line). So long as input and outputs match each other on average, the Output FIFO should always be full_ Consequently there is effectively no access delay for this kind of FIFO (unless the total FIFO
length is very small - say 3 or 4 bytes, but that would defeat the purpose of the FIFO).
2 Dimensional Tables Direct Lookup A 2 dimensional direct lookup is not supported. Since all cases of 2D lookups are expected to be accessed for bi-linear interpolation, a special bi-linear lookup has been implemented.
Bi-Linear lookup This kind of lookup is necessary for bi-linear interpolation of data from a 2D
table. Given fixed-point X and Y
coordinates (placed into the Output FIFO in the order Y, X), 4 values are returned after lookup. The values (in order) are:
Table[Int(X), Int(Y)]
Table[Int(X)+1, Int(Y)]
Table[Int(X), Int(Y)+1 I
Table[Int(X)+1, Int(Y)+l]
The order of values returned gives the best cache coherence. If the data is 8-bit, 2 values are returned each cycle over 2 cycles with the low order byte being the first data eiement. If the data is 16-bit, the 4 values are returned in 4 cycles, 1 entry per cycle. Address generation takes 2 cycles. The first cycle has the index (Y) barrel-shifted right FractY bits being multiplied by RowOffset, with the result added to ImageStart. The second cycle shifts the X index right by FractX bits, and then either the result (in the case of 8 bit data) or the result shifted left I bit (in the case of 16 bit data) is added to the result from the first cycle. This gives us address Adr =
address of Table[Int(X), Int(Y)):
Adr = ImageStart + ShiftRight(Y, FractY)* RowOffset) + ShiftRight(X, FractX) We keep a copy of Adr in AdrOld for use fetching subsequent entries.
If the data is 8 bits, the timing is 2 cycles of address generation, followed by 2 cycles of data being returned (2 table entries per cycle).
If the data is 16 bits, the tinung is 2 cycles of address generation, followed by 4 cycles of data being returned (1 entry percycle) The following 2 tables show the method of address calculation for 8 and 16 bit data sizes:
Cycle Calculation while fetching 2 x 8-bit data entries from Adr I Adr = Adr + RowOffset 2 <preparing next lookup>
Cycle Calculation while fetching 1 x 16-bit data entry from Adr 1 Adr = Adr + 2 2 Adr = AdrOld + RowOffset 3 Adr=Adr+2 4 <preparing next lookup>
In both cases, the first cycle of address generation can overlap the insertion of the X index into the FIFO, so the effective timing can be as low as I cycle for address generation, and 4 cycles of return data. If the generation of indexes is 2 steps ahead of the results, then thete is no effective address generation time, and the data is simply produced at the appropriate rate (2 or 4 cycles per set).
3 Dimensional Lookur) Direct Lookuo Since all cases of 2D lookups are expected to be accessed for tri-linear interpolation, two special tri-linear lookups have been implemented. The first is a straightforward lookup table, while the second is for tri-linear interpolation from an Image Pyramtd.
Tri-linear lookuo This type of lookup is useful for 3D tables of data, such as color conversion tables. The standard image parameters define a single XY plane of the data - i.e. each plane consists of LoageHeight rows, each row containing RowOffset bytes. In most circumstances, assuming contiguous planes, one XY plane will be LnageHeight x RowOH'set bytes after another. Rather than assume or calculate this offset, the software via the CPU must provide it in the form of a 12-bit ZOffset register. In this form of lookup, given 3 fixed-point indexes in the order Z, Y. X, 8 values are returned in order from the lookup table:
Table[Int(X), Int(Y), Int(Z)]
Table[Int(X)+1, Int(Y), Int(Z)]
Table(Int(X), Int(Y)+1, Int(Z)1 Table(Int(X)+1, Int(Y)+1, Int(Z)]
Table[Int(X), Int(Y), Int(Z)+1]
Table[Int(X)+1, Int(Y), Int(Z)+1]
Table[Int(X), Int(Y)+1, Int(Z)+l]
Table[Int(X)+1, Int(Y)+1, Int(Z)+l]
The order of values returned gives the best cache coherence. If the data is 8-bit, 2 values are returned each cycle over 4 cycles with the low order byte being the first data element. If the data is 16-bit, the 4 values are returned in 8 cycles, I
entry per cycle. Address generation takes 3 cycles. The first cycle has the index (Z) barrel-shifted right FractZ bits being multiplied by the 12-bit ZOffset and added to ImageStart. The second cycle has the index (Y) barrel-shifted right FractY bits being multiplied by RowOffset, with the result added to the result of the previous cycle. The second cycle shifts the X index right by FractX bits, and then either the result (in the case of 8 bit data) or the result shifted left I bit (in the case of 16 bit data) is added to the result from the second cycle. This gives us address Adr = address of Table[Int(X), Int(Y), Int(Z)]:
Adr = ImageStart + (ShiftRight(Z, FractZ) * ZOffset) + (ShiftRight(Y, FractY)* RowOffset) + ShiftRight(X, FractX) We keep a copy of Adr in AdrOld for use fetching subsequent entries.
If the data is 8 bits, the timing is 2 cycles of address generation, followed by 2 cycles of data being returned (2 table entries per cycle).
If the data is 16 bits, the timing is 2 cycles of address generation, followed by 4 cycles of data being returned (1 entry per cycle) The following 2 tables show the method of address calculation for 8 and 16 bit data sizes:
Cycle Calculation while fetching 2 x 8-bit data entries from Adr I Adr = Adr + RowOffset 2 Adr = AdrOld + ZOffset 3 Adr = Adr + RowOffset 4 <preparing next lookup>
Cycle Calculation while fetching 1 x 16-bit data entries from Adr t Adr = Adr + 2 2 Adr = AdrOld + RowOffset 3 Adr = Adr + 2 4 Adr, AdrOld =AdrOld + Zoffset Adr=Adr+2 6 Adr = AdrOld + RowOffset 7 Adr = Adr + 2 8 <preparing next lookup>
In both cases, the cycles of address generation can overlap the insertion of the indexes into the FIFO, so the effective timing for a single one-off lookup can be as low as I cycle for address generation, and 4 cycles of return data. If the generation of indexes is 2 steps ahead of the results, then there is no effective address generation time, and the data is simply produced at the appropriate rate (4 or 8 cycles per set).
Image Pyramid LookuR
During brushing, tiling, and warping it is necessary to compute the average color of a particular area in an image.
Rather than calculate the value for each area given, these functions make use of an image pyramid. The description and construction of an image pyramid is detailed in the section on Internal Image Formats in the DRAM interface 81 chapter of this docunient This section is concerned with a method of addressing given pixels in the pyramid in terms of 3 fixed-point indexes ordered: level (Z), Y, and X. Note that Image Pyramid lookup assumes 8 bit data entries, so the DataSize flag is completely ignored. After specification of Z, Y, and X, the following 8 pixels are returned via the Input FIFO:
The pixel at [Int(X), Int(Y)], level Int(Z) The pixel at [Int(X)+I, Int(Y)], level Int(Z) The pixel at [Int(X), Int(Y)+l J, level Int(Z) The pixel at [Int(X)+1, Int(Y)+I], level Int(Z) The pixel at [Int(X), Int(Y)], level Int(Z)+1 The pixel at [Int(X)+1, Int(Y)], level Int(Z)+1 The pixel at [Int(X), Int(Y)+1], level Int(Z)+1 The pixel at [Int(X)+I, Int(Y)+11, level Iat(Z)+I
The 8 pixels are returned as 4 x 16 bit entries, with X and X+I entries combined hi/lo. For example, if the scaled (X, Y) coordinate was (10.4, 12.7) the fust 4 pixels retumed would be: (10, 12), (11, 12), (10, 13) and (11, 13). When a coordinate is outside the valid range, clients have the choice of edge pixel duplication or returning of a constant color value via the DuplicateEdgePixels and Constant.Pixel registers (only the low 8 bits are used)_ When the Image Pyramid has been constructed, there is a simple mapping from level 0 coordinates to level Z coordinates. The method is simply to shift the X or Y coordinate right by Z bits. This must be done in addition to the number of bits already shifted to retrieve the integer portion of the coordinate (i.e. shifting right FractX and FractY bits for X and Y
ordinates respectively). To find the ImageStart and RowOffset value for a given level of the image pyraniid, the 24-bit ZOffset register is used as a pointer to a Level Information Table. The table is an array of records, each representing a given level of the pyramid, ordered by level number. Each record consists of a 16-bit offset ZOffset from ImageStart to that level of the pyramid (64-byte aligned address as lower 6 bits of the offset are not present), and a 12 bit ZRowOffset for that level. Element 0 of the table would contain a ZOffset of 0, and a ZRowOffset equal to the general register RowOffset, as it simply points to the full sized image. The ZOffset value at element N of the table should be added to ImageStart to yield the effective ImageStart of level N of the image pyramid. The RowOffset value in element N of the table contains the RowOffset value for ievel N. The software running on the CPU must set up the table appropriately before using this addressing mode. The actual address generation is outlined here in a cycle by cycle description:
Load From Cycle Register Address Other Operations 0 - - ZAdr = ShiftRight(Z, FractZ) + ZOffset Zlnt = ShiftRight(Z, FractZ) 1 ZOffset Zadr ZAdr += 2 Ylnt = ShiftRight(Y, FractY) 2 ZRowOffset ZAdr ZAdr += 2 Ylnt = ShiftRight(YInt, Zlnt) Adr = ZOffset + ImageStart 3 ZOffset ZAdr ZAdr += 2 Adr += ZrowOffset * Ylnt Xlnt = ShiftRight(X, FractX) 4 ZAdr ZAdr Adr += ShiftRight(Xlnt, Zlnt) ZOffset += ShiftRight(Xlnt, 1) FIFO Adr Adr += ZrowOffset ZOffset += ImageStart 6 FIFO Adr Adr = (ZAdr * ShiftRight(Yint,1)) + ZOffset 7 FIFO Adr Adr += Zadr 8 FIFO Adr < Cycle 0 for next retrieval>
The address generation as described can be achieved using a single Barrel Shifter, 2 adders, and a single 16x16 multiply/add unit yielding 24 bits. Although some cycles have 2 shifts, they are either the same shift value (i.e. the output of the Barrel Shifter is used two times) or the shift is I bit, and can be hard wired. The following internal registers are required: ZAdr, Adr, Zlnt, Ylnt, XInt, ZRowOffset, and ZlmageStart. The _Int registers only need to be 8 bits maximum, while the others can be up to 24 bits. Since this access method only reads from, and does not write to image pyramids, the CacheGroup2 is used to lookup the Image Pyramid Address Table (via ZAdr). CacbeGroupl is used for lookups to the image pyramid itself (via Adr). The address table is around 22 entries (depending on original image size), each of 4 bytes. Therefore 3 or 4 cache lines should be allocated to CacheGroup2, while as many cache lines as possible should be allocated to CacheGroupl. The timing is 8 cycles for retuming a set of data, assuming that Cycle 8 and Cycle 0 overlap in operation - i.e. the next request's Cycle 0 occurs during Cycle 8. This is acceptable since Cycle 0 has no memory access, and Cycle 8 has no specific operations.
Generation of Coordinates usinz VLIW Vector Processor 74 Sotne functions that are linked to Write Iterators require the X and/or Y
coordinates of the current pixel being processed in part of the processing pipeline. Particular processing may also need to take place at the end of each row, or column being processed. In most cases, the PassX and PassY flags should be sufficient to completely generate all eoordinates. However, if there are special requirements, the following functions can be used. The calculation can be spread over a number of ALUs, for a single cycle generation, or be in a single ALU 188 for a multi-cycle generation Generate Seauential fX, Yl When a process is processing pixels in sequential order according to the Sequential Read Iterator (or generating pixels and writing them out to a Sequential Write Iterator), the following process can be used to generate X. Y coordinates instead of PassX/PassY flags as shown in Fig. 23.
The coordinate generator counts up to ImageWidth in the X ordinate, and once per ImageWidth pixels increments the Y ordinate. The actual process is illustrated in Fig. 24, where the following constants are set by software:
Constant Value K, lmageWidth K2 ImageHeight (optional) The following registers are used to hold temporary variables:
Variable Value Reg, X (starts at 0 each line) Reg, Y (starts at 0) The r+aquirements are summarized as follows:
Requirements *+ + R K LU Iterators General 0 3/4 2 1/2 0 0.
Genetate Vertical Strip X Y) When a process is processing pixels in order to write them to a Venical Strip Write Iterator, and for some reason cannot use the PassX/PassY flags, the process as illustrated in Fig. 25 can be used to gener=ate X, Y coordinates. The coordinate generator simply counts up to ImageWidth in the X ordinate, and once per ImageWidth pixels increments the Y ordinate. The actual process is illustrated in Fig. 26, where the following constants are set by software:
Constant Value Kt 32 K2 ItnageWidth K3 ImageHeight The following registers are used to hold temporary variables:
Variable Value Reg, StartX (starts at 0, and is incremented by 32 once per vertical strip) RegZ X
Reg3 EndX (starts at 32 and is incremented by 32 to a maximum of ImageWidth) once per vertical strip) Reg4 Y
The requirements are summarized as follows:
Requirements *+ + R K LU Iterators General 0 4 4 3 0 0 TOTAL 0 . 4 4 3 0 0 The calculations that occur once per vertical strip (2 additions, one of which has an associated MIN) are not included in the general timing statistics because they are not really part of the per pixel timing. However they do need to be taken into account for the programming of the microcode for the particular function.
Inutee Sensor Interface (ISI 83) The Image Sensor Interface (ISI 83) takes data from the CMOS Image Sensor and makes it available for storage in DRAM. The image sensor has an aspect ratio of 3:2, with a typical resolution of 750 x 500 samples, yielding 375K (8 bits per pixel). Each 2x2 pixel block has the configuration as shown in Fig.
27. The ISI 83 is a state machine that sends control information to the Image Sensor, including frame sync pulses and pixel clock pulses in order to read the image.
Pixels are read from the image sensor and placed into the VLIW Input FIFO 78.
The VLIW is then able to process and/or store the pixels. This is illustrated further in Fig. 28_ The ISI 83 is used in conjunction with a VLIW program that stores the sensed Photo Image in DRAM. Processing occurs in 2 steps:
A small VLIW program reads the pixels from the FIFO and writes them to DRAM
via a Sequential Write Iterator.
The Photo Image in DRAM is rotated 90, 180 or 270 degrees according to the orientation of the camera when the photo was taken.
If the rotation is 0 degrees, then step I merely writes the Photo Iniage out to the final Photo Image location and step 2 is not performed. If the rotation is other than 0 degrees, the image is written out to a temporary area (for example into the Print Image memory area), and then rotated during step 2 into the final Photo Image location. Step I is very simple microcode, taking data from the VLIW Input FIFO 78 and writing it to a Sequential Write Iterator. Step 2's rotation is accomplished by using the accelerated Vark Affine Transform function. The processitig is perfontted in 2 steps in order to reduce design complexity and to re-use the Vark aff ne transform rotate logic already required for images. This is acceptable since both steps are completed in approximately 0.03 seeonds, a time imperceptible to the operator of the Artcam. Even so, the read proccss is sensor speed bound, taking 0_02 seconds to read the full frame, and approxintatety 0.01 seconds to rotate the image.
The orientation is intportant for converting between the sensed Photo Image and the internal fotmat image, since the relative positioning of R, G, and B pixels changes with orientation_. The processed image may also have to be rotated during the Print process in order to be in the correct orientation for printing. The 3D model of the Artcam has 2 image sensors, with their inputs multiplexed to a single ISI 83 (different microcode, but same ACP 31). Since each sensor is a frame store, both images can be taken simultaneously, and then transferred to memory one at a time.
Disolav Controller 88 When the "Take" button on an Artcam is half depressed, the TFT will display the current image from the image sensor (converted via a simple VLIW process). Once the Take button is fully depressed, the Taken Image is displayed. When the user presses the Print button and image processing begins, the TFT is turned off. Once the image has been printed the TFT is turned on again. The Display Controller 88 is used in those Artcam models that incorporate a flat panel display. An example display is a TFT LCD of resolution 240 x 160 pixels. The structure of the Display Controller 88 isi illustrated in Fig. 29. The Display Controller 88 State Machine contains registers that control the tinvng of the Sync Generation, where the display image is to be taken from (in DRAM via the Data cache 76 via a specific Cache Group), and whether the TFT should be active or not (via TFT Enable) at the moment. The CPU can write to these registers via the low speed bus. Displaying a 240 x 160 pixel image on an RGB
TFT requires 3 components per pixel.
The image taken from DRAM is displayed via 3 DACs, one for each of the R, G, and B output signals. At an image refresh rate of 30 frames per second (60 fields per second) the Display Controller 88 requires data transfer rates of:
240x160x3x30=3.5MBpersecond This data rate is low compared to the rest of the system. However it is high enough to cause VLIW programs to slow down during the intensive image processing. The general principles of TFT
operation should reflect this.
Image Data Formats As stated previously, the DRAM Interface 81 is responsible for interfacing between other client portions of the ACP chip and the RAMBUS DRAM. In effect, each module within the DRAM
Interface is an address generator.
There are three logical types of images manipulated by the ACP_ They are:
-CCD Image, which is the Input Image captured from the CCD.
-Internal Image fotmat - the Image format utilised internally by the Artcam device.
Print Image - the Output Itnage format printed by the Artcam These images are typically different in color space, resolution, and the output & input color spaces which can vary from camera to camera. For example, a CCD image on a low-end camera may be a different resolution, or have different color characteristics from that used in a high-end camera However all internal image formats are the same format in tertns of color space across all canteras.
In addition, the three image types can vary with respect to which direction is 'up'. The physical orientation of the camera causes the notion of a portrait or landscape image, and this must be maintained throughout processing. For this reason, the internal image is always oriented correctly, and rotation is performed on iniages obtained from the CCD and during the print opetaiion.
CCD ImaQe Orzattization Although many different CCD image sensors could be utilised, it will be assumed that the CCD itself is a 750 x 500 image sensor, yielding 375,000 bytes (8 bits per pixel). Each 2x2 pixel block having the configuration as depicted in Fig. 30.
A CCD httage as stored in DRAM has consecutive pixels with a given line contiguous in tnemory. Each line is stored one after the other. The image sensor Interface 83 is responsible for taking data from the CCD and storing it in the DRAM correctly oriented. Thus a CCD image with rotation 0 degrees has its first line G, R. G, R, G, R... and its second line as B, G, B, G. B, G.... If the CCD image should be portrait, rotated 90 degrees, the first line will be R, G, R, G, R, G and the second line G, B, G, B, G, B...etc.
Pixels are stored in an interleaved fashion since all color components are required in order to convert to the internal image fotmat.
It should be noted that the ACP 31 makes no assumptions about the CCD pixel format, since the actual CCDs for imaging may vary from Artcam to Arccam, and over time. All processing that takes place via the hardware is controlled by major microcode in an attempt to extend the usefulness of the ACP 31.
Internal Imaee Organization Internal images typically consist of a number of channels. Vark images can include, but are not limited to:
Lab Laba LabA
aA
L
L, a and b correspond to components of the Lab color space, a is a matte channel (used for compositing), and A is a bump-map channel (used during brushing, tiling and illuminating).
The VLIW processor 74 requires images to be organized in a planar configuration. Thus a Lab image would be stored as 3 separate blocks of memory:
one block for the L channel, one block for the a channel, and one block for the b channel Within each channel block, pixels are stored contiguously for a givcn row (plus some optional padding bytes), and rows are stored one after the other.
Turning to Fig. 31 there is illustrated an example form of storage of a logical itnage 100. The logical image 100 is stored in a piatuv fashion having L 101, a 102 and b 103 color components stored one after another.
Alternatively, the logical image 100 can be stored in a compressed format having an uncompressed L component 101 and compressed A and B components 105, ]06.
Turning to Fig. 32, the pixels of for line n 110 are stored together before the pixels of for line and n + 1(111).
With the image being stored in contiguous memory within a single channel.
In the 8MB-ntenmry model, the final Print Image after all processing is finished, needs to be compressed in the chrominance channels. Compression of chrominance channels can be 4:1, causing an overall compression of 12:6, or 2:1.
Other than the final Print Image, images in the Artcam are typically not compressed. Becaase of tnemory constraints, software may choose to comptess the final Print hnage in the chrominance channels by scaling each of these channels by 2:1. If this has been done, the PRIWT Vark function call utilised to print an image must be told to treat the specified chrominance channels as compressed. The PRINT function is the only function that knows how to deal with compressed chrominance, and even so, it only deals with a fixed 2:1 compression ratio.
Although it is possible to compress an image and then operate on the compressed image to create the final print image, it is not recommended due to a loss in resolution. In addition, an image should only be compressed once -as the final stage before printout. While one compression is virtually undetectable, multiple compressions may cause substantial image degradation.
Clip image Organization Clip images stored on Artcards have no explicit support by the ACP 31 _ Software is responsible for taking any images from the current Artcard and organizing the data into a form known by the ACP. If images are stored compressed on an Artcard, software is responsible for decompressing them, as there is no specific hardware support for decompression of Artcard images.
Imaee Pyramid Organization During brushing, tiling, and warping prmesses utilised to manipulate an image it is often necessary to compute the average color of a particular area in an image. Rather than calculate the value for each area given, these functions make use of an image pyramid. As illustrated in Fig. 33, an image pyramid is effectively a multi-resolutionpixel- map. The original image 115 is a 1:1 representation. Low-pass fiitering and sub-sampling by 2:1 in each dimension produces an image Ni the original size 116. This process continues until the entire image is represented by a single pixel. An image pyramid is constructed from an original internal format image, and consumes 1/3 of the size taken up by the original image (1/4 + 1/16 + 1/64 + ...). For an original image of 1500 x 1000 the cotresponding image pyramid is approximately rhMB. An image pyramid is constructed by a specific Vark function, and is used as a parameter to other Vark functions.
Print Image Organization 'fhe entire processed image is required at the same time in order to print it.
However the Print Image output can comprise a CMY dithered image and is only a transient image format, tucd within the Print Image functionality.
However, it should be noted that color conversion will need to take place from the internal color space to the print color space. In addition, color conversion can be tuned to be different for different print rolls in the camera with different ink characteristics e.g. Sepia output can be accomplished by using a specific sepia toning Aricard, or by using a sepia tone print-roll (so all Artcards will work in sepia tone).
Color Spaces As noted previously there are 3 color spaces used in the Artcam, corresponding to the different image types.
The ACP has no direct knowledge of specific color spaces. Instead, it relies on client color space conversion tables to convert between CCD, intecnal, and printer color spaces:
CCD:RGB
Internal:Lab Printer.CMY
Removing the color space conversion from the ACP 31 allows:
-Different CCDs to be used in different cameras -Different inks (in different print rolls over time) to be used in the same camera -Separation of CCD selection from ACP design path -A well defined interoal color space for accurate color processing Artcard Interface 87 The Artcaid Interfxe (AI) takes data from the linear image Sensor while an Artcard is passing under it, and makes that data available for storage in DRAM. The image sensor produces 11,000 8-bit samples per scanline, sampling the Artcard at 4800 dpi. The AI is a state machine that sends control information to the linear sensor, including LineSync pulses and PixelClock pulses in order to read the intage. Pixels are read from the linear sensor and placed into the VLIW Input FIFO 78. The VLIW is then able to process and/or store the pixels.
The Al has only a few registers:
Register Name Description NumPixels The number of pixels in a sensor line (approx 'I 1,000) Status The Print Head Interface's Status Register PixeisRemaining The number of bytes remaining in the current line Actions Reset A write to this register resets the Al, stops any scanning, and loads all registers with 0.
Scan A write to this register with a non-zero value sets the Scanning bit of the Status register, and causes the Artcard Interface Scan cycle to start.
A write to this register with 0 stops the scanning process and clears the Scanning bit in the Status register.
The Scan cycle causes the AI to transfer NumPixels bytes from the sensor to the VLIW Input FIFO 78, producing the PixelClock signals appropriately. Upon completion of NumPixels bytes, a LineSync putse is given and the Scan cycle restarts.
The PixelsRemaining register holds the number of pixels remaining to be read on the current scanline.
Note that the CPU should clear the VLIW Input FIFO 78 before initiating a Scan. The Status register has bit interpretations as follows:
Bit Name Bits Description Scanning 1 If set, the Al is currently scanning, with the number of pixels remaining to be transferred from the current line recorded in PixelsRemaining.
If clear, the Al is not currently scanning, so is not transferring pixels to the VLIW Input FIFO 78.
Artcard Interface (AIl 87 The Artcard Interface (Al) 87 is responsible for taking an Artcard image from the Artcard Reader 34 , and decoding it into the original data (usually a Vark script)_ Specifically, the Al 87 accepts signals from the Artcard scanner linear CCD 34, detects the bit pattern printed on the card, and converts the bit pattern into the original data, correcting read errors.
With no Artcard 9 inserted, the image printed from an Artcam is simply the sensed Photo Iinage cleaned up by any standard image processing routines. The Artcard 9 is the means by which users are able to modify a photo before printing it out. By the simple task of inserting a specific Artcard 9 into an Artcam, a user is able to define complex image processing to be performed on the Photo Image.
With no Artcard inserted the Photo Image is processed in a standard way to create the Print Image. When a single Artcard 9 is inserted into the Artcam, that Artcard's effect is applied to the Photo Image to generate the Print lmage.
When the Artcard 9 is removed (ejected), the printed image reverts to the Photo Image processed in a standard way.
When the user presses the button to eject an Artcard, an event is placed in the event queue maintained by the operating system running on the Artcam Central Processor 31. When the event is processed (for example after the current Print has occurred), the following things occur.
If the current Artcard is valid, then the Print Image is marked as invalid and a'Process Standard' event is placed in the event queue. When the event is eventually processed it will perform the standard image processing operations on the Photo Image to produce the Print Image.
The motor is started to eject the Artcard and a time-specific 'Stop-Motor' Event is added to the event queue.
Insertingan Artcand When a user inserts an Artcard 9, the Artcard Sensor 49 detects it notifying the ACP72. This results in the software inserting an 'Artcard Inserted' event into the event queue. When the event is processed several things occur The current Artcard is marked as invalid (as opposed to 'none').
The Print Image is marked as invalid.
The Artcard motor 37 is started up to load the Artcard The Artcard Interface 87 is instructed to read the Artcard The Artcard Interface 87 accepts signals from the Artcard scanner linear CCD
34, detects the bit pattem printed on the cand, and cotrects errors in the detected bit pattern, producing a valid Artcard data block in DRAM.
Reading Data from the Artcard CCD - General Considerations As illusttaied in Fig. 34, the Data Card reading process has 4 phases operated while the pixel data is read from the card. The phases are as follows:
Phase 1. Detect data area on Artcard Phase 2. Detect bit pattern from Artcard based on CCD pixels, and write as bytes.
Phase 3. Descramble and XOR the byte-pattern Phase 4. Decode data (Reed-Solomon decode) As illustrated in Fig. 35, the Artcard 9 must be sampled at least at double the printed resolution to satisfy Nyquist's Theorem. In practice it is better to sample at a higher rate than this. Preferably, the pixels are sampled 230 at 3 times the resolution of a printed dot in each dimension, requiring 9 pixels to define a single dot. Thus if the resolution of the Artcard 9 is 1600 dpi, and the resolution of the sensor 34 is 4800 dpi, then using a 50tnm CCD image sensor results in 9450 pixels per column. Therefore if we require 2MB of dot data (at 9 pixels per dot) then this requires 2MB*8*9/9450 = 15,978 columns = approxitnately 16,000 columns. Of course if a dot is not exactly aligned with the sampling CCD the worst and most likely case is that a dot will be sensed over a 16 pixel area (4x4) 231.
An Artcard 9 may be slightly warped due to heat damage, slightly rotated (up to, say I degree) due to differences in insertion into an Ancard reader, and can have slight differences in true data rate due to fluctuations in the speed of the reader motor 37. These changes will cause columns of data from the card not to be read as corresponding colutnns of pixel data. As illustrated in Fig. 36, a I degree rotation in the Artcard 9 can cause the pixels from a column on the card to be read as pixels across 166 columns:
Finally, the Artcard 9 should be read in a reasonable amount of time with respect to the human operator. The data on the Artcard covers most of the Artcard surface, so timing concems can be limited to the Aitcard data itself. A
reading time of 1.5 seconds is adequate for Artcard reading.
The Artcard should be loaded in 1.5 seconds. Therefore all 16,000 columns of pixel data must be read from the CCD 34 in 1.5 second, i.e. 10,667 columns per second. Therefore the time available to read one column is 1/10667 seconds, or 93,747ns. Pixel data can be written to the DRAM one column at a time, completely independently from any processes that are reading the pixel data.
The time to write one column of data (9450/2 bytes since the reading can be 4 bits per pixel giving 2 x 4 bit pixels per byte) to DRAM is reduced by using 8 cache lines. If 4lines were written out at one time, the 4 banks can be written to independenUy, and thus overlap latency reduced. Thus the 4725 bytes can be written in I 1,840ns (4725/128 * 320ns). Thus the time taken to write a given column's data to DRAM uses just under 13% of the available bandwidth.
DecodinQ an Artcard A simple look at the data sizes shows the impossibility of fitting the process into the 8MB of inemory 33 if the entire Artcard pixel data (140 MB if each bit is read as a 3x3 array) as read by the linear CCD 34 is kept. For this reason, the reading of the linear CCD, decoding of the bitmap, and the un-bitmap process should take place in real-time (while the Artcard 9 is traveling past the linear CCD 34), and these processes must effectively work without having entire data stores available.
When an Artcard 9 is inserted, the old stored Print image and any expanded Photo Image becomes invalid.
The new Artcard 9 can contain directions for creating a new image based on the currendy r.aptured Photo Image. The old Print Image is invalid, and the area holding expanded Photo Image data and image pyramid is invalid, leaving more than 5MB that can be used as scratch memory during the read process. Strictiy speaking, the iMB area whete the Artcard raw data is to be written can also be used as scratch data during the Artcard read process as long as by the time the final Reed-Solomon decode is to occur, that 1MB area is free again. The reading process described here does not make use of the extra 1MB area (except as a final destination for the data).
It should also be noted that the unscrambling process requires two sets of 2MB
areas of memory since unscrambling cannot occur in place. Fortunately the 5MB scratch area contains enough space for this process.
Turning now to Fig. 37, there is shown a flowchart 220 of the steps necessary to decode the Artcard data.
These steps include reading in the Artcard 221, decoding the read data to produce corresponding encoded XORed scrambled bitmap data 223. Next a checkerboard XOR is applied to the data to produces encoded scrambled data 224.
This data is then unscrambled 227 to produce data 225 before this data is subjected to Reed-Solomon decoding to produce the original raw data 226. Alternatively, unscrambling and XOR process can take place together, not requiring a separate pass of the data. Each of the above steps is discussed in further detail hereinafter. As noted previously with reference to Fig. 37, the Artcard Interface, therefore, has 4 phases, the first 2 of which are time-critical, and must take place while pixel data is being read from the CCD:
Phase I. Detect data area on Artcard Phase 2. Detect bit pattern from Artcard based on CCD pixels, and write as bytes.
Phase 3. Descramble and XOR the byte-pattern Phase 4. Decode data (Reed-Solomon decode) The four phases are deseribed in more detail as foliows:
Phase 1. As the Artcard 9 moves past the CCD 34 the Al must detect the start of the data area by robustly detecting special targets on the Artcard to the left of the data area. If these cannot be detected, the card is marked as invalid. The detection must occur in real-time, while the Artcard 9 is moving past the CCD 34.
If necessary, rotation invariance can be provided. In this case, the targets are repeated on the right side of the Artcard, but relative to the bottom right corner instead of the top corncr. In this way the targets end up in the correct orientation if the card is inserted the "wrong" way. Phase 3 below can be altered to detect the orientation of the data, and account for the potential rotation.
Phase 2. Once the data area has been determined, the main read process begins, placing pixel data from the CCD into an 'Artcard data window', detecting bits from this window, assembling the detected bits into bytes, and constructing a byte-image in DRAM. This must all be done while the Artcard is moving past the CCD.
Phase 3. Once all the pixels have been read from the Artcard data area, the Artcard motor 37 can be stopped, and the byte image descrambled and XORed. Although not requiring real-time performance, the process should be fast enough not to annoy the human operator. The process must take 2 MB of scrambled bit-image and write the unscrambled/XORed bit-image to a separate 2MB image.
Phase 4. The final phase in the Artcard read process is the Reed-Solomon decoding process, where the 2MB
bit-image is decoded into a IMB valid Arteard data area. Again, while not requiring real-titne performance it is still necessary to decode quickly with regard to the hurnan operator. If the decode process is valid, the card is niarked as valid. If the decode failed, any duplicates of data in the bit-image are attempted to be decoded, a process that is repeated until success or until there are no more duplicate images of the data in the bit image.
The four phase process described requires 4.5 MB of DRAM. 2MB is reserved for Phase 2 output, and 0.5MB
is reserved for scratch data during phases 1 and 2. The remaining 2MB of space can hold over 440 columns at 4725 byes per column. In practice, the pixel data being read is a few columns ahead of the phase I algorithm, and in the worst case, about 180 columns behind phase 2, comfortably inside the 440 column limit_ A description of the actual operation of each phase will now be provided in greater detail_ Phase 1- Detect data area on Artcard This phase is concerned with robustly detecting the left-hand side of the data area on the Artcard 9. Accurate detection of the data area is achieved by accurate detection of special targets printed on the left side of the card. These targets are especially designed to be easy to detect even if rotated up to I
degree.
Turning to Fig_ 38, there is shown an enlargetnent of the left hand side of an Artcard 9. The side of the card is divided into 16 bands, 239 with a target eg. 241 located at the center of each band. The bands are logical in that there is no line drawn to separate bands. Turning to Fig. 39, there is shown a single target 241. The target 241, is a printed black square containing a single white dot. The idea is to detect firstly as many targets 241 as possible, and then to join at least 8 of the detected white-dot locations into a single logical straight line. If this can be done, the start of the data area 243 is a fixed distance from this logical line. If it cannot be done, then the card is rejected as invalid.
As shown in Fig. 38, the height of the card 9 is 3150 dots. A target (TargetO) 241 is placed a fixed distance of 24 dots away from the top left corner 244 of the data area so that it falls well within the first of 16 equal sized regions 239 of 192 dots (576 pixels) with no target in the final pixel region of the card. The target 241 must be big enough to be easy to detect, yet be small enough not to go outside the height of the region if the card is rotated 1 degree. A
suitable size for the target is a 31 x 31 dot (93 x 93 sensed pixels) black square 241 with the white dot 242.
At the worst rotation of I degree, a I column shift occurs every 57 pixels.
Therefore in a 590 pixel sized band, we cannot place any part of our symbol in the top or bottom 12 pixels or so of the band or they could be detected in the wrong band at CCD read time if the card is worst case rotated.
Therefore, if the black part of the rectangle is 57 pixels high (19 dots) we can be sure that at least 9.5 black pixels will be read in the same column by the CCD (worst case is half the pixels are in one column and half in the next). To be sure of reading at least 10 black dots in the same column, we must have a height of 20 dots. To give room for erroneous detection on the edge of the start of the black dots, we increase the number of dots to 31, giving us 15 on either side of the white dot at the target's local coordinate (15, 15). 31 dots is 91 pixels, which at tnost suffers a 3 pixel shift in column, easily within the 576 pixel band.
Thus each target is a block of 31 x 31 dots (93 x 93 pixels) each with the composition:
15 columns of 31 black dots each (45 pixel width columns of 93 pixels).
I column of 15 black dots (45 pixels) followed by I white dot (3 pixels) and tben a further 15 black dots (45 pixels) 15 columns of 31 black dots each (45 pixel width columns of 93 pixels) Detect targets Targets are detected by reading columns of pixels, one column at a time rather than by detecting dots. It is necessary to look within a given band for a number of columns consisting of large numbers of contiguous black pixels to btrild up the left side of a targeL Next, it is expected to see a white region in the center of further black columns, and finally the black columns to the left of the target center.
Eight cache lines are required for good cache performance on the reading of the pixels. Each logical read fills 4 cache lines via 4 sub-reads while the other 4 cache-lines are being used.
This effectively uses up 13% of the available DRAM bandwidth.
As illustrated in Fig. 40, the detection mechanism FIFO for detecting the targets uses a filter 245, run-length encoder 246, and a FIFO 247 that requires special wiring of the top 3 elenients (S1, S2, and S3) for random access.
The columns of input pixels are processed one at a time until either all the targets are found, or until a specified number of columns have been processed. To process a column, the pixels are read from DRAM, passed dvough a filter 245 to detect a 0 or 1, and then run length encoded 246. The bit value and the number of contiguous bits of the same value are placed in FIFO 247. Each entry of the FIFO 249 is in 8 bits, 7 bits 250 to hold the run-length, and I bit 249 to hold the value of the bit detected.
The run-length encoder 246 only encodes contiguous pixels within a 576 pixel (192 dot) region.
The top 3 elements in the FIFO 247 can be accessed 252 in any random order.
The run lengths (in pixels) of these entries are filtered into 3 values: short, mediunr, and long in accordance with the following table:
Short Used to detect white dot. RunLength < 16 Medium Used to detect runs of black above or below the 16<= RunLength < 48 white dot in the center of the target.
Long Used to detect run lengths of black to the left and RunLength >= 48 right of the center dot in the target.
I.ooking at the top three entries in the FIFO 247 there are 3 specific cases of interest:
Case I S1 = white long We have detected a black column of the target to S2 = black long the left of or to the right of the white center dot.
S3 = white medium/long Case 2 S I= white long If we've been processing a series of columns of S2 = black medium Case Is, then we have probably detected the S3 = white short white dot in this column_ We know that the next Previous 8 columns were Case I entry will be black (or it would have been included in the white S3 entry), but the number of black pixels is in question. Need to verify by checking after the next FIFO advance (see Case 3).
Case 3 Prev = Case 2 We have detected part of the white dot. We S3 = black med expect around 3 of these, and then some more columns of Case 1.
Preferably, the following information per region band is kept:
TargetDetected I bit BlackDetectCount 4 bits WhiteDetectCount 3 bits PrevColumnStartPixel 15 bits TargetColumn ordinate 16 bits (15:1) TargetRow ordinate 16 bits (15:1) TOTAL 7 bytes (rounded to 8 bytes for easy addressing) Given a total of 7 bytes. It makes address generation easier if the total is assumed to be 8 bytes. Thus 16 entries requires 16 * 8 = 128 bytes, which fits in 4 cache lines_ The address range should be inside the scratch 0.5MB
DRAM area since other phases make use of the remaining 4MB data area.
When beginning to process a given pixel column, the register value S2StartPixel 254 is reset to 0. As entries in the FIFO advance from S2 to S1, they are also added 255 to the existing S2StartPixel value, giving the exact pixel position of the run currently defined in S2. Looking at each of the 3 cases of interest in the FIFO, S2StartPixei can be used to determine the start of the black area of a target (Cases I and 2), and also the start of the white dot in the center of the target (Case 3). An algorithm for processing columns can be as follows:
1 TargetDetected[0-15] := 0 BlackDetectCount{0-151 := 0 WhiteDetectCount[0-15] := 0 TargetRow[0-15] := 0 TargetColumn[0-151 := 0 PrevColStartPixel[0-15] := 0 CurrentColumn = 0 2 Do ProcessColumn 3 CurrentColumn++
4 If (CurrentColumn <= LastValidColumn) Goto 2 The steps involved in the processing a column (Process Column) are as follows:
I S2StartPixel := 0 FIFO := 0 BlackDetectCount := 0 WhiteDetectCount 0 ThisColumnDetected := FAISE
PrevCaseWasCase2 := FALSE
2 If (! TargetDetected[Target]) & (! ColumnDetected[Target]) ProcessCases Endlf 3 PrevCaseWasCase2 := Case=2 4 Advance FIFO
The processing for each of the 3 (Process Cases) cases is as follows:
Case 1:
BlackDetectCount[target] < 8 ABS(S2StartPixel - PrcvColStartPixel[Target]) OR If (0<== < 2) WhiteDetectCount[Target] = 0 BlackDetectCount[Targct]++ (max value =8) Else BlackDetectCount[Target] I
WhiteDetectCount[Target) := 0 Endif PrevCo]StartPixel[Target] = S2StartPixel ColumnDetected[Target] := TRUE
BitDetected = 1 BlackDetectCount(target] >= 8 PrevColStartPixel[Target) := S2StartPixel WhiteDetectCount[Target] != 0 ColumnDetected[Target] := TRUE
BitDetected = I
TargetDetected[Target] := TRUE
TargetColumn[Target] := CurrentColumn - 8 -(WhiteDetectCount[Target]/2) Case 2:
No special processing is recorded except for setting the 'PrevCaseWasCase2' flag for identifying Case 3 (see Step 3 of processing a column described above) Case 3:
PrevCaseWasCase2 = TRUE If (WhiteDetectCount[Target] < 2) BlackDetectCount[Target] >= 8 TargetRow[Target) = S2StartPixel +
(S2R,,,,L~r&/2) WhiteDetectCount=l Endif := ABS(S2StartPixel - PrevColStartPixel[Target)) If (0<=- < 2) WhiteDetectCount[Target)++
Else WhiteDetectCount[Targetj := I
Endif PrevColStartPixel[Target] := S2StartPixel ThisColumnDetected := TRUE
BitDetected = 0 At the end of processing a given column, a comparison is made of the current column to the maximum number of columns for target detection. If the number of columns allowed has been exceeded, then it is necessary to check how many targets have been found. If fewer than 8 have been found, the card is considered invalid.
Process targets After the targets have been detected, they should be processed_ All the targets may be available or rnerely some of them. Some targets niay also have been erroneously detected.
This phase of processing is to determine a mathematical line that passes through the center of as many targets as possible. The more targets that the line passes through, the more confident the target position has been found_ The limit is set to be 8 targets. If a line passes through at least 8 targets, then it is taken to be the right one.
It is all right to take a brute-force but straightforward approach since there is the time to do so (see below), and lowering complexity makes testing easier. It is necessary to determine the line between targets 0 and 1(if both targets are considered valid) and then determine how many targets fall on this line.
Then we determine the line between targets 0 and 2, and repeat the process. Eventually we do the same for the line between targets 1 and 2, 1 and 3 etc. and finally for the line between targets 14 and 15. Assuming all the targets have been found, we need to perform 15+14+13+ ...= 90 sets of calculations (with each set of calculations requiring 16 tests = 1440 actual calculations), and choose the line which has the maxirnum number of targets found along the line.
The algorithm for target location can be as follows:
TargetA := 0 MaxFound := 0 BestLine := 0 While (TargetA < 15) If (TargetA is Valid) Target8 = TargetA + 1 While (TargetB<= 15) If (TargetB is valid) CurrentLine :=1ine between TargetA and TargetB
TargetC := 0;
While (TargetC <= 15) If (TargetC valid AND TargetC on line AB) TargetsHit++
Endlf If (TargetsHit > MaxFound) MaxFound := TargetsHit BestLine CurrentLine Endif TargetC++
EndWhile Endlf TargetB ++
EndWhile Endlf TargetA++
EndWhile If (MaxFound < 8) Card is Invalid Else Stote expected centroids for rows based on BestLine Endlf As illustrated in Fig. 34, in the algorithm above, to determine a CurrentLine 260 from Target A 261 and target B. it is necessary to calculate Arow (264) & Acolumn (263) between targets 261, 262, and the location of Target A. It is then possible to move from Target 0 to Target I etc. by adding Orow and Ocolumn. The found (if actually found) location of target N can be compared to the calculated expected position of Target N on the line, and if it falls within the tolerance, then Target N is determined to be on the line.
To calculate Arow & Acolumn:
Arow = (rowTwA - row Tvs)/(B-A) Acolumn = (columnT.,1,~,A- columtrrõwd3)/(B-A) Then we calculate the position of Target0:
row = rowTargetA - (A * Mow) column = columnTargetA - (A * Acolunm And compare (row, column) against the actual rowT.,o and columnT,,.D. To move from one expected target to the next (e.g_ from TargetO to Targetl ), we simply add Arow and Acolumn to row and column respectively. To check if each target is on the line, we must calculate the expected position of Target0, and then perform one add and one comparison for each target ordinate_ At the end of comparing all 16 targets against a maximum of 90 lines, the result is the best line through the valid targets. If that line passes through at least 8 targets (i.e. MaxFound >= 8), it can be said that enough targets have been found to form a line, and thus the card can be processed. If the best line passes through fewer than 8, then the card is considered invalid.
The resulting algorithm takes 180 divides to calculate Arow and Acolumn, 180 multiply/adds to calculate targetO position, and then 2880 adds/comparisons. The time we have to perform this processing is the time taken to read 36 columns of pixel data = 3,374,892ns. Not even accounting for the fact that an add takes less time than a divide, it is necessary to perform 3240 mathematical operations in 3,374,892ns. That gives approximately I040ns per operation, or 104 cycles. The CPU can therefore safely perfonm the entire processing of targets, reducing complexity of design.
Update centroids based on data edge border and clockmarks Step 0: Locate the data area From Target 0(241 of Fig. 38) it is a predetermined fixed distance in rows and columns to the top left border 244 of the data area, and then a further I dot column to the vertical clock marks 276. So we use TargetA, Arow and Acolumn found in the previous stage (Arow and Acolumn refer to distances between targets) to calculate the centroid or expected location for TargetO as described previously.
Since the fixed pixel offset from TargetO to the data area is related to the distance between targets (192 dots between targets, and 24 dots between TargetO and the data area 243), simply add Arow/8 to TargetO's centroid column coordinate (aspect ratio of dots is 1: I). Thus the top co-ordinate can be defined as:
(columnD.c.,,,,,,,,T%, = columnTõ,,a + (Arow/8) (rowp,,,cd,,,,,,,Tw = rowT~,,O + (Acolumn /8) Next Arow and Acolumn are updated to give the number of pixels between dots in a single column (instead of between targets) by dividing them by the number of dots between targets:
Arow = Arow/192 Acolutntt = Ocolutnn /192 We also set the currentColutnn register (see Phase 2) to be -1 so that after=
step 2, when phase 2 begins, the cutretttColutnn register will increment from -1 to 0.
Step 1: Write out the initial centroid deltas (A) and bit history This simply involves writing setup infotmation required for Phase 2.
This can be achieved by writing Os to all the Arow and Acolumn entries for each row, and a bit history. The bit history is actually an expected bit history since it is known that to the left of the clock mark column 276 is a border column 277, and before that, a white area. The bit history therefore is 011, 010, 011, 010 etc.
Steo 2: Undate the centroids based on actual pixels read.
The bit history is set up in Step 1 according to the expected clock marks and data border_ The actual centroids for each dot row can now be more accurately set (they were initially 0) by comparing the expected data against the actual pixel values. The centroid updating mechanism is achieved by simply performing step 3 of Phase 2.
Phase 2- Detect bitpattern from Artcard based on pixels read, and write as bytes.
Since a dot from the Artcard 9 requires a minimum of 9 sensed pixels over 3 columns to be represented, there is little point in performing dot detection calculations every sensed pixel column. It is better to average the time required for processing over the average dot occurrence, and thus make the most of the available processing titne. This allows processing of a column of dots from an Artcard 9 in the time it takes to read 3 columns of data from the Artcard.
Although the most likely case is that it takes 4 columns to represent a dot, the 4~' column will be the last column of one dot and the first column of a next dot. Processing should therefore be limited to only 3 columns.
As the pixels from the CCD are written to the DRAM in 13% of the time available, 83% of the time is available for processing of I column of dots i.e. 83% of (93,747*3) = 83% of 281,241 ns = 233,430ns.
In the available time, it is necessary to detect 3150 dots, and write their bit values into the raw data area of memory. The processing therefore requires the following steps:
For each coltunn of dots on the Artcard:
Step 0: Advance to the next dot eofumn Step 1: Detect the top and bottom of an Artcard dot column (check clock marks) Step 2: Process the dot column, detecting bits and storing them appropriately Step 3: Update the centroids Since we are processing the Artcard's logical dot columns, and these may shift over 165 pixels, the worst case is that we cannot process the first column until at least 165 columns have been read into DRAM. Phase 2 would therefore finish the same amount of time after the read process had terminated. The worst case time is: 165 * 93,747ns 15,468,255ns or 0.015 seconds.
Step 0: Advance to the next dot coltunn In order to advance to the next column of dots we add Arow and t,column to the dotColumnTop to give us the centroid of the dot at the top of the column. The fust time we do this, we are currently at the clock marks column 276 to the left of the bit image data area, and so we advance to the first column of data. Since Arow and Acolumn refer to distance between dots within a column, to move between dot columns it is necessary to add Orow to colurrtn&w-t,,,,,,,Tp and Acolumn to rowdc.I,,,,,,,T,.
To keep track of what column number is being processed, the column number is recorded in a register called CurrentColumn. Every time the sensor advances to the next dot column it is necessary to increment the CurrentColumn register. The first time it is incremented, it is incremented from -1 to 0 (see Step 0 Phase I). The CurrentColumn register determines when to terminate the read process (when reaching maxColumns), and also is used to advance the DataOut Pointer to the next column of byte information once all 8 bits have been written to the byte (once every 8 dot columns). The lower 3 bits determine what bit we're up to within the cun-ettt byte. It will be the sanie bit being written for the whole colttmrt.
Step 1: Detect the tqp and bottom of an Artcard dot column.
In order to process a dot column from an Artcard, it is necessary to detect the top and bottom of a colutttn_ The column should fotm a straight line between the top and bottom of the column (except for local warping etc.).
Initially dotColumnTop points to the clock mark column 276. We simply toggle the expected value, write it out into the bit history, and move on to step 2, whose first task will be to add the Arow and Acolumn values to dotColumnTop to arrive at the first data dot of the column.
Stea 2: Process an Artcard's dot column Given the centroids of the top and bottom of a column in pixel coordinates the column should form a straight line between them, with possible minor variances due to warping etc_ Assuming the processing is to start at the top of a column (at the top centroid coordinate) and move down to the bottom of the column, subsequent expected dot centroids are given as:
rowmx, = row + Orow column. = colutnn + Acolumn This gives us the address of the expected centroid for the next dot of the column However to account for local warping and error we add another Arow and Acolumn based on the last time we found the dot in a given row. In this way we can account for small drifts that accumulate into a maximum drift of some percentage from the straight line joining the top of the column to the bottom.
We therefore keep 2 values for each row, but store them in separate tables since the row history is used in step 3 of this phase.
* Arow and Acolumn (2 @ 4 bits each = I byte) =
* row history (3 bits per row, 2 rows are stored per byte) For each row we need to read a Arow and Acolumn to determine the change to the centroid. Tfte read process takes 5% of the bandwidth and 2 cache lines:
76*(3150/32) + 2*3150 = 13,824ns = 5% of bandwidth Once the centroid has been detertnined, the pixels around the centroid need to be examined to detect the status of the dot and hence the value of the bit. In the worst case a dot covers a 4x4 pixel area. However, thanks to the fact that we are sampling at 3 times the resolution of the dot, the number of pixels required to detect the status of the dot and hence the bit value is much less than this. We only require access to 3 columns of pixel columns at any one time.
In the worst case of pixel drift due to a 1% rotation, centroids will shift I
column every 57 pixel rows, but since a dot is 3 pixels in diameter, a given column witl be valid for 171 pixel rows (3*57). As a byte contains 2 pixels, the number of bytes valid in each buffered read (4 cache lines) will be a worst case of 86 (out of 128 read).
Once the bit has been detected it must be written out to DRAM. We store the bits from 8 columns as a set of contiguous bytes to mininuze DRAIvi delay. Since all the bits from a given dot column will correspond to the next bit position in a data byte, we can read the old value for the byte, shift and OR
in the new bit, and write the byte back.
The read / shift&OR I write process requires 2 cache lines.
We need to read and write the bit history for the given row as we update it We only require 3 bits of history per row, ailowing the storage of 2 rows of history in a single byte. The read / shift&OR / write process requires 2 cache lines.
The total bandwidth required for the bit detection and storage is summarised in the following table:
Read centroid A 5%
Read 3 columns of pixel data 19%
Read/Write detected bits into byte buffer 10%
Read/Write bit history 5%
TOTAL 39%
Detecting a dot The process of detecting the value of a dot (and hence the value of a bit) given a centroid is accomplished by examining 3 pixel values and getting the result from a lookup table. The process is fairly simple and is illustrated in Fig. 42. A dot 290 has a radius of about 1.5 pixels. Therefore the pixel 291 that holds the centroid, regardless of the actual position of the centroid within that pixel, should be 100g'~ of the dot's value. If the centroid is exactly in the center of the pixel 291, then the pixels above 292 & below 293 the centroid's pixel, as well as the pixels to the left 294 & right 295 of the centroid's pixel will contain a majority of the dot's value. The further a centroid is away from the exact center of the pixel 295, the more likely that more than the center pixel will have 100% coverage by the dot.
Although Fig. 42 only shows centroids differing to the left and below the center, the same relationship obviously holds for centroids above and to the right of center. center. In Case 1, the centroid is exactly in the center of the middle pixel 295. The center pixel 295 is completely covered by the dot, and the pixels above, below, left, and right are also well covered by the dot. In Case 2, the centroid is to the left of the center of the middle pixel 291. The center pixel is still completely covered by the dot, and the pixel 294 to the left of the center is now completely covered by the dot The pixels above 292 and below 293 are still well covered. In Case 3, the centroid is below the center of the middle pixel 291. The center pixel 291 is still completely covered by the dot 291, and the pixel below center is now completely covered by the dot. The pixels left 294 and right 295 of center are still well covered. In Case 4, the centroid is left and below the center of the middle pixel. The center pixel 291 is still completely covered by the dot, and both the pixel to the left of center 294 and the pixel below center 293 are completely covered by the dot.
The algorithm for updating the centroid uses the distance of the centroid from the center of the middle pixel 291 in order to select 3 representative pixels and thus decide the value of the dot:
Pixel 1: the pixel containing the centroid Pixel 2: the pixel to the left of Pixel I if the centroid's X coordinate (column value) is <'h, otherwise the pixel to the right of Pixel 1.
Pixel 3: the pixel above pixel 1 if the centroid's Y coordinate (row value) is < th., otherwise the pixel below Pixel 1.
As shown in Fig. 43, the value of each pixel is output to a pre-calculated lookup table 301. T7te 3 pixels are fed into a 12-bit lookup table, which outputs a single bit indicating the value of the dot - on or off. The lookup table 301 is constructed at chip definition time, and can be compiled into about 500 gates. The lookup table can be a simple threshold table, with the exception that the center pixel (Pixel 1) is weighted more heavily.
Step 3: U ate the centroid ds for each row in the column The idea of the As processing is to use the previous bit history to generate a 'perfect' dot at the expected centroid location for each row in a current column. The actual pixels (from the CCD) are compared with the expected 'perfect' pixels. If the two match, then the actual centroid location must be exactly in the expected position, so the centroid As must be valid and not need updating. Otherwise a process of changing the centroid As needs to occur in order to best fit the expected centroid location to the actual data. The new centroid As will be used for processing the dot in the next column.
Updating the centroid As is done as a subsequent process from Step 2 for the following reasons:
to reduce complexity in design, so that it can be perfonned as Step 2 of Phase I there is enough bandwidth remaining to allow it to allow reuse of DRAM buffers, and to ensure that all the data required for centroid updating is available at the start of the process without special pipelining.
The centroid A are processed as Acolumn Arow respectively to reduce complexity.
Although a given dot is 3 pixels in diameter, it is likely to occur in a 4x4 pixei area. However the edge of one dot will as a result be in the same pixel as the edge of the next dot. For this reason, centroid updating requires more than simply the information about a given single dot.
Fig. 44 shows a single dot 310 from the previous column with a given centroid 311. In this example, the dot 310 extend A over 4 pixel columns 312-315 and in fact, part of the previous dot column's dot (coordinate =
(Prevcolumn, Current Row)) has entered the current column for the dot on the current row. If the dot in the current row and column was white, we would expect the rightmost pixel column 314 from the previous dot column to be a low value, since there is only the dot information from the previous column's dot (the current column's dot is white). From this we can see that the higher the pixel value is in this pixel column 315, the more the centroid should be to the right Of course, if the dot to the right was also black, we cannot adjust the centroid as we cannot get infotmation sub-pixel.
The same can be said for the dots to the left, above and below the dot at dot coordinates (PrevColtunn, CurrentRow).
From this we can say that a maximum of 5 pixel columns and rows are required.
It is possible to simplify the situation by taking the cases of row and column centroid As separately, treating them as the same problem, only rotated 90 degrees.
Taking the horizontal case first, it is necessary to change the column centroid As if the expected pixels don't match the detected pixels. From the bit history, the value of the bits found for the Current Row in the current dot column, the previous dot coltmm, and the (previous-1)th dot column are known.
The expected centroid location is also known. Using these two pieces of inforntation, it is possible to generate a 20 bit expected bit pattern should the read be 'perfect'. The 20 bit bit-pattern reptrsertts the expected A values for each of the 5 pixels across the horizontal dimension. The first nibble would represent the tightmost pixel of the leftmost dot. The next 3 nibbles represent the 3 pixels across the center of the dot 310 from the previous column, and the last nibble would be the leftmost pixel 317 of the rightmost dot (from the current column).
If the expected centroid is in the center of the pixel, we would expect a 20 bit pattern based on the following table:
Bit history Expected pixels I I I DDFDD
The pixels to the left and right of the center.dot are either 0 or D depending on whether the bit was a 0 or I
respectively. The center three pixels are either 000 or DFD depending on whether the bit was a 0 or I respectively_ These values are based on the physical area taken by a dot for a given pixel.
Depending on the distance of the centroid from the exact center of the pixel, we would expect data shifted slightly, which realiy only affects the pixels either side of the center pixel. Since there are 16 possibilities, it is possible to divide the distance from the center by 16 and use that amount to shift the expected pixels.
Once the 20 bit 5 pixel expected value has been determined it can be compared against the actual pixels read.
This can proceed by subtracting the expected pixels from the actual pixels read on a pixel by pixel basis, and finally adding the differences together to obtain a distance from the expected A
values.
Fig. 45 illustrates one form of implementation of the above algorithm which includes a look up table 320 which receives the bit history 322 and central fractional component 323 and outputs 324 the cotresponding 20 bit number which is subtracted 321 from the central pixel input 326 to produce a pixel difference 327.
This process is carried out for the expected centroid and once for a shift of the centroid left and right by I
amount in Acolumn. The centroid with the smallest difference from the actual pixels is considered to be the 'winner' and the Acolumn updated accordingly (which hopefully is 'no change'). As a result, a Acolumn cannot change by more than I each dot column.
The process is repeated for the vertical pixels, and Arow is consequentially updated.
There is a large amount of scope here for parallelism. Depending on the rate of the clock chosen for the ACP
unit 31 these units can be placed in series (and thus the testing of 3 different A could occur in consecutive clock cycles), or in parallel where all 3 can be tested simultaneously. If the clock rate is fast enough, there is less need for parallelism.
Bandwidth utilization It is necessary to read the old 0 of the As, and to write them out again. This takes 10% of the bandwidth:
2 * (76(3150/32) + 2*3150) = 27,648ns = 10% of bandwidth It is necessary to read the bit history for the given row as we update its As.
Each byte contains 2 row's bit histories, thus taking 2.596 of the bandwidth:
76((315012)/32) + 2*(3150J2) = 4,085ns = 2.5% of bandwidth In the worst case of pixel drift due to a 1% rotation, centroids will shift I
column every 57 pixel rows, but since a dot is 3 pixels in diameter, a given pixel colutnn will be valid for 171 pixel rows (3*57). As a byte contains 2 pixels, the number of bytes valid in cached reads will be a worst case of 86 (out of 128 read). The worst case timing for columns is therefore 31 % bandwidth_ 5*(((9450/(128 * 2)) * 320) * 128/86) = 88, 112ns = 3195 of bandwidth.
The total bandwidth required for the updating the centroid A is summarised in the following table:
Read/Write centroid A 10%
Read bit history 2S5To Read 5 columns of pixel data 31%
TOTAL 43.5%
Memorv usaQe for Phase 2:
The 2MB bit-image DRAM area is read from and written to during Phase 2 processing. The 2MB pixel-data DRAM area is read.
The 0.5MB scratch DRAM area is used for storing row data, namely:
Centroid array 24bits (16:8) * 2 * 3150 = 18,900 byes Bit History array 3 bits * 3150 entries (2 per byte) = 1575 bytes Phase 3 -Unscramble and XOR the raw data Returning to Fig. 37, the next step in decoding is to unscramble and XOR the raw data. The 2MB byte image, as taken from the Artcard, is in a scrambled XORed form. It must be unscrambled and re-XORed to retrieve the bit intage necessary for the Reed Solomon decoder in phase 4.
Tuming to Fig. 46, the unscrambling process 330 takes a 2MB scrambled byte image 331 and writes an unscrambled 2MB image 332. The process cannot reasonably be perfotmed in-place, so 2 sets of 2MB areas are utilised. The scrambled data 331 is in symbol block order arranged in a 16x16 array, with symbol block 0(334) having all the symbol 0's from all the code words in random order. Symbol block 1 has all the symbol 1's from all the code words in random order etc. Since there are only 255 symbols, the 256h symbol block is currentiy unused.
A linear feedback shift register is used to determine the relationship between the position within a symbol block eg. 334 and what code word eg. 355 it came from. This works as long as the same seed is used when generating the original Artcard images. The XOR of bytes from altemative source lines with OxAA and 0x55 respectively is effectively free (in time) since the bottleneck of time is waiting for the DRAM to be ready to read/write to non-sequential addresses.
The timing of the unscrambling XOR process is effectively 2MB of random byte-reads, and 2MB of random byte-writes i.e. 2 *(2MB * 76ns + 2MB * 2ns) = 327,155,712ns or approximately 0.33 seconds. This timing assumes no caching.
Phase 4- Reed Solomon decode This phase is a loop, iterating through copies of the data in the bit image, passing them to the Reed-Solomon decode module until either a successful decode is made or until there are no more copies to attempt decode from.
The Reed-Solomon decoder used can be the VLIW processor, suitably programmed or, alternatively, a separate hardwired core such as LSI Logic's L64712. 'Ile L64712 has a throughput of SOMbits per second (around 6.25MB per second), so the time may be bound by the speed of the Reed-Solomon decoder rather than the 2MB read and 1 MB write memory access time (500MB/sec for sequential accesses). The time taken in the worst case is thus 2/6.25s = approximately 0.32 seconds.
Phase 5 Running the Vark script The overall time taken to read the Artcard 9 and decode it is therefore approximately 2.15 seconds. The apparent delay to the user is actually only 0.65 seconds (the total of Phases 3 and 4), since the Artcard stops moving after 1.5 seconds.
Once the Artcard is loaded, the Artvark script must be interpreted, Rather than run the script immediateiy, the script is only run upon the pressing of the 'Print' button 13 (Fig. 1). The taken to mn the script will vary depending on the complexity of the script, and must be taken into account for the perceived delay between pressing the print button and the actual print button and the actual printing.
Alternative Artcard Fomat Of course, other artcard formats are possible. Tltere will now be described one such alternative artcard format with a number of preferable feature. Described hereinafter will be the alterttative Artcard data format, a mechanism for mapping user data onto dots on an alternative Artcard, and a fast alternative Artcard reading algorithm for use in embedded systems where resources are scarce.
Alternative Artcard Overview The Alternative Artcards can be used in both embedded and PC type applications, providing a user-friendly interface to large amounts of data or configuration information.
While the back side of an altemative Artcard has the same visual appearance regardless of the application (since it stores the data), the front of an atternative Artcard can be application dependent. It must make sense to the user in the context of the application.
Alternative Artcard technology can also be independent of the printing resolution. The notion of storing data as dots on a card simply means that if it is possible put more dots in the sante space (by increasing resolution), then tltose dots can represent more data The prefetTed etnbodiment assumes utilisation of 1600 dpi printing on a 86 mm x 55 mm card as the sample Artcard, but it is simple to determine alternative equivalent layouts and data sizes for other card sizes and/or other print resolutions. Regardless of the print resolution, the reading technique remain the same.
After all decoding and other overhead has been taken into account, alternative Artcards are capable of storing up to 1 Megabyte of data at print resolutions up to 1600 dpi. Altemative Artcards can store megabytes of data at print resolutions greater than 1600 dpi. The following two tables summarize the effective alt.ernative Artcard data storage capacity for certain print resolutions:
Format of an alternative Artcard The structure of data on the alternative Artcard is therefore specifically designed to aid the recovery of data_ This section describes the format of the data (back) side of an alternative Artcard.
Dots The dots on the data side of an alternative Artcard can be monochrome. For example, black dots printed on a white background at a predetermined desired print resolution. Consequently a "black dot" is physically different from a "white dot". Fig. 47 illustrates various examples of magnified views of black and white dots. The monochromatic scheme of black dots on a white background is preferably chosen to maximize dynamic range in blurry reading environments. Although the black dots are printed at a particular pitch (eg.
1600 dpi), the dots themselves are slightly larger in order to create continuous lines when dots are printed contiguously. In the example images of Fig. 47, the dots are not as merged as they may be in reality as a result of bleeding.
There would be more smoothing out of the black indentations. Although the alternative Artcard system described in the preferred embodiment allows for flexibly different dot sizes, exact dot sizes and ink/printing behaviour for a particular printing technology should be studied in more detail in order to obtain best results.
In describing this artcard embodiment, the term dot refers to a physical printed dot (ink, thermal, electro-photographic, silver-halide etc) on an alternative Artcard. When an alternative Artcard reader scans an alternative Artcard, the dots must be sampled at least double the printed resolution to satisfy Nyquist's Theorem The term pixel refers to a sample value from an alternative Artcard reader device. For example, when 1600 dpi dots are scanned at 4800 dpi there are 3 pixels in each dimension of a dot, or 9 pixels per dot.
The sampling process will be further explained hereinafter.
Turning to Fig. 48, there is shown the data surface 1101 a sample of alternative Artcard. Each alternative Artcard consists of an "active" region 1102 surrounded by a white border region 1103. The white border 1103 contains no data information, but can be used by an alternative Artcard reader to calibrate white levels. The active region is an array of data blocks eg. 1104, with each data block separated from the next by a gap of 8 white dots eg.
1106. Depending on the print resolution, the number of data blocks on an alternative Artcard will vary. On a 1600 dpi alternative Artcard, the array can be 8 x 8. Each data block 1104 has dimensions of 627 x 394 dots. With an inter-block gap 1106 of 8 white dots, the active area of an alternative Artcard is therefore 5072 x 3208 dots (8.lnun x S.lmm at 1600 dpi).
Data blocks Turning now to Fig. 49, there is shown a single data block 1107. The active region of an alternative Artcard consists of an array of identically structured data blocks 1107. Each of the data blocks has the following structure: a data region 1108 sutrounded by clock-marks 1109, borders 11 10, and targets 1 I 11. The data region holds the encoded data proper, while the clock-marks, borders and targets are present specifically to help locate the data region and ensure accurate recovery of data from within the region.
Each data block 1107 has dimensions of 627 x 394 dots. Of this, the central area of 595 x 384 dots is the data region 1108. The surrounding dots are used to hold the clock-marks, borders, and targets.
Borders and Clockmarks Fig. 50 illustrates a data block with Fig. 51 and Fig. 52 illustrating magnified edge portions thereof. As illustrated in Fig. 51 and Fig. 52, there are two 5 dot high border and clockmark regions 1170, 1177 in each data block:
one above and one below the data region. For example, The top 5 dot high region consists of an outer black dot border line 1112 (which stretches the length of the data block), a white dot separator line 1113 (to ensure the border line is independent), and a 3 dot high set of clock marks 1114. The clock marks alternate between a white and black row, starting with a black clock mark at the 8th column from either end of the data block. There is no separation between clockmark dots and dots in the data region.
The clock marks are symmetric in that if the alternative Artcard is inserted rotated 180 degrees, the same relative border/clockmark regions will be encountered. The border 1112, 1113 is intended for use by an alternative Artcard reader to keep vertical tracking as data is read from the data region.
The clockmarks 1114 are intended to keep horizontal tracking as data is read from the data region. The separation between the border and clockmarks by a white line of dots is desirable as a result of blurring occurring during reading.
The border thus becomes a black line with white on either side, making for a good frequency response on reading. The clockmarks alternating between white and black have a similar result, except in the horizontal rather than the vertical dimension. Any aiternative Artcard reader must locate the clockmarks and border if it intends to use them for tracking.
The next section deals with targets, which are designed to point the way to the clockmarks, border and data.
Targets in the Target region As shown in Fig. 54, there are two 15-dot wide target regions 1116, 11 17 in each data block: one to the left and one to the right of the data region. The target regions are separated from the data region by a single column of dots used for orientation. The purpose of the Target Regions 1116, 1117 is to point the way to the clockmarks, border and data regions. Each Target Region contains 6 targets eg. 1 118 that are designed to be easy to find by an alternative Artcard reader. Turning now to Fig. 53 there is shown the structure of a single target 1120. Each target 1120 is a 15 x 15 dot black square with a center saructure 1121 and a run-length encoded target number 1122. The center structure 1121 is a simple white cross, and the target number component 1122 is simply two columns of white dots, each being 2 dots long for each part of the target number. Thus target number 1's target id 1 122 is 2 dots long, target number 2's target id 1122 is 4 dots wide etc.
As shown in Fig. 54, the targets are arranged so that they are rotation invariant with regards to card insertion.
This means that the left targets and right targets are the same, except rotated 180 degrees. In the left Target Region 1116, the targets are arranged such that targets 1 to 6 are located top to bottom respectively. In the right Target Region, the targets are arranged so that target numbers I to 6 are located bottom to top. The target number id is always in the half closest to the data region. The magnified view portions of Fig. 54 reveals clearly the how the right targets are simply the same as the left targets, except rotated 180 degrees.
As shown in Fig. 55, the targets 1124, 1125 are specifically placed within the Target Region with centers 55 dots apart. In addition, there is a distance of 55 dots from the center of target 1(1124) to the first clockmark dot 1126 in the upper clockmark region, and a distance of 55 dots from the center of the target to the first clockmark dot in the lower clocktnark region (not shown). The first black clockmark in both regions begins directly in line with the target center (the 8th dot position is the center of the 15 dot-wide target).
The simplified schematic illustrations of Fig. 55 illustrates the distances between target centers as well as the distance from Target 1(1124) to the first dot of the first black clockmark (1126) in the upper border/clockmark region.
Since there is a distance of 55 dots to the clockmarks from both the upper and lower targets, and both sides of the altemative Artcard are sytnmetrical (rotated through 180 degrees), the card can be read left-to-right or right-to-left.
Regardless of reading direction, the orientation does need to be determined in order to extract the data from the data region.
Orientation colonuis As illustrated in Fig. 56, there are two 1 dot wide Orientation Columns 1127, 1128 in each data block: one directly to the left and one directly to the right of the data region. The Orientation Columns are present to give orientation infonnation to an alternative Artcard reader: On the left side of the data region (to the right of the Left Targets) is a single column of white dots 1127. On the right side of the data region (to the left of the Right Targets) is a single column of black dots 1128. Since the targets are rotation invariant, these two columns of dots allow an alternative Artcard reader to determine the orientation of the alternative Artcard - has the card been inserted the right way, or back to front. From the alternative Artcard reader's point of view, assuming no degradation to the dots, there are two possibilities:
* If the column of dots to the left of the data region is white, and the column to the right of the data region is black, then the reader will know that the card has been inserted the same way as it was written.
* If the column of dots to the left of the data region is black, and the column to the right of the data region is white, then the reader will know that the card has been inserted backwards, and the data region is appropriately rotated. The reader must take appropriate action to correctly recover the information from the alternative Artcard.
Data Region As shown in Fig. 57, the data region of a data block consists of 595 columns of 384 dots each, for a total of 228,480 dots_ These dots must be interpreted and decoded to yield the original data. Each dot represents a single bit, so the 228,480 dots represent 228,480 bits, or 28,560 bytes. The interpretation of each dot can be as follows:
Black White 0 The actual interpretation of the bits derived from the dots, however, requires understanding of the mapping from the original data to the dots in the data regions of the alternative Artcard_ Mapping original data to data region dots There will now be described the process of taking an original data file of maximum size 910,082 bytes and mapping it to the dots in the data regions of the 64 data blocks on a 1600 dpi alternative Artcatd. An alternative Artcard reader would reverse the process in order to extract the original data from the dots on an alternative Artcard.
At first glance it seems trivial to map data onto dots: binary data is comprised of Is and Os, so it would be possible to simply write black and white dots onto the card. This scheme however, does not allow for the fact that ink can fade, parts of a card may be damaged with dirt, grime, or even scratches. Without error-detection encoding, there is no way to detect if the data retrieved from the card is correct. And without redundancy encoding, there is no way to correct the detected errors. The aim of the mapping process then, is to make the data recovery highly robust, and also give the alternative Artcard reader the ability to know it read the data cotrectly.
There are [hree basic steps involved in mapping an original data file to data region dots * Redundancy encode the original data * Shuffle the encoded data in a deterministic way to reduce the effect of localized alternative Artcard damage * Write out the shuffled, encoded data as dots to the data blocks on the alternative Artcard Each of these steps is examined in detail in the followine sections.
Redundancy encode using ReedSolomon encoding The mapping of data to altemative Artcard dots relies heavily on the method of redundancy encoding employed. Reed-Solomon encoding is preferably chosen for its ability to deal with burst errors and effectively detect and correct errors using a minimum of redundancy. Reed Solomon encoding is adequately discussed in the standard texts such as Wicker, S., and Bhargava, V., 1994, Reed-Solomon Codes and their Applications, IEEE Press.
Rorabaugh, C, 1996, Error Coding Cookbook, McGraw-Hill. Lyppens, H., 1997, Reed-Solomon Error Correction, Dr. Dobb's Journai, January 1997 (Volume 22, Issue 1).
A variety of different parameters for Reed-Solomon encoding can be used, including different symbol sizes and different levels of redundancy. Preferably, the following encoding parameters are used:
* m=8 s t=64 Having m=8 means that the symbol size is 8 bits (I byte). It also means that each Reed-Solomon encoded block size n is 255 bytes (28 - I symbols). In order to allow correction of up to t symbols, 2t symbols in the final block size must be taken up with redundancy symbols. Having t=64 means that 64 bytes (symbols) can be corrected per block if they are in error. Each 255 byte block therefore has 128 (2 x 64) redundancy bytes, and the remaining 127 bytes (k=127) are used to hold original data. Thus:
* n=255 * k=127 The practical result is that 127 bytes of original data are encoded to become a 255-byte block of Reed-Solomon encoded data. The encoded 255-byte blocks are stored on the alternative Artcard and later decoded back to the original 127 bytes again by the alternative Artcard reader. The 384 dots in a single column of a data block's data region can hold 48 bytes (384/8). 595 of these columns can hold 28,560 bytes.
This amounts to 112 Reed-Solomon blocks (each block having 255 bytes). The 64 data blocks of a complete alternative Artcard can hold a total of 7168 Reed-Solomon blocks (1,827,840 bytes, at 255 bytes per Reed-Solomon block).
Two of the 7,168 Reed-Solomon blocks are reserved for control infomtation, but the remaining 7166 are used to store data. Since each Reed-Solomon block holds 127 bytes of actual data, the total amount of data that can be stored on an altemative Artcard is 910,082 bytes (7166 x 127). If the original data is less than this amount, the data can be encoded to fit an exact number of Reed-Solomon blocks, and then the encoded blocks can be replicated until all 7,166 are used. Fig. 58 illustrates the overall form of encoding utilised.
Each of the 2 Control blocks 1132, 1133 contain the sanie encoded information required for decoding the remaining 7,166 Reed-Solomon blocks:
The number of Reed-Solomon blocks in a full n-tessage (16 bits stored lo/hi), and The number of data bytes in the last Reed-Solomon block of the message (8 bits) These two numbers are repeated 32 tintes (consutning. 96 bytes) with the remaining 31 bytes reserved and set to 0. Each control block is then Reed-Solomon encoded, tuming the 127 bytes of control information into 255 bytes of Reed-Solomon encoded data.
The Conttnl Block is stored twice to give greater chance of it surviving. In addition, the repetition of the data within the Control Block has particular significance when using Reed-Solomon encoding. In an uncorrupted Reed-Solomon encoded block, the first 127 bytes of data are exactly the original data, and can be looked at in an attempt to recover the original message if the Control Block fails decoding (niore than 64 symbols are cotrupted). Thus, if a Control Block fails decoding, it is possible to examine sets of 3 bytes in an effort to determine the most likely vaiues for the 2 decoding parameters. It is not guaranteed to be recoverable, but it has a better chance through redundancy.
Say the last 159 bytes of the Control Block are destroyed, and the first 96 bytes are perfectly ok. Looking at the first 96 bytes will show a repeating set of numbers. These numbers can be sensibly used to decode the remainder of the message in the remaining 7,166 Reed-Solomon blocks.
By way of example, assume a data file containing exactly 9,967 bytes of data.
The number of Reed-Solomon blocks trquired is 79. The first 78 Reed-Solomon blocks are completely utilized, consunting 9,906 bytes (78 x 127).
The 79th block has only 61 bytes of data (with the remaining 66 bytes all Os).
The alternative Artcard would consist of 7,168 Reed-Solomon blocks. The first 2 blocks would be Control Blocks, the next 79 would be the encoded data, the next 79 would be a duplicate of the encoded data, the next 79 would be another duplicate of the encoded data, and so on. After storing the 79 Reed-Solomon blocks 90 times, the remaining 56 Reed-Solomon blocks would be another duplicate of the first 56 blocks from the 79 blocks of encoded data (the final 23 blocks of encoded data would not be stored again as there is not enough room on the alternative Artcard). A hex representation of the 127 bytes in each Control Block data before being Reed-Solomon encoded would be as illustrated in Fig. 59.
Scramble the Encoded Data Assuming all the encoded blocks have been stored contiguously in memory, a maximum 1,827,840 bytes of data can be stored on the alternative Artcard (2 Control Blocks and 7,166 inforntation blocks, totalling 7,168 Reed-Solomon encoded blocks). Preferably, the data is not directly stored onto the alternative Artcard at this stage however, or all 255 bytes of one Reed-Solomon block will be physically together on the card. Any dirt, grime, or stain that causes physical damage to the card has the potential of damaging more than 64 bytes in a single Reed-Solomon block, which would make that block unrecoverable. If there are no duplicates of that Reed-Solomon block, then the entire altetnative Artcard cannot be decoded.
The solution is to take advantage of the fact that there are a large number of bytes on the alternative Artcard, and that the alternative Artcard has a reasonable physical size. The data can therefore be scrambled to ensure that symbols from a single Reed-Solomon block are not in close proximity to one another. Of course pathological cases of card degradation can cause Reed-Solomon blocks to be unrecoverable, but on average, the scrambiing of data makes the card much more robust. The scrambling scheme chosen is simple and is illustrated schematically in Fig 14. All the Byte Os from each Reed-Solomon block are placed together 1136, then all the Byte Is etc. There will therefore be 7,168 byte 0's, then 7,168 Byte 1's etc. Each data block on the alternative Artcard can store 28,560 bytes.
Consequently there are approximately 4 bytes from each Reed-Solomon block in each of the 64 data blocks on the alternative Artcard.
Under this scrambling scheme, complete damage to 16 entire data blocks on the alternative Artcard will result in 64 symbol errors per Reed-Solomon block. This tneans that if there is no other damage to the altetnative Artcard, the entire data is completely recoverable, even if there is no data duplication.
Write the scrambled encoded data to the alternative Artcard Once the original data has been Reed-Solomon encoded, duplicated, and scrambled, there are 1,827,840 bytes of data to be stored on the alternative Arteard. Each of the 64 data blocks on the alternative Artcard stores 28,560 bytes.
The data is simply written out to the alternative Artcard data blocks so that the first data block contains the first 28,560 bytes of the scrambled data, the second data block contains the next 28,560 bytes etc.
As illustrated in Fig. 61, within a data block, the data is written out column-wise left to right.'Chus the left-most column within a data block contains the first 48 bytes of the 28,560 bytes of scrambled data, and the last column contains the last 48 bytes of the 28,560 bytes of scrambled data. Within a column, bytes are written out top to bottom, one bit at a time, starting from bit 7 and finishing with bit 0. If the bit is set (1), a black dot is placed on the alternative Artcar+d, if the bit is clear (0), no dot is placed, leaving it the white background color of the card.
For example, a set of 1,827,840 bytes of data can be created by scrambling 7,168 Reed-Solomon encoded blocks to be stored onto an altetnative Artcard. The first 28,560 bytes of data are written to the first data block The first 48 bytes of the first 28,560 bytes are written to the fust column of the data block, the next 48 bytes to the next coltnnn and so on. Suppose the first two bytes of the 28,560 bytes are hex D3 5F. Those first two bytes will be stored in column 0 of the data block. Bit 7 of byte 0 will be stored first, then bit 6 and so on. Then Bit 7 of byte I will be stored through to bit 0 of byte 1. Since each "I" is stored as a black dot, and each "0" as a white dot, these two bytes will be represented on the altemative Artcard as the following set of dots:
* D3 (I 101 0011) becomes: black, black, white, black, white, white, black, black * 5F (0101 1111) becomes: white, black, white, black, black, black, black, black Decoding an alternative Artcard This section deals with extracting the original data from an alternative Artcard in an accurate and robust manner. Specifically, it assumes the alternative Artcard format as described in the previous chapter, and describes a tttetltod of extracting the original pre-encoded data from the alternative Artcard.
There are a number of general considerations that are part of the assumptions for decoding an alternative Artcard.
User The purpose of an alternative Artcard is to store data for use in different applications. A user inserts an altemative Artcard into an altetnative Artcard reader, and expects the data to be loaded in a "reasonable time". From the user's perspective, a motor transport moves the alternative Artcard into an alternative Artcard reader. This is not perceived as a problematic delay, since the alternative Artcard is in motion.
Any time after the alternative Artcard has stopped is perceived as a delay, and should be minimized in any alternative Artcard reading scheme. Ideally, the entire altemative Aruxrd would be read while in motion, and thus there would be no perceived delay after the card had stopped moving.
For the purpose of the preferred embodiment, a reasonable time for an alternative Artcard to be physically loaded is defined to be 1.5 seconds. There should be a minimization of time for additional decoding after the alternative Artcatd has stopped moving. Since the Active region of an alternative Artcard covers most of the altetnative Artcard surface we can limit our timing concerns to that region.
Sampling Dots The dots on an altemative Artcard must be sampled by a CCD reader or the like at least at double the printed resolution to satisfy Nyquist's Theorem. In practice it is better to sample at a higher rate than this. In the altetnative Artcard reader environment, dots are preferably sampled at 3 times their printed resolution in each dimension, requiring 9 pixels to define a single dot. If the resolution of the alternative Artcard dots is 1600 dpi, the alternative Artcard reader's image sensor must scan pixels at 4800 dpi. Of course if a dot is not exactly aligned with the sampling sensor, the worst and most likely case as illustrated in Fig. 62, is that a dot will be sensed over a 4x4 pixel area.
Each sampled pixel is I byte (8 bits). The lowest 2 bits of each pixel can contain significant noise. Decoding algorithms must therefore be noise tolerant.
Alignment/Rotation It is extremely unlikely that a user will insert an alternative Artcard into an alternative Artcard reader perfectly aligned with no rotation. Certain physical constraints at a reader entrance and motor aransport grips will help ensure that once inserted, an altemative Artcard will stay at the original angle of insertion relative to the CCD. Preferably this angle of rotation, as illustrated in Fig. 63 is a maximum of I degree. There can be some slight aberrations in angle due to jitter and motor rumble during the teading process, but these are assumed to essentially stay within the I-degree limit.
The physical dimensions of an alternative Artcard are 86mm x 55mm. A I degree rotation adds 1.5mm to the effective height of the card as 86mm passes under the CCD (86 sin 1 ), which will affect the required CCD length.
The effect of a I degree rotation on alternative Artcard reading is that a single scanline from the CCD will include a number of different columns of dots from the alternative Artcard.
This is illustrated in an exaggerated form in Fig. 63 which shows the drift of dots across the columns of pixels. Although exaggerated in this diagram, the actual drift will be a maximum 1 pixel column shift every 57 pixels.
When an altemative Artcard is not rotated, a single column of dots can be read over 3 pixel scanlines. The more an alternative Artcard is rotated, the greater the local effect. The more dots being read, the longer the rotation effect is applied. As either of these factors increase, the larger the number of pixel scanlines that are needed to be read to yield a given set of dots from a single column on an alternative Artcard.
The following table shows how many pixel scanlines are required for a single column of dots in a particular alternative Artcard structure.
Region Height 0 rotation 1 rotation Active region 3208 dots 3 pixel columns 168 pixel columns Data block 394 dots 3 pixel columns 21 pixel columns To read an entire alternative Artcard, we need to read 87 mm (86mm + Imm due to 1 rotation). At 4800 dpi this implies 16,252 pixel columns.
CCD (or other I.inear Image Sensor) Length The length of the CCD itself must accommodate:
the physical height of the alternative Artcard (55 mm), vertical slop on physical alternative Artcard insertion (lmm) insertion rotation of up to I degree (86 sin 1 = 1.5mm) These factors combine to form a total length of 57Smm.
When the alternative Artcard Image sensor CCD in an alternative Artcard reader scans at 4800 dpi, a single scanline is 10,866 pixels. For simplicity, this figure has been rounded up to 11,000 pixels. The Active Region of an alternative Artcard has a height of 3208 dots, which implies 9,624 pixels. A
Data Region has a height of 384 dots, which implies 1,152 pixels.
DRAM Size The amount of inemory tequined for alternative Artcard reading and decoding is ideally minimized. The typical placement of an altemative Artcand reader is an embedded system where memory resources are precious. This is made more problematic by the effects of rotation. As described above, the more an alternative Artcard is rotated, the more scanlines are requited to effectively tecover original dots.
There is a trade-off between algorithmic complexity, user perceived delays, robustness, and memory usage.
One of the sitnplest reader algorithms would be to simply scan the whole alternative Artcard, and then to process the whole data without real-time constraints. Not only would this require huge reserves of inemory, it would take longer than a reader algorithm that occurred concurrently with the alternative Artcard reading process.
The actual amount of memory required for reading and decoding an alternative Artcard is twice the amount of space required to hold the encoded data, together with a small amount of scratch space (1-2 KB). For the 1600 dpi alternative Artcard, this implies a 4 MB memory requirement. The actual usage of the memory is detailed in the following algorithm description.
Transfer rate DRAM bandwidth assumptions need to be made for timing considerations and to a certain extent affect algorithmic design, especially since alternative Artcard readers are typically part of an embedded system.
A standard Rambus Direct RDRAM architectute is assumed, as defined in Rambus Ine, Oct 1997, Direct Rambus Technolog), Disclosure, with a peak data transfer rate of 1.6GB/sec.
Assuming 75% efficiency (easily achieved), we have an average of 1.2GB/sec data transfer rate. The average tinte to access a block of 16 bytes is therefore 12ns.
Dirty Data Physically damaged alternative Artcards can be inserted into a reader.
Altennative Artcards tnay be scratched, or be stained with grime or dirt. A altettative Artcard reader can't assume to read everything perfeetly. The effect of dirty data is made worse by blurring, as the dirty data affects the surrounding clean dots.
Blurry Environment Tltere are two ways that blurring is inttodttced into the alternative Artcard reading environment:
* Natural blurring due to natttre of the CCD's distance from the alternative Artcard.
* Warping of alternative Artcand Natural blurring of an alternative Artcard image occurs when there is overlap of sensed data from the CCD.
Blutring can be useful, as the overlap ensures there are no high frequencies in the sensed data, and that there is no data missed by the CCD. However if the area covered by a CCD pixel is too latge, theie will be too much blurring and the sampling required to recover the data will not be tnet. Fig. 64 is a schematic illustration of the overlapping of sensed data.
Another fomt of blutring occurs when an alternative Artcard is slightly warped due to heat damage. When the watping is in the vertical dimension, the distance between the altetnative Artcard and the CCD will not be constant, and the level of blutring will vary across those areas.
Black and white dots were chosen for alternative Artcards to give the best dynanric range in blurry reading environments. Blurring can cause problems in attempting to detenmine whether a given dot is black or white.
As the blurring increases, the more a given dot is influenced by the surrounding dots. Consequently the dynamic range for a particular dot decreases. Consider a white dot and a black dot, each surrounded by all possible sets of dots. The 9 dots are blurred, and the center dot sampled. Fig. 65 shows the distribution of resultant center dot values for black and white dots.
The diagram is intended to be a representative blurring. The curve 1140 from 0 to around 180 shows the range of black dots. The curve 1141 from 75 to 250 shows the range of white dots.
However the greater the blurring, the more the two curves shift towards the center of the range and therefore the greater the intersection area, which nteans the more difficult it is to determine whether a given dot is black or white. A
pixel value at the center point of intersection is ambiguous - the dot is equally likely to be a black or a white.
As the blurring increases, the likelihood of a read bit error increases.
Fortunately, the Reed-Solomon decoding algorithm can cope with these gracefully up to t symbol errors. Fig. 65 is a graph of number predicted number of alternative Artcard Reed-Solomon blocks that cannot be recovered given a particular symbol error rate. Notice how the Reed-Solomon decoding scheme perfornu well and then substantially degrades. If there is no Reed-Solomon block duplication, then only 1 block needs to be in error for the data to be unrecoverable. Of course, with block duplication the chance of an alt.ernative Artcard decoding increases.
Fig. 66 only illustrates the symbol (byte) errors corresponding to the number of Reed-Solomon blocks in error. There is a trade-off between the amount of blurring that can be coped with, compared to the amount of damage that has been done to a card. Since all etror detection and correction is perfomied by a Reed-Solomon decoder, there is a finite number of errors per Reed-Solomon data block that can be coped with.
The more errors introduced through blutring, the fewer the number of etrors that can be coped with due to altemative Artcard damage.
Overview of alternative Artcard Decoding As noted previously, when the user inserts an alternative Artcard into an alternative Artcard reading unit, a motor transport ideally carries the alternative Artcard past a monochrome linear CCD image sensor. The card is sampled in each dimension at three times the printed resolution. Alternative Artcard reading hardware and software compensate for rotation up to 1 degree, jitter and vibration due to the motor transport, and blurring due to variations in alternative Artcard to CCD distance. A digital bit image of the data is extracted from the sampled image by a complex motltod described here. Reed-Solomon decoding corrects arbitrariiy distributed data corruption of up to 25% of the raw data on the alternative Artcard. Approximately 1 MB of corrected data is extracted from a 1600 dpi card.
The steps involved in decoding are so as indicated in Fig. 67.
= The decoding process requires the following steps:
* Scan 1144 the alternative Artcard at three times printed resolution (eg scan 1600 dpi alternative Artcard at 4800 dpi) * Extract 1145 the data bitmap from the scanned dots on the card.
* Reverse 1146 the bitmap if the alternative Artcard was inserted backwards.
* Unscramble 1147 the encoded data * Reed-Solomon 1148 decode the data from the bitmap Algorithmic Overview Phase 1- Real time bit itnage extraction A simple comparison between the available memory (4 MB) and the memory required to hold all the scanned pixels for a 1600 dpi alternative Artcatd (172.5 MB) shows that unless the card is read multiple titnes (not a realistic option), the extraction of the bitmap from the pixel data must be done on the fly, in real time, while the altemative Arocurl is moving past the CCD. Two tasks must be accomplished in this phase:
* Scan the alternative Artcard at 4800 dpi * Extract the data bitrnap from the scanned dots on the card The rotation and unscrambling of the bit image cannot occur until the whoie bit image has been extracted. It is therefore necessary to assign a memory region to hold the extracted bit image. The bit image fits easily within 2MB, leaving 2MB for use in the extraction process.
Rather than extracting the bit image while looking only at the current scanline of pixels from the CCD, it is possible to allocate a buffer to act as a window onto the alternative Artcard, storing the last N scanlines read. Memory requirements do not allow the entire altetnative Artcard to be stored this way (172.5MB would be required), but allocating 2MB to store 190 pixel columns (each scanline takes less than 11,000 bytes) makes the bit image extraction process simpler.
The 4MB memory is therefore used as follows:
* 2 MB for the extracted bit innage * -2 MB for the scanned pixels * 1.5 KB for Phase 1 scxatch data (as required by algorithm) The time taken for Phase I is 1.5 seconds, since this is the time taken for the alternative Artcard to travel past the CCD and physically load.
Phase 2- Data extraction from bit image Once the bit image has been extracted, it must be unscrambled and potentially rotated 180 . It must then be decoded. Phase 2 has no real-time requiretnents, in that the alternative Artcard has stopped moving, and we are only concerned with the user's perception of elapsed time. Phase 2 therefore involves the remaining tasks of decoding an alternative Artc:atd:
= Re-organize the bit image, reversing it if the alternative Artcard was inserted backwards * Unscramble the encoded data * Reed-Solomon decade the data trom the bit image The input to Phase 2 is the 2MB bit image buffer. Unscrambling and rotating cannot be performed in situ, so a second 2MB buffer is required. Tlte 2MB buffer used to hold scanned pixels in Phase I is no longer required and can be used to store the rotated unscrambled data.
The Reed-Solomon decoding task takes the unscrambled bit image and decodes it to 910,082 bytes. The decoding can be performed in situ, or to a specified location elsewhere. The decoding process does not require any additional memory buffers.
The 4MB metnory is therefore used as follows:
' 2 MB for the extracted bit image (from Phase 1) ' -2 MB for the unscrambled, potentially rotated bit image ~ < 1 KB for Phase 2 scratch data (as required by algorithm) The time taken for Phase 2 is hardware dependent and is bound by the time taken for Reed-Solomon decoding. Using a dedicated core such as LSI Logic's L64712, or an equivalent CPU/DSP combination, it is estimated that Phase 2 would take 032 seconds.
Phase 1- Extract Bit Image This is the real-time phase of the algorithm, and is concerned with extracting the bit image from the altetnative Artcard as scanned by the CCD.
As shown in Fig. 68 Phase I can be divided into 2 asynchronous process streams. The first of these streams is simply the real-time reader of alternative Artcard pixels from the CCD, writing the pixels to DRAM_ The second stream involves looking at the pixels, and extracting the bits_ The second process stream is itself divided into 2 processes. The first process is a global process, concerned with locating the start of the alternative Artcard. The second process is the bit image extraction proper.
Fig. 69 illustrates the data flow from a data/process perspective.
Timing For an entire 1600 dpi alternative Artcard, it is necessary to read a maximum of 16,252 pixel-colunuts. Given a total time of 1.5 seconds for the whole alternative Artcard, this implies a maximum time of 92,296ns per pixel column during the course of the various processes.
Process 1- Read pixels from CCD
The CCD scans the alternative Artcard at 4800 dpi, and generates 11,000 1-byte pixel samples per column.
This process simply takes the data from the CCD and writes it to DRAM, completely independently of any other process that is reading the pixel data from DRAM. Fig. 70 illustrates the steps involved.
The pixels are written contiguously to a 2MB buffer that can hold 190 full columns of pixels. The buffer always holds the 190 columns most recently read. Consequently, any process that wants to read the pixel data (such as Processes 2 and 3) must firstly know where to look for a given colurnn, and secondly, be fast enough to ensure that the data required is actually in the buffer.
Process 1 makes the current scanline number (CutrentScanl.ine) available to other processes so they can ensure they are not attempting to access pixels from scanlines that have not been read yet The time taken to write out a single column of data (11,000 bytes) to DRAM is:
11,000/16 * 12 = 8,256ns Process I therefore uses just under 9% of the available DRAM bandwidth (8256/92296).
Process 2- Detect start of alternative Artcard This process is concemed with locating the Active Area on a scanned alternative Artcard. The input to this stage is the pixel data from DRAM (placed there by Process 1). The output is a set of bounds for the first 8 data blocks on the altemative Artcard, required as input to Process 3. A high level overview of the process can be seen in Fig. 71.
An alternative Artcard can have vertical slop of lmttt upon insertion. With a rotation of I degree there is further vertical slop of 1 Smm (86 sin 1 ). Consequently there is a total vertical slop of 2.5mm. At 1600dpi, this equates to a slop of approximately 160 dots. Since a single data block is only 394 dots high, the slop is just under half a data block. To get a better estimate of where the data blocks are located the alternative Artcard itself needs to be detected.
Process 2 therefore consists of two parts:
' Locate the start of the alternative Artcard, and if found, ' Calculate the bounds of the first 8 data blocks based on the siart of the alternative Artcard.
Locate the Start of the alternative Artcard The scanned pixels outside the alternative Artcard area are black (the surface can be black plastic or sotne other non-reflective surface). The border of the alternative Artcard area is white. If we process the pixel columns one by one, and filter the pixels to either black or white, the transition point from black to white will mark the start of the altereative Artcard. The highest level process is as follows:
for (Column=0; Column < MAX COLUMN; Column++) {
Pixel = ProcessColutnn(Column) if (Pixel) return (Pixel, Column) success!
return failure // no alternative Artcard found The ProcessColumn function is simple. Pixels from two areas of the scanned column are passed through a threshold filter to determine if they are black or white. It is possible to then wait for a certain number of white pixels and announce the start of the alternative Artcard once the given number has been detected. The logic of processing a pixel column is shown in the following pseudocode. 0 is retumed if the alternative Artcard has not been detected during the column. Otherwise the pixel number of the detected location is returned.
// Try upper region first count=0 for (i=O; i<UPPER REGIOIV BOUND; i++) {
if (GetPixel(column, i) <'IHRF.SHOLD) {
count = 0 U pixel is black }
else count++ U pixel is white if (count > WHTIE ALTERNATIVE ARTCARD) return i // Try lower region next. Process pixels in reverse count = 0 for (i=MAX_PIXEL_BOUND; i>LOWER_REGION_BOUND; i-) {
if (GetPixel(column, i) <THRESHOLD) {
count = 0 pixel is black }
else {
count++ // pixel is white if (count > WHTTE_ALTERNATIVE ARTCARD) return i }
//Not in upper bound or in lower bound. Return failure return 0 Calculate Data Block Bounds At this stage, the alternative Artcard has been detected. Depending on the rotation of the alternative Artcard, either the top of the alternative Artcard has been detected or the lower part of the alternative Artcard has been detected.
The second step of Process 2 determines which was detected and sets the data block bounds for Phase 3 appropriately.
A look at Phase 3 reveals that it works on data block segment bounds: each data block has a StartPixel and an EndPixel to determine where to look for targets in order to locate the data block's data region.
If the pixel value is in the upper half of the card, it is possible to simply use that as the first StartPixel bounds.
If the pixel value is in the lower half of the card, it is possible to tnove back so that the pixel value is the last segment's EndPixel bounds. We step forwards or backwards by the atternative Artcard data size, and thus set up each segtttent with appropriate bounds. We are now ready to begin extracting data from the alternative Artcard.
// Adjust to become first pixel if is lower pixel if (pixel > LOWER_REGION BOUND) {
pixel -= 6 * 1152 if (pixel <0) pixel = 0 }
for (i=O; i<6; i++) {
endPixel = pixel + 1152 segment[i].MaxPixel= MAX PIXEI._BOLJND
segment(il.SetBounds(pixel, endPixel) pixel = endPixel The MaxPixel value is defined in Process 3, and the SetBounds function simply sets StartPixel and EndPixel clipping with respect to 0 and MaxPixel.
Process 3- Extract bit data from pixels This is the heart of the altetnative Artcard Reader algorithm. This process is concerned with extracting the bit data from the CCD pixel data. The process essentially creates a bit-image from the pixel data, based on scratch information created by Process 2, and maintained by Process 3. A high level overview of the process can be seen in Fig. 72.
Rather than simply read an alternative Artcard's pixel column and detemvne what pixels belong to what data block, Process 3 works the other way around. It knows where to look for the pixels of a given data block. It does this by dividing a logical altemative Artcard into 8 segments, each containing 8 data blocks as shown in Fig. 73.
The segments as shown match the logical alternative Ancard. Physically, the alternative Artcard is likely to be rotated by some amount. The segments remain locked to the logical altemative Artcard structure, and hence are rotation-independent. A given segment can have one of two states:
* LookingForTargets: where the exact data block position for this segment has not yet been determined. Targets are being located by scanning pixel column data in the bounds indicated by the segment bounds.
Once the data block has been located via the targets, and bounds set for black & white, the state changes to ExtractingBitlmage.
* ExtractingBitlmage: where the data block has been accurately located, and bit data is being extracted one dot column at a time and written to the alternative Artcard bit image. The following of data block clockmarks gives accurate dot recovery regardless of rotation, and thus the segment bounds are ignored. Once the entire data block has been extracted, new segment bounds are calculated for the next data block based on the current position. The state changes to LookingForTargers.
The process is complete when all 64 data blocks have been extracted, 8 from each region.
Each data block consists of 595 columns of data, each with 48 bytes.
Preferably, the 2 orientation columns for the data block are each extracted at 48 bytes each, giving a total of 28,656 bytes extracted per data block. For simplicity, it is possible to divide the 2MB of memory into 64 x 32k chunks.
The nth data block for a given segment is stored at the location:
StartBuffer + (256k * n) Data Structure for Segments Each of the 8 segments has an associated data structure. The data structure defining each segment is stored in the scratch data area. The structure can be as set out in the following table:
DataName Comment CurrentState Defines the cutrent state of the segment. Can be one of:
LookingForTargets F.xiractingBitJmage Initial value is LookingForTargets Used during LookingForTargets:
StartPixel Upper pixel bound of segment. Initially set by Process 2.
EndPixel Lower pixel bound of segment. Initially set by Process 2 MaxPixel The maximum pixel number for any scanline.
It is set to the same value for each segment: 10,866.
CurrentColumn Pixel column we're up to while looking for targets.
FinalColumn Defines the last pixel column to look in for targets.
LocatedTargets Points to a list of located Targets_ PossibleTargets Points to a set of pointers to Target structures that represent currently investigated pixel shapes that may be targets AvailableTargets Points to a set of pointers to Target structures that are currently unused.
TargetsFound The number of Targets found so far in this data block.
PossibleTargetCount The number of elements in the PossibleTargets list AvailabletargetCount The number of elements in the AvailableTargets list Used during ExtractingBitJmage:
BitImage The start of the Bit Image data area in DRAM where to store the next data block:
Segment 1= X, Segment 2 = X+32k etc Advances by 256k each time the state changes from ExtractingBitImageData to Looking ForTargets CurrentByte Offset within BitImage where to store next extracted byte CurrentDotColumn Holds current clockmarkJdot column number.
Set to -8 when transitioning from state LookingForTarget to ExtractingBitImage.
UpperClock Coordinate (column/pixel) of current upper clockmarkJborder LowerClock Coordinate (column/pixel) of current lower clockmark/border CurrentDot The center of the current data dot for the current dot column.
Initially set to the center of the first (topmost) dot of the data column.
DataDelta What to add (column/pixel) to CurrentDot to advance to the center of the next dot.
BlackMax Pixel value above which a dot is definitely white WhiteMin Pixel value below which a dot is definitely black MidRange The pixel value that has equal likelihood of coming from black or white.
When all smarts have not determined the dot, this value is used to determine it. Pixels below this value are black, and above it are white.
High Level of Process 3 Process 3 simply iterates through each of the segments, performing a single line of processing depending on the segment's current state. The pseudocode is straightforward:
blockCount = 0 while (blockCount < 64) for (i=0; i<8; i++) {
finishedBlock = segment[i].ProcessState() if (finishedBlock) blockCount++
Process 3 must be halted by an external controlling process if it has not terminated after a specified amount of time. This wiU only be the case if the data cannot be exttacted. A simple niechanism is to start a countdown after Process I has finished reading the altemative Artcard. If Process 3 has not finished by that time, the data from the altetnative Artcard cannot be recovered.
GtirraitState = LooldngForTargets Targets are detected by reading columns of pixels, one pixel-column at a time rather than by detecting dots within a given band of pixels (between StartPixel and EndPixel) eertain patterns of pixels are detected. The pixel columns are processed one at a time until either all the targets are found, or until a specified number of columns have been processed. At that time the targets can be processed and the data area located via clockmarks. The state is changed to ExtractingBitlmage to signify that the data is now to be extracted.
If enough valid targets are not located, then the data block is ignored, skipping to a column definitely within the missed data block, and then beginning again the process of looking for the targets in the next data block. This can be seen in the following pseudocode:
finishedBlock = FALSE
if(CurrentColumn < Processl.CurrentScanlrne) [
ProcessPixelColumn() CutrentColtunn++
if ((TargetsFound = 6) II (CurrentColumn > LastColumn)) {
if (TargetsFound >= 2) ProcessTargets() if (TargetsFound >= 2) {
BuildClockmarkEstimates() SetB lackAndWhiteBoundsQ
CurrentState = ExtractingBitImage CumentDotColutnn = -8 }
else {
// data block cannot be recovered. Look for // next instead. Must adjust pixel bounds to // take account of possible 1 degree rotation.
finishedBlock = TRUE
SetBounds(StartPixel-12, EndPixel+12) Bitlmage += 256KB
CurrentByte = 0 LastColumn += 1024 TargetsFound = 0 }
}
return finishedBlock ProcessPixelColumn Each pixel column is processed within the specified bounds (between StartPixel and EndPixel) to search for certain patterns of pixels which will identify the targets. The structure of a single target (target number 2) is as previously shown in Fig. 54:
From a pixel point of view, a target can be identified by:
Left black region, which is a number of pixel columns consisting of large numbers of contiguous black pixels to build up the first part of the target.
* Target center, which is a white region in the center of further black columns * Second black region, which is the 2 black dot columns after the targot center * Target number, which is a black-surrounded white region that defines the target number by its length * Third black region, which is the 2 black coiumns after the target number An overview of the required process is as shown in Fig. 74.
Since identification only relies on black or white pixels, the pixels 1150 from each column are passed through a filter 1151 to detect black or white, and then run length encoded 1152. The run-lengths are then passed to a state machine 1153 that has access to the last 3 run lengths and the 4th last color.
Based on these values, possible targets pass through each of the identification stages.
The GatherMin&Max process 1155 simply keeps the minimum & maximum pixel values encountered during the processing of the segment These are used once the targets have been located to set BlackMax, WhiteMin, and MidRange values.
Each segment keeps a set of target structutr,s in its search for targets.
While the target structures themselves don't move around in memory, several segment variables point to lists of pointers to these target structures. The three pointer lists are repeated here:
LocatedTargets Points to a set of Target structures that represent located targets.
PossibleTargets Points to a set of pointers to Target structures that represent currently investigated pixel shapes that may be targets.
AvailableTargets Points to a set of pointers to Target structures that are currently unused.
There are counters associated with each of these list pointers: TargetsFound, PossibleTargetCount, and AvailableTargetCount respectively.
Before the alternative Artcard is loaded, TargetsFound and PossibleTargetCount are set to 0, and AvailableTargetCount is set to 28 (the maximum number of target structures possible to have under investigation since the minimum size of a target border is 40 pixels, and the data area is approximately 1152 pixels). An example of the target pointer layout is as illustrated in Fig. 75.
As potential new targets are found, they are taken from the AvailableTargets list 1157, the target data structure is updated, and the pointer to the structure is added to the PossibleTargets tist 1158. When a target is completely verified, it is added to the LocatedTargets list 1159. If a possible target is found not to be a target after all, it is placed back onto the AvailableTargets list 1157. Consequently there are always 28 target pointers in circulation at any time, moving between the lists.
The Target data structure 1160 can have the following form:
DataName Comment CurrentState The current state of the target search DetectCount Counts how long a target has been in a given state StartPixel Where does the target start? All the lines of pixels in this target should start within a tolerance of this pixel value.
TargetNumber Which target number is this (according to what was read) Column Best estimate of the target's center column ordinate Pixel Best estimate of the target's center pixel ordinate The ProcessPixelColumn function within the find targets module 1162 (Fig. 74) then, goes through all the run lengths one by one, comparing the runs against existing possible targets (via StartPixel), or creating new possible targets if a potential target is found where none was previously known. In all cases, the comparison is only made if SO.color is white and Sl.oolor is black.
The pseudocode for the ProcessPixelColumn set out hereinafter. When the first target is positively identified, the last column to be checked for targets can be determined as being within a maximum distance from it. For 1 rotation, the maximum distance is 18 pixel cohmtmm pixel = StartPixel t=O
target=PossibleTarget[t]
while ((pixel < EndPixel) && (Targetsi'-ound < 6)) {
if ((SO.Color = white) && (S I.Color = black)) {
do {
keepTrying = FALSE
if ( (target != NULL) &&
(target >AddToTarget(Column, pixel, S 1, S2, S3)) ) {
if (target->CurrentState = IsATarget) {
Remove target from PossibleTargets List Add target to LocatedTargets List TargetcFound++
if (TargetsFound - I ) FinalColumn = Column + MAX TARGET DELTA }
}
else if (target->CurrentState = NotATarget) {
Remove target from PossibleTargets List Add target to AvailableTargets List keepTrying = TRUE
}
else {
t++ // advance to next target target = PossibleTarget[t]
else {
tmp = AvailableTargets{0]
if (tmp->AddToTarget(Column,pixel,S 1,S2,S3) Remove tmp from AvailableTargets list Add tmp to PossibleTargets list t++ target t has been shifted right }
} while (keepTrying) pixel += S i .RunLength Advance SO/S 1/S2/S3 }
AddToTarget is a function within the find targets module that determines whether it is possible or not to add the specific run to the given target:
* If the run is within the tolerance of target's starting position, the run is directly related to the current target, and can therefore be applied to it.
* If the run starts before the target, we assume that the existing target is still ok, but not relevant to the run. The target is therefore left unchanged, and a return value of FALSE tells the caller that the run was not applied.
The caller can subsequenfly check the run to see if it starts a whole new target of its own.
* If the run starts after the target, we assume the target is no longer a possible target. The state is changed to be NotATarget, and a return value of TRUE is returaed.
If the run is to be applied to the target, a specific action is performed based on the current state and set of runs in S1, S2, and S3. The AddToTarget pseudocode is as follows:
IvIAX_TARGET_DELTA = 1 if (CurentState != NothingKnown) if (pixel > StartPixel) run starts after target {
diff = pixel - StartPixel if (diff> MAX_TARGET DELTA) {
CurrentState = NotATarget return TRiJE
}
}
else {
diff = StartPixel - pixel if (diff > MAX_TARGET_DELTA) return FALSE
}
}
runType = DetemtineRunType(S1, S2, S3) EvaluateState(runType) StartPixel = currentPixel retum TRUE
Types of pixel runs are identified in DetermineRunType is as follows:
Types of Pixel Runs Type How identified (Sl is always black) TargetBorder S 1= 40 < RunLength < 50 S2 = white run TargetCenter S I = 15 < RunLength < 26 S2 = white run with [RunLength < 12]
S3 = black run with [ 15 < RunLength < 26]
TargetNumber S2 = white run with [RunLength <= 40]
The EvaluateState procedure takes action depending on the current state and the run type.
The actions are shown as follows in tabular form:
CurrentState Type of Pixel Run Action NothingKnown TargetBorder DetectCount = I
CurrentState = LeftOfCenter LeftOfCenter TargetBorder DetectCount++
if (DetectCount > 24) CurrentState = NotATarget TargetCenter DetectCount = 1 CurrentState = InCenter Column = currentColumn Pixel = currentPixel + S I.RunLength CurrentState = NotATarget InCenter TargetCenter DetectCount++
tmp = currentPixel + S 1.RunLength if (tmp < Pixel) Pixel = tmp if (DetectCount > 13) CurrentState = NotATarget TargetBorder DetectCount = 1 CurrentState = RightOfCenter CurrentState = NotATarget RightOfCenter TargetBorder DetectCount++
if (DetectCount >= 12) CurrentState = NotATarget TargetNumber DetectCount = I
CurrentState = InTargetNumber TargetNumber = (S2.RunLength+ 2)/6 CurrentState = NotATarget InTargetNumber TargetNumber tmp = (S2.RunLength+ 2)/6 if (tmp > TargetNumber) TargetNumber = tmp DetectCount++
if (DetectCount >= 12) CurrentState = NotATarget CurrentState Type of Pixel Run Action TargetBorder if (DetectCount >= 3) CurrentState = IsATarget else CurrentState = NotATarget CurrentState = NotATarget IsATarget or -NotATarget Processing Targets he located targets (in the LocatedTargets list) are stored in the order they were located. Depending on alternative Artcard rotation these targets will be in ascending pixel order or descending pixel order. In addition, the target numbets recovered from the targets may be in error. We may have also have recovered a false target. Before the clockmark estimates can be obtained, the targets need to be processed to ensure that invalid targets are discarded, and valid targets have target numbers fixed if in error (e.g. a damaged target number due to dirt). Two main steps are involved:
* Sort targets into ascending pixel order * Locate and fix erroneous target numbers The first step is simple. The nature of the target retrieval means that the data should already be sorted in either ascending pixel or descending pixel. A simple swap sort ensures that if the 6 targets are already sorted con-ectly a maximum of 14 comparisons is made with no swaps. If the data is not sorted, 14 comparisons are made, with 3 swaps_ The following pseudocode shows the sorting process:
for (i = 0; i <TargetsFound-1; i++) oldTarget = LocatedTargets[i]
bestPixel = oldTarget->Pixel best = i j=i+1 while (jlTargetsFound) if (LocatedTargets[j]-> Pixel < bestPixel) best = j j++
if (best != i) // move only if necessary LocatedTargets[i] = LocatedTargets[best]
L.ocatedTargets[best] = oldTarget }
Locating and fixing erroneous target numbers is only slightly more complex_ One by one, each of the N
targets found is assumed to be con=t. The other targets are compared to this "cotrect" target and the number of targets that require change should target N be correct is counted. If the number of changes is 0, then all the targets must afready be cotrect. Otherwise the target that requires the fewest changes to the others is used as the base for change. A
change is registered if a given target's target number and pixel position do not correlate when compared to the "correct" target's pixel position and target number. The change may mean updating a target's target number, or it may mean elimination of the target. It is possible to assume that ascending targets have pixels in ascending order (since they have already been sorted).
kPixelFactor = I1(55 * 3) bestTarget = 0 bestChanges = TargetsFound + 1 for (i-0; i< TotalTargetsFound; i++) {
numberOfChanges = 0;
fromPixel = (LocatedTargets[i])->Pixel fromTargetNumber = LocatedTargets[i].TargetNumber for (j=1; j< TotalTargetsFound; j++) {
toPixel = LocatedTargets[j)->Pixel deltaPixel = toPixel - fromPixel if (deltaPixel >= 0) deltaPixel += PIXELS_BE'IWEEN TARGET_CENTRESrl else deltaPixel -= PIXELS_BEIWEEN TARGET CENTRES/2 targetNtumber =deltaPixel * kPixelFactor targetNumber += fromTargetNumber if (targetNumber < I )A(targetNumber > 6) II
(targetNumber != L.ocatedTargets[j]-> TargetNumber) numbetOiChanges++
if (numberOfChanges < bestChanges) {
bestTarget = i bestChanges = numberOfChanges }
if (bestChanges < 2) break;
}
In most cases this function will terminate with bestChanges = 0, which means no changes are required.
Otherwise the changes need to be applied. The functionality of applying the changes is identical to counting the changes (in the pseudocode above) until the comparison with targetNumber. The change application is:
if ((targetNumber < I )II(targetNumber > TARGETS_PER_BLOCK)) {
LocatedTargets(j] = NULL
TargetsFound--}
else {
LocatedTargets(j]-> TargetNumber = targetNumber At the end of the change loop, the LocatedTargets list needs to be compacted and all NULL targets removed.
At the end of this procedure, there may be fewer targets. Whatever targets remain may now be used (at least 2 targets are required) to locate the clockmarks and the data region.
Building Clockmark Estimates from Targets As shown previously in Fig. 55, the upper region's first clockmark dot 1126 is 55 dots away from the center of the first target 1124 (which is the same as the distance between target centers). The center of the clockmark dots is a further 1 dot away, and the black border line 1123 is a further 4 dots away from the first clockmark dot. The lower region's fust clocktnark dot is exactly 7 targets-distance away (7 x 55 dots) from the upper region's first clockmark dot 1126.
It cannot be assumed that Targets 1 and 6 have been located, so it is necessary to use the upper-most and lower-most targets, and use the target numbers to determine which targets are being used. It is necessary at least 2 targets at this point. In addition, the target centers are only estimates of the actual target centers. It is to locate the target center more accurately. The center of a target is white, surrounded by black. We Iherefore want to find the local maximum in both pixel & column dimensions. This involves reconstructing the continuous image since the maximum is unlikely to be aligned exactly on an integer boundary (our estimate).
Before the continuous image can be constructed around the target's center, it is necessary to create a better estimate of the 2 target centers. The existing target centers actually are the top left coordinate of the bounding box of the target center. It is a simple process to go through each of the pixels for the atea defining the center of the target, and find the pixel with the highest value. There may be more than one pixel with the same maximum pixel value, but the estimate of the center value only requires one pixel.
The pseudocode is straightforward, and is performed for each of the 2 targets:
CENTER_WIDTH = CENTER_MGHT = 12 maxPixel = Ox00 for (i=O; i<CBN'IER_WIDTH; i++) for (j=0; j<CEN'IER_MGHT; j++) t -p = GetPixel(colunut+i, pixel+j) if (p > maxPixel) maxPixel = p centerColumn = column + i centerPixel = pixel + j }
Target.Column = centerColumn Target.Pixel = centerPixel At the end of this process the target center coordinates point to the whitest pixel of the target, which should be within one pixel of the actual center. The process of building a more accurate position for the target center involves reconstructing the continuous signal for 7 scanline slices of the target, 3 to either side of the estimated target center.
The 7 maximum values found (one for each of these pixel dimension slices) are then used to reconstruct a continuous signal in the column dimension and thus to locate the maximum value in that dimension.
Given estimates column and pixel, determine a 1/ betterColumn and betterPixel as the center of // the target for (y=O; y<7; y++) for (x=O; x<7; x++) samples[x] = GetPixel(column-3+y, pixel-3+x) FindMax(samples, pos, maxVal) reSamples[y] = maxVal if(y-3) betterPixel = pos + pixel }
FindMax(reSamples, pos, maxVal) betterColumn = pos + column FindMax is a function that reconstructs the original I dimensional signal based sample points and returns the position of the maximum as well as the maximum value found. The method of signal reconsttuction/resampling used is the Lanczos3 windowed sinc function as shown in Fig. 76.
The Lanczos3 windowed sinc function takes 7 (pixel) samples from the dimension being reconstructed, centered around the estimated position Y. i.e. at X-3, X-2, X-1, X, X+1, X+2, X+3. We reconstruct points from X-1 to X+1, each at an interval of 0.1, and determine which point is the maximum. The position that is the maximum value becomes the new center. Due to the nature of the kernel, only 6 entries are required in the convolution kernel for points between X and X+I. We use 6 points for X-1 to X, and 6 points for X to X+1, requiring 7 points overall in order to get pixel values from X-1 to X+1 since sonte of the pixels required are the same.
Given accurate estimates for the upper-most target from and lower-most target to, it is possible to calculate the position of the fust clockmark dot for the upper and lower regions as follows:
TARGETS_PER_BLOCK = 6 numTargetsDiff = to.TargetNum - from.TargetNum deltaPixel = (to.Pixel - from.Pixel) / numTargetsDiff deltaColumn = (to.Column - from.Column) / numTargetsDiff UpperClock.pixel = from.Pixel - (from.TargetNum*deltaPixel) UpperClock.column = from.Column-(from.TargetNum*deltaColumn) 1/ Given the first dot of the upper clockmark, the // first dot of the lower clockmark is straightforward.
LowetClock.pixel = UpperClock.pixel +
((TARGETS_PER_ BLOCK+I) * deltaPixel) LowetClock.column = UpperClock.column +
((TARGETS_PER- BLOCK+I) * deltaColumn) This gets us to the first clockmark doL It is necessary move the column position a further I dot away from the data area to reach the center of the clockmark. It is necessary to also move the pixel position a further 4 dots away to reach the center of the border line. The pseudocode values for deltaColumn and deltaPixel are based on a 55 dot distance (the distance between targets), so these deltas must be scaled by 1/55 and 4/55 tespectively before being applied to the clockmark coordinates. "I7 s is represented as:
kDeltaDotFactor = 1/DOTS_BETWF.EN TARGET CENTRES
deltaColumn *= kDeltaDotFactor deltaPixel *= 4 * kDeltaDotFactor UpperClock.pixel -= deltaPixel UpperClock.column -= deltaColumn LowerClock.pixel += deltaPixel LowerClock.column += deltaColumn UpperClock and Lov/erClock are now valid clockmark estimates for the first clockmarks directly in line with the centers of the targets.
Setting Black and White Pixel/Dot Ranges Before the data can be extracted from the data area, the pixel ranges for black and white dots needs to be ascertained. The n nimum and maximum pixels encountered during the search for targets were stored in WhiteMin and BlackMax respectively, but these do not represent valid values for these variables with respect to data extraction.
They are merely used for storage convenience. The following pseudocode shows the method of obtaining good values for WhiteMin and BlackMax based on the min & max pixels encountered:
MinPixel = WhiteMin MaxPixel = BlackMax MidRange = (MinPixel + MaxPixel) / 2 WhiteMin = MaxPixel - 105 BlackMax = MinPixel + 84 CurrentState = ExtractingBitlmage The F.xtractingBitlnwge state is one where the data block has already been accurately located via the targets, and bit data is currently being extracted one dot column at a time and written to the alternative Artcard bit image. The following of data block clockmarks/borders gives accurate dot recovery regardless of rotation, and thus the segment bounds are ignored. Once the entire data block has been extracted (597 columns of 48 bytes each; 595 columns of data + 2 orientation columns), new segment bounds are calculated for the next data block based on the current position. The state is changed to LookingForTargets.
Processing a given dot column involves two tasks:
* The first task is to locate the specific dot column of data via the clockmarks.
* The second task is to run down the dot column gathering the bit values, one bit per dot.
These two tasks can only be undertaken if the data for the column has been read off the alternative Artcard and ttansfetred to DRAM. This can be determined by checking what scanline Process I is up to, and comparing it to the clockmark columns. If the dot data is in DRAM we can update the clockmarks and then extract the data from the column before advancing the clockmarks to the estimated value for the next dot column. The process overview is given in the following pseudocode, with specific functions explained hereinafter:
finishedBlock = FALSE
if((UpperClock.column < Process 1.CurrentScani.ine) &&
(LowerClock_coiumn < Process I.CurrentScanLine)) DetermineAccurateClockMarks() DetermineDataInfo() if (CurrentDotColumn >= 0) ExtractDataFromColumnO
AdvanceClockMarks() if (CurrentDotCoiumn = FINAL-COLUMN) {
finishedBlock = TRUE
currentState = LookingForTargets SetBounds(UpperClock.pixel, LowerClock.pixel) BitItnage += 256KB
CurrentByte = 0 TargetsFound = 0 }
return finishedB lock Locating the dot colunw A given dot column needs to be located before the dots can be read and the data extracted. This is accomplished by following the clockmarks/borderline along the upper and lower boundaries of the data block. A
software equivalent of a phase-locked-loop is used to ensure that even if the clockmarks have been damaged, good estimations of clockmark positions will be made. Fig. 77 illustrates an example data block's top left which corner reveals that there are clockmarks 3 dots high 1166 extending out to the target area, a white row, and then a black border line.
Initially, an estimation of the center of the first black clockmark position is provided (based on the target positions). We use the black border 1168 to achieve an accurate vertical position (pixel), and the clockmark eg. 1166 to get an accurate horizontal position (column). These are reflected in the UpperClock and LowerClock positions.
The clockmark estimate is taken and by looking at the pixel data in its vicinity, the continuous signal is reconstructed and the exact center is deterarined. Since we have broken out the two dimensions into a clockmark and border, this is a simple one-dimensional process that needs to be perfonnied twice. However, this is only done every second dot column, when there is a black clockmark to register against. For the white clockmarks we simply use the estimate and leave it at that. Alternatively, we could update the pixel coordinate based on the bonder each dot column (since it is always present). In practice it is sufficient to update both ordinates every other column (with the black clockmarks) since the resolution being worked at is so fine. The process therefore becomes:
// Tutn the estimates of the clockmarks into accurate positions only when there is a black clockmark /1(ie every 2nd dot coiumn, starting from -8) if (BitO(CurrentDotColumn) = 0) 1/ even column {
DetermineAccurateUpperpot{,enterQ
DetermineAccurateLowerpotCenterQ
If there is a deviation by more than a given tolerance (MAX_CLOCKMARK_DEVIATION), the found signal is ignored and only deviation from the estimate by the maximum tolerance is allowed. In this respect the functionality is similar to that of a phase-locked loop. Thus DetermineAccurateUpperDotCenter is implemented via the following pseudocode:
/! Use the estimated pixel position of // the border to determine where to look for // a more accurate clockmark center. The clockmark // is 3 dots high so even if the estimated position // of the border is wrong, it won't affect the // fixing of the clockmark position.
MAX-CLOCKMARK_DEVIATION = 0S
diff = GetAccurateColumn(UpperClock.column, UpperClock.pixel+(3*PD{ELS_PER_DOT)) diff = UpperClockcolumn if (diff> MAX_CLOCKMARK_DEVIATION) diff = MAX CLOCKMARIC DEVIATION
else if (diff < -MAX CLOCKMARK DEVIATION) diff = -MAX CLOCKMARK,-DEVIATION
UpperClock.column += diff // Use the newly obtained clockmark center to // determine a more accurate border position.
diff = GetAccuratePixel(UpperClockcoiumn, UpperClockpixel) diff -= UpperClock.pixel if (diff > MAX_CLOCKMARK_DEVIATION) diff = MAX CLOCKMARK_DEVIATION
else if (diff < -MAX_CLOCKMARK_DEVIATION) diff = -MAX_CLOCKMARK DEVIATION
UpperClockpixel += diff DetemtineAccurateLowerpotCenter is the same, except that the direction from the border to the clockmark is in the negative direction (-3 dots rather than +3 dots)_ GetAccuratePixel and GetAceurateColumn are functions that determine an accurate dot center given a coordinate, but only from the perspective of a single dimension. Determining accurate dot centers is a process of signal reeonstntction and then finding the location whete the minimum signal value is found (this is differcnt to locating a target oenter, which is locating the maximum value of the signal since the target center is white, not black). The method chosen for signal reconstruction/resampling for this application is the Lanezos3 windowed sinc function as previously discussed with reference to F'ig. 76.
It may be that the clockmark or border has been damaged in some way - perhaps it has been scratched. If the new center value retrieved by the resampling differs from the estimate by more than a tolerance amount, the center value is only moved by the maximum tolorartce. If it is an invalid position, it should be close enough to use for data retrieval, and future clockmarks will resynchronize the position.
Determining the center of the first data dot and the deltas to subsequent dots Once an accurate UppeaClock and LowerClock position has been determined, it is possible to calculate the center of the first data dot (CurrentDot), and the delta amounts to be added to that center position in order to advance to subsequent dots in the column (DataDelta).
The first thing to do is calculate the deltas for the dot column. This is achieved simply by subtracting the UpperClock from the LowerClock, and then dividing by the number of dots between the two points. It is possible to actually multiply by the inverse of the number of dots since it is constant for an alterttative Artcard, and multiplying is fister. It is possible to use different constants for obtaining the deltas in pixel and column dimensions_ The delta in pixels is the distance between the two borders, while the delta in columns is between the centers of the two cloclcmarks. Thus the funetion DetermineDatalnfo is two parts. The first is given by the pseudocode:
kDeltaColumnFactor = 1/(DOTS_PER_DATA_COLUMN + 2+ 2 - 1) kDeltaPixelFactor = 1/(DOTS PER DATA COLUMN + 5+ 5- 1) delta = LowerClockcolumn - UppeiClockcolumn DataDelta.column = delta * kDeltaColumnFactor delta = LowerClockpixel - UppetClockpixel DataDeltapixel = delta * kDeltaPixelFactor It is now possible to determine the center of the first data dot of the column. There is a distance of 2 dots from the center of the clockmark to the center of the first data dot, and 5 dots from the center of the border to the center of the first data dot. Thus the second part of the function is given by the pseudocode:
CutrentDot.coltunn = UppetClockcolutnn + (2*DataDeltacolumn) CtrrentDot.pixel = Upper(.'lockpixel + (5*DataDe1ta pixel) Running down a dot column Since the dot column has been located from the phase-locked loop tracking the clockmarks, all that remains is to sample the dot column at the ccnter of each dot down that column. The variable CurrentDot points is determined to the center of the first dot of the current column. We can get to the next dot of the column by simply adding DataDelta (2 additions: I for the column ordinate, the other for the pixel ordinate). A
sample of the dot at the given coordinate (bi-linear interpolation) is taken, and a pixel value representing the center of the dot is determined. The pixel value is then used to determine the bit value for that dot. However it is possible to use the pixel value in context with the center value for the two surrounding dots on the same dot line to make a better bit judgement.
We can be assured that all the pixels for the dots in the dot column being extracted are cun-ently loaded in DRAM, for if the two ends of the line (clockmarks) are in DRAM, then the dots between those two clockmarks must also be in DRAM. Additionally, the data block height is short enough (only 384 dots high) to ensure that simple deltas are enough to traverse the length of the line. One of the reasons the card is divided into 8 data blocks high is that we cannot make the same rigid guarantee across the entire height of the card that we can about a single data block.
The high level process of extracting a single line of data (48 bytes) can be seen in the following pseudocode.
The dataBuffer pointer increments as each byte is stored, ensuring that consecutive bytes and columns of data are stored consecutively.
bitCount = 8 curr = Ox00 // definitely black next = GetPixel(CurrentDot) for (i=0; i < DOTS_PER DATA_COLUMN; i++) {
CurrentDot += DataDelta prev = curr curr = next next = GetPixel(CurrentDot) bit = DetermineCenterpot(prev, curr, next) byte = (byte 1) 1 bit bitCount-if (bitCount = 0) {
*(Bitimage I CurrentByte) = byte CurrentByte++
bitCount = 8 }
}
The GetPixel function takes a dot coordinate (ftxed point) and samples 4 CCD
pixels to ariive at a center pixel value via bilinear interpolation_ The DetermineCenterDot function takes the pixel values representing the dot centers to either side of the dot whose bit value is being determined, and attempts to intelligently guess the value of that center dot's bit value. From the generalized blutring curve of Fig. 64 there are three conunon cases to consider:
* The dot's center pixel value is lower than WhiteMin, and is therefore definitely a black dot. The bit value is therefore definitely 1.
* The dot's center pixel value is higher than BlackMax, and is therefore definitely a white doL The bit value is therefore definitely 0.
* The dot's center pixel value is sontewhere between BlackMax and WhiteMin.
The dot may be black, and it may be white. The value for the bit is therefore in question. A number of schemes can be devised to make a reasonable guess as to the value of the bit. "Iltese schemes must balance complexity against accuracy, and also take into account the fact that in some cases, there is no guaranteed solution. In those cases where we make a wrong bit decision, the bit's Reed-Solomon symbol will be in error, and must be coirected by the Reed-Solomon decoding stage in Phase 2.
The scheme used to detennine a dot's value if the pixel value is between BlackMax and WhiteMin is not too complex, but gives good results. It uses the pixel values of the dot centers to the left and right of the dot in question, using their values to help detenn-kine a more likely value for the center dot:
* If the two dots to either side are on the white side of MidRange (an average dot value), then we can guess that if the center dot were white, it would likely be a "definite"
white. The fact that it is in the not-sure region would indicate that the dot was black, and had been affected by the surrounding white dots to make the value less sure.
The dot value is therefore assumed to be black, and hence the bit value is I.
* If the two dots to either side are on the black side of MidRange, then we can guess that if the center dot were black, it would likely be a "definite" black. The fact that it is in the not-sure region would indicate that the dot was white, and had been affected by the surrounding black dots to make the value less sure. The dot value is therefore assumed to be white, and hence the bit value is 0.
* If one dot is on the black side of MidRange, and the other dot is on the white side of MidRange, we simply use the center dot value to decide. If the center dot is on the black side of MidRange, we choose black (bit value 1). Otherwise we choose white (bit value 0).
The logic is represented by the following:
if (pixel < WhiteMin) definitely black bit = Ox01 else if (pixel > BlackMax) definitely white bit = Ox00 else if ((prev > MidRange) && (next> MidRange)) //prob black bit - OxOl else if ((prev < MidRange) && (next < MidRange)) //prob white bit = OxOO
else if (pixel < MidRange) bit = Ox01 else bit = OxOO
From this one can see that using surrounding pixel values can give a good indication of the value of the center dot's state. The scheme described here only uses the dots from the same row, but using a single dot line history (the previous dot line) would also be straightforward as would be alternative arrangements.
Updating dockroarlts for the next column Once the center of the first data dot for the column has been determined, the clockmark values are no longer needed. They are conveniently updated in readiness for the next column after the data has been retrieved for the column. Since the clockmark direction is perpendicular to the traversal of dots down the dot column, it is possible to use the pixel delta to update the column, and subtract the column delta to update the pixel for both clocks:
UpperClock.column += DataDelta.pixel LowerClockcolumn += DataDeltapixel UpperClock.pixel -= DataDeltacoiumn LowetCtock.pixel -= DataDelta.column These are now the estimates for the next dot column.
'lmmng The timing requirement will be met as long as DRAM utilization does not exceed 100%, and the addition of parallel algorithm timing multiplied by the algorithm DRAM utiGzation does not exceed 100%. DRAM utilization is specified relative to Processl, which writes each pixel once in a consecutive manner, consuming 99'0 of the DRAM
bandwidth.
The timing as described in this section, shows that the DRAM is easily able to cope with the demands of the alternative Artcard Reader algotithm. The timing bottleneck will therefore be the implementation of the algorithm in terms of logic speed, not DRAM access. The algorithms have been designed however, with simple architectures in mind, requiring a minimum number of logical operations for every memory cycle.
From this point of view, as long as the implementation state machine or equivalent CPU/DSP architecutre is able to perform as described in the following sub-sections, the target speed will be met.
Locating the brgets Targets are located by reading pixels within the bounds of a pixel column.
Each pixel is read once at most.
Assuming a run-length encoder that operates fast enough, the bounds on the location of targets is memory access. The accesses will therefore be no worse than the timing for Process 1, which means a 9% utiii7ation of the DRAM
bandwidth.
The total utilization of DRAM during target location (including Processl) is therefore 18%, meaning that the target locator will always be catching up to the alternative Artcard image sensor pixel reader.
Processing the targets The timing for sorting and checking the target numbers is trivial. The finding of better estimates for each of the two target centers involves 12 sets of 12 pixel reads, taking a total of 144 reads. However the fixing of accurate target centers is not trivial, requiring 2 sets of evaluations_ Adjusting each target center requires 8 sets of 20 different 6-entry convolution ketnels. Thus this totals 8 x 20 x 6 multiply-accumulates = 960. In addition, there ane 7 sets of 7 pixels to be retrieved, requiring 49 memory accesses. The total number per target is therefore 144 + 960 + 49 = 1153, which is approximately the same number of pixels in a column of pixels (1152).
Thus each target evaluation consumes the tiate taken by otherwise processing a row of pixels. For two targets we effectively consume the time for 2 columns of pixels.
A target is positively identified on the first pixel column after the target number. Since there are 2 dot columns before the orientation column, there are 6 pixel columns. The Target Location process effectively uses up the ftrst of the pixel columns, but the remaining 5 pixel columns are not processed at all.
Therefore the data area can be located in 2/5 of the time- available without impinging on any other process time.
The remaining 3/5 of the time available is ample for the trivial task of assigning the ranges for black and white pixels, a task that may take a couple of machine cycles at most.
Extracti;ng data There are two parts to consider in terms of timing:
* Getting accurate clockmarks and border values * Extracting dot values Clockmarks and border values are only gathered every second dot column.
However each time a clockmark estimate is updated to become more accurate, 20 different 6-entry convolution kernels must be evaluated. On average thete ate 2 of these per dot column (there are 4 every 2 dot-columns).
Updating the pixel ordinate based on the border only requires 7 pixels from the same pixel scanline. Updating the column ordinate however, requires 7 pixels from different columns, hence different scanlines. Assuming worst case scenario of a cache miss for each scanline entry and 2 cache misses for the pixels in the same scanGne, this totals 8 cache misses.
Extracting the dot information involves only 4 pixel reads per dot (rather than the average 9 that define the dot). Considering the data area of 1152 pixels (384 dots), at best this will save 72 cache reads by only reading 4 pixel dots instead of 9. The worst case is a rotation of 1 which is a single pixel translation every 57 pixets, which gives only slightly worse savings.
It can then be safely said that at worst, we will be reading fewer cache lines less than that consumed by the pixels in the data area. The accesses will thetefore be no worse than the tinting for Process I, which implies a 9%
utilization of the DRAM bandwidth.
The total utilization of DRAM during data extraction (including Process 1) is therefore 18%, meaning that the data extractor will always be catching up to the alternative Artcard intage sensor pixel nader. This has implications for the Process Targets process in that the processing of targets can be performed by a relatively inefficient method if necessary, yet sdll catch up quickly during the extracting data prooess-Phase 2- Decode Bit Image Phase 2 is the non-real-time phase of alternative Artcard data recovery algorithm. At the start of Phase 2 a bit image has been extracted from the alternative Artcard_ It represents the bits read from the data regions of the alternative Artcard. Some of the bits will be in error, and perhaps the entire data is rotated 180 because the alternative Artcard was rotated when inserted. Phase 2 is concerned with reliably extracting the original data from this encoded bit image.
There are basically 3 steps to be carried out as illustrated in Fig. 79:
* Reorganize the bit image, reversing it if the alternative Artcard was inserted backwards * Unscramble the encoded data * Reed-Solomon decode the data from the bit image Each of the 3 steps is defined as a separate process, and performed consecutively, since the output of one is required as the input to the next. It is straightforward to combine the first two steps into a single process, but for the purposes of clarity, they are treated separately here.
From a data/process perspective, Phase 2 has the structure as illustrated in Fig. 80.
The timing of Processes I and 2 are likely to be negligible, consuming less than 1/1000t' of a second between them. Process 3 (Reed Solomon decode) consumes approximately 0.32 seconds, making this the total time required for Phase 2.
Reorganize the bit image, reversing it if necessary The bit map in DRAM now represents the retrieved data from the alternative Artcard. However the bit image is not contiguous. It is broken into 64 32k chunks, one chunk for each data block.
Each 32k chunk contains only 28,656 useful bytes:
48 bytes from the leftmost Orientation Column 28560 bytes from the data region proper 48 bytes from the rightmost Orientation Column 4112 unused bytes The 2MB buffer used for pixel data (stored by Process 1 of Phase 1) can be used to hold the reorganized bit image, since pixel data is not required during Phase 2. At the end of the reorganization, a correctly oriented contiguous bit image will be in the 2MB pixel buffer, ready for Reed-Solomon decoding.
If the card is correctly oriented, the leftmost Orientation Column will be white and the rightmost Orientation Column will be black. If the card has been rotated 180 , then the leftmost Orientation Column will be black and the rightmost Orientation Column will be white.
A simple method of determining whether the card is correctly oriented or not, is to go through each data block, checking the first and last 48 bytes of data until a block is found with an overwhelming ratio of black to white bits. The following pseudocode demonstrates ihis, returning TRUE if the card is correctly oriented, and FALSE if it is not totalCountL = 0 totalCountR = 0 for (i=O; i<64; i++) blackCountL = 0 blackCountR = 0 currBuff = dataBuffer for (j=0; j<48; j++) blackCountL += CountBits(*currBufl) currBuff++
}
currBuff += 28560 for (j_0; j<48; j++) blackCountR += CountBits(*cuirBuff) currBuff++
}
dataBuffer += 32k if (blackCountR > (blackCountL * 4)) return TRUE
if (btackCountL> (blackCountR * 4)) return FALSE
totalCountL += blackCountL
totalCountR += blackCountR
}
return (totalCountR > totalCountL) The data must now be reorganized, based on whether the card was oriented correctly or not. The simplest case is that the card is correctly oriented. In this case the data only needs to be moved around a little to remove the orientation columns and to make the entire data contiguous. This is achieved very simply in situ, as described by the following pseudocode:
DATA_BYTES_pER_pATA BLOCK=28560 to = dataBuffer from = dataBuffer + 48) // left orientation column for (i=0; i<64; i++) I
BlockMove(from, to, DATA Bl''IFS_YER-DATA BI:OCK) from += 32k to += DATA BYIES_PER DATA_BLOCK
}
The other case is that the data actually needs to be reversed. The atgoritfim to reverse the data is quite simple, but for simplicity, requires a 256-byte table Reverse where the value of Reverse[N] is a bit-reversed N.
DATA_BYTE.S_PER_DATA_BLOCK = 28560 to = outBuffer for (i=O; i<64; i++) {
from = dataBuffer + (i * 32k) from += 48 /1 skip orientation column from += DATA_Bl'TF.S_PER_DATA_BLOCK - 1 // end of block for (j=0; j < DATA_BYTF.S_PER_DATA_BLOCK; j++) [
*to++ = Reverse[*from]
from--The tiniing for either process is negligible, consuming less than 1/1000'" of a second:
* 2MB contiguous reads (2048/16 x 12ns = 1,536ns) * 2MB effectively contiguous byte writes (2048/16 x 12ns = 1,536ns) Unscramble the encoded intage Tbe bit image is now 1,827,840 contiguous, comectly oriented, but scrambled bytes. The bytes must be unscrambled to create the 7,168 Reed-Solomon blocks, each 255 bytes long. The unscrambling process is quite straightforward, but requires a separate output buffer since the unscrambling cannot be performed in situ. Fig. 80 illustrates the unscrambling process conducted memory The following pseudocode defines how to perform the unscrambling process:
groupSize = 255 numBytes = 1827840;
inBuffer = sctambledButf'er.
outBuffer = unscrambledBuffer;
for (i=0; i<groupSize; i++) for (j=i; j<numBytes; j+=groupSize) outBuffer[j] = *inBuffer++
The tinring for this process is negligible, consuniing less than 1/10006 of a second:
* 2MB contiguous reads (2048/16 x 12ns = 1,536ns) * 2MB non-contiguous byte writes (2048 x 12ns = 24,576ns) At the end of this process the unscrambled data is ready for Reed-Solomon decoding.
Reed Solomon decode The final part of reading an alternative Artcard is the Reed-Solomon decode process, where approximately 2MB of unscrambled data is decoded into approximately 1 MB of valid alternative Artcard data.
The algorithm performs the decoding one Reed-Solomon block at a time, and can (if desired) be performed in situ, since the encoded block is larger than the decoded block, and the redundancy bytes are stored after the data bytes_ The first 2 Reed-Solomon blocks are control blocks, containing information about the size of the data to be extracted from the bit image. This meta-information must be decoded first, and the resultant information used to decode the data proper. The decoding of the data proper is simply a case of decoding the data blocks one at a time.
Duplicate data blocks can be used if a particular block fails to decode.
The highest level of the Reed-Solomon decode is set out in pseudocode:
// Constants for Reed Solomon decode sourceBlockL.ength = 255;
destBlockl.ength = 127;
numControlBlocks = 2;
O Decode the control information if (! GetControlData(source, destB locks, lastBlock)) return error destBytes = ((destBlocks-1) * destBlockL.ength) + lastBlock offsetToNextDuplicate = destBlocks * sourceBlockLength A Slcip the control blocks and position at data source += numControlBlocks * sourceBlockLength !1 Decode each of the data blocks, trying U duplicates as necessary blocksInEiror = 0;
for (i=O; i<destBlocks; i++) {
found = DecodeBlock(sottrce, dest);
if (! found) {
duplicate = source + offsetToNextDuplicate while ((! found) && (duplicate<sourceEnd)) found = DecodeBlock(dupticate, dest) duplicate += offsetToNextDuplicate }
if (! found) blocksInError++
source += sourceBlockLength dest += destBlockLength }
return destBytes and blocksInEn-or DecodeBlock is a standard Reed Solomon block decoder using m=8 and t=64.
The GetControlData function is straightforward as long as there are no decoding errors. The function simply calls DecodeB lock to decode one control block at a tinie until successful.
The control parameters can then be extracted from the first 3 bytes of the decoded data (destBlocks is stored in the bytes 0 and 1, and lastBlock is stored in byte 2). If there are decoding errors the function must traverse the 32 sets of 3 bytes and decide which is the most likely set value to be correct. One simple method is to find 2 consecutive equal copies of the 3 bytes, and to declare those values the correct ones_ An alternative method is to count occurrences of the different sets of 3 bytes, and announce the most common occurrence to be the correct one.
The time taken to Reed-Solomon decode depends on the implementation. While it is possible to use a dedicated core to perform the Reed-Solomon decoding process (such as LSI
Logic's L64712), it is preferable to select a CPU/DSP combination that can be more generally used throughout the embedded system (usually to do something with the decoded data) depending on the application. Of course decoding time must be fast enough with the CPU/DSP
combination.
The L64712 has a throughput of 50Mbits per second (around 6.25MB per second), so the time is bound by the speed of the Reed-Solomon decoder rather than the maximum 2MB read and 1 MB
write memory access time. The time taken in the worst case (all 2MB requires decoding) is thus 2/6.25s =
approximately 0.32 seconds. Of course, many further refinements are possible including the following:
The blurrier the reading environment, the more a given dot is influenced by the surrounding dots. The current reading algorithm of the preferred embodiment has the ability to use the surrounding dots in the same column in order to make a better decision about a dot's value. Since the_previous column's dots have already been decoded, a previous column dot history could be useful in detertitining the value of those dots whose pixel values are in the not-sure range.
A different possibility with regard to the initial stage is to remove it entirely, make the initial bounds of the data blocks larger than necessary and place greater intelligence into the ProcessingTargets functions. This may reduce overall complexity. Care must be taken to maintain data block independence.
Furiher the control block mechanism can be made more robust:
' The control block could be the first and last blocks rather than make them contiguous (as is the case now). This may give greater protection against certain pathological damage scenarios.
* The second refinement is to place an additional kvel of redundancy/error detection into the control block structure to be used if the Reed-Solomon decode step fails. Something as simple as parity might improve the likelihood of control information if the Reed-Solomon stage fails.
Phase 5 Running the Vark scriQt The overall time taken to read the Artcard 9 and decode it is therefore approximately 2_ 15 seconds. The apparent delay to the user is actually only 0.65 seconds (the total of Phases 3 and 4), since the Artcard stops moving after 1.5 secotids.
Once the Artcard is loaded, the Artvark script must be intetpreted, Rather than run the script immediately, the script is only run upon the pressing of the 'Print' button 13 (Fig. 1). The taken to run the script will vary depending on the complexity of the script, and must be taken into account for the perceived delay between pressing the print button and the actual print button and the actual printing.
As noted previously, the VLIW processor 74 is a digital processing system that accelerates computationally expensive Vark functions. The balance of functions perfotmed in software by the CPU core 72, and in hardware by the VLIW processor 74 will be implementation dependent. The goal of the VLIW
processor 74 is to assist all Artcard styles to execute in a time that does not seem too slow to the user. As CPUs become faster and more powerful, the number of functions requiring hardware acceleration becomes less and less. The VLIW processor has a microcoded ALU sub-system that allows general hardware speed up of the following time-critical functions.
1) Image access mechanisms for general software processing 2) Image convolver.
3) Data driven iniage warper 4) Image scaling 5) Image tessellation 6) Affine transform 7) Image compositor 8) Color space transform 9) Histogram collector 10) Illumination of the Image 11) Brush stamper 12) Histogram collector 13) CCD image to internal image conversion 14) Construction of image pyramids (used by warper & for brushing) The following table summarizes the time taken for each Vark operation if implemented in the ALU model.
The method of implementing the function using the ALU model is described hereinafter.
Operation Speed of Operation 1500 * 1000 image 1 channel 3 channels Image composite I cycle per output pixel 0.015 s 0.045 s Image convolve k/3 cycles per output pixel (k = kernel size) 3x3 convolve 0.045 s 0.135 s 5x5 convolve 0.125 s 0.375 s 7x7 convolve 0.245 s 0.735 s Image warp 8 cycles per pixel 0.120 s 0.360s Histogram collect 2 cycles per pixel 0.030 s 0.090 s Image Tessellate 1/3 cycle per pixel 0.005 s 0.015 s Image sub-pixel Translate I cycle per output pixel -Color lookup replace 'h cycle per pixel 0.008 s 0.023 Color space transform 8 cycles per pixel 0.120 s 0.360 s Convert CCD image to 4 cycles per output pixel 0.06 s 0.18 s internal itnage (including color convert & scale) Construct image pyramid 1 cycle per input pixel 0.015 s 0.045 s Scale Maximum of: 0.015 s 0.045 s (minimum) 2 cycles per input pixel (fftinimum) 2 cycles per output pixel 2 cycles per output pixel (scaled in X only) Affine transform 2 cycles per output pixel 0.03 s 0.09 s Brush rotatekranslate and ?
composite Tile Image 4-8 cycles per output 0.015 s to 0.030 s 0.060 s to 0.120 s to for pixel 4 channels (Lab, texture) Illuminate image Cycles per pizel Ambient only 0.008 s 0.023 s Directional light l 0.015 s 0.045s Directional (bm) 6 0.09 s 0.27 s Omni light 6 0.09 s 0.27 s Omni (bm) 9 0.137 s 0.41 s Spotlight 9 0.137 s 0.41 s Spotlight (bm) 12 0.18 s 0.54 s (bm) = bumpmap For example, to convert a CCD image, collect histogram & perform lookup-color replacement (for image enhancement) takes: 9+2+05 cycles per pixel, or 11.5 cycles. For a 1500 x 1000 image that is 172,500,000, or approximately 0.2 seconds per component, or 0.6 seconds for all 3 components.
Add a simple warp, and the total comes to 0.6 + 0.36, almost 1 second.
ImaQe Convolver A convolve is a weighted average around a center pixel. The average may be a simple sum, a sum of absolute values, the absolute value of a sum, or sums truncated at 0.
The image convolver is a general-purpose convolver, allowing a variety of functions to be implement.ed by varying the values within a variable-sized coefficient kemel. The kernel sizes supported are 3x3, 5x5 and 7x7 only.
Turning now to Fig. 82, there is illustrated 340 an example of the convolution process. The pixel component values fed into the convolver process 341 come from a Box Read Iterator 342.
The Iterator 342 provides the image data row by row, and within each row, pixel by pixel. The output from the convolver 341 is sent to a Sequential Write Iterator 344, which stores the resultant image in a valid image format.
A Coefficient Kernel 346 is a lookup table in DRAM. The kemel is arranged with coefficients in the same order as the Box Read Iterator 342. Each coefficient entry is 8 bits. A simple Sequential Read Iterator can be used to index into the kerne1346 and thus provide the coefficients. It simulates an image with ImageWidth equal to the kernel size, and a Loop option is set so that the kernel would continuously be provided.
One form of implementation of the convolve process on an ALU unit is as illustrated in Fig. 81.The following constants are set by software:
Constant Value Ki Kernel size (9, 25, or 49) The control logic is used to count down the number of multiply/adds per pixel.
When the count (accumulated in Latch2) reaches 0, the control signal generated is used to write out the current convolve value (from Latch,) and to reset the count. In this way, one control logic block can be used for a number of parallel convolve streams.
Each cycle the multiply ALU can perform one multiply/add to incorporate the appropriate part of a pixel. The number of cycles taken to sum up all the values is therefore the number of entries in the kernel. Since this is compute bound, it is appropriate to divide the image into multiple sections and process them in parallel on different ALU units.
On a 7x7 kernel, the time taken for each pixel is 49 cycles, or 490ns. Since each cache line holds 32 pixels, the time available for memory access is 12,740ns. ((32-7+1) x 490ns). The time taken to read 7 cache lines and write I
is worse case 1,120ns (8*140ns, all accesses to same DRAM bank). Consequendy it is possible to process up to 10 pixels in parallel given unlimited resources. Given a limited number of ALUs it is possible to do at best 4 in parallel.
The time taken to therefore perform the convolution using a 7x7 kernel is 0.18375 seconds (1500*1000 * 490ns / 4 183,750,000ns).
On a 5x5 kernel, the time taken for each pixel is 25 cycles, or 250ns. Since each cache line holds 32 pixels, the time available for memory access is 7,000ns. ((32-5+1) x 250ns). The time taken to read 5 cache lines and write I
is worse case 840ns (6 * 140ns, all accesses to same DRAM bank). Consequently it is possible to process up to 7 pixels in parallel given unlimited resources. Given a limited number of ALUs it is possible to do at best 4. The time taken to therefore perform the convolution using a 5x5 kernel is 0.09375 seconds (1500*
1000 * 250ns / 4= 93,750,000ns).
On a 3x3 kernel, the time taken for each pixel is 9 cycles, or 90ns. Since each cache line holds 32 pixels, the time available for memory access is 2,700ns. ((32-3+1) x 90ns). The time taken to read 3 cache lines and write I is worse case 560ns (4 * 140ns, all accesses to same DRAM bank). Consequently it is possible to process up to 4 pixels in parallel given unlimited resources. Given a limited number of ALUs and Read/Write Iterators it is possible to do at best 4. The time taken to therefore perform the convolution using a 3x3 kemel is 0.03375 seconds (1500*1000 * 90ns /
4 = 33,750,000ns).
Consequently each output pixel takes kernelsize/3 cycles to compute. The actual timings are summarised in the following table:
Kernel size Time taken to Time to process Time to Process calculate output pixel 1 channel at 1500x1000 3 channels at 1500x1000 3x3 (9) 3 cycles 0.045 seconds 0.135 seconds ig~ 8 1/3 cycles 0.125 seconds 0.375 seconds 16 1/3 cycles 0.245 seconds 0.735 seconds L7x Image Compositor Compositing is to add a foreground image to a background image using a matte or a channel to govern the appropriate proportions of background and foreground in the final image. Two styles of compositing are preferably supported, regular compositing and associated compositing. The rules for the two styles are:
Regular composite: new Value = Foreground + (Background - Foreground) a Associated composite: new value = Foreground + (1- a) Background The difference then, is that with associated compositing, the foreground has been pre-multiplied with the matte, while in regular compositing it has not. An example of the compositing process is as illustrated in Fig. 83.
The alpha channel has values from 0 to 255 corresponding to the range 0 to 1.
Reeular Composite A regular composite is implemented as:
Foreground + (Background - Foreground) * = = / 255 The division by 3{255 is approximated by 257X/65536. An implementation of the compositing process is shown in more detail in Fig. 84, where the following constant is set by software:
Constant Value K, 257 Since 4 Iterators are required, the composite process takes I cycle per pixel, with a utilization of only half of the ALUs. The composite process is only run on a single channel. To composite a 3-channel image with another, the compositor must be run 3 times, once for each channel.
The time taken to composite a full size single channel is 0.015s (1500 * 1000 * I* lOns), or 0.045s to composite all 3 channels.
To approximate a divide by 255 it is possible to multiply by 257 and then divide by 65536. It can also be achieved by a single add (256 * x + x) and ignoring (except for rounding purposes) the final 16 bits of the result.
As shown in Fig. 42, the compositor process requires 3 Sequential Read Iterators 351-353 and I Sequential Write Iterator 355, and is implemented as microcode using a Adder ALU in conjunction with a multiplier ALU.
Composite time is I cycle (IOns) per-pixel. Different microcode is required for associated and regular compositing, although the average time per pixel composite is the same.
The composite process is only run on a single channel. To composite one 3-channel image with another, the compositor must be run 3 times, once for each channel. As the a channel is the same for each composite, it must be read each time. However it should be noted that to transfer (read or write) 4 x 32 byte cache-lines in the best case takes 320ns. The pipeline gives an average of 1 cycle per pixel composite, taking 32 cycles or 320ns (at 100MHz) to composite the 32 pixels, so the a channel is effectively read for free. An entire channel can therefore be composited in:
1500/32 * 1000 * 320ns = 15,040,000ns = 0.015seconds.
The time taken to composite a full size 3 channel image is therefore 0.045 seconds.
Constrect Image Pvramid Several functions, such as warping, tiling and brushing, require the average value of a given area of pixels.
Rather than calculate the value for each area given, these functions preferably make use of an image pyramid. As illustrated previously in Fig. 33, an image pyramid 360 is effectively a multi-resolution pixelmap. The original image is a 1:1 representation. Sub-sampling by 2:1 in each dimension produces an image 1/4 the original size. This process continues until the entire image is represented by a single pixel.
An image pyramid is constructed from an original image, and consumes 1/3 of the size taken up by the original image (1/4 + 1/16 + 1/64 + ...). For an original image of 1500 x 1000 the corresponding image pyramid is approximately th MB
The image pyramid can be constructed via a 3x3 convolve performed on I in 4 input image pixels advancing the center of the convolve kernel by 2 pixels each dimension. A 3x3 convolve results in higher accuracy than simply averaging 4 pixels, and has the added advantage that coordinates on different pyramid levels differ only by shifting I
bit per level.
The construction of an entire pyramid relies on a software loop that calls the pyramid level construction function once for each level of the pyramid.
The timing to produce I level of the pyramid is 9/4 * 1/4 of the resolution of the input image since we are generating an image 1/4 of the size of the original. Thus for a 1500 x 1000 image:
T'tming to produce level I of pyramid = 9/4 * 750 * 500 = 843, 750 cycles Timing to produce level 2 of pyramid = 9/4 * 375 * 250 = 210,938 cycles Timing to produce level 3 of pytamid = 9/4 * 188 * 125 = 52. 735 cycles Etc.
The total time is 3/4 cycle per original image pixel (image pyramid is 1/3 of original image size, and each pixel takes 9/4 cycles to be calculated, i.e. 1/3 * 9/4 = 3/4). In the case of a 1500 x 1000 image is 1,125,000 cycles (at 100MHz), or 0.011 seconds. This timing is for a single color channel, 3 color channels require 0.034 seconds processing time.
General Data Driven Ima eg Watper The ACP 31 is able to carry out image warping manipulations of the input image. The principles of image warping are well-known in theory. One thorough text book reference on the process of warping is "Digital Image Warping" by George Wolberg published in 1990 by the IEEE Computer Society Press, Los Afamitos, California. The warping process utilizes a warp map which forms part of the data fed in via Artcard 9_ The warp map can be arbitrarily dimensioned in accordance with requirements and provides information of a mapping of input pixels to output pixels.
Unfortunately, the utilization of arbitrarily sized warp maps presents a number of problems which must be solved by the image warper.
Turning to Fig. 85, a warp map 365, having dimensions AxB comprises array values of a certain magnitude (for example 8 bit values from 0 - 255) which set out the coordinate of a theoretical input image which maps to the cotresponding "theoretical" output image having the same array coordinate indices. Unfortunately, any output image eg. 366 will have its own dimensions CxD which may further be totally different from an input image which niay have its own dimensions ExF. Hence, it is necessary to facilitate the remapping of the warp map 365 so that it can be utilised for output image 366 to determine, for each output pixel, the corresponding area or region of the input image 367 from which the output pixel color data is to be constructed. For each output pixel in output image 366 it is necessary to first determine a corresponding warp map value from warp map 365.
This may include the need to bilinearly interpolate the surrounding warp map values when an output image pixel maps to a fractional position within warp map table 365. The result of this process will give the location of an input image pixel in a "theoretical" image which will be dimensioned by the size of each data value within the warp map 365. These values must be re-scaled so as to map the theoretical image to the corresponding actual input image 367.
In order to determine the actual value and output image pixel should take so as to avoid aliasing effects, adjacent output image pixels should be examined to determine a region of input image pixels 367 which will contribute to the final output image pixel value. In this respect, the image pyramid is utilised as will become more apparent hereinafter.
The image warper perfotms several tasks in order to warp an image_ Scale the warp map to match the output image size.
Detemune the span of the region of input image pixels represented in each output pixel.
- Calculate the final output pixel value via tri-linear interpolation from the input image pyramid Scale warro map As noted previously, in a data driven warp, there is the need for a warp map that describes, for each output pixel, the center of a corresponding input image map. Instead of having a single warp map as previously described, containing interleaved x and y value information, it is possible to treat the X and Y coordinates as separate channels.
Consequently, preferably there are two warp maps: an X warp map showing the warping of X coordinates, and a Y warp map, showing the warping of the Y coordinates. As noted previously, the warp map 365 can have a different spatial resolution than the image they being scaled (for example a 32 x 32 warp-map 365 may adequately describe a warp for a 1500 x 1000 image 366). In addition, the warp maps can be represented by 8 or 16 bit values that correspond to the size of the image being warped.
There are several steps involved in producing points in the input image space from a given warp map:
1. Detetmining the corresponding position in the warp map for the output pixel 2. Fetch the values from the warp map for the next step (this can require scaling in the resolution domain if the warp map is only 8 bit values) 3. Bi-linear interpolation of the warp map to determine the actual value 4. Scaling the value to correspond to the input image domain The first step can be accomplished by multiplying the current X/Y coordinate in the output image by a scale factor (which can be different in X & Y). For example, if the output image was 1500 x 1000, and the warp map was 150 x 100, we scale both X & Y by 1/10.
Fetching the values from the warp map requires access to 2 Lookup tables. One Lookup table indexes into the X warp-tnap, and the other indexes into the Y warp-map. The lookup table either reads 8 or 16 bit entries from the lookup table, but always returns 16 bit values (clearing the high 8 bits if the original values are only 8 bits).
The next step in the pipeline is to bi-linearly interpolate the looked-up warp map values.
Finally the result from the bi-linear interpolation is scaled to place it in the same domain as the image to be warped. Thus, if the warp map range was 0-255, we scale X by 1500/255, and Y
by 1000/255.
The interpolation process is as illustrated in Fig. 86 with the following constants set by software:
Constant Value Ki Xscale (scales 0-ImageWidth to 0-WarpmapWidth) K2 Yscale (scales 0-ImageHeight to O-WarpmapHeight) K3 XrangeScale (scales warpmap range (eg 0-255) to 0-ImageWidth) Ka YrangeScale (scales warpmap range (eg 0-255) to 0-ImageHeight) The following lookup table is used:
Lookup Size Details LUt and WarpmapWidth x Warpmap lookup.
LU2 WarpmapHeight Given [X,Y] the 4 entries required for bi-linear interpolation are returned. Even if entries are only 8 bit, they are returned as 16 bit (high 8 bits 0).
Transfer time is 4 entries at 2 bytes per entry.
Total time is 8 cycles as 2 lookups are used.
Span calculation The points from the warp map 365 locate centers of pixel regions in the input image 367. The distance between input image pixels of adjacent output image pixels will indicate the size of the regions, and this distance can be approximated via a span calculation.
Turning to Fig. 87, for a given current point in the warp map P1, the previous point on the same line is called P0, and the previous line's point at the same position is called P2. We determine the absolute distance in X & Y
between PI and P0, and between P1 and P2. The maximum distance in X or Y
becomes the span which will be a square approximation of the actual shape.
Preferably, the points are processed in a vertical strip output order, PO is the previous point on the same line within a strip, and when P 1 is the first point on line within a strip, then PO refers to the last point in the previous strip's corresponding line. P2 is the previous line's point in the same strip, so it can be kept in a 32-entry history buffer. The basic of the calculate span process are as illustrated in Fig. 88 with the details of the process as illustrated in Fig. 89.
The following DRAM FIFO is used:
Lookup Size Details FIFO8 8 ImageWidth bytes. P2 history/lookup (both X & Y in same FIFO) [ImageWidth x 2 entries at Pl is put into the FIFO and taken out again at the same 32 bits per entry] pixel on the following row as P2.
Transfer time is 4 cycles (2 x 32 bits, with I cycle per 16 bits) Since a 32 bit precision span history is kept, in the case of a 1500 pixel wide image being warped 12,000 bytes temporary storage is required.
Calculation of the span 364 uses 2 Adder ALUs (1 for span calculation, I for looping and counting for PO and P2 histories) takes 7 cycles as follows:
Cycle Action I A=ABS(Pl~-P2,) Store Pl. in P2. history 2 B = ABS(Pl. - P0,) Store P1õ in P0, history 3 A=MAX(A,B) 4 B=ABS(Ply-P2y) Store Ply in P2y history A = MAX(A, B) 6 B=ABS(Pty-P0y) Store Ply in P0y history 7 A = MAX(A, B) The history buffers 365, 366 are cached DRAM. The 'Previous Line' (for P2 history) buffer 366 is 32 entries of span-precision. The 'Previous Point' (for P0 history). Buffer 365 requires L register that is used most of the time (for calculation of points I to 31 of a line in a strip), and a DRAM buffered set of history values to be used in the calculation of point 0 in a strip's line.
32 bit precision in span history requires 4 cache lines to hold P2 history, and 2 for P0 history. P0's history is only written and read out once every 8 lines of 32 pixels to a temporary storage space of (ImageHeight*4) bytes. Thus a 1500 pixel high image being warped re,quitrs 6000 bytes temporary storage, and a total of 6 cache lines.
'Iri-linear intetpolation Having determined the center and span of the area from the input image to be averaged, the final part of the warp process is to determine the value of the output pixel. Since a single output pixel could theoretically be represented by the entire input image, it is potentially too time-consuming to actually read and average the specific area of the input image contributing to the output pixel. Instead, it is possible to approximate the pixel value by using an image pyranud of the input intage.
If the span is I or less, it is necessary only to read the original image's pixels around the given coordinate, and perform bi-linear interpolation. If the span is greater than l, we must read two appropriate levels of the image pyramid and perform tri-linear interpolation. Performing linear interpolation between two levels of the image pyramid is not sttietly conect, but gives acceptable results (it errs on the side of bluning the resultant image).
Turning to Fig. 90, generally speaking, for a given span 's', it is necessary to read image pyramid levels given by lnZs (370) and ln2s+l (371). Ln2s is simply decoding the highest set bit of s. We must bi-linear interpolate to determine the value for the pixel value on each of the two levels 370,371 of the pyramid, and then interpolate between levels.
As shown in Fig. 91, it is necessary to first interpolate in X and Y for each pyrantid level before interpolating between the pyratnid levels to obtain a final output value 373.
The image pyramid address mode issued to generate addresses for pixel coordinates at (x, y) on pytamid level s & s+l. Each level of the image pyramid contains pixels sequential in x.
Hence, reads in x are likely to be cache hits.
Reasonable cache coherence can be obtained as local regions in the output image are typically locally coherent in the input image (perhaps at a different scale however, but coherent within the scale)_ Since it is not possible to know the relationship between the input and output images, we ensure that output pixels are written in a vertical strip (via a Vertical-Strip Iterator) in order to best make use of cache coherence.
Tri-linear interpolation can be completed in as few as 2 cycles on average using 4 multiply ALUs and all 4 adder ALUs as a pipeline and assunring no menwry access required. But since all the interpolation values are derived from the image pyramids, interpolation speed is completely dependent on cache coherence (not to mention the other units are busy doing warp-map scaling and span calculations). As many cache lines as possible should therefore be available to the image-pyramid reading. The best speed will be 8 cycles, using 2 Multiply ALUs.
The output pixels are written out to the DRAM via a Vertical-Strip Write Iterator that uses 2 cache lines. The speed is therefore limited to a minimum of 8 cycles per output pixel. If the scaling of the warp map requires 8 or fewer cycles, then the overall speed will be unchanged. Otherwise the throughput is the time taken to scale the warp map. In most cases the warp map will be scaled up to match the size of the photo.
Assuming a warp map that requires 8 or fewer cycles per pixel to scale, the time taken to convert a single color component of image is therefore 0.12s (1500 * 1000 * 8 cycles * l Ons per cycle).
Histogram Collector The histogram collector is a microcode program that takes an image channel as input, and produces a histogram as output. Each of a channel's pixels has a value in the range 0-255. Consequently there are 256 entries in the histogram table, each entry 32 bits - large enough to contain a count of an entire 150ox 1000 image.
As shown in Fig. 92, since the histogram represents a summary of the entire image, a Sequential Read Iterator 378 is sufficient for the input. The histogram itself can be completely cached, requiring 32 cache lines (1 K).
The microcode has two passes: an initialization pass which sets all the counts to zero, and then a "count" stage that increments the appropriate counter for each pixel read from the image.
The first stage requires the Address Unit and a single Adder ALU, with the address of the histogram table 377 for initialising.
Relative Microcode Address Unit Adder Unit 1 Address A = Base address of histogram 0 Write 0 to Out 1= A
A+(Adderl.Outl 2) A = A - 1 1 Rest of processing Rest of processing The second stagc processes the actual pixels from the image, and uses 4 Adder ALUs:
Adder 1 Adder 2 Adder 3 Adder 4 Address Unit I A=O A=-I
2 Out 1= A A= Adder l.Out 1 A= A= A+ 1 Out 1= Read 4 bytes BZ A pixel Z = pixel - Adr.Outl from: (A +
2 Adderl.Outl (Adderl.Outl 2)) 3 Outl = A Outl = A Outl = A Write Adder4.Out1 to:
A = (A + (Adder 2.Out 2) Adder3.Out 1 4 Write Adder4.Out1 to:
(A + (Adder 2.Out 2) Flush caches The Zero flag from Adder2 cycle 2 is used to stay at microcode address 2 for as long as the input pixel is the same. When it changes, the new count is written out in mierocode address 3, and processing resumes at microcode address 2. Microcode address 4 is used at the end, when there are no more pixels to be mad.
Stage 1 takes 256 cycles, or 2560ns. Stage 2 varies according to the values of the pixels. The worst case time for lookup table replacement is 2 cycles per image pixel if every pixel is not the same as its neighbor. The time taken for a single color lookup is 0.03s (1500 x 1000 x 2 cycle per pixel x l Ons per cycle = 30,000,000ns). The time taken for 3 color components is 3 times this amount, or 0.09s.
Color Transform Color transfotmation is achieved in two main ways:
Lookup table replacetnent Color space conversion LookuD Table Realacement As illustrated in Fig. 86, one of the simplest ways to transform the color of a pixel is to encode an arbitrarily complex transform function into a lookup table 380. The component color value of the pixel is used to lookup 381 the new component value of the pixel. For each pixel read from a Sequential Read Itetator, its new value is read from the New Color Table 380, and written to a Sequential Write Iterator 383. The input image can be processed simultaneously in two halves to make effective use of memory bandwidth. The following lookup table is used:
Lookup Size Details LU, 256 entries Replacetnent(X]
8 bits per entry Table indexed by the 8 highest significant bits of X.
Resultant 8 bits treated as fixed point 0:8 The total process requires 2 Sequential Read Iterators and 2 Sequential Write iterators. The 2 New Color Tables require 8 cache lines each to hold the 256 bytes (256 entries of 1 byte).
The average tinie for lookup table replacement is therefore 44 cycle per image pixel. The time taken for a single color lookup is 0.0075s (1500 x 1000 x SFi cycle per pixel x lOns per cycle = 7,500,000ns). The time taken for 3 color components is 3 times this amount, or 0.0225s. Each color component has to be processed one after the other under control of software.
Color Space Conversion Color Space conversion is only required when moving between color spaces. The CCD images are captured in RGB color space, and printing occurs in CMY color space, while clients of the ACP 31 likely process images in the Lab color space. All of the input color space channels are typically required as input to deterntine each output channel's component value. Thus the logical process is as illustrated 385 in Fig. 94.
Simply, conversion between Lab, RGB, and CMY is fairly straightforward.
However the individual color profile of a particular device can vary considerably. Consequently, to allow future CCDs, inks, and printers, the ACP
31 performs color space conversion by means of tri-linear interpolation from color space conversion lookup tables.
Color coherence tends to be area based rather than line based. To aid cache coherence during tri-linear interpolation lookups, it is best to process an image in vertical strips. Thus the read 386-388 and write 389 iterators would be Vertical-Strip Iterators.
Tri-linear color space conversion For each output color component, a single 3D table mapping the input color space to the output color component is required. For example, to convert CCD images from RGB to Lab, 3 tables calibrated to the physical characteristics of the CCD are required:
RGB->L
RGB->a RGB->b To convert from Lab to CMY, 3 tables calibrated to the physical characteristics of the ink/printer are required:
Lab->C
Lab->M
Lab->Y
The 8-bit input color components are treated as fixed-point numbers (3:5) in order to index into the conversion tables. The 3 bits of integer give the index, and the 5 bits of ftaction are used for interpolation. Since 3 bits gives 8 values, 3 dimensions gives 512 entries (8 x 8 x 8). The size of each entry is I byte, requiring 512 bytes per table.
The Convert Color Space process can therefore be implemented as shown in Fig.
95 and the following lookup table is used:
Lookup Size Details LU, 8 x 8 x 8 entries ConveR(X, Y. Z]
512 entries Table indexed by the 3 highest bits of X. Y, and Z.
8 bits per entry 8 entries returned from Tri-linear index address unit Resultant 8 bits treated as fixed point 8:0 Transfer time is 8 entries at I byte per entry Tri-linear interpolation returns interpolation between 8 values. Each 8 bit value takes I cycle to be returned from the lookup, for a total of 8 cycles_ The tri-linear interpolation also takes 8 cycles when 2 Multiply ALUs are used per cycle. General tri-linear interpolation information is given in the ALU
section of this document. The 512 bytes for the lookup table fits in 16 cache lines.
Tlte time taken to convert a single color component of image is therefore 0.
105s (1500 * 1000 * 7 cycles *
l Ons per cycle). To convert 3 components takes 0.415s. Fortunately, the color space conversion for printout takes place on the fly during printout itself, so is not a perceived delay.
If color components are converted separately, they must not overwrite their input color space components since alI color components from the input color space are required for converting each component.
Since only 1 multiply unit is used to perform the interpolation, it is alternatively possible to do the entire Lab->CMY conversion as a single pass. This would require 3 Vertical-Strip Read Iterators, 3 Vertical-Strip Write Iterators, and access to 3 conversion tables simultaneously. In that case, it is possible to write back onto the input image and thus use no extra tnemory. However, access to 3 conversion tables equals 1/3 of the caching for each, that could lead to high latency for the overall process.
Affine Transfotm Prior to compositing an image with a photo, it may be necessary to rotate, scale and translate it. If the image is only being translated, it can be faster to use a direct sub-pixel translation function. However, rotation, scale-up and translation can all be incorporated into a single affine transform.
A general affine transform can be included as an accelerated function. Affine transfotms are limited to 2D, and if scaling down, input images should be pre-scaled via the Scale function.
Having a general affine transform function allows an output image to be constructed one block at a time, and can reduce the tinie taken to perform a number of transformations on an image since all can be applied at the same time.
A transformation matrix needs to be supplied by the client - the matrix should be the inverse matrix of the transformation desired i.e. applying the matrix to the output pixel coordinate will give the input coordinate.
A 2D matrix is usually represented as a 3 x 3 atray:
a b 0 c d 0 e f 1 Since the 3d column is always[0, 0, 11 clients do not need to specify it.
Clients instead specify a, b, c, d, e, and f.
Given a coordinate in the output image (x, y) whose top left pixel coordinate is given as (0, 0), the input coordinate is specified by: (ax + cy + e, bx + dy + f). Once the input coordinate is determined, the input image is sampled to arrive at the pixel value. Bi-littear interpolation of input image pixels is used to determine the value of the pixel at the calculated coordinate. Since affine transforms preserve parallel lines, images are processed in output vertical strips of 32 pixels wide for best average input image cache coherence.
11uee Multiply ALUs are required to perform the bi-linear interpolation in 2 cycles. Multiply ALUs I and 2 do linear interpolation in X for lines Y and Y+1 respectively, and Multiply ALU 3 does linear interpolation in Y
between the values output by Multiply ALUs I and 2.
As we move to the right across an output line in X, 2 Adder ALUs calculate the actual input image coordinates by adding 'a' to the current X value, and 'b' to the current Y
value respectively. When we advance to the next line (either the next line in a vertical strip after processing a maximum of 32 pixels, or to the first line in a new vertical strip) we update X and Y to pre-calculated start coordinate values constants for the given block The process for calculating an input coordinate is given in Fig. 96 where the following constants are set by software:
Calculate Pixel Once we have the input image coordinates, the input image must be sampled. A
lookup table is used to retum the values at the specified coordinates in readiness for bilinear interpolation. The basic process is as indicated in Fig.
97 and the following lookup table is used:
Lookup Size Details LU, Image Bilinear Image lookup [X, Y]
width by Table indexed by the integer part of X and Y.
Image 4 entries returned from Bilinear index address unit. 2 per cycle.
height Each 8 bit entry treated as fixed point 8:0 8 bits per Transfer time is 2 cycles (2 16 bit entries in FIFO hold the 4 8 bit entries) entry The affine transform requires all 4 Multiply Units and all 4 Adder ALUs, and with good cache coherence can perform an affine transfotrn with an average of 2 cycles per output pixel.
This timing assumes good cache coherence, which is true for non-skewed images. Worst case timings are severely skewed images, which meaningful Vark scripts are unlikely to contain.
The time taken to transform a 128 x 128 image is therefore 0.00033 seconds (32,768 cycles). If this is a clip image with 4 channels (including a channel), the total time taken is 0.00131 seconds (131,072 cycles).
A Vertical-Strip Write Iterator is required to output the pixels. No Read Iterator is required. However, since the affine transfotm accelerator is bound by time taken to access input image pixefs, as tnatty cache lines as possible should be allocated to the read of pixels from the input image. At least 32 should be available, and preferably 64 or inore.
Sc ' Scaling is essentially a re-sampling of an image. Scale up of an image can be performed using the Affine Ttansfotm function. Generalized scaling of an image, including scale down, is performed by the hardware acccletated Scale function. Scaling is performed independently in X and Y, so different scale factors can be used in each ditnension.
The generalized scale unit must match the Affine Transfotm scale function in tettns of registration. The generalized scaling process is as illustrated in Fig. 98. The scale in X is accomplished by Fant's re-sampling algorithm as illustrated in Fig. 99.
Where the following constants are set by software:
Constant Value K, Number of input pixels that contribute to an output pixel in X
KZ 1/K, The following tegisters are used to hold temporary variables:
Variable Value Latch, Amount of input pixel remaining unused (starts at I and decrements) Latch2 Amount of input pixels remaining to contribute to current output pixel (starts at K, and decrements) Latch3 Next pixel (in X) Latch4 Current pixel Latchs Accumulator for output pixel (unscaled) Latch6 Pixel Scaled in X (output) The Scale in Y process is illustrated in Fig. 100 and is also accomplished by a sliehtlv altered version of Fant's re-sampling algorithm to account for processing in order of X pixels.
Where the following constants are set by software:
Constant Value K, Number of input pixels that contribute to an output pixel in Y
K2 l /K, The following registers are used to hold'temporary variables:
Variable Value Latch, Amount of input pixel remaining unused (starts at l and decrements) Latch2 Amount of input pixels remaining to contribute to current output pixel (starts at K, and decrements) Latch3 Next pixel (in Y) Latch4 Curtent pixel Latchs Pixel Scaled in Y(output) The following DRAM FIFOs are used:
Lookup Size Details FIFO1 ImageWidthou-r entries 1 row of image pixels already scaled in X
8 bits per entry t cycle transfer time FIFO2 ImageWidthoUT entries I row of image pixels aiready scaled in X
16 bits per entry 2 cycles transfer time (I byte per cycle) Tessellate Image Tessellation of an image is a fonn of tiling. It involves copying a specially designed "tile" multiple times horizontally and vertically into a second (usually larger) image space. When tessellated, the small tile forms a seamless picture. One example of this is a small tile of a section of a brick wall. It is designed so that when tessellated, it forms a full brick wall. Note that there is no scaling or sub-pixel translation involved in t;essellation.
The most cache-coherent way to perform tessellation is to output the image sequentially line by line, and to repeat the same line of the input image for the duration of the line. When we finish the line, the input image must also advance to the next line (and repeat it multiple times across the output line).
An overview of the tessellation function is illustrated 390 in Fig_ 101. The Sequential Read Iterator 392 is set up to continuously read a single line of the input tile (StartLine would be 0 and EndLine would be 1). Each input pixel is written to all 3 of the Write lterators 393-395. A counter 397 in an Adder ALU counts down the number of pixels in an output line, terminating the sequence at the end of the line.
At the end of processing a line, a small software routine updates the Sequential Read Iterator's StartLine and EndLine registers before restaRing the microcode and the Sequential Read Iterator (which clears the FIFO and repeats line 2 of the tile). The Write Iterators 393-395 are not updated, and simply keep on writing out to their respective parts of the output image. The net effect is that the tile has one line repeated across an output line, and then the tile is repeated vertically too.
This ptncess does not fully use the memory bandwidth since we get good cache coherence in the input image, but it does allow the tessellation to function with tiles of any size. The process uses I Adder ALU. If the 3 Write Iterators 393-395 each write to 1/3 of the image (breaking the image on tile sized boundaries), then the entire tessellation process takes place at an average speed of 1/3 cycle per output image pixel. For an intage of 1500 x 1000, this equates to .005 seconds (5,000,000ns).
Sub-pixel Ttanslator Before compositing an image with a background, it may be necessary to translate it by a sub-pixel amount in both X and Y. Sub-pixel transforms can increase an image's size by I pixel in each dimension. The value of the region outside the image can be client determined, such as a constant value (e.g.
black), or edge pixel replication. Typically it will be better to use black.
The sub-pixel translation process is as illustrated in Fig. 102. Sub-pixel translation in a given dimension is defined by:
Pixel. = Pixe1;. * (1-Transiation) + Pixel., * Translation It can also be represented as a fonn of interpolation:
Pixel., = Pixel;,., + (Pixel;,, - Pixeli,,,)= Ttanslation Implementation of a single (on average) cycle interpolation engine using a single Multiply ALU and a single Adder ALU in conjunction is straightforward. Sub-pixel translation in both X &
Y requires 2 interpolation engines In order to sub-pixel translate in Y, 2 Sequential Read Iterators 400,401 are required (one is reading a line ahead of the other from the same image), and a single Sequential Write Iterator 403 is required.
The first intetpolation engine (interpolation in Y) accepts pairs of data from 2 streams, and linearly interpolates between them. The second inteipolation engine (intapolation in X) accepts its data as a single 1 dimensional stream and linearly interpolates between values. Both engines interpolate in I cycle on average.
Each interpolation engine 405, 406 is capable of performing the sub-pixel translation in I cycle per output pixel on average. The overall time is therefore I cycle per output pixel, with requirements of 2 Multiply ALUs and 2 Adder ALUs.
The time taken to output 32 pixels from the sub-pixel translate function is on average 320ns (32 cycles). This is enough time for 4 full cache-line accesses to DRAM, so the use of 3 Sequeatial Iterators is well within titning limits.
The total time taken to sub-pixel translate an image is therefore I cycle per pixel of the output image. A
typical image to be sub-pixel translated is a tile of size 128 * 128. The output image size is 129 * 129. The process takes 129 * 129 * l Ons = 166,410ns.
The Image Tiler function also makes use of the sub-pixel translation algorithm, but does not require the writing out of the sub-pixel-translated data, but rather processes it further.
ImaQe Tiler The high level algorithm for tiling an image is carried out in software. Once the placement of the tile has been detetmined, the appropriate colored tile must be composited. 'Ihe actual compositing of each tile onto an image is carried out in hardware via the microcoded ALUs. Compositing a tile involves both a texture application and a color application to a background image. In some cases it is desirable to compare the actual amount of texture added to the background in relation to the intended amount of texture, and use this to scale the color being applied. In these cases the texture must be applied first.
Since color application functionality and texture application functionality are somewhat independen[. they are separated into sub-functions.
The number of cycles per 4-channel tile composite for the different texture styles and coloring styles is summarised in the following table:
Constant Pixel color color Replace texture 4 4.75 25% background + tile texture 4 4.75 Average height algorithm 5 5.75 Average height algorithm with feedback 5.75 6.5 Tile Colorine and Comoositin~
A tile is set to have either a constant color (for the whole tile), or takes each pixel value from an input image.
Both of these cases may also have feedback from a texturing stage to scale the opacity (similar to thinning paint).
The steps for the 4 cases can be summarised as:
- Sub-pixel translate the tile's opacity values, - Optionally scale the tile's opacity (if feedback from texture application is enabled).
- Determine the color of the pixel (constant or from an image map).
- Composite the pixel onto the background image.
Each of the 4 cases is treated separately, in order to minimize the time taken to perform the function. The summary of time per color compositing style for a single color channel is described in the following table:
Tiling color style No feedback from Feedback from texture (cycles per texture pixel) (cycles per pixel) Tile has constant color per pixel 1 2 Tile has per pixel color from input image 1.25 2 Constant color In this case, the tile has a constant color, determined by software. While the ACP 31 is placing down one tile, the software can be determining the placement and coloring of the next tile.
The color of the tile can be determined by bi-linear interpolation into a scaled version of the image being tiled.
The scaled version of the image can be created and stored in place of the image pyramid, and needs only to be performed once per entire tile operation. If the tile size is 128 x 128, then the image can be scaled down by 128:1 in each dimension.
Without feedback When there is no feedback from the texturing of a tile, the tile is simply placed at the specified coordinates.
The tile color is used for each pixel's color, and the opacity for the composite comes from the tile's sub-pixel translated opacity channel. In this case color channels and the texture channel can be processed completely independently between tiling passes.
The overview of the process is illustrated in Fig. 103. Sub-pixel translation 410 of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the mask to be used in compositing 411 the constant tile color 412 with the background image from background sequential Read iterator.
Compositing can be performed using I Multiply ALU and 1 Adder ALU in an average time of 1 cycle per composite. Requirements are therefore 3 Multiply ALUs and 3 Adder ALUs. 4 Sequential Iterators 413-416 are n qttired, taking 320ns to read or write their contents. With an average number of cycles of I per pixel to sub-pixel translate and composite, there is sufficient time to read and write the buffers.
With feedback When there is feedback from the texturing of a tile, the tiie is placed at the specified coordinates. The tile color is used for each pixel's color, and the opacity for the composite comes from the tile's sub-pixel translated opacity channel scaled by the feedback parameter. Thus the texture values must be calculated before the color value is applied.
The overview of the process is illustrated in Fig. 97. Sub-pixel translation of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the tnask to be scaled according to the feedback read from the Feedback Sequential Read Iterator 420.
The feedback is passed it to a Scaler (I Multiply ALU) 421.
Compositing 422 can be performed using 1 Multiply ALU and I Adder ALU in an average time of 1 cycle per composite. Requirements are therefore 4 Multiply ALUs and al14 Adder ALUs.
Although the entire process can be accomplished in I cycle on avetage, the bottleneck is the memory access, since 5 Sequential Itenitors are n:quired.
With sufficient buffering, the average time is 1.25 cycles per pixel.
Color from Input Imaee One way of coloring pixels in a tile is to take the color from pixels in an input image. Again, there are two possibilities for compositing: with and without feedback from the texturing.
Without feedback In this case, the tile color simply comes from the relative pixel in the input image. 'Ilie opacity for compositing comes from the tile's opacity channel sub-pixel shi8ecl.
The overview of the process is illustrated in Fig. 105. Sub-pixel translation 425 of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the mask to be used in compositing 426 the tile's pixel color (read from the input image 428 ) with the background image 429.
Compositing 426 can be performed using I Multiply ALU and I Adder ALU in an average time of I cycle per composite. Requirements are therefore 3 Multiply ALUs and 3 Adder ALUs.
Although the entire process can be accomplished in I cycle on average, the bottleneck is the memory access, since 5 Sequential Iterators are required.
With sufficient buffering, the average time is 1.25 cycles per pixel.
With feedback In this case, the tile color still comes from the relative pixel in the input image, but the opacity for compositing is affected by the relative amount of texture height actually applied during the texturing pass. This process is as illustrated in Fig. 106.
Sub-pixel translation 431 of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the mask to be scaled 431 according to the feedback read from the Feedback Sequential Read Iterator 432.
The feedback is passed to a Scaler (I
Multiply ALU) 431.
Compositing 434 can be performed using I Multiply ALU and I Adder ALU in an average time of 1 cycle per composite.
Requirements are therefore al14 Multiply ALUs and 3 Adder ALUs. Although the entire process can be accomplished in I cycle on average, the bottleneck is the memory access, since 6 Sequential Iterators are required.
With sufficient buffering, the average time is 1 S cycles per pixel.
Tile Texturine Each tile has a surface texture defined by its texwre chaonel. The texture must be sub-pixel translated and then applied to the output image. There are 3 styles of teacture compositing:
Replace texture 250% background + tile's texture Average height algorithm In addition, the Average height algorithm can save feedback parameters for color compositing.
The time taken per texture compositing style is summarised in the following table:
Tiling color style Cycles per pixel Cycles per pixel (no feedback from (feedback from texture) texture) Replace texture 1 -25% background + tile texture value 1 -Average height algorithm 2 2 Replace texture In this instance, the texture from the tile replaces the texture channel of the image, as illustrated in Fig. 107.
Sub-pixel translation 436 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from this sub-pixel translation is fed directiv to the Sequential Write lterator 437.
The time taken for replace texture compositing is 1 cycle per pixel. There is no feedback, since 100% of the texture value is always applied to the background. There is therefore no requirement for processing the channels in any particutar order.
25% Backeround + Tile's Texture In this instance, the texture from the tile is added to 25% of the existing texture value. The new value must be greater than or equal to the original value. In addition, the new texture value must be clipped at 255 since the texture channel is only 8 bits. The process utilised is iliustrated in Fig. 108.
Sub-pixel transiation 440 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from this sub-pixel translation 440 is fed to an adder 441 where it is added to'/. 442 of the background texture value. Min and Max functions 444 are provided by the 2 adders not used for sub-pixel ttanslation and the output written to a Sequential Write Iterator 445.
The time taken for this style of texture compositing is 1 cycle per pixel.
There is no feedback, since 100% of the texture value is considered to have been applied to the background (even if clipping at 255 occurred). There is therefore no requirement for processing the channels in any particular order.
Averaee heisht aleorithm In this texture application algorithm, the average height under the tile is computed, and each pixel's height is compared to the average height. If the pixel's height is less than the average, the stroke height is added to the background height. If the pixel's height is greater than or equal to the average, then the stroke height is added to the average height. Thus background peaks thin the stroke. The height is constrained to increase by a minimum amount to prevent the background from thinning the stroke application to 0 (the minimum amount can be 0 however). 'Me height is also clipped at 255 due to the 8-bit resolution of the texture channel.
There can be feedback of the difference in texture applied versus the expected amount applied. The feedback amount can be used as a scale factor in the application of the tile's color.
In both cases. the average texture is provided by software, calculated by performing a bi-level interpolation on a scaled version of the texture map. Software detetmines the next tile's average textune height while the current tile is being applied. Software must also provide the minimum thickness for addition, which is typically constant for the entire tiling process.
Without feedback With no feedback, the texture is simply applied to the background texture, as shown in Fig. 109.
4 Sequential Iterators are required, which means that if the process can be pipelined for 1 cycle, the memory is fast enough to keep up.
Sub-pixel translation 450 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. Each Min & Max function 451,452 requires a separate Adder ALU in order to complete the entire operation in I cycle. Since 2 are already used by the sub-pixel translation of the texture, there are not enough remaining for a I cycle average time.
The average time for processing I pixel's texture is therefore 2 cycles. Note that there is no feedback, and hence the color channel order of compositing is irrelevant.
With feedback This is conceptually the same as the cate without feedback, except that in addition to the standard processing of the texture application algorithm, it is necessary to also record the proportion of the texture actually applied. The proportion can be used as a scale factor for subsequent compositing of the tile's color onto the background image. A
flow diagram is illustrated in Fig. I 10 and the following lookup table is used:
Lookup Size Details LU, 256 entries 1/N
16 bits per entry Table indexed by N (range 0-255) Resultant 16 bits treated as fixed point 0:16 Each of the 256 entries in the software provided 1IN table 460 is 16 bits, thus requiring 16 cache lines to hold continuously.
Sub-pixel translation 461 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. Each Min 462 & Max 463 function requires a separate Adder ALU in order to complete the entire operation in I cycle. Since 2 are already used by the sub-pixel ttanslation of the texture, there are not enough remaining for a I cycle average time.
The average time for processing 1 pixel's texture is therefore 2 cycles.
Sufficient space must be allocated for the feedback data area (a tile sized image channel). The texture must be applied before the tile's color is applied, since the feedback is used in scaling the tile's opacity.
CCD Imaee Interuolator Images obtained from the CCD via the ISI 83 (Fig. 3) are 750 x 500 pixels.
When the image is captured via the ISI, the orientation of the camera is used to rotate the pixels by 0, 90, 180, or 270 degrees so that the top of the image cotresponds to 'up'. Since every pixel only has an R, G, or B color component (rather than all 3), the fact that these have been rotated must be taken into account when interpreting the pixel values. Depending on the orientation of the camera, each 2x2 pixel block has one of the configurations illustrated in Fig. i 11:
Several processes need to be performed on the CCD captured image in order to transform it into a useful form for processing:
Up-interpolation of low-sample rate color components in CCD image (interpreting correct orientation of pixels) Color conversion from RGB to the intemal color space Scaling of the intemal space image from 750 x 500 to 1500 x 1000.
Writing out the image in a planar fotmat The entire channel of an image is required to be available at the same time in order to allow warping. In a low memory model (8MB), there is only enough space to hold a single channel at full resolution as a temporary object.
Thus the color conversion is to a single color channel. The limiting factor on the process is the color conversion, as it involves tri-linear interpolation from RGB to the internal color space. a process that takes 0.026ns per channel (750 x 500 x 7 cycles per pixel x l Ons per cycle = 26:250,000ns).
It is important to perform the color conversion before scaling of the intemal color space image as this reduces the number of pixels scaled (and hence the overall process time) by a factor of 4.
The requirements for all of the transformations may not fit in the ALU scheme.
The transformations are therefore broken into two phases:
Phase 1: Up-interpolation of low-sample rate color components in CCD image (interpreting correct orientation of pixels) Color conversion from RGB to the intemal color space Writing out the image in a planar format Phase 2: Scaling of the intemal space image from 750 x 500 to 1500 x 1000 Separating out the scale function implies that the small color converted image must be in memory at the same time as the large one. The output from Phase 1 (0.5 MB) can be safely written to the memory area usually kept for the image pyramid (1 MB). The output from Phase 2 can be the general expanded CCD
image. Separation of the scaling also allows the scaling to be accomplished by the Affine Transform, and also allows for a different CCD resolution that may not be a simple 1:2 expansion.
Phase 1: Up-interpolation of low-sample rate color components.
Each of the 3 color components (R, G, and B) needs to be up interpolated in order for color conversion to take place for a given pixel. We have 7 cycles to perfotm the interpolation per pixel since the color conversion takes 7 cycles.
Interpolation of G is straightforward and is illustrated in Fig. 112.
Depending on orientation, tfie actual pixel value G altetnates between odd pixels on odd lines & even pixels on even lines, and odd pixels on even lines & even pixels on odd lines. In both cases, linear interpolation is all that is required. Interpolation of R and B components as illustrated in Fig. 113 and Fig. 113, is more complicated, since in the horizontal and vertical directions, as can be seen from the diagrams, access to 3 rows of pixels simultaneously is required, so 3 Sequential Read Iterators are required, each one offset by a single row. In addition, we have access to the previous pixel on the same row via a latch for each row.
Each pixel therefore contains one component from the CCD, and the other 2 up-interpolated. When one component is being bi-linearly interpolated, the other is being linearly interpolated. Since the interpolation factor is a constant 0.5, interpolation can be calculated by an add and a shift 1 bit right (in 1 cycle), and bi-linear int.erpolation of factor 0.5 can be calcuhtted by 3 adds and a shift 2 bits right (3 cycles).
The total number of cycles required is therefore 4, using a single multiply ALU.
Fig. 115 illusttates the case for rotation 0 even line even pixel (EL, EP), and odd line odd pixel (OL, OP) and Fig. 116 illustrates the case for rotation 0 even line odd pixel (EL, OP), and odd line even pixel (OL, EP). The other rotations are simply different fonns of these two expressions.
Color conversion Color space conversion from RGB to Lab is achieved using the same method as that descn"bed in the general Color Space Convert funetion, a process that takes 8 cycles per pixel. Phase I
processing can be described with reference to Fig. 117.
The up-interpolate of the RGB takes 4 cycles (1 Multiply ALU), but the conversion of the color space takes 8 cycles per pixel (2 Multiply ALUs) due to the lookup transfer time.
Phase 2 Scaline the image This phase is concemed with up-interpolating the image from the CCD resolution (750 x 500) to the working photo resolution (1500 x 1000). Scaling is accomplished by runtting the Affme transfontt with a scale of 1:2. The timing of a general affine transform is 2 cycles per output pixel, which in this case means an elapsed scating time of 0.03 seconds.
liluminate Imaee Once an image has been processed, it can be illuminated by one or more light sources. Light sources can be:
1_ Directional - is infmitely distant so it casts parallel light in a single direction 2. Omni - casts unfocused lights in ail directions.
3. Spot - casts a focused beam of light at a specific target point. There is a cone and penumbra associated with a spotlight.
The scene may also have an associated bump-map to cause reflection angles to vary. Ambient light is also optionally present in an illuminated scene.
In the process of acceletated illumination, we are concemed with illuminating one image channel by a single light source. Multiple light sources can be applied to a single image channel as multiple passes one pass per light source. Multiple channels can be processed one at a time with or without a bump-map.
The normal surfane vector (N) at a pixel is computed from the bump-map if pre.sent The default nomtal vector, in the absence of a bump-map, is perpendicular to the image plane i.e.
N=[0, 0, l].
The viewing vector V is always perpendicular to the image plane i.e. V = j0, 0, 1].
For a directional light source, the light source vector (L) from a pixel to the light source is constant across the entire image, so is computed once for the entire image. For an omni light source (at a finite distance), the light source vector is computed independently for each pixel.
A pixel's reflection of ambient light is computed according to: I,k,Od A pixel's diffuse and specular reflection of a light source is computed according to the Phong model:
f,alP[kaOe(1=1=L) + ksOs(R=V)"]
When the light source is at infmity, the light source intensity is constant across the image.
Each light source has three contributions per pixel Ambient Contribution Diffuse contribution Specular contribution The light source can be defined using the following variables:
dL Distance from light source f,a Attenuation with distance [f.,, = I / dL ]
R Normalised reflection vector [R = 2N(N.L )- L]
I. Ambient light intensity (p Diffuse light coefficient k. Ambient reflection coefficient kd Diffuse reflection coefficient k, Specular reflection coefficient kx Specular color coefficient L Normalised light source vector N Normalised surface normal vector n Specular exponent Od Object's diffuse color (i.e. image pixel color) O. Object's specular color (kuOd + (I- ku)lP) V Normalised viewing vector [V = [0, 0, 1]]
The same reflection coefficients (kõ k,, kd) are used for each color component.
A given pixel's value will be equal to the ambient contribution plus the sum of each light's difl'use and specular contribution.
Sub-Processes of Illumination Calculation In order to calculate diffuse and specular contributions, a variety of other calculations are required. These are calculations of:
N
L
N=L
R=V
fõ, f-P
Sub-processes are also defined for calculating the contributions of:
ambient diffuse specular The sub-processes can then be used to calculate the overall illumination of a light source. Since there are only 4 multiply ALUs, the microcode for a particular type of light source can have sub-processes intermingled appropriately for perfotmance.
Calculation of I/JX
The Vark lighting model uses vectors. In many cases it is important to calculate the inverse of the length of the vector for normalization purposes. Calculating the inverse of the length requires the calculation of I/SquareRoot[X]_ Logically, the process can be represented as a process with inputs and outputs as shown in Fig. 118.
Referring to Fig. 119, the calculation can be made via a lookup of the estimation, followed by a single iteration of the following function:
Vn+l -'/: Vn(3 - XV.2) The number of iterations depends on the accuracy required_ In this case only 16 bits of precision are required.
The table can therefore have 8 bits of precision, and only a single iteration is necessary. The following constant is set by software:
Constant Value K, 3 The following lookup table is used:
Lookup Size Details LU, 256 entries I/SquareRoot[XJ
8 bits per entry Table indexed by the 8 highest significant bits of X.
Resultant 8 bits treated as fixed point 0:8 Calculation of N
N is the surface normal vector. When 8tene is no bump-map, N is constant. When a bump-map is present, N
must be calculated for each pixeL
No bttmo-man When there is no bump-map, there is a fixed norma! N that has the following properties:
N=[XN, YN, ZNI -[0= 0, 11 lIMI = I
lnfmi =1 normalizsd N = N
These properties can be used instead of specifically calculating the notmal vector and 14INII and thus optimize other calculations.
With bump-map As illustrated in Fig. 120, when a bump-map is present, N is calculated by comparing bump-map values in X
and Y dimensions. Fig. 120 shows the calculation of N for pixel P1 in terms of the pixels in the same row and column, but not including the value at P I itself. The calculation of N is made resolution mdependent by multiplying by a scale factor (same scale factor in. X & Y). This process can be represented as a process having inputs and outputs (ZN is always 1) as illustrated in Fig. 121.
As ZN is always 1. Consequently XN and YN are not normalued yet (since ZN =
1). Normalization of N is delayed until after calculation of N.L so that there is only I multiply by l4jNJI instead of 3.
An actual process for calculating N is illustrated in Fig. 122.
The following constant is set by software:
Constant Value K, ScaleFactor (to make N resolution independent) Calculation of L
Directional liehts When a light source is infinitely distant, it has an effective constant light vector L. L is normalized and calculated by software such that:
L = [XL, YL, ZL]
IILII =1 l4Iu1 = I
These properties can be used instead of specifically calculating the L and 141LI) and thus optimize other calculations. This process is as illustrated in Fig. 123.
Omni liQhts and Spotlights When the light source is not infinitely distant, L is the vector from the current point P to the light source PL. Since P
[Xp, Yp, 0], L is given by:
L = [XL, YL, ZLl XL = XP - XPL
YL=YP-YeL
ZI. - -ZPL
We notmalize XL, YL and ZL by multiplying each by 141LIJ. The calcutation of 1AILf J (for later use in notmalizing) is accomplished by calculating V = XL2 + YL2+ ZL2 and then calculating V-' In this case, the calculation of L can be represented as a process with the inputs and outputs as indicated in Fig. 124.
Xp and YP are the coordinates of the pixel whose illumination is being calculated. Zp is always 0.
The actual process for calculating L can be as set out in Fig- 125.
Where the following constants are set by software:
Constant Value K, XPL
K3 ZPi (as ZP is 0) K4 I-zm Calculation ofN.L
Calculating the dot product of vectors N and L is defined as:
XNXL + YNYL + ZNZL
No bumn-mat) _ When there is no bump-map N is a constant [0, 0, 1]. N.L therefore reduces to ZL.
With bump-map When there is a bump-map, we must calculate the dot product directly. Rather than take in normalized N
components, we norinalize after taking the dot product of a non-normalized N
to a notmalized L. L is either normalized by software (if it is constant), or by the Calculate L process.
This process is as illustrated in Fig. 126.
Note that ZN is not required as input since it is defined to be 1. However 1fNIJ is required instead, in order to notmalize the result One actual process for calculating N.L is as illustrated in Fig. 127.
Calculation of R*V
R=V is required as input to specular contnbution calculations. Since V=[0, 0, 1], only the Z components are required. R= V therefore reduces to:
R=V = 2Zr,(N.L ) - ZL
In addition, since the un-normalized ZN = I, normalized ZN = 14INII
No bumo-mao The sitnplest implementation is when N is constant (i.e. no bump-map). Since N
and V are constant, N.L and R=V can be simplified:
V = [0, 0, 11 N = [0, 0, 1]
L a [Xt., Yi, ZLl N.L = ZL
R=V =2ZN(N.L)-ZL
x24_ZL
= ZL
When L is constant (Directional light source), a normalized ZL can be supplied by soRware in the form of a constant whenever R-V is t+equired. When L varies (Omni lights and Spotlights), nomialiaed ZL must be calcutated on the fly. It is obtained as output from the Calculate L process_ With bumtrmao When N is not constant, the process of calculating R=V is simply an implementation of the generalized formula:
R*V = 2ZN(N.L ) - ZL
The inputs and outputs are as shown in Fig. 128 with the an actual implementation as shown in Fig. 129.
Calculation of Attenuation Factor Directional lights When a light source is infinitely distant, the intensity of the light does not vary across the image. The attenuation factor f. is therefore 1. This constant can be used to optimize illumination calculations for infinitely distant light sources.
Omni liehts and Saotli~ltts When a light source is not infinitely distant, the intensity of the light can vary according to the following formula:
f. = fo + fi/d + f2/dZ
Appropriate settings of coefficients fo, fl, and f, allow light intensity to be attenuated by a constant, linearly with distance, or by the square of the distance.
Since d = JILIJ, the calculation of f. can be represented as a process with the following inputs and outputs as illustrated in Fig. 130.
The actual process for calculating f,a can be defined in Fig. 131.
Where the following constants are set by sofftware:
Constant Value K, F2 f~
K3 Fo Calculation of Cone and Penumbra Factor Directional lights and Omni lights These two light sources are not focused, and therefore have no cone or penumbra. The cone-penumbra scaling factor f, is therefore 1. This constant can be used to optimize iliutnination calculations for Directional and Omni light sources.
S tli ts A spotlight focuses on a particular target point (PT). The intensity of the Spotlight varies according to whether the particular point of the image is in the cone, in the penumbra, or outside the cone/penuttlbra region.
Turning now to Fig. 132, there is illustrated a gtaph of f, with respect to the penumbra position. Inside the cone 470, fW is 1, outside 471 the penumbra fW is 0. From the edge of the cone through to the end of the penumbra, the light intensity varies accotding to a cubic function 472.
The various vectors for penumbra 475 and cone 476 calculation are as illustrated in Fig. 133 and Fig_ 134.
Looking at the surface of the image in I dimension as shown in Fig. 134, 3 angles A, B, and C are defined. A
is the angle between the target point 479, the light source 478, and the end of the cone 480. C is the angle between the target point 479, light source 478, and the end of the penumbra 481 _ Both are fixed for a given light source. B is the angle between the target point 479, the light source 478, and the position being calculated 482, and therefore changes with every point being calculated on the image.
We normalize the range A to C to be 0 to 1, and find the distance that B is along that angle tange by the formula:
(B-A)/(C-A) The range is forcxd to be in the range 0 to 1 by ttuncation, and this value used as a lookup for the cubic approximation of f,.
The calculation of f.Q can therefore be represented as a ptvicess with the inputs and outputs as illusttated in Fig. 135 with an actual process for calculating fv is as shown in Fig. 136 where the following constants are set by software:
Constant Value K, XLT
K5 1/(C-A). [MAXNUM if no penumbra]
The following lookup tables are used:
Lookup Size Details LU, 64 entries Arcos(X) 16 bits per entry Units are same as for constants KS and KQ
Table indexed by highest 6 bits Result by linear interpolation of 2 entries Timing is 2 * 8 bits * 2 enaries = 4 cycles LU2 64 entries Light Response function f, 16 bits per entry F(l) = 0, F(0) = 1, others are according to cubic Table indexed by 6 bits (1:5) Result by linear interpolation of 2 entries Timing is 2* 8 bits = 4 cycles Calculation of Ambient Contnbution Regardless of the number of lights being applied to an image, the ambient light contribution is performed once for each pixel, and does not depend on the bump-map.
The ambient calculation process can be represented as a process with the inputs and outputs as illustrated in Fig. 131. The implementation of the process requires multiplying each pixel from the input image (Od) by a constant value (I,k,), as shown in Fig. 138 where the following constant is set by software:
Constant Value K, Ik.
Calculation of DitTuse Contribution Each light that is applied to a surface produces a diffuse illumination. The diffuse illumination is given by the formula:
diffuse = kdbd(N.L ) There are 2 different implementations to consider.
Implementation 1- constant N and L
When N and L are both constant (Directional light and no bump-map):
N.L =ZL
Therefore:
ditfitse = kdOdZL
Since Od is the only variable, the actual process for calculating the difl'use contribution is as illustrated in Fig.
139 where the following constant is set by software:
Constant Value Ki kd(N.L ) = kdZL
Implementation 2- non-constant N & L
When either N or L are non-constant (either a bump-map or illumination from an Omni light or a Spotlight), the diffuse calculation is performed directly according to the formula:
diffuse =1caOd(N.L ) The diffuse calculation process can be represented as a process with the inputs as illusttated in Fig. 140. N.L
can either be calculated using the Calculate N.L Process, or is provided as a constant. An actual process for calculating the ditl'use contribution is as shown in Fig. 141 where the following constants are set by software:
Constant Value Ki kd Calculation of 3cecular Contribution Each light that is applied to a surface produces a specular illumination. The specular illumination is given by the formula:
specular = kOs(R=V) where O, = kKOd + (l-ktt)lP
There are two implementations of the Calculate Specular process.
Implementation t- constant N and L
The first implementation is when both N and L are constant (Directional light and no bump-map). Since N, L
and V are constant, N.L and R=V are also constant:
V=[0,0, 1]
N = [0, 0, 1]
L[XL,1'L,ZL]
N.L = ZL
R=V = 2ZN(N.L ) - ZL
=2ZL-ZL
-ZL
The specular calculation can thus be reduced to:
specular = kOs ZL"
= kyZL"(k.Od + (1-1.)IP) = kJ(-ZL"Od + (1-k.)1PksZ( Since only Od is a variable in the specular calculation, the calculation of the specular contribution can therefore be represented as a process with the inputs and outputs as indicated in Fig. 142 and an actual process for calculating the specular contribution is illustrated in Fig. 143 where the following constants are set by software:
Constant Value K, kjcwZL"
K2 (1-ku)IpksZL"
lmnlementation 2- non constant N and L
This implementation is when either N or L are not constant (either a bump-map or illumination from an Omni light or a Spotlight). This implies that R=V must be supplied, and hence R=V"
must also be calculated.
The specular calculation process can be represented as a process with the inputs and outputs as shown in Fig.
144. Fig. 145 shows an actual process for calculating the specular contribution where the following constants are set by software:
Constant Value Ki l4 KZ kx K3 (I-ku)l:P
The following lookup table is used:
Lookup Size DetaiLs LU, 32 entries X"
16 bits per Table indexed by 5 highest bits of integer R=V
entry Result by linear interpolation of 2 entries using fraction of R.V.
Interpolation by 2 Multiplies.
The time taken to retrieve the data from the lookup is 2= 8 bits * 2 entries = 4 cycles.
When ambient light is the only illumination If the ambient contribution is the only light source, the process is very straightforward since it is not necessary to add the ambient light to anything with the overall process being as illustrated in Fig. 146. We can divide the image vertically into 2 sections, and process each half simultaneously by duplicating the ambient light logic (thus using a total of 2 Multiply ALUs and 4 Sequential Iterators). The timing is therefore'/~
cycle per pixel for ambient light application.
The typical illumination case is a scene lit by one or more lights. In these cases, because ambient light calculation is so cheap, the ambient calculation is included with the processing of each light source. The first light to be processed should have the cotrect I,k, setting, and subsequent lights should have an l,ka value of 0 (to prevent multiple ambient contributions).
If the ambient light is processed as a separate pass (and not the fust pass), it is necessary to add the ambient light to the current calculated value (requiring a read and write to the same address). The process overview is shown in Fig. 147.
The process uses 3 Image Iterators, I Multiply ALU, and takes I cycle per pixel on average.
Infinite LiQht Source In the case of the infinite light source, we have a constant light source intensity across the image. Thus both L
and f., are constant.
No Bumo Map When there is no bump-map, there is a constant normal vector N[0, 0, 1 J. The complexity of the illumination is greatly reduced by the constants of N, L, and f.. The process of applying a single Directional light with no bump-map is as illustrated in Fig. 147 where the following constant is set by software:
Constant Value K, IP
For a single infinite light source we want to perform the logical operations as shown in Fig. 148 where K, through Ka are constants with the following values:
Constant Value K, Kd(NsL) = Kd Lz KZ kK
K3 Ka(NsH)" = K. Hz2 The process can be simplified since K2, K3, and Ke are constants. Since the complexity is essentially in the calculation of the specular and diffuse contributions (using 3 of the Multiply ALUs), it is possible to safely add an ambient calculation as the 4'" Multiply ALU. The first infmite light source being processed can have the true ambient light parameter Ik; and all subsequent infmite lights can set Ik. to be 0. The ambient light calculation becomes effectively fi-ee.
If the infinite light source is the fust light being applied, there is no need to include the existing contributions made by other light sources and the situation is as illustrated in Fig. 149 where the constants have the following values:
Constant Value K, kd(LsN) = kdLz Ks (1- k,(NsH)")IP = (I - k,Hz")IP
IC6 kxks(NsH)" IP = kuksHz"Ip K7 I.k.
If the infinite light source is not the fust light being applied, the existing contribution made by previously processed lights must be included (the same constants apply) and the situation is as illustrated in Fig. 148.
In the first case 2 Sequential Iterators 490,491 are required, and in the second case, 3 Sequential Iterators 490, 491, 492 (the extra Iterator is required to read the previous light contributions). In both cases, the application of an infinite light source with no bump map takes I cycle per pixel, including optional application of the ambient light.
With Bump Map When there is a bump-map, the normal vector N must be calculated per pixel and applied to the constant light source vector L. 1AjNjj is also used to calculate R=V, which is required as input to the Calculate Specular 2 process.
The following constants are set by software:
Constant Value K, XL
K2 yL
K, ZL
Bump-map Sequential Read Iterator 490 is responsible for reading the current line of the bump-map. lt provides the input for determining the slope in X. Bump-map Sequential Read Iterators 491, 492 and are responsible for reading the line above and below the current line. They provide the input for determining the slope in Y.
Omni Liehts In the case of the Omni light source, the lighting vector L and attenuation factor fõ, change for each pixel across an image. Therefore both L and f,,,, must be calculated for each pixel.
No Bump Map When there is no bump-map, there is a constant normal vector N [0, 0, 1].
Although L must be calculated for each pixel, both N.L and R=V are simplified to ZL. When there is no bump-map, the application of an Omni light can be calculated as shown in Fig. 149 where the following constants are set by software:
Constant Value K, XP
KZ YP
The algorithm optionally includes the contributions from previous light sources, and aiso includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0.
The algorithm as shown requires a total of 19 multiply/accumulates. The times taken for the lookups are I
cycle during the calculation of L, and 4 cycles during the specular contribution. The processing time of 5 cycles is therefore the best that can be accomplished. The time taken is increased to 6 cycles in case it is not possible to optimally microcode the ALUs for the function. The speed for applying an Omni light onto an image with no associated bump-map is 6 cycles per pixel.
With Bumtrman When an Omni light is applied to an image with an associated a bump-map, calculation of N, L, N.L and R=V are all necessary. The process of applying an Omni light onto an image with an associated bump-map is as indicated in Fig.
150 where the following constants are set by software:
Constant Value K, XP
The algorithm optionally includes the contnbtttions from previous light sources, and also includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0.
The algorithm as shown requires a total of 32 multiply/accumulates. The times taken for the lookups are I
cycle each during the calculation of both L and N, and 4 cycles for the specular contribution. However the lookup required for N and L are both the same (thus 2 LUs implement the 3 LUs). The processing time of 8 cycles is adequate.
The time taken is extended to 9 cycles in case it is not possible to optimally microcode the ALUs for the function. The speed for applying an Omni light onto an image with an associated bump-map is 9 cycles per pixel.
S tli ts Spotlights are similar to Omni lights except that the attenuation factor fõ is modified by a cone/penumbra factor fp that effectively focuses the light around a target No bumn-map When there is no bump-map, there is a constant normal vector N [0, 0, 1].
Although L must be calculated for each pixel, both N.L and R=V are simplified to ZL. Fig. 151 illustrates the application of a Spotlight to an image where the following constants are set by software:
Constant Value K, X, K, IP
The algorithm optionally includes the contributions from previous light sources, and also includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0.
The algorithm as shown requires a total of 30 multiply/accumulates. The times taken for the lookups are I
cycle during the calculation of L, 4 cycles for the specular contribution, and 2 sets of 4 cycle lookups in the cone/penumbra calculation.
With bumo-map When a Spotlight is applied to an image with an associated a bump-map, calculation of N, L, N.L and R=V
are all necessary. The process of applying a single Spotlight onto an image with associated bump-map is illustrated in Fig. 152 where the following constants are set by software:
The algorithm optionally includes the contributions from previous light sources, and also includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0. The algorithm as shown requires a total of 41 multiply/accumulates.
Print Head 44 Fig. 153 illustrates the logical layout of a single print Head which logically consists of 8 segments, each printing bi-level cyan, magenta, and yellow onto a portion of the page.
Loading a seernent for printing Before anything can be printed, each of the 8 segments in the Print Head must be loaded with 6 rows of data corresponding to the following relative rows in the final output image:
Row 0 = Line N, Yellow, even dots 0, 2,4,6,8,...
Row I = Line N+8, Yellow, odd dots 1, 3, 5, 7, ...
Row 2= Line N+10, Magenta, even dots 0, 2, 4, 6, 8, ...
Row 3= Line N+18, Magenta, odd dots 1, 3, 5, 7, ...
Row 4= Line N+20, Cyan, even dots 0, 2, 4, 6, 8, ...
Row 5= Line N+28, Cyan, odd dots 1, 3, 5, 7, _-Each of the segments prints dots over different parts of the page. Each segment prints 750 dots of one color, 375 even dots on one row, and 375 odd dots on another. 71te 8 segments have dots corresponding to positions:
Segment First dot Last dot Each dot is represented in the Print Head segment by a single bit. The data must be loaded I bit at a time by placing the data on the segment's BitValue pin, and clocked in to a shift register in the segment according to a BitClock. Since the data is loaded into a shift register, the order of loading bits must be correct_ Data can be clocked in to the Print Head at a maximum rate of 10 MHz Once all the bits have been loaded, they must be transferred in parallel to the Print Head output buffer, ready for printing. The transfer is accomplished by a single pulse on the segment's ParallelXferClock pin_ Controlline the Print In order to conserve power, not all the dots of the Print Head have to be printed simultaneously. A set of control lines enables the printing of specific dots. An external controller, such as the ACP, can change the number of dots printed at once, as well as the duration of the print pulse in accordance with speed and/or power requirements.
Each segment has 5 NozzleSelect lines, which are decoded to select 32 sets of nozzles per row. Since each row has 375 nozzles, each set contains 12 nozzles. There are also 2 BankEnable lines, one for each of the odd and even rows of color. Finally, each segment has 3 ColorEnable lines, one for each of C, M, and Y colors. A pulse on one of the ColorEnable lines causes the specified noules of the color's specified rows to be printed. A pulse is typically about 2 s in duration.
If all the segments are controlled by the same set of NozzleSelect, BankEnable and ColorEnable lines (wired externally to the print head), the following is true:
If both odd and even banks print simuNaneously (both BankEnable bits are set), 24 nozzles fire simultaneously per segment, 192 nozzles in all, consuming 5.7 Watts.
If odd and even banks print independently, only 12 nozzles fire simultaneously per segment, 96 in all, consuming 2.85 Watts.
Print Head Interface 62 The Print Head Interface 62 connects the ACP to the Print Head, providing both data and appropriate signals to the external Print Head. The Print Head Interface 62 works in conjunction with both a VLIW processor 74 and a software algorithm running on the CPU in order to print a photo in approximately 2 seconds.
An overview of the inputs and outputs to the Print Head Interface is shown in Fig. 154. The Address and Data Buses are used by the CPU to address the various registers in the Print Head Interface. A single BitClock output line connects to all 8 segments on the print head. The 8 DataBits lines lead one to each segment, and are clocked in to the 8 segments on the print head simuhaneously (on a BitClock pulse). For example, dot 0 is transferred to segmenta, dot 750 is transfermd to segment,, dot 1500 to segment2 etc. simultaneously.
The VLIW Output FIFO contains the dithered bi-level C, M, and Y 6000 x 9000 resolution print image in the correct order for output to the 8 DataBits. The ParallelXferClock is connected to each of the 8 segments on the print head, so that on a single pulse, all segments Iransfer their bits at the same time. Finally, the NozzleSelect, BankEnable and ColorEnable lines are connected to each of the 8 segments, allowing the Print Head Interface to control the duration of the C, M, and Y drop pulses as well as how many drops are printed with each pulse. Registers in the Print Head Interface allow the specification of pulse durations between 0 and 6 s, with a typical duration of 2 s.
Printing an Image There are 2 phases that must occur before an image is in the hand of the Artcam user.
1. Preparation of the image to be printed 2. Printing the prepared image Preparation of an image only needs to be performed once. Printing the image can be performed as many times as desired_ Prenare the Image Preparing an image for printing involves:
I. Convert the Photo Image into a Print Image 2. Rotation of the Print Image (internal color space) to align the output for the orientation of the printer 3. Up-interpolation of compressed channels (if necessary) 4. Color conversion from the intemal color space to the CMY color space appropriate to the specific printer and ink At the end of image preparation, a 4.5MB correctly oriented 1000 x 1500 CMY
image is ready to be printed.
Convert Photo Image to Print Image The conversion of a Photo Image into a Print Image requires the execution of a Vark sa-ipt to perform image processing. The script is either a default image enhancement script or a Vark script taken from the cutrently inserted Artcard. The Vark script is executed via the CPU, accelerated by functions performed by the VLIW Vector Processor.
Rotate the Print Imaee The image in memory is originally oriented to be top upwards. This allows for straightforward Vark processing. Before the image is printed, it must be aligned with the print roll's orientation_ The re-alignment only needs to be done once. Subsequent Prints of a Print Image will already have been rotated appropriately.
The transformation to be applied is simply the inverse of that applied during capture from the CCD when the user pressed the "Image Capture" button on the Artcam. If the original rotation was 0, then no ttansformation needs to take place. If the original rotation was +90 degrees, then the rotation before printing needs to be -90 degrees (same as 270 degrees). The method used to apply the rotation is the Vark accelerated Affine Transform function. The Affine Transform engine can be called to rotate each color channel independently.
Note that the color channels carmot be rotated in place. Instead, they can make use of the space previously used for the expanded single channel (I.5MB).
Fig. 155 shows an example of rotation of a Lab image where the a and b channels are compressed 4:1. The L
channel is rotated into the space no longer required (the single channel area), then the a channel can be rotated into the space left vacant by L. and finally the b channel can be rotated. The total time to rotate the 3 channels is 0.09 seconds.
It is an acceptable period of time to elapse before the 5rst print image.
Subsequent prints do not incur this overhead.
Up Interpolate and color convert The Lab image must be converted to CMY before printing. Different processing occurs depending on whether the a and b channels of the Lab image is compressed. If the Lab image is compressed, the a and b channels must be decompressed before the color conversion occurs. If the Lab image is not compressed, the color conversion is the only necessary step. The Lab image must be up interpolated (if the a and b channels are compressed) and converted into a CMY image. A single VLIW process combining scale and color transform can be used.
The method used to perform the color conversion is the Vark accelerated Color Convert function. The Affine Transform engine can be called to rotate each color channel independently. The color channels cannot be rotated in place. Instead, they can make use of the space previously used for the expanded single channel (1.5MB).
Print the Image Printing an image is concerned with taking a correctly oriented 1000 x 1500 CMY image, and generating data and signals to be sent to the external Print Head. The process involves the CPU working in conjunction with a VLIW
process and the Print Head Interface.
The resolution of the image in the Artcam is 1000 x 1500. The printed image has a resolution of 6000 x 9000 dots, which makes for a very straightforward relationship: I pixel = 6 x 6 =
36 dots. As shown in Fig. 156 since each dot is 16.6 m, the 6 x 6 dot square is 100 m square. Since each of the dots is bi-level, the output must be dithered.
The image should be printed in approximately 2 seconds. For 9000 rows of dots this implies a time of 222 s time between printing each row. The Print Head Interface must generate the 6000 dots in this time, an average of 37ns per dot. However, each dot comprises 3 colors, so the Print Head Interface must generate each color component in approximately 12ns, or 1 clock cycle of the ACP (IOns at 100 MHz). One VLIW
process is responsible for calculating the next line of 6000 dots to be printed. The odd and even C, M, and Y dots are generated by dithering input from 6 different 1000 x 1500 CMY image lines. The second VLIW process is responsible for taking the previously calculated line of 6000 dots, and correctly generating the 8 bits of data for the 8 segments to be transferred by the Print Head Interface to the Print Head in a single transfer.
A CPU process updates registers in the fist VLIW process 3 times per print line (once per color component =
27000 times in 2 secondsO, and in the 2nd VLIW process once every print line (9000 times in 2 seconds). The CPU
works one line ahead of the VLIW process in order to do this.
Finally, the Print Head Interface takes the 8 bit data from the VLIW Output FIFO, and outputs it unchanged to the Print Head, producing the BitClock signals appropriately. Once all the data has been transfemed a ParallelXferClock signal is generated to load the data for the next print line. In conjunction with transferring the data to the Print Head, a separate ttmer is generating the signals for the different print cycles of the Print Head using the NozzleSelect, ColorEnable, and BankEnable lines a specified by Print Head Interface internal registers.
The CPU also controls the various motors and guillotine via the parallel interface during the print process.
Generate C. M. and Y Dots The input to this process is a 1000 x 1500 CMY image correctly oriented for printing. The image is not compressed in any way. As illustrated in Fig. 157, a VLIW microcode program takes the CMY image, and generates the C, M, and Y pixels required by the Print Head Interface to be dithered.
The process is run 3 times, once for each of the 3 color components. The process consists of 2 sub-processes run in parallel - one for producing even dots, and the other for producing odd dots. Each sub-process takes one pixel from the input image, and produces 3 output dots (since one pixel = 6 output dots, and each sub-process is concerned with either even or odd dots). Thus one output dot is generated each cycle, but an input pixel is only read once every 3 cycles.
The original dither cell is a 64 x 64 cell, with each entry 8 bits. This original cell is divided into an odd cell and an even cell, so that each is sti1164 high, but only 32 entries wide. The even dither cell contains original dither cell pixels 0, 2, 4 etc., while the odd contains original dither cell pixels 1, 3, 5 etc. Since a dither cell repeats across a line, a single 32 byte line of each of the 2 dither cells is required during an entire line, and can therefore be completely cached. The odd and even lines of a single process line are staggered 8 dot lines apart, so it is convenient to rotate the odd dither cell's lines by 8 lines. Therefore the same offset into both odd and even dither cells can be used.
Consequently the even dither cell's line corresponds to the even entries of line L in the original dither cell, and the even dither cell's line corresponds to the odd entries of line L+8 in the original dither cell.
"Me process is run 3 times, once for each of the color components. The CPU
software routine must ensure that the Sequential Read Iterators for odd and even lines are pointing to the con-ect image lines corresponding to the print heads. For example, to produce one set of 18,000 dots (3 sets of 6000 dots):
= Yellow even dot line = 0, therefore input Yellow image line = 0/6 = 0 = Yellow odd dot line = 8, therefore input Yellow image line = 8/6 = I
= Magenta even line = 10, therefore input Magenta image line = 10/6 = 1 = Magenta odd line = 18, therefore input Magenta image line = 18/6 = 3 = Cyan even line = 20, therefore input Cyan image line = 20/6 = 3 = Cyan odd line = 28, therefore input Cyan image line = 28/6 = 4 Subsequent sets of input image lines are:
= Y=[0, 1], M=[l, 3], C=[3, 4]
= Y=[0, 1], M=[I, 3], C=[3, 4]
= Y=[0, 1], M=[2, 3], C=[3, 5]
= Y=[0, 1], M=[2, 3], C=[3, 5]
= Y=[0, 2], M=[2, 3], C=[4, 5]
The dither cell data however, does not need to be updated for each color component The dither cell for the 3 colors becomes the same, but offset by 2 dot lines for each component The Dithered Output is written to a Sequential Write lterator, with odd and even dithered dots written to 2 separate outputs. The same two Write iterators are used for all 3 color components, so that they are contiguous within the break-up of odd and even dots.
While one set of dots is being generated for a print line, the previously generated set of dots is being merged by a second VLIW process as described in the next section.
Generate Merged 8 bit Dot Output This process, as illustrated in Fig. 158, takes a single line of dithered dots and generates the 8 bit data stream for output to the Print Head Interface via the VLIW Output FIFO. The process requires the entire line to have been prepared, since it requires semi-random access to most of the dithered line at once. The following constant is set by software:
Constant Value K, 375 The Sequential Read Iterators point to the line of previously generated dots, with the Iterator registers set up to limit access to a single color component The distance between subsequent pixels is 375, and the distance between one line and the next is given to be I byte. Consequently 8 entries are read for each "line". A single "line" corresponds to the 8 bits to be loaded on the print head. The total number of "lines" in the image is set to be 375. With at least 8 cache lines assigned to the Sequential Read Iterator, complete cache coherence is maintained_ Instead of counting the 8 bits, 8 Microcode steps count implicitly.
The generation process first reads all the entries from the even dots, combining 8 entries into a single byte which is then output to the VLIW Output FIFO. Once all 3000 even dots have been read, the 3000 odd dots are read and processed. A software routine must update the address of the dots in the odd and even Sequential Read Iterators once per color component, which equates to 3 times per line. The two VLIW
processes require all 8 ALUs and the VLIW Output FIFO. As long as the CPU is able to update the registers as described in the two processes, the VLIW
processor can generate the dithered image dots fast enough to keep up with the printer.
Data Card Reader Fig. 159, there is illustrated on form of card reader 500 which allows for the insertion of Artcards 9 for reading. Fig. 158 shows an exploded perspective of the reader of Fig. 159.
Cardreader is interconnected to a computer system and includes a CCD reading mechanism 35. The cardreader includes pinch rollers 506, 507 for pinching an inserted Artcard 9. One of the roller e.g. 506 is driven by an Artcard motor 37 for the advancement of the card 9 between the two rollers 506 and 507 at a uniformed speed. The Artcard 9 is passed over a series of LED lights 512 which are encased within a clear plastic mould 514 having a semi circular cross section. The cross section focuses the light from the LEDs eg 512 onto the surface of the card 9 as it passes by the LEDs 512. From the surface it is reflected to a high resolution linear CCD 34 which is constructed to a resolution of approximately 480 dpi. The surface of the Artcard 9 is encoded to the level of approximately 1600 dpi hence, the linear CCD 34 supetsamples the Artcard surface with an approximately three times multiplier. The Artcard 9 is further driven at a speed such that the linear CCD 34 is able to supersample in the direction of Artcard movement at a rate of approximately 4800 readings per inch. The scanned Artcard CCD data is forwarded from the Artcard reader to ACP 31 for processing. A sensor 49, which can comprise a light sensor acts to detect of the presence of the card 13.
The CCD reader includes a bottom subshate 516, a top substrate 514 which comprises a transparent molded plastic. In between the two substrates is inserted the linear CCD array 34 which comprises a thin long linear CCD
array constructed by means of semi-conductor manufacturing processes.
Tuming to Fig. 160, there is illustrated a side perspective view, partly in section, of an example construction of the CCD reader unit. The series of LEDs eg. 512 are operated to emit light when a card 9 is passing across the surface of the CCD reader 34. The emitted light is transmitted through a portion of the top substrate 523. The substrate includes a portion eg. 529 having a curved circumference so as to focus light emitted from LED 512 to a point eg. 532 on the surface of the card 9. The focused light is reflected from the point 532 towards the CCD atray 34.
A series of microlenses eg. 534, shown in exaggerated fotm, are formed on the surface of the top substrate 523. The microlenses 523 act to focus light received across the surface to the focused down to a point 536 which corresponds to point on the surface of the CCD reader 34 for sensing of light falling on the light sensing portion of the CCD array 34.
A number of refinements of the above arrangement are possible. For example, the sensing devices on the linear CCD 34 may be staggered. The corresponding microlenses 34 can also be correspondingly formed as to focus light into a staggered series of spots so as to correspond to the staggered CCD sensors.
To assist reading, the data surface area of the Artcard 9 is modulated with a checkerboard pattem as previously discussed with reference to Fig. 38. Other forms of high frequency modulation may be possible however.
It will be evident that an Artcard printer can be provided as for the printing out of data on storage Artcard.
Hence, the Artcard system can be utilized as a general form of information distribution outside of the Artcam device.
An Artcard printer can prints out Artcards on high quality print surfaces and multiple Artcards can be printed on same sheets and later separated. On a second surface of the Artcard 9 can be printed information relating to the files etc.
stored on the Artcard 9 for subsequent storage.
Hence, the Artcard system allows for a simplified form of storage which is suitable for use in place of other forms of storage such as CD ROMs, magnetic disks etc. The Artcards 9 can also be mass produced and thereby produced in a substantially inexpensive form for redistribution.
Print Rolls Turning to Fig. 162, there is illustrated the print roll 42 and print-head portions of the Artcam. The paper/film 611 is fed in a continuous "web-like" process to a printing mechanism 15 which includes further pinch rollers 616 - 619 and a print head 44 The pinch roller 613 is connected to a drive mechanism (not shown) and upon rotation of the print roller 613, "paper" in the form of film 611 is forced through the printing mechanism 615 and out of the picture output slot 6. A
rotary guillotine mechanism (not shown) is utilised to cut the roll of paper 611 at required photo sizes.
It is therefore evident that the ptinter roll 42 is responsible for supplying "papet" 611 to the print mechanism 615 for printing of photographically imaged pictures.
In Fig. 163, there is shown an exploded perspective of the print roll 42_ The printer roll 42 includes output printer paper 611 which is output under the operation of pinching rollers 612, 613.
Referring now to Fig. 164, there is illustrated a more fully exploded perspective view, of the print roll 42 of Fig. 163 without the "paper" film roll. The print roll 42 includes tlu ee main parts comprising ink reservoir section 620, paper roll sections 622, 623 and outer casing sections 626, 627.
Turning first to the ink reservoir section 620, which includes the ink reservoir or ink supply sections 633. The ink for printing is contained within three bladder type containers 630 - 632.
The printer roll 42 is assumed to provide full color output inks. Hence, a first ink reservoir or bladder container 630 contains cyan colored ink. A second reservoir 631 contains magenta colored ink and a third reservoir 632 contains yellow ink. Each of the reservoirs 630 -632, although having different volumetric dimensions, are designed to have substantially the same volumetric size.
The ink reservoir sections 621, 633, in addition to cover 624 can be made of plastic sections and are designed to be mated together by means of heat sealing, ultra violet radiation, etc.
Each of the equally sized ink reservoirs 630 -632 is connected to a corresponding ink channel 639 - 641 for allowing the flow of ink from the reservoir 630 - 632 to a corresponding ink output port 635 - 637. The ink reservoir 632 having ink channel 641, and output port 637, the ink reservoir 631 having ink channel 640 and output port 636, and the ink reservoir 630 having ink channel 639 and output port 637.
In operation, the ink reservoirs 630 - 632 can be filled with corresponding ink and the section 633 joined to the section 621. The ink reservoir sections 630 - 632, being collapsible bladders, allow for ink to traverse ink channels 639 - 641 and therefore be in fluid communication with the ink output ports 635 - 637. Further, if required, an air inlet port can also be provided to allow the pressure associated with ink channel reservoirs 630 - 632 to be maintained as required.
The cap 624 can be joined to the ink reservoir section 620 so as to form a pressurized cavity, accessible by the air pressure inlet port.
The ink reservoir sections 621, 633 and 624 are designed to be connected together as an integral unit and to be inserted inside printer roll sections 622, 623. The printer roll sections 622, 623 are designed to mate together by means of a snap fit by means of male portions 645 - 647 mating with corresponding female portions (not shown). Similarly, female portions 654 - 656 are designed to mate with corresponding male portions 660 - 662. The paper roll sections 622, 623 are therefore designed to be snapped together. One end of the film within the role is pinched between the two sections 622, 623 when they are joined together. The print film can then be rolled on the print roll sections 622, 625 as required.
As noted previously, the ink reservoir sections 620, 621, 633, 624 are designed to be inserted inside the paper roll sections 622, 623. The printer roll sections 622, 623 are able to be rotatable around stationery ink reservoir sections 621, 633 and 624 to dispense film on demand.
The outer casing sections 626 and 627 are further designed to be coupled around the print roller sections 622, 623. In addition to each end of pinch rollers eg 612, 613 is designed to clip in to a corresponding cavity eg 670 in cover 626, 627 with roller 613 being driven extemally (not shown) to feed the print film and out of the print roll.
Finally, a cavity 677 can be provided in the ink reservoir sections 620, 621 for the insertion and gluing of an silicon chip integrated circuit type device 53 for the storage of information associated with the print roll 42.
As shown in Fig. 155 and Fig. 164, the print roll 42 is designed to be inserted into the Artcam camera device so as to couple with a coupling unit 680 which includes connector pads 681 for providing a connection with the silicon chip 53. Further, the connector 680 includes end connectors of four connecting with ink supply ports 635 - 637. The ink supply ports are in tum to connect to ink supply lines eg 682 which are in turn interconnected to printheads supply ports eg. 687 for the flow of ink to print-head 44 in accordance with requirements.
The "media" 611 utilised to form the roll can comprise many different materials on which it is designed to print suitable images. For example, opaque rollable plastic material may be utilized, transparencies may be used by using transparent plastic sheets, metallic printing can take place via utilization of a metallic sheet film. Further, fabrics could be utilised within the printer roll 42 for printing images on fabric, although care must be taken that only fabrics having a suitable stiffness or suitable backing material are utilised.
When the print media is plastic, it can be coated with a layer which fixes and absorbs the ink. Further, several types of print media may be used, for example, opaque white matte, opaque white gloss, transparent film, frosted transparent film, lenticular array film for stereoscopic 3D prints, metallised film, film with the embossed optical variable devices such as gratings or holograms, media which is pre-printed on the reverse side, and media which includes a magnetic recording layer. When udlising a metallic foil, the metallic foil can have a polymer base, coated with a thin (several micron) evaporated layer of aluminum or other metal and then coated with a clear protective layer adapted to receive the ink via the ink printer mechanism.
In use the print roll 42 is obviously designed to be inserted inside a camera device so as to provide ink and paper for the printing of images on demand. The ink output ports 635 - 637 meet with corresponding ports within the camera device and the pinch rollers 672, 673 are operated to allow the supply of paper to the camera device under the control of the camera device.
As illustrated in Fig. 164, a mounted silicon chip 53 is insert in one end of the print roll 42. In Fig. 165 the authentication chip 53 is shown in more detail and includes four communications leads 680 - 683 for communicating details from the chip 53 to the con;esponding camera to which it is inserted.
Tuming to Fig. 165, the chip can be separately created by means of encasing a small integrated circuit 687 in epoxy and running bonding leads eg. 688 to the extemal communications leads 680 - 683. The integrated chip 687 being approximately 400 microns square with a 100 micron scribe boundary.
Subsequently, the chip can be glued to an appropriate surface of the cavity of the print roll 42. In Fig. 166, there is illustrated the integrated circuit 687 interconnected to bonding pads 681, 682 in an exploded view of the arrangement of Fig. 165.
Authentication Chin Authentication Chips 53 The authentication chip 53 of the prefen=ed embodiment is responsible for ensuring that only correctly manufactured print rolls are utilized in the camera system. The authentication chip 53 utilizes technologies that are generally valuable when utilized with any consumables and are not restricted to print roll system. Manufacturers of other systems that require consumables (such as a laser printer that requires toner cartridges) have struggled with the problem of authenticating consumables, to varying levels of success. Most have resorted to specialized packaging.
However this does not stop home refill operations or clone manufacture. The prevention of copying is important to prevent poorly manufactured substitute consumables from damaging the base system. For example, poorly filtered ink may clog print nozzles in an ink jet printer, causing the consumer to blame the system manufacturer and not admit the use of non-authorized consumables.
To solve the authentication problem, the Authentication chip 53 contains an authentication code and circuit specially designed to prevent copying. The chip is manufactured using the standard Flash memory manufacturing process, and is low cost enough to be included in consumables such as ink and toner cartridges. Once programmed, the Authentication chips as described here are compliant with the NSA export guidelines. Authentication is an extremely large and constantly growing field. Here we are concemed with authenticating consumables only.
Symbolic Nomenclature The following symbolic nomenclature is used throughout the discussion of this embodiment:
Symbolic Nomenclature Description F[X] Function F, taking a single parameter X
F[X, Y] Function F, taking two parameters, X and Y
X IY X concatenated with Y
X A Y Bitwise X AND Y
X v Y Bitwise X OR Y (inclusive-OR) X Y Bitwise X XOR Y (exclusive-OR) --X Bitwise NOT X (complement) X<- y X is assigned the value Y
X<- {Y, Z) The domain of assignment inputs to X is Y and Z.
X= Y X is equal to Y
X#Y X is not equal to Y
uX Decrement X by 1(floor 0) X Increment X by 1(with wrapping based on register length) Erase X Erase Flash memory register X
SetBits[X, Y] Set the bits of the Flash memory register X based on Y
Z F ShiftRight[X, Y] Shift register X right one bit position, taking input bit from Y and placing the output bit in Z
Basic Terms A message, denoted by M, is plaintext. The process of transforming M into cyphertext C, where the substance of M
is hidden, is called encryption. The process of transforming C back into M is called decryption. Referring to the encryption function as E, and the decryption function as D, we have the following identities:
E[M] = C
D[C] = M
Therefore the following identity is true:
D[E[M]] = M
Symmetric CryptoQraohy A symmetric encryption algorithm is one where:
the encryption function E relies on key Ki, the decryption function D relies on key K2, K2 can be derived from Ki, and Ki can be derived from K2.
In most symmetric algorithms, K, usually equals K2. However, even if K, does not equal K2, given that one key can be derived from the other, a single key K can suffice for the mathematical defmition. Thus:
EK[M] = C
DK[C] = M
An enormous variety of symmetric algorithms exist, from the textbooks of ancient history through to sophisticated modem algorithms. Many of these are insecure, in that modem cryptanalysis techniques can successfully attack the algorithm to the extent that K can be derived. The security of the particular symmetric algorithm is normally a function of two things: the strength of the algorithm and the length of the key. The following algorithms include suitable aspects for utilization in the authentication chip.
DES
Blowfish IDEA
DES
DES (Data Encryption Standard) is a US and international standard, where the same key is used to encrypt and decrypt. The key length is 56 bits. It has been implemented in hardware and software, although the original design was for hardware only. The original algorithm used in DES is described in US
patent 3,962,539. A variant of DES, called triple-DES is more secure, but requires 3 keys: Ki, K2, and K3.The keys are used in the following manner:
EK3[Dx2[EK1[M]11 = C
DK3[Ex2[Dxi[C]]l = M
The main advantage of triple-DES is that existing DES implementations can be used to give more security than single key DES. Specifically, triple-DES gives protection of equivalent key length of 112 bits. Triple-DES does not give the equivalent protection of a 168-bit key (3 x 56) as one might naively expect.
Equipment that performs triple-DES
decoding and/or encoding cannot be exported from the United States.
Blowfish Blowfish, is a symmetric block cipher fust presented by Schneier in 1994. It takes a variable length key, from 32 bits to 448 bits. In addition, it is much faster than DES. The Blowfish algorithm consists of two parts: a key-expansion part and a data-encryption part. Key expansion converts a key of at most 448 bits into several subkey arrays totaling 4168 bytes. Data encryption occurs via a 16-round Feistel network. All operations are XORs and additions on 32-bit words, with four index array lookups per round. It should be noted that decryption is the same as encryption except that the subkey arrays are used in the reverse order. Complexity of implementation is therefore reduced compared to other algorithms that do not have such symmetry.
Designed by Ron Rivest in 1995, RC5 has a variable block size, key size, and number of rounds. Typically, however, it uses a 64-bit block size and a 128-bit key. The RC5 algorithm consists of two parts: a key-expansion part and a data-encryption part. Key expansion converts a key into 2r+2 subkeys (where r= the number of rounds), each subkey being w bits. For a 64-bit blocksize with 16 rounds (w=32, r=16), the subkey arrays total 136 bytes. Data encryption uses addition mod 2', XOR and bitwise rotation.
IDEA
Developed in 1990 by Lai and Massey, the first incatnation of the IDEA cipher was called PES. After differential cryptanalysis was discovered by Biham and Shamir in 1991, the algorithm was strengthened, with the result being published in 1992 as IDEA. IDEA uses 128 bit-keys to operate on 64-bit plaintext blocks. The same algorithm is used for encryption and decryption. It is generally regarded to be the most secure block algorithm available today. It is described in US Patent No.5,214,703, issued in 1993.
Asymmetric Cryptoeraphy As altemative an asymmetric algorithm could be used. An asymmetric encryption algorithm is one where:
the encryption function E relies on key K,, the decryption function D relies on key K2, K2 cannot be derived from K, in a reasonable amount of time, and K, cannot be derived from K2 in a reasonable amount of time.
Thus:
EK,[M] = C
DK2[C] = M
These algorithms are also called public-key because one key K, can be made public. Thus anyone can encrypt a message (using K,), but only the person with the corresponding decryption key (K2) can decrypt and thus read the message. In most cases, the following identity also holds:
EK2[M] = C
DK, [C] = M
This identity is very important because it implies that anyone with the public key K, can see M and know that it came from the owner of K,. No-one else could have generated C because to do so would imply knowledge of K2. The property of not being able to derive K, from K2 and vice versa in a reasonable time is of course clouded by the concept of reasonable time. What has been demonstrated time after time, is that a calculation that was thought to require a long time has been made possible by the introduction of faster computers, new algorithms etc. The security of asymmetric algorithms is based on the difficulty of one of two problems: factoring large numbers (more specifically large numbers that are the product of two large primes), and the difficulty of calculating discrete logarithms in a finite field. Factoring large numbers is conjectured to be a hard problem given today's understanding of mathematics. The problem however, is that factoring is getting easier much faster than anticipated. Ron Rivest in 1977 said that factoring a 125-digit number would take 40 quadrillion years. In 1994 a 129-digit number was factored. According to Schneier, you need a 1024-bit number to get the level of security today that you got from a 512-bit number in the 1980's. If the key is to last for some years then 1024 bits may not even be enough. Rivest revised his key length estimates in 1990: he suggests 1628 bits for high security lasting until 2005, and 1884 bits for high security lasting until 2015. By contrast, Schneier suggests 2048 bits are required in order to protect against corporations and governments until 2015.
A number of public key cryptographic algorithms exist. Most are impractical to implement, and many generate a very large C for a given M or require enormous keys. Still others, while secure, are far too slow to be practical for several years. Because of this, many public-key systems are hybrid - a public key mechanism is used to transmit a symmetric session key, and then the session key is used for the actual messages. All of the algorithms have a problem in terms of key selection. A random number is simply not secure enough. The two large primes p and q must be chosen carefully -there are certain weak combinations that can be factored more easily (some of the weak keys can be tested for). But nonetheless, key selection is not a simple matter of randomly selecting 1024 bits for example. Consequently the key selection process must also be secure.
Of the practical algorithms in use under public scrutiny, the following may be suitable for utilization:
RSA
DSA
E1Gamal RSA
The RSA cryptosystem, named after Rivest, Shamir, and Adleman, is the most widely used public-key cryptosystem, and is a de facto standard in much of the world. The security of RSA is conjectured to depend on the difficulty of factoring large numbers that are the product of two primes (p and q). There are a number of restrictions on the generation of p and q. They should both be large, with a similar number of bits, yet not be close to one another (otherwise pq = 4pq). In addition, many authors have suggested that p and q should be strong primes. The RSA
algorithm patent was issued in 1983 (US patent number 4,405,829).
DSA
DSA (Digital Signature Standard) is an algorithm designed as part of the Digital Signature Standard (DSS). As defined, it cannot be used for generalized encryption. In addition, compared to RSA, DSA is 10 to 40 times slower for signature verification. DSA explicitly uses the SHA-1 hashing algorithm (see definition in One-way Functions below). DSA key generation relies on fmding two primes p and q such that q divides p-1.
According to Schneier, a 1024-bit p value is required for long term DSA
security. However the DSA standard does not permit values of p larger than 1024 bits (p must also be a multiple of 64 bits). The US Govemment owns the DSA
algorithm and has at least one relevant patent (US patent 5,231,688 granted in 1993).
ElGamal The ElGamal scheme is used for both encryption and digital signatures. The security is based on the difficulty of calculating discrete logarithms in a finite field. Key selection involves the selection of a prime p, and two random numbers g and x such that both g and x are less than p. Then calculate y = gx mod p. The public key is y, g, and p. The private key is x.
Crypto~raphic Challenge-Response Protocols and Zero Knowledae Proofs The general principle of a challenge-response protocol is to provide identity authentication adapted to a camera system.
The simplest form of challenge-response takes the form of a secret password. A
asks B for the secret password, and if B responds with the correct password, A declares B authentic. There are three main problems with this kind of simplistic protocol. Firstly, once B has given out the password, any observer C will know what the password is.
Secondly, A must know the password in order to verify it. Thirdly, if C
impersonates A, then B will give the password to C (thinking C was A), thus compromising B. Using a copyright text (such as a haiku) is a weaker alternative as we are assuming that anyone is able to copy the password (for example in a country where intellectual property is not respected). The idea of cryptographic challenge-response protocols is that one entity (the claimant) proves its identity to another (the verifier) by demonstrating knowledge of a secret known to be associated with that entity, without revealing the secret itself to the verifier during the protocol. In the generalized case of cryptographic challenge-response protocols, with some schemes the verifier knows the secret, while in others the secret is not even known by the verifier. Since the discussion of this embodiment specifically concerns Authentication, the actual cryptographic challenge-response protocols used for authentication are detailed in the appropriate sections. However the concept of Zero Knowledge Proofs will be discussed here. The Zero Knowledge Proof protocol, first described by Feige, Fiat and Shamir is extensively used in Smart Cards for the purpose of authentication.
The protocol's effectiveness is based on the assumption that it is computationally infeasible to compute square roots modulo a large composite integer with unknown factorization. This is provably equivalent to the assumption that factoring large integers is difficult. It should be noted that there is no need for the claimant to have significant computing power. Smart cards implement this kind of authentication using only a few modular multiplications. The Zero Knowledge Proof protocol is described in US Patent 4,748,668.
One-way Functions A one-way function F operates on an input X, and retums F[X] such that X
cannot be determined from F[X]. When there is no restriction on the format of X, and F[X] contains fewer bits than X, then collisions must exist. A collision is defined as two different X input values producing the same F[X] value - i.e.
X, and X, exist such that X, X, yet F[Xj = F[X2]. When X contains more bits than F[X], the input must be compressed in some way to create the output.
In many cases, X is broken into blocks of a particular size, and compressed over a number of rounds, with the output of one round being the input to the next. The output of the hash function is the last output once X has been consumed. A
pseudo-collision of the compression function CF is defined as two different initial values V i and V2 and two inputs X, and X2 (possibly identical) are given such that CF(Vi, Xi) = CF(V2, X2). Note that the existence of a pseudo-collision does not mean that it is easy to compute an X2 for a given X,.
We are only interested in one-way functions that are fast to compute. In addition, we are only interested in deterministic one-way functions that are repeatable in different implementations. Consider an example F where F[X] is the time between calls to F. For a given F[X] X cannot be determined because X
is not even used by F. However the output from F will be different for different implementations. This kind of F
is therefore not of interest.
In the scope of the discussion of the implementation of the authentication chip of this embodiment, we are interested in the following forms of one-way functions:
Encryption using an unknown key Random number sequences Hash Functions Message Authentication Codes Encryption Using an Unknown Kev When a message is encrypted using an unknown key K, the encryption function E
is effectively one-way. Without the key, it is computationally infeasible to obtain M from EK[MJ without K. An encryption function is only one-way for as long as the key remains hidden. An encryption algorithm does not create collisions, since E creates EK[M] such that it is possible to reconstruct M using function D. Consequently F[XJ contains at least as many bits as X (no information is lost) if the one-way function F is E. Symmetric encryption algorithms (see above) have the advantage over Asymmetric algorithms for producing one-way functions based on encryption for the following reasons:
The key for a given strength encryption algorithm is shorter for a symmetric algorithm than an asymmetric algorithm Symmetric algorithms are faster to compute and require less software/silicon The selection of a good key depends on the encryption algorithm chosen.
Certain keys are not strong for particular encryption algorithms, so any key needs to be tested for strength. The more tests that need to be performed for key selection, the less likely the key will remain hidden.
Random Number Seouences Consider a random number sequence Ra, Ri, ..., RI, R. We define the one-way function F such that F[X] returns the Xd' random number in the random sequence. However we must ensure that F[X] is repeatable for a given X on different implementations. The random number sequence therefore cannot be truly random. Instead, it must be pseudo-random, with the generator making use of a specific seed.
There are a large number of issues concerned with defming good random number generators. Knuth, describes what makes a generator "good" (including statistical tests), and the general problems associated with constructing them.
The majority of random number generators produce the i'h random number from the i-1& state - the only way to determine the ith number is to iterate from the 0 i number to the id. If i is large, it may not be practical to wait for i iterations. However there is a type of random number generator that does allow random access. Blum, Blum and Shub defme the ideal generator as follows:"... we would like a pseudo-random sequence generator to quickly produce, from short seeds, long sequences (of bits) that appear in every way to be generated by successive flips of a fair coin".
They defined the 2 mod n generator, more commonly refetred to as the BBS
generator. They showed that given certain assumptions upon which modem cryptography relies, a BBS generator passes extremely stringent statistical tests.
The BBS generator relies on selecting n which is a Blum integer (n = pq where p and q are large prime numbers, p;t q, p mod 4 = 3, and q mod 4 = 3). The initial state of the generator is given by a where o= Z mod n, and x is a random integer relatively prime to n. The io' pseudo-random bit is the least significant bit of x; where x; = xi_,Z mod n. As an extra property, knowledge of p and q allows a direct calculation of the i's number in the sequence as follows: x; = a'"
mod n, where y= 2' mod ((p-1)(q-1)) Without knowledge of p and q, the generator must iterate (the security of calculation relies on the difficulty of factoring large numbers). When first defined, the primary problem with the BBS generator was the amount of work required for a single output bit. The algorithm was considered too slow for most applications. However the advent of Montgomery reduction arithmetic has given rise to more practical implementations. In addition, Vazirani and Vazirani have shown that depending on the size of n, more bits can safely be taken from xi without compromising the security of the generator. Assuming we only take I bit per x;, N bits (and hence N iterations of the bit generator function) are needed in order to generate an N-bit random number. To the outside observer, given a particular set of bits, there is no way to detennine the next bit other than a 50/50 probability. If the x, p and q are hidden, they act as a key, and it is computationally unfeasible to take an output bit stream and compute x, p, and q. It is also computationally unfeasible to determine the value of i used to generate a given set of pseudo-random bits.
This last feature makes the generator one-way. Different values of i can produce identical bit sequences of a given length (e.g. 32 bits of random bits). Even if x, p and q are known, for a given F[i], i can only be derived as a set of possibilities, not as a certain value (of course if the domain of i is known, then the set of possibilities is reduced further).
However, there are problems in selecting a good p and q, and a good seed x. In particular, Ritter describes a problem in selecting x. The nature of the problem is that a BBS generator does not create a single cycle of known length. Instead, it creates cycles of various lengths, including degenerate (zero-length) cycles. Thus a BBS generator cannot be initialized with a random state - it might be on a short cycle.
Hash Functions Special one-way functions, known as Hash functions map arbitrary length messages to fixed-length hash values. Hash functions are referred to as H[M]. Since the input is arbitrary length, a hash function has a compression component in order to produce a fixed length output. Hash functions also have an obfuscation component in order to make it difficult to fmd collisions and to determine information about M from H[M]. Because collisions do exist, most applications require that the hash algorithm is preimage resistant, in that for a given Xi it is difficult to fmd X2 such that H[Xi] =
H[XZ]. In addition, most applications also require the hash algorithm to be collision resistant (i.e. it should be hard to find two messages Xi and X2 such that H[X,] = H[XZ]). It is an open problem whether a collision-resistant hash function, in the idealist sense, can exist at all. The primary application for hash functions is in the reduction of an input message into a digital "fingerprint" before the application of a digital signature algorithm. One problem of collisions with digital signatures can be seen in the following example.
A has a long message M, that says "I owe B $10". A signs H[Mi] using his private key. B, being greedy, then searches for a collision message M2 where H[M,] = H[M1] but where M2 is favorable to B, for example "I owe B$lmillion". Clearly it is in A's interest to ensure that it is difficult to find such an Mz.
Examples of collision resistant one-way hash functions are SHA-1, MD5 and RIPEMD-160, all derived from MD4.
Ron Rivest introduced MD4 in 1990. It is mentioned here because all other one-way hash functions are derived in some way from MD4. MD4 is now considered completely broken in that collisions can be calculated instead of searched for. In the example above, B could trivially generate a substitute message M2 with the same hash value as the original message Mi.
Ron Rivest introduced MD5 in 1991 as a more secure MD4. Like MD4, MD5 produces a 128-bit hash value.
Dobbertin describes the status of MD5 after recent attacks. He describes how pseudo-collisions have been found in MD5, indicating a weakness in the compression function, and more recently, collisions have been found. This means that MD5 should not be used for compression in digital signature schemes where the existence of collisions may have dire consequences. However MD5 can still be used as a one-way function. In addition, the HMAC-MD5 construct is not affected by these recent attacks.
SHA-1 is very similar to MD5, but has a 160-bit hash value (MD5 only has 128 bits of hash value). SHA-1 was designed and introduced by the NIST and NSA for use in the Digital Signature Standard (DSS). The original published description was called SHA, but very soon afterwards, was revised to become SHA-I, supposedly to correct a security fiaw in SHA (although the NSA has not released the mathematical reasoning behind the change). There are no known cryptographic attacks against SHA-1. It is also more resistant to brute-force attacks than MD4 or MD5 simply because of the longer hash result. The US Government owns the SHA-l and DSA algorithms (a digital signature authentication algorithm defined as part of DSS) and has at least one relevant patent (US patent 5,231,688 granted in 1993).
RIPEMD-160 is a hash function derived from its predecessor RIPEMD (developed for the European Community's RIPE project in 1992). As its name suggests, RIPEMD-160 produces a 160-bit hash result. Tuned for software implementations on 32-bit architectures, RIPEMD-160 is intended to provide a high level of security for 10 years or more. Although there have been no successful attacks on RIPEMD-160, it is comparatively new and has not been extensively cryptanalyzed. The original RIPEMD algorithm was specifically designed to resist known cryptographic attacks on MD4. The recent attacks on MD5 showed similar weaknesses in the RIPEMD 128-bit hash function.
Although the attacks showed only theoretical weaknesses, Dobbertin, Preneel and Bosselaers further strengthened RIPEMD into a new algorithm RIPEMD-160.
Message Authentication Codes The problem of message authentication can be summed up as follows:
How can A be sure that a message supposedly from B is in fact from B?
Message authentication is different from entity authentication. With entity authentication, one entity (the claimant) proves its identity to another (the verifier). With message authentication, we are concemed with making sure that a given message is from who we think it is from i.e. it has not been tampered en route from the source to its destination.
A one-way hash function is not sufficient protection for a message. Hash functions such as MD5 rely on generating a hash value that is representative of the original input, and the original input cannot be derived from the hash value. A
simple attack by E, who is in-between A and B, is to intercept the message from B, and substitute his own. Even if A
also sends a hash of the original message, E can simply substitute the hash of his new message. Using a one-way hash function alone, A has no way of knowing that B's message has been changed. One solution to the problem of message authentication is the Message Authentication Code, or MAC. When B sends message M, it also sends MAC[M] so that the receiver will know that M is actually from B. For this to be possible, only B must be able to produce a MAC of M, and in addition, A should be able to verify M against MAC[M]. Notice that this is different from encryption of M -MACs are useful when M does not have to be secret. The simplest method of constructing a MAC from a hash function is to encrypt the hash value with a symmetric algorithm:
Hash the input message H[M]
Encrypt the hash EK[H[M]]
This is more secure than first encrypting the message and then hashing the encrypted message. Any symmetric or asymmetric cryptographic function can be used. However, there are advantages to using a key-dependant one-way hash function instead of techniques that use encryption (such as that shown above):
Speed, because one-way hash functions in general work much faster than encryption;
Message size, because EK[H[M]] is at least the same size as M, while H[M] is a fixed size (usually considerably smaller than M);
Hardware/software requirements - keyed one-way hash functions are typically far less complexity than their encryption-based counterparts; and One-way hash function implementations are not considered to be encryption or decryption devices and therefore are not subject to US export controls.
It should be noted that hash functions were never originally designed to contain a key or to support message Use well-defined and well-behaved technology Reduce cost Regardless of the autiientication scheme used, the circuitry of the authentication part of the chip must be resistant to physical attack. Physical attack comes in four main ways, although the form of the attack can vary:
Bypassing the Authentication Chip altogether Physical examination of chip while in operation (destnuctive and non-destructive) Physical decomposition of chip Physical alteration of chip Ideally, the chip should be exportable from the U.S., so it should not be possible to use an Authentication chip 53 as a secure encryption device. This is low priority requirement since there are many companies in other countries able to manufacture the Authentication chips. In any case, the export restrictions from the U.S. may change.
Authentication Existing solutions to the problem of authenticating consumables have typically relied on physical patents on packaging. However this does not stop home refill operations or clone manufacture in countries with weak industrial property protection. Consequently a much higher level of protection is required. It is not enough to provide an authentication method that is secret, relying on a home-brew security method that has not been scrutinized by security experts. Security systems such as Netscape's original proprietary system and the GSM Fraud Prevention Netwotk used by cellular phones are examples where design secrecy caused the vulnerability of the security. Both security systems were broken by conventional means that would have been detected if the companies had followed an open design process. The solution is to provide authentication by means that have withstood the scrutiny of experts. A number of protocols that can be used for consumables authentication. We only use security methods that are publicly described, using known behaviors in this new way. For all protocols, the security of the scheme relies on a secret key, not a secret algorithm. All the protocols rely on a time-variant challenge (i_e. the challenge is different each time), where the response depends on the challenge and the secret. The challenge involves a random number so that any observer will not be able to gather useful information about a subsequent identification.
Two protocols are presented for each of Presence Only Authentication and Consumable Lifetime Authentication. Although the protocols differ in the number of Authentication Chips required for the authentication process, in all cases the System authenticates the consumable.
Certain protocols will wodc with either one or two chips, while other protocols only work with two chips. Whether one chip or two Authentication Chips are used the System is still responsible for making the authentication decision.
Sinp-le Chip Authentication When only one Authentication chip 53 is used for the authentication protocol, a single chip (referred to as ChipA) is responsible for proving to a system (refen-ed to as System) that it is authentic. At the start of the protocol, System is unsure of ChipA's authenticity. System undertakes a challenge-response protocol with ChipA, and thus determines ChipA's authenticity. In all protocols the authenticity of the consumable is directly based on the authenticity of the chip, i.e. if ChipA is considered authentic, then the consumable is considered authentic. The data flow can be seen in Fig. 167. In single chip authentication protocols, System can be software, hardware or a combmation of both. It is important to note that System is considered insecure - it can be easily reverse engineered by an attacker, either by examining the ROM or by examining circuitry. System is not specially engineered to be secure in itself.
Double Chip Authentication In other protocols, two Authentication Chips are required as shown in Fig.
168. A single chip (referred to as ChipA) is responsible for proving to a system (refen-ed to as System) that it is authentic. As part of the authentication process, System makes use of a trusted Authentication Chip (refertrd to as ChipT). In double chip authentication protocols, System can be software, hardware or a combination of both. However ChipT must be a physical Authentication Chip.
In some protocols ChipT and ChipA have the same intemal structure, while in others ChipT and ChipA have different internal structures.
Presence Only Authentication (Insecure State Data) For this level of consumable authentication we are only concerned about validating the presence of the Authentication chip 53. Although the Authattication Chip can contain state infonnation, the transmission of that state information would not be considered secure. Two protocols are presented. Protocol 1 requires 2 Authentication Chips, while Protocol2 can be impiemented using either I or 2 Authentication Chips.
Protocol I
Protocol I is a double chip protocol (two Authentication Chips are required).
Each Authentication Chip contains the following values:
K Key for FK[X]. Must be secret.
R Current random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each invocation of the Random function.
Each Authentication Chip contains the following logical functions:
Random[l Retums R, and advances R to next in sequence.
F[X] Retums FK[X], the result of applying a one-way fnnction F to X based upon the sectet key K.
The protocol is as follows:
System requests Random[] from ChipT;
ChipT retums R to System;
System requests F[R] from both ChipT and ChipA;
ChipT n'mnts Ficr[R] to System;
ChipA refums FKAR) to System;
System compares FKT[R] with FKA[R]. If they are equal, then ChipA is considered valid. If not, then ChipA is considered invalid.
11m data flow can be seen in Fig. 169. The System does not have to comprehend FK[R] messages. It must merely check that the responses from ChipA and ChipT are the same. The System therefore does not require the key. The security of Protocol 1 lies in two places:
The security of F[X], Only Authentication chips contain the seeret key, so anything that can produce an F[X] from an X that matches the F[X] generated by a tntsted Attthentiration chip 53 (ChipT) must be autttetttic.
The domain of R generated by all Authetnication chips must be Iatge and non-detenninistic. If the domain of R
generated by all Authentication chips is small, then there is no need for a clone manufactum to crack the key.
Instead, the clone manufacttmer could iacoaporate a ROM in their dtip that had a record of all of the responses from a genuine chip to the codes sent by the system. The Random function does not strictly have to be in the Autltentication Chip, since System can potentially generate the same tandom number sequence.
However it simplifies the design of System and ensures the security of the random number generator will be the same for all implementations that use the Authentication Chip, reducing possible error in system implementation.
Protocol I has several advantages:
K is not revealed during the authentication process Given X, a clone chip cannot generate FK[X] without K or access to a real Authentication Chip.
System is easy to design, especially in low cost systems such as ink-jet printers, as no enctyption or decryption is required by System itself.
A wide range of keyed one-way functions exists, including symmetric cryptography, random number sequences, and message authentication codes.
One-way functions require fewer gates and are easier to verify than asymmetric algoriduns).
Secure key size for a keyed one-way function does not have to be as large as for an asymmetric (public key) algorithm. A minimum of 128 bits can provide appropriate security if F[X] is a symmetric cryptographic function.
However there are problems with this protocol:
It is susceptible to chosen text attack An attacker can plug the chip into their own system, generate chosen Rs, and observe the output. In order to find the key, an attacker can also search for an R that will generate a specific F[Mj since multiple Authentication chips can be tested in paralleL
Depending on the one-way fitttction chosen, key generation can be complicated.
The method of selecting a good key depends on the algorithm being used. Certain keys are weak for a given algorithm.
Ihe choice of the keyed one-way functions itself is non-trivial. Some require licensing due to patent protection.
A man-in-the middle could take action on a plaintext message M before passing it on to ChipA - it would be preferable if the man-in-the-middle did not see M until after ChipA had seen it. It would be even more preferable if a man-in-the-middle didn't see M at all.
If F is symmetric encryption, because of the key size needed for adequate security, the chips could not be exported fivm the USA since they could be used as strong encryption devices.
If Protocol I is implemented with F as an asymmetric encryption algorithm, there is no advantage over the symmetric case - the keys needs to be longer and the encryption algorithm is more expensive in silicon. Protocol I must be itnplemented with 2 Authentication Chips in order to keep the key secure. This means that each System requires an Authentication Chip and each consumable requires an Authentication Chip.
Protocol 2 In some cases, System may contain a large amount of processing power.
Altematively, for instances of systems that are manufactured in large quantities, integtation of ChipT into System may be desirable. Use of an asymmetrical enctyption algorithm allows the ChipT portion of System to be insecure.
Protocol 2 therefore, uses asymmetric cryptography. For this protocol, each chip contains the following values:
K Key for FJX] and DKjXJ. Must be sec,ret in ChipA. Does not have to be secret in ChipT.
R Curnnt random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each utvocation of the Random function.
The following fimctions are defined:
EIXI ChipT only. Retums EK[X] where E is asymmetric encrypt fnnction E.
D[X] ChipA only. Retums DK[X) where D is asyrnmetric decrypt fanction D.
Random[] ChipT only. Retums R I EK[R], where R is random number based on seed S. Advances R to next in random number sequence_ The public key KT is in ChipT, while the secret key KA is in ChipA. Having KT
in ChipT has the advantage that ChipT
can be implemented in software or hardware (with the proviso that the seed for R is diffen:nt for each chip or system).
Protocol 2 therefore can be implemented as a Single Chip Protocol or as a Double Chip Protocol. The protocol for authentication is as follows:
System calls ChipT's Random function;
ChipT returns R I EKAR] to System;
System calls ChipA's D function, passing in FKT[R];
ChipA returns R, obtained by DKA[EKT[R]];
System compares R from ChipA to the original R generated by ChipT. If they are equal, then ChipA is considered valid. If not, ChipA is invalid.
The data flow can be seen in Fig. 170. Protocol 2 has the following advantages:
KA (the secret key) is not revealed during the authentication process Given EKT[X], a clone chip cannot generate X without KA or access to a real ChipA.
Since KT # Kk, ChipT can be implemented completely in software or in insecure hardware or as part of System.
Only ChipA (in the consumable) is required to be a sectue Authentication Chip.
If ChipT is a physical chip, System is easy to design.
There are a number of well-documented and cryptanalyzed asymmetric algorithms to chose from for implementation, including patent-free and license-free solutions.
However, Protocol 2 has a number of its own problems:
For satisfactory security, each key needs to be 2048 bits (compared to minimum 128 bits for synunetric ctyptography in Protocol 1). The associated intermediate memory used by the encryption and decryption algorithms is correspondingly latger.
Key generation is non-trivial. Random numbers are not good keys.
If ChipT is implemented as a core, there may be difficulties in linking it into a given System ASIC.
If QtipT is implemented as software, not only is the implementation of System open to programming error and non-rigorous testing, but the integrity of the compiler and mathematics primitives must be rigorously checked for each impiementation of System. This is more complicated and costly than simply using a well-tested chip.
Although many symmetric algorithms are specifically strongthened to be resistant to differential c yptanalysis (which is based on chosen text attacks), the private key K, is susceptible to a chosen text attack If ChipA and ChipT are instattces of the same Authentication Chip, each chip must contain both asymmetric encrypt and decrypt functionality. Consequently each chip is larger, more complex, and more expensive than the chip required for Protocol 1.
If the Authentication Chip is broken into 2 chips to save cost and reduce complexity of design/test, two chips still need to be manufactured, reducing the economies of scale. This is offset by the relative numbers of systems to consumables, but must still be taken into account.
Protocol 2 Authentication Chips could not be exported from the USA, since they would be considered strong enayption devices.
Even if the process of choosing a key for Protocol 2 was straightforward, Protocol 2 is impractical at the present time due to the high cost of silicon implementation (both key size and functional implementation). Therefore Protocol 1 is the protoeol of choice for Presence Only Authentication.
Clone Consumable usine Real Authentication Chio Protocols I and 2 only check that ChipA is a real Authentication Chip. They do not check to see if the consumable itself is valid. The fundamental assumption for authentication is that if ChipA is valid, the consumable is validd It is therefore possible for a clone manufaciurer to insert a real Authentication Chip into a clone consumable. There are two cases to consider.
In cases where state data is not written to the Authentication Chip, the chip is completely reusable. Clone manufacturers could therefore recycle a valid consumable into a clone consumable. This may be made more difficult by melding the Authentication Chip into the consumable's physical packaging, but it would not stop refill operators.
In cases where state data is written to the Authentication Chip, the chip may be new, partially used up, or completely used up. However this does not stop a clone manufacturer from using the Piggyback attack, where the clone manufacturer builds a chip that has a real Authentication Chip as a piggyback The Attacker's chip (ChipE) is therefore a man-in-the-middle. At power up, ChipE reads all the memory state values from the real Authentication chip 53 into its own memory. ChipE then examines requests from System, and takes different actions depending on the request Authentication requests can be passed direexly to the real Authentication chip 53, while read/write requests can be simulated by a memory that resembles real Authentication Chip behavior. In this way the Authentication chip 53 will always appear fresh at power-up. ChipE can do this because the data access is not authenticated.
In order to fool System into thinking its data accesses were successfiil, ChipE still requires a real Authentication Chip, and in the second case, a clone chip is required in addition to a real Authentication Chip. Consequently Protocols I and 2 can be useful in situations where it is not cost effective for a clone manufacturer to embed a real Authentication chip 53 into the consumable. If the consumable caanot be recycled or refilled easily, it may be protection enough to use Protocols 1 or 2. For a clone operation to be successful each clone consumable must include a valid Authentication Chip. The chips would have to be stolen en masse, or taken fivm old consumables. The quantity of these reclaimed chips (as well as the effort in reclaiming them) should not be enough to base a business on, so the added protection of secure data transfer (see Protocols 3 and 4) may not be useful.
Loneevitv of Kev A general problem of these two protocols is that once the authentication key is chosen, it cannot easily be changed. In sotne iostances a key-compromise is not a problem, while for others a key compromise is disastrous. For example, in a car/car-key Systeni/Consumable scenario, the customer has only one set of car/car-keys. Each car has a different authentication key. Consequently the loss of a car-key only compromises the individual car. If the owner considers this a problem, they must get a new lock on the car by replacing the System chip inside the car's electraucs. The owner's keys must be reprogrammed/replaced to work with the new car System Authentication Chip_ By conuast, a c.ompromise of a key for a high volume consumable market (for example ink cartridges in printers) would allow a clone ink cartridge manufacturer to make their own Authentication Chips. The only solution for existing systems is to update the System Authentication Chips, which is a costly and logistically difficult exercise. In any case, consumers' Systems already work - they have no incentive to hobble their existing equipment.
Consumable Lifetime Authentication In this level of consumable authentication we are concemed with validating the existence of the Authentication Chip, as well as ensuring that the Authentication Chip lasts only as long as the consumable. In addition to validating that an Authentication Chip is present, writes and reads of the Authentication Chip's memory space must be authenticated as well. In this section we assume that the Authentication Chip's data storage integrity is secure - certain parts of inemory are Read Only, others are ReadfWrite, while others are Decrement Only (see the chapter entitled Data Storage Integrity for more information). Two protocols are presented. Protocol 3 requires 2 Authentication Chips, while Protocol 4 can be implemented using either 1 or 2 Audtetttication Chips.
Protocol 3 This protocol is a double chip protocol (two Authentication Chips are required). For this protocol, each Authentication Chip contains the following values:
K, Key for calculating FKi[X]. Must be secret.
K2 Key for calculating FK2[X]. Must be secret.
R Cunent random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each successful authentication as defined by the Test function.
M Memory vector of Authentication chip 53. Part of this space should be different for each chip (does not have to be a random number).
Each Authentication Chip contains the following logical functions:
FIX[ Internal function only. Rettuns FK[X], the result of applying a one-way function F to X based upon either key K, or key K2 Random[[ Retums R I FKi[R]=
Test[X, Y] Retums land advances R if FK2[R I X] = Y. Otherwise returns 0. The time taken to return 0 must be identical for all bad inputs.
Read[X, Yi Retums M I FK2[X I M] if FKI[Xj = Y. Otherwise returns 0. The time taken to return 0 must be identical for all bad inputs.
Write[Xl Writes X over those parts of M that can legitimately be written over.
To authenticate ChipA and read ChipA's memory M:
System calls ChipT's Random function;
ChipT produces R I FK[R] and returns these to System;
System calls ChipA's Read function, passing in R, FK[R];
ChipA returns M and FK[R I M];
System calls ChipT's Test function, passing in M and FK[R I M];
System checks response from ChipT. If the response is l, then ChipA is considered authentic. If 0, ChipA is considered invalid To authenticate a write of M~ to ChipA's memory M:
Systetn calls ChipA's Write function, passing in Mõ.;
The authentication procedure for a Read is carried out;
If ChipA is authentic and M. = M, the write sueceoded. Othawise it failed.
The data flow for read authentication is shown in Fig. 171. The first thing to note about Protocol 3 is that FK[X] cannot be called directly. Instead FK[X] is called indirectly by Random, Test and Read:
Random[] calls FK,[X] X is not chosen by the caller. It is chosen by the Random function. An attacker must perform a brute force search using multiple calls to Random, Read, and Test to obtain a desired X, FK,[X]
pair-Test[X,Y] calls FK2[R I X] Does not return result directly, but compares the result to Y and then returns I or 0. Any attempt to deduce K2 by calling Test multiple times trying different values of F"[R I X] for a given X
is reduced to a brute force search where R cannot even be chosen by the attacker.
Read[X, Y] calls FKt[X] X and FK,[X] must be supplied by caller, so the caller must already know the X, FKI[X] pair. Since the call retarns 0 if Y# FK,[X], a caller can use the Read function for a brute force attack on K.
Read[X, Y] calls FK2[X I Mj, X is supplied by caller, however X can only be those values already given out by the Random function (since X and Y are validated via K,). Thus a chosen text attack must first collect pairs from Random (effectively a brute force attack). In addition, only part of M
can be used in a chosen text attack smce some of M is constant (read-only) and the decrement-only part of M can only be used once per consumable. In the next consumable the read-only part of M will be different.
Having FK[X] being called indirectly prevents chosen text attacks on the Authentication Chip. Since an attacker can only obtain a chosen R. FK,[R] pair by calling Random, Read, and Test multiple times until the desired R appeats, a brute force attack on K, is required in order to perform a limited chosen text attack on K2. Any attempt at a chosen text attack on K2 would be limited since the text cannot be coittpletety chosen:
parts of M are read-only, yet different for each Authentication Chip. The second thing to note is that two keys are used Given the small size of M, two different keys K, and K2 are used in order to ensure there is no correiation between F[R] and F[P4M]. K, is therefore used to help protect K2 against diffetcntial attacks. It is not enough to use a single bnger key since M is only 256 bits, and only part of M changes during the lifetime of the consumable. Othmwise it is potentially possible that an attacker via some as-yet mtdisoovered teclmique, could determine the effect of the limited changes in M to particular bit combinations in R and thus calculate FKjX I M] based on FKl[X]. As an added precaution, the Random and Test functions in ChipA
should be disabled so that in order to genetate R, FK[R] pairs, an attacker must use instances of ChipT, each of which is more expensive than ChipA (since a system must be obtained for each ChipT).
Similarly, there should be a minunum delay between calls to Random, Read and Test so that an attacker cannot call these functions at high speed. Thus each d-ip can only give a specific number of X, FK[X] pairs away in a certain time period. The only specific timing requirement of Pcotoeol3 is thai the return value of 0(indicating a bad input) must be produced in the same amount of time regardless of where the error is in the input. Attackeas can therefore not leam anything about what was bad about the input vaiue. This is true for both RD and TST fimdions.
Another thing to note about Protocol 3 is that Reading data from ChipA also requires authentication of ChipA. The SYstem can be sure that the contents of inemory (M) is what ChipA claims it to be if FK2[R I MJ is retutned comectly. A
clone chip may paetettd that M is a cenain value (for example it may pretmd that the constmtable is full), but it cannot tetutn Fra[R I M] for any R passed in by System. Thus the effective signature FK2[R I M] assures System that not only did an authentic ChipA send M, but also that M was not ahered in between ChipA
and System. Finaliy, the Write function as defined does not authenticate the Write. To authenticate a write, the System must perform a Read after each Write_ There are some basic advantages with Protocol 3:
K, and K2 are not revealed during the authentication process Given X, a clone chip cannot generate FK2[X I M] without the key or access to a real Authentication Chip.
System is easy to design, especially in low cost systems such as ink-jet printers, as no encryption or decryption is requirod by System itsoif.
A wide range of key based one-way functions exists, including symmetric cryptography, random number sequences, and message authentication codes.
Keyed one-way functions require fewer gates and are easier to verify than asymmetric algorithms).
Secure key size for a keyed one-way function does not have to be as large as for an asymmetric (public key) algorithm. A minimum of 128 bits can provide appropriate security if F[X] is a symmetric cryptographic function.
Consequently, with Protocol 3, the only way to authenticate ChipA is to read the contents of ChipA's memory. The security of this protocol depends on the underlying FK[X] scheme and the domain of R over the set of all Systems.
Although FK[X] can be any keyed one-way function, there is no advantage to implement it as asymmetric encryption.
The keys need to be longer and the encryption algorithm is more expensive in silicon. This leads to a second protocol for use with asymmetric algorithms - Protocol 4. Protocol 3 must be implemented with 2 Authentication Chips in order to keep the keys secure. This means that each System requires an Authentication Chip and each consumable requires an Authentication Chip Protocol 4 In some cases, System may contain a large amount of processing power.
Altematively, for instances of systems that are manufactured in large quantities, integration of ChipT into System may be desirable. Use of an asymmetrical encryption algorithm can allow the ChipT portion of System to be insecure.
Protocol 4 therefore, uses asymmetric cryptography. For this protocol, each chip contains the following values:
K Key for EK[X] and DK[X]. Must be secret in ChipA. Does not have to be secret in ChipT.
R Current random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each successful aut4tentication as defined by the Test function.
M Memory vector of Authentication chip 53. Part of this space should be different for each chip, (does not have to be a random number).
There is no point in verifying anything in the Read function, since anyone can encrypt using a public key.
Consequently the following functions are defined:
E[Xl lntemal function only. Retunu EK[X] where E is asymmetric encrypt function E.
D[X] Intemal function only. Returns DK[X] where D is asymmetric decrypt function D.
RandomQ ChipT only. Returns EK[R].
Test[X, Y] Retums 1 and advances R if DK[R I X] = Y. Otherwise retutns 0. The time taken to return 0 must be identical for all bad inputs.
Read[XJ Returns M I EK[R I M) where R = DK[X] (does not test input).
Write[XJ Writes X over those parts of M that can legitimately be written over.
The public key KT is in ChipT, while the secret key KA is in ChipA. Having KT
in ChipT has the advantage that ChipT
can be implemented in software or hardware (with the proviso that R is seeded with a different random number for each system). To authenticate ChipA and m,ad ChipA's memory M:
System cal(s ChipT's Random fnnction;
ChipT produces ad returns EKT[R] to System;
System calls ChipA's Read fnnction, passing in EKT[R];
ChipA retun:ts M I FKA[R I MI, first obtaining R by DKA[EKT(R]];
System calls ChipT's Test function, passittg in M and EKA[R I M];
ChipT calculates DKT{FcA[R I M]] and compares it to R I M.
System checks response from ChipT. If the response is 1, then ChipA is considered authentic. If 0, ChipA is considered invalid.
To authenticate a write of Mõ, to ChipA's memory M:
System calls ChipA's Write function, passing in Mõ,_;
The authentication procedure for a Read is carried out;
If ChipA is authentic and M. = M, the write succeeded. Otherwise it failed.
The data flow for read authentication is shown in Fig. 172. Only a valid ChipA
would know the value of R., since R is not passed into the Authenticate fnnction (it is passed in as an encrypted value). R must be obtained by decrypting E[R], which can only be done using the secret key Kk. Once obtained, R must be appended to M and then the result re-encoded. ChipT can then verify that the decoded form of EyA[R I M] = R j M and hence ChipA is valid. Since KT # KA
EKT[R] * EKA[R]. Protocol 4 has the following advantages:
KA (the secret key) is not revealed during the authentication process Given EKr[X], a clone chip cannot generate X without KA or access to a real ChipA.
Since KT # K, ChipT can be implemented completely in software or in insec.une hardware or as part of System.
Only ChipA is required to be a secure Authentication Chip.
Since ChipT and ChipA contain different keys, intense testing of ChipT will reveal nothing about KA.
If ChipT is a physical chip, System is easy to design.
There are a number of well-documented and cryptanalyzed asymmetric algorithms to chose from for implementation, including patent-free and license-free sohrtions.
Even if System could be rewired so that CitipA requests were drtvoted to ChipT, ChipT could never answer for ChipA since KT :$: KA. The attack would have to be directed at the System ROM
itself to bypass the Authentication protocol.
However, Protocol 4 has a number of disadvantages:
All Authentication Chips need to contain both asymmetric encrypt and decrypt functionatity. Consequently each chip is larger, more complex, and more expensive than the chip required for Protocol 3.
For satisfactory security, each key needs to be 2048 bits (compared to a minimum of 128 bits for symmetric cryptography in Protocol 1). The associated intennediate memory used by the encryption and decryption algorithms is con-espondingly larger.
Key generation is non-trivial. Random numbers are not good keys.
If ChipT is implemented as a core, there may be difficulties in linking it into a given System ASIC.
If ChipT is implemented as software, not only is the implementation of System open to progranuning error and non-rigorous testing, but the integrity of the compiler and mathematics primitives must be rigorously checked for each implementation of System. This is more complicated and costly than simply using a well-tested chip.
Although many symmetric algorithms are specifically strengthened to be resistant to differential cryptanalysis (which is based on chosen text attacks), the private key KA is susceptible to a chosen text attack Protocol 4 Authentication Chips could not be exported from the USA, since they would be considered strong encryption devices.
As with Protocol 3, the only specific timing requirement of Protocol 4 is that the return value of 0 (indicating a bad input) must be produced in the same amount of time regardless of where the error is in the input. Attackers can therefore not learn anything about what was bad about the input value. This is true for both RD and TST functions.
Variation on call to TST
If there are two Authentication Chips used, it is theoretically possible for a clone manufacturer to replace the System Authentication Chip with one that retums 1(success) for each call to TST. The System can test for this by calling TST
a number of times - N times with a wrong hash value, and expect the result to be 0. The fmal time that TST is called, the ttue retumed value from ChipA is passed, and the return value is trusted.
The question then arises of how many times to call TST. The number of calls must be random, so that a clone chip manufacturer cannot know the number ahead of time. If System has a clock, bits from the clock can be used to determine how many false calls to TST should be made. Otlterwise the returned value from ChipA can be used. In the latter case, an attacker could still rewire the System to pemlit a clone ChipT to view the returned value from ChipA, and thus know which hash value is the correct one. The worst case of course, is that the System can be completely replaced by a cione System that does not require authenticated consumables - this is the limit case of rewiring and changing the System. For this reason, the variation on calls to TST is optional, depending on the System, the Consumable, and how likely modifications are to be made.
Adding such logic to System (for example in the case of a small desktop printer) may be considered not worthwhile, as the System is made more complicated. By contrast, adding such logic to a camera may be considered worthwhile.
Clone Consumable using Real Authentication Chin It is important to decrement the amount of consumable remaining before use that consumable portion. If the consumable is used first, a clone consumable could fake a loss of contact during a write to the special known address and then appear as a fresh new consumable. It is imporlant to note that this attack still requires a real Authentication Chip in each consumable.
Longevity of Kev A general problem of these two protocois is that once the authentication keys are chosen, it cannot easily be changed.
In some instances a key-compromise is not a problem, while for others a key compromise is disastrous.
Choosin~ a yrotocol Even if the choice of keys for Protocols 2 and 4 was straightforward, both protocols are impracti.cal at the present time due to the high cost of silicon implementation (both due to key size and functional implementation). Therefore Protoools I and 3 are the two protocols of choice. However, Protocols I and 3 contain much of the same components:
both require read and write access;
both require implementation of a keyed one-way function; and both require random number generation functionality.
Protocol 3 requires an additional key (K2), as well as some minimal state machine changes:
a state machine alteration to enable FK,[X] to be called during Random;
a Test fimction which calls FroC]
a state machine alteration to the Read function to call FKI[X] and FK2[XJ
Protocol 3 only requires minimal changes over Protocol 1. It is more secure and can be used in all places where Presence Only Autfientication is reqttind (Protocol 1). It is therefore the protocol of dioice. Given that Protocols I and 3 both make use of keyed one-way functions, the choice of one-way function is examined in more detail here. The following table outlines the attributes of the applicabk choices. The attributes are worded so that the attribute is seen as an advantage.
u A
"' Q pW
a 4 4 .. 3 U W v E- ao x t? x ~ x Free of patents Random key generation Can be exported from the USA
Fast Preferred Key Size (bits) for use in this application Block size (bits) 64 64 64 64 256 512 512 512 Cryptanalysis Attack-Free (apart from weak keys) Output size given input size N ?N 2N ?N 2N 128 128 160 160 Low storage requirements Low silicon complexity NSA designed An examination of the table shows that the ehoice is effectively between the 3 HMAC conshuds and the Random Sequence. The problem of key size and key geneiation elitninates the Random Sequence. Given that a number of attacks have alrestdy been ea<ried out on MD5 and since the hash result is only 128 bits, HMAC-MD5 is also eliminated. The choice is themfore between HMAGSHA 1 and HMAC-RIPEMD 160.
RIPEMD-160 is relatively new, and has not been as extensively pyptattalyud as SHAI. However, SHA-1 was designed by the NSA, so tltis may be seen by some as a negative attribute.
Given that there is not much between the two, SHA- I will be used for the HMAC
conshuct..
Choosing A Random Number Generator Each of the protocols described (1-4) requires a random number generator. The generator must be "good" in the sense that the random numbers generated over the life of all Systems cannot be predicted. If the random numbers were the same for each System, an attacker could easily record the correct responses from a real Authentication Chip, and place the responses into a ROM lookup for a clone chip. Witlt such an attack there is no need to obtain K, or K2. Therefote the random numbers from each System must be different enough to be unpredictable, or non-detenninistic. As such, the initial value for R (the random seed) should be programmed with a physically generated random nwnber gathered from a physically random phenomenon, one where there is no information about whether a particular bit will be 1 or 0.
The seed for R must NOT be generated with a computer-run random number generator. Otherwise the generator algorithm and seed may be compromised enabling an attacker to generate and thenrfore know the set of all R values in all Systems.
Having a diPferent R seed in each Authentication Chip means that the fust R
will be both random and unpredictable across all chips. The question therefore arises of how to generate subsequent R values in each chip.
The base case is not to change R at all. Consequently R and FKI[RJ will be the same for each call to Random[]. If they are the same, then FKI(R] can be a constant rather than calculated. An attacker could then use a single valid Authentication Chip to generate a valid lookup table, and then use that lookup table in a clone chip programmed especially for that System. A constant R is not secure.
The simplest eonceptua.i method of changing R is to increment it by 1. Since R
is randan to begin with, the values across differing systems are still ltkely to be random. However given an initial R, all subsequent R values can be determined directly (there is no need to iterate 10,000 times - R will take on values from Ro to Ra+ 10000). An incrementing R is immune to the earlier attack on a constant R. Since R is always diffenent, there is no way to construct a lookup table for the particular System without wasting as many real Authentication Chips as the clone chip will replace.
Rather than increment using an adder, another way of changing R is to implement it as an LFSR (Linear Feedback Shift Register). This has the advantage of less silicon than an adder, but the advantage of an attacker not being able to directly detennine the range of R for a particular System, since an LFSR value-domain is determined by sequendal access. To determine which values an given initial R will generate, an attacker must iterate through the possibilities and enumetate them. The advantages of a changing R are also evident in the LFSR
solution. Since R is always diffenmt, there is no way to construct a lookup table for the particular System without using-up as many real Authentication Chips as the clone chip will replace (and only for that System). There is thenrfore no advantage in having a mons complex function to change R Regardless of the function, it will always be possible for an attaoker to iterate through the lifetime set of values in a simulation. 'ihe primary security lies in the initial randomness of R. Using an LFSR to change R(apart frotn using less silicon than an adder) simply has the advantage of not being restricted to a consecutive numeric range (i.e. knowing R, RN cannot be dinxtly calculated; an attacker must itemte through the LFSR N times).
The Random number generator within the Authentiea<ion Chip is aherefore an LFSR with 160 bits. Tap selection of the 160 bits for a maximal-period LFSR (i.e. the LFSR will cycle through all 2"0-1 states, 0 is not a valid state) yields bits 159, 4, 2, and 1, as shown in Fig. 173. The LFSR is sparse, in that not many bits are used for feedba.ck (only 4 out of 160 bits are used). This is a problem for cryptographic applications, but not for this application of non-sequential number generation. The 160-bit seed value for R can be any random number except 0, since an LFSR filled with Os will produce a never-ending stream of Os. Since the LFSR described is a maximal period LFSR, all 160 bits can be used directly as R There is no need to construct a number sequentially from output bits of ba. After each successfiil call to TST, the tandom number (R) must be advanced by XORing bits 1, 2, 4, and 159, and shifting the result into the high order bit. 'Ibe new R and corresponding FyjR] can be retrieved on the next call to Random.
Holding out Against Loeical Attadcs Protocol 3 is the authentication scheme used by the Authentication Chip. As such, it should be resistant to defeat by logical means. While the effect of various types of attacks on Protocol 3 have been mentioned in discussion, this section details each type of attack in turn with reference to Protocol 3.
Brate Force attack A Brute Force attack is guaranteed to break Protocol 3. However the length of the key means that the time for an attacker to perform a brute force attack is too long to be worth the effort.
An attacker only needs to break K2 to build a clone Authentication Chip. K, is merely present to strengthen K2 against other foctns of attack. A Brute Force Attack on K2 must therefore break a 160-bit key. An attack against K2 requires a maximum of 2160 attempts, with a 50%
chance of fuiding the key after only 2159 attempts. Assuming an an-ay of a trillion processors, each running one million tests per second, 2'5' (7.3 x 10 7) tests takes 23 x 1023 yeats, which is longer than the lifetime of the universe. There are only 100 million personal computers in the world. Even if these were all connected in an attack (e.g. via the Internet), this number is still 10,000 times smaller than the trillion-processor attack described. Further, if the manufacture of one trillion processors becomes a possibility in the age of nanocomputers, the time taken to obtain the key is longer than the lifetime of the universe. -Guessing the key attack It is theoretically possible that an atta:cker can simply "guess the key". In fact, given enough time, and trying every possible number, an attacker will obtain the key. This is identical to the Brute Force attack described above, where 2'5' attempts must be made before a 50% chance of success is obtained. The chances of someone simply guessing the key on the first try is 2160. For comparison, the chance of someone winning the top prize in a U.S. state lottery and being killed by lightning in the same day is only 1 in 261. The chance of someone guessing the Authentication Chip key on the first go is 1 in 2160, which is comparative to two people choosing exactly the same atoms frotn a choice of all the atoms in the Earth i.e. extremely unlikely.
Ouantum Comnuter attack To break KZ, a quantum computer containing 160 qubits embedded in an appropriate algorithm must be built. An attack against a 160-bit key is not feasible. An outside estimate of the possibility of quantum computers is that 50 qubits may be achievable within 50 years. Even using a 50 qubit quantum computer, 210 tests are required to crack a 160 bit key. Assuming an army of I billion 50 qubit quantum computers, each able to try 2S0 keys in I microsecond (beyond the current wildest estimates) fmding the key would take an average of 18 billion years.
CNahertext Only attack An attacker can latmch a Cyphertext Only attack on K, by calling monitoring calls to RND and RD, and on KZ by monitoring calls to RD and TST. However, given that all these calls also reveal the plaintext as well as the hashed form of the plaintext, the attack would be tiansformed into a strottger form of attack - a Known Plaintext attack.
Known Plaintext attack It is easy to connect a logic analyzer to the connection between the System and the Authentication Chip, and thereby monitor the flow of data. This flow of data results in known plaintext and the hashed form of the plaintext, which can therefore be used to launch a Known Plaintext attack against both K, and K2.
To launch an attack against K,, multiple calls to RND and TST must be made (with the call to TST being successful, and therefore requiring a call to RD on a valid chip). This is straightforward, requiring the attacker to have both a System Authentication Chip and a Consumable Authentication Chip. For each K, X, HK,[X] pair revealed, a K2 Y, HK2[Y] pair is also revealed. The attacker must collect these pairs for further analysis. The question arises of how many pairs must be collected for a meaningful attack to be launched with this data. An example of an attack that requires collection of data for statistical analysis is Differential Cryptanalysis. However, there are no known attacks against SHA-1 or HMAC-SHA1, so there is no use for the collected data at this time.
Chosen Plaintext attacks Given that the cryptanalyst has the ability to modify subsequent chosen plaintexts based upon the results of previous experiments, KZ is open to a partial focm of the Adaptive Chosen Plaintext attack, which is certainly a stronger form of attack than a simple Chosen Plaintext attack. A chosen plaintext attack is not possible against K,, since there is no way for a caller to modify R, which used as input to the RND function (the only function to provide the result of hashing with K,). Clearing R also has the effect of clearing the keys, so is not useful, and the SSI command calls CLR before storing the new R-value.
Adaptive Chosen alaintext attacks This kind of attack is not possible against K,, since K, is not susceptible to chosen plaintext attacks. However, a partial form of this attack is possible against KZ, especially since both System and consumables are typically available to the attacker (the System may not be available to the attacker in some instances, such as a specific car). The HMAC
conshnct provides security against all forms of chosen plaintext attacks. This is primarily because the HMAC construct has 2 secret input variables (the result of the original hash, and the secret key). Thus finding collisions in the hash function itself when the input variable is secret is even harder than fmding collisions in the plain hash function. This is because the fotmer requires direct access to SHA-I (not permitted in Protocol 3) in order to generate pairs of input/output fi+om SHA-1. The only values that can be collected by an attacker are HMAC[R] and HMAC[R I M].
These are not attacks against the SHA-1 hash function itseli; and reduce the attack to a Diffemtttial Cryptanalysis attacl4 examiaiug statistical differences between collected data. Given that there is no Differential Cryptanalysis attack known against SHA-1 or HMAC, Protocol 3 is resistant to the Adaptive Chosen Plaintext attacks.
Purnoseful F.rnor Attack An attacker can only launch a Purposeful &ror Attack on the TST and RD
functions, since these are the only functions that validate input against the keys. With both the TST and RD functions, a 0 value is produced if an error is found in the input - no further information is given. In addition, the time taken to produce the 0 result is independent of the input, giving the attacker no information about which bit(s) were wrong. A
Purposeful Error Attack is therefore finitless.
ChainmQ attack Any form of chaining attack assumes that the message to be hashed is over several blocks, or the input variables can somehow be set. The HMAC-SHA1 algorithm used by Protocol 3 only ever hashes a single 512-bit block at a time.
Consequently chaining attacks are not possible against Protocol 3.
Birthday attack The strongest attack known against HMAC is the birthday attack, based on the frequency of collisions for the hash function. However this is totally impractical for minimally reasonable hash functions such as SHA-1. And the.bfathday attack is only possible when the attacker has control over the message ihat is signed. Protocol 3 uses hashing as a fonm of digital signature. The System sends a number that must be incorporated into the response irnm a valid Audtientication Chip. Since the Authentieation Chip must respond with H[R I
M], but has no control over the input vahie R, the birthday attack is not possible. This is because the message has effectively aloeady been generated and signed. An attacker must instead search for a collision message that hashes to the same value (analogous to finding one person who shares your birthday). The clone chip must themfore attempt to find a new value R2 such tbat the bash of R2 and a chosen M2 yields the same hash value as H[R I M]. However the System Authentication Chip does not reveal the correct hash value (the TST function only retums I or 0 depending on whether the hash value is correct). Therefore the only way of finding out the correct hash value (in order to find a collision) is to interrogate a real Aathentieation Chip. But to find the correct value means to update M, and since the decaement-only parts of M are one-way, and the read-only parts of M cannot be changed, a clone consumable would have to update a real consumable before attempting to find a collision. The altemative is a Brute Force attack search on the TST fiutction to find a success (requiring each clone consumable to have access to a System consumable). A
Brute Force Search, as described above, takes longer than the lifetime of the universe, in this case, per authentication. Due to the fact that a timely gathering of a hash value implies a real consumable must be decremented, there is no point for a clone consumable to launch this kind of attack.
Substitution with a complete lookup table 'llte random number seed in each System is 160 bits. The worst case situation for an Authentication Chip is that no state data is changed. Consequently there is a constant value retumed as M.
However a clone chip must stlll retum FK2[R I Mj, which is a 160 bit value. Asstaning a 160-bit lookup of a 160-bit result, this requires 73 x l0u bytes, or 6.6 x IOM terabytes, certainly more space than is feasible for the near future.
This of course does not even take into account the method of collecting the values for the ROM. A complete lookup table is therefore completely impossible.
Substitutiott with a snacse lookuo table A sparse lookup table is only feasible if the messages sent to the Authentieation Chip are somehow predictable, rather thaa effectively random. The random number R is seeded with an unknown random number, gathered from a naturally random event There is no possibility for a clone manufacturer to lrnow what the possible range of R is for all Systertts, since each bit has a 500/a chance of being a 1 or a 0. Since the range of R in all systems is unknown, it is not possible to build a sparse lookup table that can be used in all systems. The general aparse lookup table is therefore not a possible attack. However, it is possible for a clone manufacduxr to irnow what the range of R is for a given System. This can be accomplished by loading a LFSR with the aunent resalt fiom a call to a specific System Authentication Chip's RND
funaion, and iterating somo itumber of tQUes into the futtue. If this is done, a special ROM can be buih which will only contain the responses for that particular range of R, i.e. a ROM specifically for the consumables of that particular System. But the attacker still needs to place emrect information in the ROM.
The attacker will therefore need to find a valid Authentication Chip and call it for each of the values in R.
Suppose the clone Authentication Chip reports a full consumable, and then allows a single use before simulating loss of connection and insertion of a new full consumable. "Ihe clone wnsumable would therefore need to contain responses for authentication of a full consumable and authentication of a partially used consumable. The worst case ROM contains entries for full and partially used consumables for R over the lifetime of System. However, a valid Auttkxttication Chip must be used to genetate the information, and be partially used in the process. If a given System only produces about n R-values, the sparse lookup-ROM required is lOn bytes multiplied by the number of different vahies for M. The time taken to build the ROM depends on the amount of time enforced between calis to RD.
After all this, the clone manufachwer must rely on the consumer retuming for a refiQ since the cost of building the ROM in the Srst place consumes a single consumable. The clone manufactuner's business in such a situation is consequently in the refills. The time and cost then, depends on the size of R
and the number of different values for M
that must be incorporated in the lookup. In addition, a custom clone consumable ROM must be built to match each and every System, and a different valid Authentication Chip must be used for each SysOem (in order to provide the full and partially used data). The use of an Authentication Chip in a System must therefore be examined to determine whether or not this kind of attack is worthwhile for a clone manufacturer. As an example, of a camera system that has about 10,000 prints in its lifetime. Assume it has a single Detaenent Only value (number of prints remaining), and a delay of I second between calls to RD. In such a system, the sparse table will take about 3 hours to build, and consumes lOOK.
Remember that the constcuction of the ROM requaw the consumption of a valid Authentication Chip, so any money charged must be worth more than a single consumable and the clone consunuible combined. 'lhus it is not cost effective to perform this function for a single consumable (unless the clone consumable somehow contained the equivalent of muldple authentic consumables). If a clone manufaciurer is going to go to the iroubk of build'mg a custom ROM for each owner of a System, an easier approach would be to update System to completely ignore the Authentication Chip.
Consaluatdy, tbis attack is possible as a per-System attack, and a decision must be made about the chance of this occutring for a given System/Consumable combination. The chance will depend on the cost of the consumable and Authentication (:hips, the kmgevity of the consumablo, the profit margin on the consumable, the time taken to generate the ROM, the size of the resultant ROM, and whether customers will come back to the clone manufacturer for refills that use the same clone chip etc.
Diffennttial ctvotanalvsis Existing differential attacks are heavily dependent on the struature of S
boxes, as used in DES and other similar afgorithms. Aldwugh other algorithms such as HMAC-SHA1 used in Protocol 3 have no S boxes, an attacker can undertake a differential-like attack by undptaking statistical analysis of:
Minimal-differettce inputs, and their corresponding outputs Minimal-difference outpuls, and their corresponding inputs To taimch an attack of this nature, sets of input/output pairs must be collected. The coUection from Protocol 3 can be via Known Plaintext, or from a Partially Adaptive Chusen Plaintext attack.
Obviously the lat0er, being chosen, will be more useful. Hashing algorithms in genetal are designed to be resistant to differential analysis. SHA-1 in particular has been specifically strengthened, especially by the 80 word expansion so that minimal differences in input produce will still produce outputs tltat vary in a larga number of bit positions (compared to 128 bit hash functions). In addition, the infonnation collected is not a direct SHA-1 input/output set, due to the nature of the HMAC algorithm. The HMAC
atgorithm hashes a known value with an unknown value (the key), and the resuit of this hash is then rehashed with a separate unknown value. Since the attacker does not Irnow the secret value, nor the result of the fust hash, the inputs and outputs from SHA-1 are not known, making any differential attack extremely difficult. The following is a more detailed discussion of minimally different inputs and outputs from the Authentication Chip.
Minimal Difference Inputs This is where an attacker takes a set of X, FK[X] values where the X values are minimally different, and examines the statistical differences between the outputs FK[X]. The attack relies on X
values that only differ by a minimal number of bits. The question then arises as to how to obtain minimally different X
values in order to compare the FK[X] values.
KI:With Ki, the attacker needs to statistically examine minimally different X, FKI[X] pairs. However the attacker cannot choose any X value and obtain a related FKI[X] value. Since X, FKAX]
pairs can only be generated by calling the RND function on a System Authentication Chip, the attacker must call RND
multiple times, recording each observed pair in a table. A search must then be made through the observed values for enough minimally different X
values to undertake a statistical analysis of the FKJX] values.
K1:With K2, the attacker needs to statisticalty examine minimally different X, FK2[X] pairs. The only way of generating X, FK2[X] pairs is via the RD function, which produces Fr2[X] for a given Y, FKI[Y] pair, where X = Y I M.
This means that Y and the changeable part of M can be chosen to a limited extent by an attacker. 'Ihe amount of choice must therefore be limited as much as possible.
The fust way of limiting an attacker's choice is to limit Y, since RD requires an input of the format Y, FKI[Y].
Although a valid pair can be readily obtained from the RND function, it is a pair of RND's choosing. An aitacker can only provide their own Y if they have obtained the appropriate pair from RND, or if they know Ki. Obtaining the appropriate pair from RND requires a Brute Force search. Knowing K, is only logically possible by performing cryptanalysis on pairs obtained from the RND function - effectively a known text attack. Although RND can only be called so many times per second, K, is common across System chips. Therefore known pairs can be generated in paralleL
The second way to limit an attacker's choice is to limit M, or at least the attacker's ability to choose M. The limiting of M is done by making some parts of M Read Only, yet different for each Authentication Chip, and other parts of M
Decrement Only. The Read Only parts of M should ideally be different for each Authentication Chip, so could be information such as serial numbers, batch numbers, or random numbers. The Decrement Only parts of M mean that for an attacker to try a different M, they can only decrement those parts of M so many times - after the Decrement Only parts of M have been reduced to 0 those parts cannot be changed again.
Obtaining a new Authentication chip 53 provides a new M, but the Read Only portions will be differbnt from the previous Authentication Chip's Read Only portions, thus reducing an attackes's ability to choose M even furtlter.
Consequently an attacker can only gain a limited number of chances at choosing values for Y and M.
Minimal Difference Outputs This is where an attacker takes a set of X, FK(X] vahies where the FK[X]
values are mmima(ly different, and examines the statistical differences between the X values. The attack relies on FK[X]
values that only differ by a minimal number of bits. For both K, and K2, there is no way for an attadcer to generate an X
value for a given FK[X]. To do so would violate the fact that F is a one-way function. Consequently the only way for an attacker to mount an attack of this nature is to record all observed X, FK[X] pairs in a table. A search must then be made through the observed values for enough minimally diiT'erent FK[X] values to undertake a statistical analysis of the X values. Given that this requires more work than a minimally different input attack (which is extremely limited due to the trstriction on M and the choice of R), this attack is not fruitful.
Message substitution attacks In order for this kind of attack to be carried out, a clone consumable must contain a real Authentication chip 53, but one that is effectively reusable since it never gets decremented. The clone Authentication Chip would interc.ept messages, and substitute its own. However this auack does not give success to the attacker. A clone Authentication Chip may choose not to pass on a WR command to the reat Authentication Chip.
However the subsequent RD
command must return the cotrect response (as if the WR had succeeded). To return the comect response, the hash value must be known for the specific R and M. As described in the Birthday Attack section, an attacker can only determine the hash value by actually updating M in a real Chip, which the atiaclcer does not want to do. Even changing the R sent by System does not help since the System Authentication Chip must match the R
during a subsequent TST. A
Message substitution attack would therefore be unsuccessful. This is only true if System updates the amount of consumable remaining before it is used.
Reverse eneineerine the key eenetator If a pseudo-random number generator is used to generate keys, there is the potential for a clone manufacture to olnain the generator program or to deduce the random seed used. This was the way in which the Netscape security program was initially broken.
Bypassinc authentication altoQether Protocol 3 requires the System to update the consumable state data before the consumable is used, and follow every write by a read (to authenticate the write). Thus each use of the consumable requires an authentication. If the System adheres to these two simple rules, a clone manufacturer will have to simulate authentication via a method above (such as sparse ROM lookup).
Reuse of Authentication Chius As described above, Protocol 3 requires the Systern to update the consumable state data before the consamable is used, and follow every write by a read (to authenticate the write). Thus each use of the consumable requires an authentication. If a consumable has been used up, then its Authentication Chip will have had the appropriate state-data values deaemented to 0. The chip can therefore not be used in another consumable. Note that this only holds true for Authett-tication Chips that hold Decrement-Only data items. If there is no state data decremented with each usage, there is nothing stopping the reuse of the chip. This is the basic diffecetce between Presence-Only Authentication and Consumable Lifetime Authentication. Pcotocol 3 allows both. The bottom line is that if a consumable has Deorement Only data items that are used by the System, the Audtentication Chip camot be reused without being coinpletely reptngrmnmed by a valid Programming Station that has knowledge of the secret key.
Management decision to omit authentication to save costs Aithough not stricxly an extemal attack, a decision to omit authentication in future Systems in order to save costs will have widely varying effects on different markets. In the case of high volume consumables, it is essential to remember that it is very d"df'icutt to introduce autLentication after the tnaticet has started, as systans ceqniriag authenticated consutnables will not work with older consumables still in circulation.
Likewise, it is impractical to discontinue audwAiaation at any stage, as otda Systems will not work with the new, uoauthenticated, consumables. In he second case, older Systems can be individually ahtred by replacing the System Authentication Chip by a simple chip that has the same programming interface, but whose TST function always succeeds. Of course the System may be programmed to test for an atways-succeeding TST function, and shut down. In the case of a specialized pairing, such as a car/car-keys, or door/door-key, or some other similar situation, the omission of authentication in fumre systems is trivial and non-repercussive. This is because the consumer is sold the entire set of System and Consumable Authentication Chips at the one time.
Garrote/bn'be attack This fam of attaclt is only suecessfal in one of two cictmstanoes:
Ki, K2, and R are already recorded by the chip-programmer, or the attacker can coerce future values of Ki, K2i and R to be recorded.
If humans or computer systems extemal to the Programmmg Station do not know the keys, there is no amount of force or bribery that can reveal them. The level of security against this kind of attack is ultimately a decision for the System/Consumable owner, to be made according to the desired level of service.
For example, a car c,anpany may wish to keep a record of all keys manufactured, so that a person can request a new key to be made for their car.
However this allows the potential compromise of the entite key database, allowing an attacker to ntake lceys for any of the manufacturer's existing cars. It does not allow an attacker to make keys for any new cars. Of course, the key database itself may also be encrypted with a further key that requires a certain number of people to combine their key portions together for access. If no record is kept of which key is used in a particular car, there is no way to make additional keys should one become lost Thus an owner wili have to replace his car's Authentication Chip and all his car-keys. This is not necessarily a bad situation. By contrast, in a consumable such as a printer ink cartridge, the one key combination is used for all Systems and all consumables. Certainly if no backup of the keys is kept, there is no human with knowledge of the key, and therefore no attack is posstble. However, a no-backup situation is not desirable for a consumable such as ink cartridges, since if the key is lost no more consumables can be made. The manufacturer should therefore keep a backup of the key information in several parts, where a~errain number of people must together combine their portions to reveal the full key information. This may be required if case the chip programming station needs to be reloaded In any case, none of these attacks are against Protoeol3 itselC since no humans are involved in the authentication process. Instead, it is an attack against the progranunuig stage of the chips.
IRWAC-SHAI
The mechanism for authenfication is the HMAC-SHAI algoridun, acting on one oF
HMAC-SHAI (R, Ki), or HMAC-SHAI (R I M, K2) We will now examine the HMAC-SHA1 algorithm in greater detail than covered so far, and descnbas an optimization of the algorithm that requines fewer memory resources than the original definition.
HMAC
The HMAC algorithm, proceeds, given the following definitions:
H = the hash function (e.g. MD5 or SHA-1) n = number ofbits output fimrn H(e.g.160 for SHA-1,128 bits for MDS) M= the data to which the MAC function is to be applied K= the secret key shared by the two parfies ipad= 0x36 repeated 64 times opad = Ox5C repeated 64 times The HMAC algorithm is as follows:
Extend K to 64 bytes by appending OxOO bytes to the end of K
XOR the 64 byte string created in (1) with ipad Append data sa~eam M to the 64 byte string created in (2) Apply H to the su+eam geimated in (3) XOR the 64 byte string created in (1) with opad Append the H result from (4) to the 64 byte string resulting from (5) Apply H to the output of (6) and output the result Thus:
HMAC[Ml ? H[(K opad) I H[(IC iPad)1Mll HMAC-SHAI algorithm is simply HMAC with H= SHA-1.
'Ilhe SHAI bashing algorithm is defined in the algorithm as sunnmarized here.
Nine 32-bit constants are defined. 'Ihene are 5 constants used to initialize the chaining variables, and there are 4 additive constants.
Initial Chaining Values Additive Constaats hi 0x67452301 ys Ox5A827999 h2 OxEFCDAB89 Y2 Ox6ED9EBA1 h3 Ox98BADCFE Y3 Ox8F1BBCDC
hi 0x10325476 y4 OxCA62C1D6 hs OxC3D2E1F0 Non-optimized SHA-1 requires a total of 2912 bits of data storage:
Five 32-bit chaining variables are defined: Hi, H2, H3, I'14 and H5.
Five 32-bit working variables are defined: A, B, C, D, and E.
One 32-bit tetnporary variable is defined: t Eighty 32-bit temporary registers ane defined: X.
The following functions are defined for SHA-1:
Symbolic Nomenclature Description + Addition modulo 2 32 X Y Result of rotating X left through Y bit positions f(X,Y,Z) (XAY)V(-XAZ) g(X.Y.Z) (XAY)V(XAZ)V(YAZ) h(X,1',Z) X Y Z
ne hashing algoritlun consists of firstly padding the input message to be a multiple of 512 bits and initializing the chaining variables Hi.s with h,_s. The padded message is then processed in 512-bit chunks, with the output hash value being the final 160-bit value given by the concatenation of the chaining variables: H, I HZ I H3 I H. I HS. The steps of the SHA-1 algorithm are now examined in greater detail.
Step I. Prearocessine The first step of SHA-1 is to pad the input message to be a multiple of 512 bits as follows and to initialize the chaining variables.
Steps to follow to preprocess the Input message Pad the input message Append a 1 bit to the message Append 0 bits such that the length of the padded message is 64-bits short of a multiple of 512 bits.
Append a 64-bit value containing the length in bits of the original input message. Store the length as most significant bit through to least significant bit.
Ittitialize the chaining variables H, E-- hl, HZ F- hZ, H3 E-- h3, H4 +- h4, H5 F- hs Step 2. Processing The padded input message can now be processed. We process the message in 512-bit blocks. Each 512-bit block is in the form of 16 x 32-bit words, refen ed to as InputWordo.1s.
Steps to follow for each 512 bit block (InputWord..,s) Copy the 512 input bits into Xo.1s For j-0 to 15 Xj = InputWortt.
Expand XQ_is into Xi&79 For j=16 to 79 Xi F- ((Xi-s Xi.s X}14 7Ci.is) 1) Initialize working variables A F- Hi, B<- H2, C+- H3, D E- Hi, E E- Hs Round I For j-0 to 19 tf- ((A 5)+f(B,C,D)+E+X;+y,) Et-D,D<--C,C<-(B 30),BF-A,AFt Round 2 Forj=20to39 t<-- ((A 5)+h(B, C, D)+E+Xj +y2) E~D,DFC,C<-(B 30),BF-A,AF-t Round 3 For j= 40 to 59 tE- ((A 5) + g(B, C, D) + E + Xi +y3) E<--D,D<--C,CF(B 30),BF-A,At-t Round4 Forj=60to79 tF ((A 5)+h(B,C, D)+E+Xj +y4) E+-D,D+-C,CE-(B 30),B.,--A,AF-t Update chaining variables H, E- H, + A, H2 <- H2 + B, H3 E--H3+C,I-I4<-H4 + D, Hst-Hs+E
Step 3. Completion ARa aIl the 512-bit blodcs of the padded input message have been processed, the output hash value is the fina1160-bit value given by: H, I H2 1 H31 H4 I Hs-Optimization for Hardware Imglementation The SHA-1 Step 2 procedure is not optimized for hardware. In particular, the 80 temporaty 32-bit registers use up valuable silicon on a hardware implemetttion. 'tltis section describes an optanization to the SHA-1 algorithm that only uses 16 temporary registers. The reduction in silicon is from 2560 bits down to 512 bits, a saving of over 2000 bits. It may not be important in some applications, but in the Authentication Chip storage space must be reduced where possible. Ihe optimization is based on the fact that ahhough the original 16-word mossage black is expanded into an 80-word message block, the 80 words are not updated during the algorithm. In addition, the words rely on the previous 16 words only, and hence the expanded words can be calculated on-the-fly during procxssing, as long as we keep 16 words fa the backward tofermces. We requi<e rotating oonntas to keep tcack of which register we are up 0o using, but the effect is to save a large amount of storage. Rather than index X by a single value j, we use a 5 bit counter to cotmt thcnugh the iterations.l7tis can be achieved by initializing a 5-bit register with either 16 or 20, and decrementing it until it reaches 0. In order to update the 16 temporary variables as if they were 80, we require 4 indexes, each a 4-bit register. Al14 indexes increment (with wraparound) during the course of the algorithm.
Steps to follow for each 512 bit block (InputWords-is) Initialize working variables A E- Hl, B t-- H2, C<- H3, D E-- H4, E<- Hs N, E- 13,N2E-8,N3<-2,N4F--0 Round 0 Do 16 times:
Copy the 512 input bits into Xa. X1,14 = InputWordN4 u t Nl, N2, N3).pda N4 Round IA Do 16 times:
tF- ((A 5)+t(B, C. D)+E+XN4+y1) [ 1'll, N2, Nalapdw N.
EF-D,DE-C,C+--(B 30),BFA,AE-t Round 1 B Do 4 times:
XN4 <-- \\XNI (D XNZ XN3 (D XN4) 1) t<--((A 5)+t(B,C,D)+E+XN4+y,) N 1, N2, N3. N4 E<--D,DE-C,C<---(B 30),BE-A,AE--t Round 2 Do 20 times:
XN4t- ((XNl Xm0XN3(DXN4) 1) t E- ((A 5) + h(B, C, D) + E+ XN4 + y2) N 1, N2, N3, N4 EE-D,DF--C,C*-(B 30),BE-A,AF-t Round 3 Do 20 times:
XN4E'((+'N14) XN2 XIi3(D XN4) 1) t t- ((A 5) +g(B, C, D)+E+XI.,4+y3) N l, N2, N3. N4 E<-D,D4-C,CF(B 30),BF-A,AF-t Round 4 Do 20 times:
XN4 + " ' (\~NI XN2 (D XN3 (D XN4) 1) t F- ((A 5) + h(B, C, D) + E+ XN4 + y4) N 1, N2, N3, N4 EFD,DE-C,CE-(B 30),BF-A,Af--t Update chaining variables Hl F- HI + A, H2 <-- H2 + B, H3<-- H3+C,H4F-H4+D, Hs<-Hs+E
The inerementing of NI, N2, and N3 during Rounds 0 and lA is optional_ A
software implementation would not increinent them, since it takes time, and at the end of the 16 times through the loop, all 4 counters will be their original values. Designers of hardware may wish to ineranent all 4 counters together to save on caitrol logic. Round 0 can be cocnplebely omitted if the caller loads the 512 bits of )Cai3.
HMAC-SHAI
In the Authentication Chip implementation, the HMAC-SHA1 unit only ever perfoims hashing on two types of inputs:
on R using Kl and on R I M using Kz. Since the inputs ane two constant lengths, rather than have HMAC and SHA-1 as separate entities on chip, they can be canbined and the hardware optimized.
The padding of inessages in SHA-1 Step 1(a 1 bit, a string of 0 bits, and the length of the message) is necessary to ensure that different messages will not look the same after padding. Since we only deal with 2 types of messages, our padding can be constant Os. In addition, the optimized version of the SHA-1 algorithm is used, where only 16 32-bit words are used for temporary storage. These 16 registers are loaded directly by the optitnized HMAC-SHAI hardware. The Nine 32-bit constants his and yi.4 are still required, although the fact that they are constants is an advantage for hardware implementation. Hardware optimized HMAC-SHA-1 requires a total of 1024 bits of data storage:
Five 32-bit chaining variables are defined: Hi, H2, H3i H4 and H5.
Five 32-bit working variables are defined: A, B, C, D, and E.
Five 32-bit variables for tempor;ry storage and final result: Buff1601_5 One 32 bit temporary variable is defined: t Sbtteen 32-bit temporary registers are defined: X.
The following two sections describe the steps for the two types of calls to HMAC-SHA 1.
HFP, Ka In the case of producing the keyed hash of R using Ki, the original input message R is a constant length of 160 bits.
We can therefore take advantage of this fact during processing. Rather than load Xa,s during the first part of the SHA-1 algoritfim, we load Xais directly, and thereby omit Round 0 of the optitnized Process Block (Step 2) of SHA-l. The pseudocode takes on the following steps:
Step Description Action 1 Process K ipad X04 +- K, 0x363636...
2 X, is +- Ox363636...
3 Hj_s F hi_s 4 Proocss Block Process R XO-4 E-- R
6 Xs-ts <-- 0 7 Process Block 8 Buff1601.s F- HI.s 9 Process K opad Xa <-- K, Ox5C5C5C...
Xs-is <-- Ox5C5C5C...
11 HI s <- hl-s 12 Process Block 13 Process previous H[x) Xo 4 t- Result 14 Xs.ts F 0 Process Block 16 Get results Buff1601.s E-- HI.s H(R1M.K71 In the case of producing the keyed hash of R I M using K2, the original input message is a constant length of 416 (256+160) bits. We can thenefoe take advantage of this fact during proce.ssing. Rather than load Xa.1s during the first part of the SHA-1 algorithm, we load Xau directly, and 1ha-eby omit Round 0 of the optimized Process Bloek (Step 2) of SHA-1. The pseudocode takes on the following steps:
Step Description Action 1 Process K ipad Xa +-- KZ Ox363636...
2 XS_lS +- 0x363636...
3 Hl_s E-- hi-s 4 Process Block Process R I M Xo.4 F- R
6 Xs.iZF-- M
7 Xu-15 FO
8 Process Block 9 Temp E- Hl_S
Process K opad Xa+- Kz Ox5C5C5C...
11 X, 15 F- Ox5C5C5C...
12 Hi_S E- hi-s 13 Process Block 14 Process previous H[x] Xa4 E--Temp Xs.15 E- 0 16 Process Block 17 Get results Result F- Hi_s Data Soaee Inteeritv Each Authentication Chip contains some non-volatile mernory in order to hold the variables required by Authentication Protocol 3. The following non-volatite variables are defined:
Variable Name Size (in bits) Description M[0..15] 256 16 words (each 16 bits) containing state data such as serial numbers, media remaining etc.
K, 160 Key used to transform R during authentication.
K2 160 Key used to transform M during authentication.
R 160 Cutrent random number AccessMode[0..15] 32 The 16 sets of 2-bit AccessMode values for M[nj.
MinTicks 32 The minimum number of clock ticks between calls to key-based functions Sl Written I If set, the secret key information (KF, K2, and R) has been written to the chip. If clear, the secret information has not been written yet.
IsTrusted I If set, the RND and TST functions can be called, but RD and WR functions cannot be called.
If clear, the RND and TST functions cannot be called, but RD and WR functions can be called.
Total bits 802 Note that if these variables are in Flash memory, it is not a simple matter to write a new value to replace the old. The memory must be erased first, and then the appropriate bits set. This has an effect on the algorithms used to change Flash memory based variables. For example, Flash memory cannot easily be used as shift registers. To update a Flash memory variable by a general opetation, it is necessary to follow these steps:
Read the entire N bit value into a general purpose register, Perform the operation on the general pucpose register;
Erase the Flash memory correspond'mg to the variable; and Set the bits of the Flash memory bcation based on the bits set in the general-putpose register.
A RESET of the Authentication Chip has no effect on these non-volatile variables.
M and AccessMode Variables M[0] through M[15] are used to hold consumable state data, such as serial numbers, batch numbers, and amount of consumable remaining. Each M[n] register is 16 bits, making the entire M vector 256 bits (32 bytes). Clients cannot read from or written to individual M[n] variables. Instead, the entire vector, referred to as M, is read or written in a single logical access. M can be read using the RD (tead) command, and written to via the WR (write) command.
The commands only succeed if K, and K2 are both defined' (SIWritten = 1) and the Authentication Chip is a consumable non-trusted chip (IsTtusted = 0). Although M may contain a number of different data types, they differ only in their write permissions. Each data type can always be read. Once in client memory, the 256 bits can be interpreted in any way chosen by the client The entire 256 bits of M are read at one time instead of in smalleer amounts for reasons of security, as described in the chapter entitled Authentication.
The different write permissions are outlined in the following table:
Data Type Access Note Read Only Can never be written to ReadWrite Can always be written to Decrement Only Can only be written to if the new value is less than the old value. Decrement Only values are typically 16-bit or 32-bit values, but can be any multiple of 16 bits.
To accomplish the protection required for writing, a 2-bit access mode value is defined for each M[n]. The following table defines the mtetprdation of the 2-bit access mode bit-pattem:
Bits Op Interpretation Action taken during Write command 00 RW ReadWrite The new 16-bit value is always written to M[n].
01 MSR Decrement Only The new 16-bit value is only written to M[n] if it is (Most Significant less than the value currently in M[n]. This is used for Region) access to the Most Significant 16 bits of a Decrattent Only number.
NMSR Decrement Only The new 16-bit value is only written to M[n] if (Not the Most M[n+l] can also be written. The NMSR access mode Significant Region) allows multiple precision values of 32 bits and more (multiples of 16 bits) to deerement 11 RO Read Only The new 16-bit value is ignored.
M[n] is left unchanged.
The 16 sets of access mode bits for the 16 M[n] registers are gathered togedter in a single 32-bit AccessMode regisw.
The 32 bits of the AccessMode tegister correspond to M[n] with n as follows:
MSB LSB
Each 2-bit value is stored in hi/lo fonnat Consequently, if M[0-5] were access mode MSR, with M[6-15] access mode RO, the 32-bit AccessMode register would be:
11-11-11-11-11-11-11-11-11-i i-01-01-O1-01-01-01 During execution of a WR (write) command, AccessMode[n) is examined for each M[n], and a decision made as to whether the new M[n] value will replace the old. The AccessMode register is set using the Authentication Chip's SAM (Set Access Mode) command. Note that the Decrement Only comparison is unsigned, so any Decrement Only values that require negative ranges must be shifted into a positive range. For example, a consumable with a Decrement Only data item range of -50 to 50 must have the range shifted to be 0 to 100.
The System must then interpnet the range 0 to 100 as being -50 to 50. Note that most instances of Decrement Only ranges are N to 0, so there is no range shift required. For Decrement Only data items, arrange the data in order from most significant to least significant 16-bit quantities from M[n] onward. The access mode for the most significant 16 bits (stored in M[n]) should be set to MSR.
The remaining registers (M[n+1], M[n+2] etc) should have the'v access modes set to NMSR. If erroneously set to NMSR, with no associated MSR region, each NMSR region will be considered independently instead of being a multi-precision comparison.
K, K, is the 160-bit secret key used to transform R during the authentication protocoL K, is progcammed along with KZ
and R with the SSI (Set Secret Information) command. Since K, must be kept secret, clients cannot directly read K,.
The commands that make use of K, are RND and RD. RND returns a pair R, FK,[R]
where R is a random number, while RD requires an X, FK,[X] pair as input. K, is used in the keyed one-way hash function HMAC-SHA1. As such it should be programmed with a physically generated raadom number, gathered from a physically random phenomenon. K, must NOT be generated with a computer-run random number generator. The security of the Authentication chips depends on K,. K2 and R being generated in a way that is not deterministic. For example, to set K,, a person can toss a fair coin 160 times, recording heads as 1, and tails as 0. K, is automatically cleared to 0 upon execution of a CLR command. It can only be programmed to a non-zero value by the SSI command.
K
K2 is the 160-bit secret key used to transform M I R during the authentication protocol. K2 is programmed along with K, and R with the SSI (Set Secret Infonnation) command Since K2 must be kept secret, clients cannot diroctly read K2.
The commands that make use of K2 are RD and TST. RD reduns a pair M, Fr2[M I
X] where X was passed in as one of the parameters to the RD function. TST requires an M, FK2[M I R] pair as input, where R was obtained from the Authentication Chip's RND function. K2 is used in the keyed one-way hash function HMAC-SHAI. As such it should be programmed with a physically generated random number, gathered &om a physically random phenomenon. K2 must NOT be generated with a computer-run random number generator. The security of the Authentication chips depends on Ki, K2 and R being generated in a way that is not deterministic.
For example, to set K2, a person can toss a fair coin 160 times, recording heads as 1, and tails as 0. K2 is automatically cleared to 0 upon execution of a CLR
commancl. It can only be progratnmed to a non-zero value by the SSI ootnmand.
R and IsTrusted R is a 160-bit random number seed that is programmed along with K, and K2 with the SSI (Set Secret Information) command. R does not have to be kept secret, since it is given freely to callers via the RND command. However R must be ehanged only by the Authentication Chip, and not set to any chosen value by a caller. R is used during the TST
command to ensuce that the R from the previous call to RND was used to generate the Fx2[M I R] value in the non-trusted Authentication Chip (ChipA). Both RND and TST are only used in tnisted Authentication Chips (ChipT).
IsTrusted is a 1-bit flag register that determines whether or not the Authentication Chip is a trusted chip (ChipT):
If the IsTntsted bit is set, the chip is considered to be a nusted chip, and hence clients can call RND and TST
functions (but not RD or WR).
If the IsTrusted bit is clear, the chip is not c.omidened to be trusted Therefore RND and TST functions cannot be called (but RD and WR fuactions can be called instead). System never needs to call RND or TST on the consumable (since a clone chip would simply return I to a function such as TST, and a constant value for RND).
The IsTrusted bit has the added advantage of reducing the number of availabk R, FK,(Rj pairs obtainable by an attacker, yet still maintain the integrity of the Authentication protocoL To obtain valid R, FK,IRj pairs, an attacker requires a System Authentication Chip, which is more expensive and less readily available than the consumables. Both R and the IsTrusted bit are cleared to 0 by the CLR command. They are both written to by the issuing of the SSI
command. The IsTrusted bit can only set by storing a non-zero seed value in R
via the SSI command (R must be non-zero to be a valid LFSR state, so this is quite teasatable). R is changed via a 160-bit maximal period LFSR with taps on bits 1, 2, 4, and 159, and is changed only by a successful call to TST
(where 1 is retumed).
Authentication Chips destined to be trusted Chips used in Systems (ChipT) should have their IsTrusted bit set during programming, and Authentication Chips used in Consumables (ChipA) should have their IsTrusted bit kept clear (by storing 0 in R via the SSI command during progranmiing). There is no command to read or write the IsTrusted bit directly. The security of the Aut4-enticahon Chip does not only rely upon the randomness of K, and K2 and the strength of the HMAC-SHA 1 algorithm. To prevent an attacker from building a sparse lookup table, the security of the Authentication Chip also depends on the range of R over the lifetime of all Systems. What this means is that an attacker must not be able to deduce what values of R there are in produced and future Systems. As such R should be ptogrammed with a physically generated n~ndom number. gathered from a physically random phenomenon. R must NOT be generated with a computer-run random number generator. The generation of R must not be deterministic. For example, to generate an R for use in a trusted System chip, a person can toss a fair coin 160 times, recording heads as 1, and tails as 0. 0 is the only.non-valid initial value for a trusted R is 0 (or the IsTrusted bit will not be set).
SlWrittett The SIWritten (Secret Infotination Written) 1-bit register holds the status of the secret infotmation stored within the Authentication Chip. The secret information is K,, KZ and R A client cannot directly access the SlWritten bit. Instead, it is cleared via the CLR cotttmand (which also clears K,, K2 and R). When the Authentication Chip is programmed with secret keys and random numba seed using the SSI command (regardless of the value wrttten), the SlWritt.en bit is set automatically. Although R is strictly not secret, it must be writben together with K, and K2 to ensure that an attacker cannot generate their own random number seed in order to obtaia ahosen R, FK,[R] pairs. The SlWritten status bit is used by all funetions that access K,, K2, or R If the SlWritten bit is clear, then ealls to RD, WR, RND, and TST are interpreted as calls to CLR
MinTicks There are two mechanisms for pmventing an attacker from generating multipie calls to TST and RD functions in a short period of time. The first is a clock limiting hardware compottettt that prevents the intemal clock from operating at a speed more than a particular maximum (e.g. 10 MHz). The second mechanisin is the 32-bit MinTicks register, which is used to specify the minimum number of clock ticks that must elapse between calls to key-based functions. The MinTicks variable is cleared to 0 via the CLR conunand. Bits can then be set via the SMT (Set MinTicks) command.
The input parameter to SMT contains the bit pattem that represents which bits of MinTicks are to be set. The practical effect is that an attacker can only increase the value in MinTicks (since the SMT function only sets bits). In addition, there is no fimction provided to allow a caller to read the current value of this register. The value of MinTicks depends on the operating clock speed and the notion of what constitutes a reasonable time between key-based function calls (application specific). The duration of a single tick depends on the operating dock speed. This is the maximum of the input clock speed and the Authentication Chip's clock-limiting hardware. For example, the Authentication Chip's clock-limiting hardware may be set at 10 MHz (it is not changeable), but the input clock is I MHz In this case, the value of I tick is based on 1 MHz, not 10 MHz If the input clock was 20 MHz instead of 1 MHz, the value of I tick is based on 10 MHz (since the clock speed is limited to 10 MHz).
Once the duration of a tick is known, the MinTicks value can to be set. The value for MinTicks is the minimum nwnber of ticks required to pass between calls to the key-based RD and TST
functions. The value is a real-time number, and divided by the length of an operating tick. Suppose the input clock speed matches the maximum clock speed of 10 MHz If we want a minimum of I second between calls to key based functions, the value for MinTtcks is set to 10,000,000. Consider an attacker attempting to collect X, FKi[X] pairs by calling RND, RD and TST multiple times. If the MinTicks value is set such that the amount of time between calls to TST is I second, then each pair requires I second to generate. To generate 2" pairs (only requiring 125 GB of storage), an attacker requires more than I year. An attack requiring 264 pairs would require 5.84 x I011 years using a single chip, or 584 years if I billion chips were used, making such an attack completely impractical in terms of time (not to mention the storage requirements!).
With regards to KI, it should be noted tltat the MinTicks variable only slows down an attacker and causes the attack to cost more since it does not stop an attacker using multiple System chips in parallel. However MinTicks does make an attack on K2 more difficult, since each consumable has a differatt M(part of M
is random read-only data). In order to launch a differential attack, minimally different inputs are required, and this can only be achieved with a single consumable (containing an effectively constant patt of M). Minimally different inputs require the attacker to use a single chip, and MinTicks causes the use of a single chip to be slowed down.
If it takes a year just to get the data to start searching for values to begin a differential attack this incteases the cost of attack and reduces the effective market time of a clone co swttable.
Authentication Chin Commands The System communicates with the Authentication Chips via a simple operation command set. This section details the actual commands and paramdms necessary for implementation of P+=otocol3. The Authentication Chip is defined here as conununicatmg to System via a serial interface as a minimum implementation.
It is a trivial matter to define an equivalent chip that openates over a wider interface (such as 8, 16 or 32 bits). Each eommand is defined by 3-bit opcode. The interpretation of the opcode can depend on the current value of the IsTrusted bit and the current value of the IsWritten bit. The following operations are defined:
Op T W Mn Input Output Description 000 - - CLR - - Clear 001 0 0 SSI [160, 160, 160] - Set Secret Information 010 0 1 RD [160,160] [256,160] Read M secureiy 010 1 l RND - [ 160, 160] Random 011 0 1 WR [256] - Write M
011 1 1 TST [256, 160] [11 Test 100 0 1 SAM [32) [32] Set Access Mode 101 - I GiT - [ 1] Get Is Tntsted 110 - I SMT [32] Set MinTicks Op = Opcode, T = IsTrusted value, W= IsWritten value, Mn = Mnemonic, [n] = number of bits required for parameter Any command not defined in this table is interpreted as NOP (No Operation).
Examples include opcodes 110 and I 1 I
(regardless of IsTmsted or IsWritten values), and any opcode other than SSI
when IsWritten = 0. Note that the opcodes for RD and RND are the same, as are the opcodes for WR and TST. The actual command nm upon receipt of the opcode will depend on the curnent value of the IsTrusted bit (as long as IsWritten is 1). Where the IsTrusted bit is clear, RD and WR functions will be called. Where the IsTrusted bit is set, RND
and TST functions will be called. The two sets of commands are mutually exclusive between tmsted and non-tusLad Authentication Chips, and the same opcodes enforces this relationship. Each of the commands is examined in detail in the subsequent sections. Note that some algorithms are specifically designed because Flash memory is assumed for the implementation of non-volatile variables.
CLR Clear Input None Output None Changes All The CLR (Clear) Command is designed to completely erase the contents of all Authentication Chip memory. This includes all keys and secret information, access mode bits, and state data.
After the execution of the CLR command, an Authentication Chip will be in a programmable state, just as if it had been freshly manufactured. It can be reprogrammed with a new key and reused. A CLR command consists of simply the CLR command opcode. Since the Authentication Chip is serial, this must be transfetred one bit at a time. The bit order is LSB to MSB for each conunand component. A CLR conunand is therefore sent as bits 0-2 of the CLR
opcode. A total of 3 bits are trinsfernd. The CLR command can be called directly at any time. The order of erasure is important. SlWritten must be cleared fust, to disable further calls to key access functions (such as RND, TST, RD and WR). If the AccessMode bits are cleared before SlWritten, an attacker could remove power at some point after they have been cleared, and manipulate M, thereby have a better chance of retrieving the secret infotmation with a partial chosen text attack. The CLR command is implemented with the following steps:
Step Action 1 Erase SlWriuen Erase IsTrusted Erase K, Erase K2 Erase R
Erase M
2 Erase AccessMode Erase MinTicks Once the chip has been cleared it is ready for reprogramming and reuse. A
blank chip is of no use to an attacker, since although they can create any value for M (M can be read from and written to), key-based futtctions will not provide any infotmation as Ki and K2 will be incortact. It is not necessary to consume any input parameter bits if CLR is called for any opcode other than CLR. An attacker will simply have to RESET
the chip. The reason for calling CLR is to ensure that all secret information has been destroyed, making the chip useless to an attacker.
SSI - Set Secret Information Input: Ki, K2, R = [160 bits, 160 bits, 160 bits]
Output: None Changes: Ki, K2, R, SlWriltea, IsTtus6ed The SSI (Set Secret Information) command is used to load the K,, K2 and R
variables, and to set SlWritten and IsTrusted flags for later calls to RND, TST, RD and WR commands. An SSI
command consists of the SSI command opcode followed by the secret information to be stored in the Ki, K2 and R
registers. Since the Authentication Chip is serial, this must be transfemod one bit at a time. The bit order is LSB to MSB
for each conunand component An SSI
conunand is therefore sent as: bits 0-2 of the SSI opcode, followed by bits 0-159 of the new value for Ki, bits 0-159 of the new value for K2, and finally bits 0-159 of the seed value for R. A total of 483 bits are ttansfeired. The Kt, K2, R, SlWritten, and IsTntsted reglsters are all cleared to 0 with a CLR eoaunand.
They can only be set using the SSI
command.
The SSI command uses the flag SlWritten to store the fact dtat data has been loaded into K,, K2, and R. If the SlWritten and IsTntsted flags are clear (this is the case a8er a CLR
instruction), then Ki, K2 and R are loaded with the new values_ If either flag is set, an attempted call to SSI results in a CLR
command being executed, since only an attacker or an erroneous client would attempt to change keys or the random seed without calling CLR fnst. The SSI
command also sets the IsTrusted flag depending on the value for R. If R = 0, then the chip is considered untrustworthy, and therefore IsTrust.ed remains at 0. If R?~ 0, then the chip is considered tivstworthy, and therefore IsTrusted is set to 1. Note that the setting of the IsTrusted bit only occurs during the SSI
command. If an Authentication Chip is to be reused, the CLR command must be called fust The keys can then be safely reprogrammed with an SSI command, and fresh state information loaded into M using the SAM and WR commands. The SSI
command is implemented with the following steps:
Step Action I CLR
2 K, <- Read 160 bits from client 3 K2 Read 160 bits from client 4 R<- Read 160 bits from client IF (R # 0) IsTrusted F- I
6 SI Written E- 1 RD - Read Input: X, FKI[X] _[160 bits, 160 bits]
Output: M, FK2[X M] = [256 bits, 160 bits]
Changes: R
The RD (Read) conunand is used to securely read the entire 256 bits of state data (M) from a non-trusted Authentication Chip. Only a valid Authentication Chip will respond correctly to the RD request. The output bits from the RD command can be fed as the input bits to the TST command on a trusted Authentication Chip for verification, with the fust 256 bits (M) stored for later use if (as we hope) TST retums 1.
Since the Authentication Chip is serial, the cotnmand and input parazttetas must be transferred one bit at a time. The bit order is LSB to MSB for each command component A RD command is therefore: bits 0-2 of the RD opcode, followed by bits 0-159 of X, and bits 0-159 of FKAX]. 323 bits are transfetred in total. X and FKj[X] are obtained by calling the trusted Authentication Chip's RND
command. The 320 bits output by the trusted chip's RND command can therefore be fed directly into the non-tnuted chip's RD command, with no need for these bits to be stored by System. The RD
cornmand can only be used when the following conditions have been met:
SlWritten = 1 indicating that Ki, K2 and R have been set up via the SSI
command; and IsTrusted = 0 indicating the chip is not uusted since it is not permitted to generate random ntnnber sequences;
In addition, calls to RD must wait for the MinTicksRemaining register to reach 0. Once it has done so, the register is reloaded with MinTicks to ensure ihat a minimum time will elapse betweeit calls to RD. Once MinTicksRemaining has been reloaded with MinTicks, the RD command va-ifies that the input parameters are valid This is accomplished by intemally generating FK1[X] for the input X, and then comparing the result against the input FKI[X]. This generation and comparison must take the same amount of time regardless of whether the input parameters are correct or not. If the times are not the same, an attacker can gain infonnation about which bits of FKI[X] are incorrect. The only way for the input parameters to be invalid is an enroneous System (passing the wrong bits), a case of the wrong consumable in the wrong System, a bad trusted chip (generating bad pairs), or an attack on the Authentication Chip. A constant value of 0 is retumed when the input parameters are wrong. The time taken for 0 to be returned must be the same for all bad inputs so that attackers can leam nothing about what was invalid. Once the input parameters have been verified the output values are calculated. The 256 bit content of M are transferred in the following order: bits 0-15 of M[0], bits 0-15 of M[1], through to bits 0-15 of M[15]. Fr2[X I M) is calculated and output as bits 0-159. The R register is used to store the X value during the validation of the X, FKI[X] pair. This is because RND and RD are mutually exclusive.
The RD command is implemented with the following steps:
Step Action I IF (MinTicksRemaining * 0 2 MinTicksRemaining F- MinTicks 3 R E- Read 160 bits from client 4 Hash f- Calculate FKi[R]
OK <- (Hash = next 160 bits from client) Note that this operation must take constant time so an attacker cannot determine how much of their guess is correct.
6 IF (OK) Output 256 bits of M to client ELSE
Output 256 bits of 0 to client 7 Hash <-- Calculate Fr2[R I MJ
8 IF (OK) Output 160 bits of Hash to client ELSE
Output 160 bits of 0 to client RND - Rffitdom Input: None Output: R, FKI[R] _[160 bits, 160 bits]
Changes: None The RND (Random) command is used by a client to obtain a valid R, FK,[R] pair for use in a subsequent authentication via the RD and TST commands. Since there are no input parameters, an RND command is therefore simply bits 0-2 of the RND opcode. The RND command can only be used when the following conditions have been met:
SlWritten = I indicating K, and R have been set up via the SSI command;
IsTrusted = I indicating the chip is permitted to generate random number sequences;
RND returns both R and FK,[Rj to the caller. The 288-bit output of the RND
command can be fed straight into the non-trusted chip's RD command as the input parameters. Tlwre is no need for the client to store them at all, since they are not required again. However the TST command will only succeed if the random number passed into the RD
command was obtained fust from the RND command. If a caller only calls RND
multiple times, the same R, F,r,[R]
pair will be returned each time. R will only advance to the next random number in the sequence after a successful call to TST. See TST for more information. The RND command is implemented with the following steps:
Step Action I Output 160 bits of R to client 2 Hash <-- Calculate FK,[R]
3 Output 160 bits of Hash to client TST - Test Input: X, FK2[R I X] [256 bits, 160 bits]
Output: I or 0=[l bit]
Changes: M, R and MinTicksRemaining (or all registers if attack detected) The TST (Test) command is used to authenticate a read of M from a non-trusted Authentication Chip. The TST (Test) comm.aad consists of the TST command opcode followed by input parameters: X
and Fr2[R ~ Xj. Since the Authentication Chip is sexia(, this must be transfen'ed one bit at a time. The bit order is LSB to MSB for each command component. A TST command is therefore: bits 0-2 of the TST opcode, followed by bits 0-255 of M, bits 0-159 of Fn[R I M). 419 bits are transferned in total. Since the last 416 input bits are obtained as the output bits from a RD command to a non-trusted Authenlication Chip, the entire data does not even have to be stored by the client.
Instead, the bits can be passed directly to the trusted Authentication Chip's TST command. Only the 256 bits of M
should be kept from a RD command. The TST command can only be used when the following conditions have been met:
SlWritten = I indicating K2 and R have been set up via the SSI command;
IsTnisted =1 indicating the chip is pemtitted to generate random number sequences;
In addition, calls to TST must wait for the MinTicksRemaining register to reach 0. Once it has done so, the register is reloaded with MinTicks to ensure that a minimum time will elapse between calls to TST. TST causes the internal M
value to be replaced by the input M value. FrAlVl I K] is then calculated, and compared against the 160 bit input hash value. A single output bit is produced: I if they are the same, and 0 if they are diffenent. The use of the intemal M value is to save space on chip, and is the reason why RD and TST are mutuaily exclusive commands. If the output bit is 1, R
is updated to be the next random number in the sequence. This forces the caller to use a new random number each time RD and TST are called. The resultant output bit is not output until the entire input string has been compared, so that the time to evaluate the comparison in the TST fimction is always the same.
Thus no attacker can compare execution times or number of bits processed before an output is given.
The next random number is generated from R using a 160-bit maximal period LFSR
(tap selections on bits 159, 4, 2, and 1). The initial 160-bit value for R is set up via the SSI command, and can be any random number except 0 (an LFSR filled with Os will produce a never-ending stream of Os). R is transfomled by XORing bits 1, 2, 4, and 159 together, and shifting all 160 bits right I bit using the XOR result as the input bit to blsy. The new R will be retumed on the next call to RND. Note that the time taken for 0 to be returned from TST
must be the same for all bad inputs so that attackers can leam nothing about what was invalid about the input.
The TST command is implemented with the following steps:
Step Action 1 IF (MinTicksRemaining * 0 2 MinTicksRemaining t- MinTicks 3 M<-- Read 256 bits from client 4 IF(R=0) GOTO CLR
Hash <- Calculate FK2[R I M]
6 OK E-- (Hash = next 160 bits from client) Note that this operation must take constant time so an attacker cannot determine how much of their guess is correct.
7 IF (OK) Temp<- R
Erase R
Advance TEMP via LFSR
R <-- TEMP
8 Output 1 bit of OK to client Note that we can't simply advance R directly in Step 7 since R is Flash memory, and must be erased in order for any set bit to become 0. If power is removed from the Authentication Chip during Step 7 after erasing the old value of R, but before the new value for R has been written, then R will be erased but not telxogrammed. We therefore have the situation of IsTtusted=1, yet R=O, a situation only possible due to an atiacker. Step 4 detects this event, and takes action if the attack is detected. This problem can be avoided by having a second 160-bit Flash register for R and a Validity Bit, toggled after the new value has been loaded. It has not been included in this implementation for reasons of space, but if chip space allows it, an extra 160-bit Flash register would be useful for this purpose.
WR - Writc Input: M~ = (256 bits]
Output: None Changes: M
A WR (Write) command is used to update the writeable parts of M containing Authentication Chip state data. The WR
command by itself is not secure. It must be followed by an authenticated read of M (via a RD command) to ensure that the change was made as specified. The WR command is called by passing the WR
command opcode followed by the new 256 bits of data to be written to- M. Since the Authentication Chip is serial, the new value for M must be transferned one bit at a time. The bit order is LSB to MSB for each command component. A WR txrmmand is therefore: bits 0-2 of the WR opcode, followed by bits 0-15 of M[O], bits 0-15 of M[l], through to bits 0-15 of M[15].
259 bits are transferred in total. The WR command can only be used when SIWritten = 1, indicating that KI, KZ and R
have been set up via the SSI command (if SlWritten is 0, then Ki, K2 and R
have not been setup yet, and the CLR
command is calkd instead). The ability to write to a specific M[n] is govemed by the corresponding Access Mode bits as stored in the AccessMode register. The AccessMode bits can be set using the SAM command. When writing the new value to M[n] the fact that M[n] is Flash memory must be taken into account. All the bits of M[n] must be erased, and then the appropriate bits set. Since these two steps occur on different cycles, it leaves the possibility of attack open.
An attacker can remove power after erasure, but before }rogramming with the new value. However, there is no advantage to an attacker in doing this:
A Read/Write M[n] changed to 0 by this means is of no advantage since the attacker could have written any value using the WR command anyway.
A Read Only M[n] changed to 0 by this means allows an additional known text pair (where the M(n] is 0 instead of the original value). For futurc use M[n] values, they are already 0, so no information is given.
A Decrement Only M[n] changed to 0 simply speeds up dte time in which the consumable is used up. It does not give any new infonnation to an attacker that using the consumable would give.
The WR command is implemented with the following steps:
Step Action I DecEncountered *- 0 EqEncountered E-- 0 nE-15 2 Temp E- Read 16 bits from client 3 AM = AccessMode[--n]
Compare to the previous value LT F- (Temp < M[--n]) [comparison is unsignedj EQ (Temp = M[--n]) 6 WE<--(AM=RW)v ((AM = MSR) A LT) v ((AM = NMSR) A (DecEncountered v LT)) 7 DecEncountered t- ((AM = MSR) A LT) v ((AM = NMSR) A DecEncountered) v ((AM = NMSR) A EqEncountered A LT) EqEncountered F- ((AM = MSR) A EQ) v ((AM = NMSR) A EqEncountered A EQ) Advance to the next Access Mode set and write the new M[-n] if applicable 8 IF (WE) Erase M[--n]
M[--n] 4- Temp n 11 IF (n at 0) SAM - Set AccessMode Input: AccessMode_ = [32 bits]
Output: AccessMode = [32 bits]
Changes: AccessMode The SAM (Set Access Mode) command is used to set the 32 bits of the AccessMode register, and is only available for use in consumable Authentication Chips (where the IsTrusted flag = 0). The SAM
command is called by passing the SAM command opcode followed by a 32-bit value that is used to set bits in the AccessMode register. Since the Authentication Chip is serial, the data must be transfen-ed one bit at a time.
The bit order is LSB to MSB for each command component A SAM command is therefone: bits 0-2 of the SAM opcode, followed by bits 0-31 of bits to be set in AccessMode. 35 bits are transferred in total. The AccessMode register is only cleared to 0 upon execution of a CLR command. Since an access mode of 00 indicates an access mode of RW
(read/write), not setting any AccessMode bits after a CLR means that all of M can be read from and written to. The SAM
command only sets bits in the AccessMode register. Consequently a client can change the access mode bits for M[n] from RW to RO (read only) by setting the appropriate bits in a 32-bit word, and calling SAM with that 32-bit value as the input parameter. This allows the programming of the access mode bits at different times, perhaps at different stages of the manufacturing process.
For example, the read only random data can be written to during the initial key programming stage, while allowing a second programming stage for items such as consumable serial numbers.
Since the SAM command only sets bits, the effect is to allow the access mode bits corresponding to M[n] to progress from RW to either MSR, NMSR, or RO. It should be noted that an access mode of MSR can be changed to RO, but this would not help an attacker, since the authentication of M after a write to a doctored Authentication Chip would detect that the write was not successful and hence abort the operation. The setting of bits corresponds to the way that Flash memory works best. The only way to clear bits in the AccessMode register, for example to change a Decrement Only M[n] to be Read/Write, is to use the CLR conunand. The CLR command not only erases (clears) the AccessMode register, but also clears the keys and all of M. Thus the AccessMode[n] bits corresponding to M[n] can only usefully be changed once between CLR c,anmands. The SAM command retums the new value of the AccessMode register (after the appropriate bits have been set due to the input parameter). By calling SAM with an input parameter of 0, AccessMode will not be changed, and therefore the current value of AccessMode will be retumed to the caller.
The SAM command is implemented with the following steps:
Step Action I Temp <- Read 32 bits from client 2 SetBits(AccessMode, Temp) 3 Output 32 bits of AccessMode to client GIT- Get Is Trusted Input: None Output: IsTrustad = [I bit]
Changes: None The GIT (Get Is Trusted) command is used to read the current value of the IsTrusted bit on the Authentication Chip. If the bit retutned is 1, the Authentication Chip is a tnLsted System Authetttication (.:hip. If the bit reumed is 0, the Authentioation Chip is a consumable Authentication Chip. A GIT command consists of simply the GIT command opcode. Since the Authentication Chip is sorial, this must be transfen-ed one bit at a time. The bit order is LSB to MSB
for each command component. A GIT command is therefore sent as bits 0-2 of the GIT opcode. A total of 3 bits are transferred. The GIT command is implemented with the following steps:
Step Action 1 Output IsTrusted bit to client SMT - Set MinTicks Input: MinTicks. = [32 bits]
Output: None Changes: MinTicks The SMT (Set MinTicks) command is used to set bits in the MinTicks register and hence defme the minimum number of ticks that must pass in between calls to TST and RD. The SMT comntand is called by passing the SMT command opcode followed by a 32-bit value that is used to set bits in the MinTicks register. Since the Authentication Chip is serial, the data must be transfetred one bit at a time. The bit order is LSB
to MSB for each command component An SMT command is therefore: bits 0-2 of the SMT opcode, followed by bits 0-31 of bits to be set in MinTicks. 35 bits are transferred in total. The MinTicks register is only cleared to 0 upon execution of a CLR command. A value of 0 indicates that no ticks need to pass between calls to key-based functions. The functions may therefore be called as &equently as the clock speed Iimiting hardware allows the chip to tun.
Since the SMT command only sets bits, the effect is to allow a client to set a value, and only increase the time delay if fnrdter calls are made. Setting a bit that is already set has no effect, and setting a bit that is ciear only serves to slow the chip down further. The setting of bits cotresponds to the way that Flash memory works best The only way to clear bits in the MinTicks register, for example to change a value of 10 ticks to a value of 4 ticks, is to use the CLR
command. However the CLR command clears the MinTicks register to 0 as well as clearing all keys and M. It is thet+efone useless for an attacker. Thus the MinTicks negister can only usefully be changed once between CLR
commands.
The SMT command is implemented with the following steps:
Step Action 1 Temp <- Read 32 bits from client 2 SetBits(MinTicks, Temp) Proeramminst Authentication Chins Authentication Chips must be programmed with logically secure infonmation in a physically secure environment Consequently the programming procedures cover both logical and physical security. Logical security is the process of ensurmg that Ki, K2, R, and the random M[n] values are generated by a physically random process, and not by a computer. It is also the process of ensuring that the order in which parts of the chip are progtammed is the most logically secure. Physical security is the process of ensuring that the programming station is physically secure, so that K, and K2 remain secret, both during the key generation stage and during the lifetime of the storage of the keys. In addition, the progamming station must be resistant to physical attempts to obtain or destroy the keys. The Authentication Chip has its own security mechanisnis for ensuring that K, and K2 are kept secret, but the Programming Station must also keep K, and K2 safe.
Overview After manufacture, an Authentication Chip must be progiammed before it can be used. In all chips values for K, and K2 must be established. If the chip is destined to be a System Authentication Chip, the initial value for R must be determined. If the chip is destined to be a consumable Authentication Chip, R
must be set to 0, and initial values for M
and AccessMode must be set up. The following stages are therefore identified:
Determine Interaction between Systems and Consumables Determine Keys for Systems and Consumables Determine MinTicks for Systems and Consumables Program Keys, Random Seed, MinTicks and Unused M
Program State Data and Access Modes Once the consumable or system is no longer required, the attached Authentication Chip can be reused. This is easily accomplished by reprogrammed the chip starting at Stage 4 again. Each of the stages is examined in tlte subsequent sections.
Stage 0: Manufacture Tlie manufacture of Authentication Chips does not require any special security. There is no secret information programmed into the chips at manufacturing stage. The algorithms and chip ptncess is not special. Standard Flash processes are used. A theft of Authentication Chips between the chip manufacdrrer and programming station would only provide the clone manufacburer with blank chips. 'Ihis merely compromises the sale of Authentication chips, not anything authenticated by Authentication C.hips. Since the programming station is the only mechanism with consumable and system product keys, a clone manufacturer would not be able to program the chips with the correct key. Clone manufacturets would be able to program the blank chips for their own systems and consumables, but it would be difficult to place these items on the market without detection. I:n addition, a single theft would be difficult to base a business around.
S
&Me 1: Detennine Interaction between Systems and Consumables The decision of what is a System and what is a Consumable needs to be determined before any Authentication Chips can be programmed. A decision needs to be made about which Consumables can be used in which Systems, since all connected Systems and Consumables must share the same key infornurtion. They also need to share state-data usage mechanisms even if some of the interpretations of that data have not yet been determined. A simple example is that of a car and car-keys. The car itself is the System, and the car-keys are the consumables. There are several car-keys for each car, each containing the same key information as the specific car.
However each car (System) would contain a different key (sharod by its car-keys), since we don't want car-keys from one car working in another. Another example is that of a photocopier that requires a particular toner cartridge. In simple betms the photocopier is the System, and the toner cartridge is the consumable. However the decision must be made as to what compatibility there is to be between cartridges and photocopies. The decision has historically been made in terms of the physical packaging of the toner cartridge: certain cartridges will or won't fit in a new model photooopier based on the design decisions for that copier_ When Authentication Chips are used, the components that must work together must share the same key infotmation.
[n addition, each type of consumable requires a diffenant way of dividittg M
(the state data). Although the way in which M is used will vary from application to application, the method of allocating M[n] and AccessMode[n] will be the same:
Define the consumable state data for specific use Set some M[n] registers aside for future use (if required). Set these to be 0 and Read Only. The value can be tested for in Systems to maintain compatibility.
Set the remaining M[n] registers (at least one, but it does not have to be M[15]) to be Read Only, with the contents of each M[n] completely random. This is to make it more difficult for a clone manufacturer to attack the authentication keys.
The following examples show ways in which the state data may be organized.
Example 1 Suppose we have a car with associated car-keys. A 16-bit key number is more than enough to uniquely identify each car-key for a given car. The 256 bits of M could be divided up as follows:
M(n) Access Description 0 RO Key number (16 bits) 1-0 RO Car engine number (64 bits) 5-8 RO For future expansion = 0(64 bits) 8-15 RO Random bit data (128 bits) 71 If the car manufacturer keeps all logica! keys for all cars, it is a trivial matter to manufadure a new physical car-key for a given car should one be lost. The new car-key would contain a new Key Number in M[0], but have the same K, and K2 as the car's Authentication Chip. Car Systems could allow specific key numbers to be invalidated (for example if a key is lost). Such a system might require Key 0 (the master key) to be inserted first, then all valid keys, then Key 0 again. Only those valid keys would now work with the car. In the worst case, for example if all car-keys are lost, then a new set of logical keys could be generated for the car and its associated physical car-keys if desired. "Ihe Car engine number would be used to tie the key to the particular car. Future use data may include such things as rental inforination, such as driver/renter details.
Examnle 2 Suppose we have a photocopier image unit which should be replaced every 100,000 copies. 32 bits are required to stota the number of pages remaining. The 256 bits of M could be divided up as follows:
Mini Access Description 0 RO Serial number (16 bits) 1 RO Batch number (16 bits) 2 MSR Page Count Remaining (32 bits, hi/lo) 4-7 RO For futtu+e expansion = 0(64 bits) 8-15 RO Random bit data (128 bits) If a lower quality image unit is made that must be replaced after only 10,000 copies, the 32-bit page count can still be used for compaftility with existing photocopiers. This allows several consumable types to be used with the same system.
Examole 3 Consider a Polaroid camera consumable containing 25 photos. A 16-bit countdown is all that is required to store the number of photos remaining. The 256 bits of M could be divided up as follows:
M[n] Access Description 0 RO Serial number (16 bits) 1 RO Batch number (16 bits) 2 MSR Photos Remaining (16 bits) 3-6 RO For future expansion = 0(64 bits) 7-15 RO Random bit data (144 bits) The Photos Remaining value at M[2] allows a number of consumable types to be built for use with the same camera System. For example, a new consumable with 36 photos is trivial to program.
Suppose 2 years after the introduction of the camera, a new type of camera was intr-oduced. It is able to use the old consumable, but also can process a new film type. M[3] can be used to define Film Type. Old film types would be 0, and the new film types would be some new value. New Systems can take advantage of this. Original systems would detect a non-zero value at M[3] and realize incompatibility with new film types. New Systems would understand the value of M[3] and so react appropriately. To maintain compatibility with the old consumable, the new consumable and System needs to have the same key information as the old one. To make a cleart break with a new System and its own special eon.sumables, a new key set would be required.
Examnle 4 Consider a printer consumable containing 3 inks: cyan, magenta, and yellow.
Each ink amount can be decremented separately. The 256 bits of M could be divided up as follows:
M[n] Access Description 0 RO Serial number (16 bits) I RO Batch number (16 bits) 2 MSR Cyan Remaining (32 bits, hi/lo) 4 MSR Magenta Remaining (32 bits, hi/lo) NMSR
6 MSR Yellow Remaining (32 bits, hi/lo) 8-11 RO For future expansion = 0 (64 bits) 12-15 RO Random bit data (64 bits) Stage 2: Determine Keys for Systems and Consumables Once the decision has been made as to which Systems and consumables are to share the same keys, those keys must be defined. The values for K, and K2 must therefore be determined. In most cases, K, and KZ will be generated once for all time. All Systems and consumables that have to work together (both now and in the future) need to have the same K, and K2 values. K, and K2 must therefore be kept secret since the entire security mechanism for the System/Consumable combination is made void if the keys are compromised. If the keys are compromised, the damage depends on the number of systems and consumables, and the ease to which they can be reprogrammed with new non-compromised keys: In the case of a photocopier with toner cartridges, the worst case is that a clone manufacturer could then manufacture their own Authentication Chips (or worse, buy them), program the chips with the known keys, and then in.sert them into their own consumables. In the case of a car with car-keys, each car has a different set of keys.
This leads to two possible general scenarios. The fust is that after the car and car-keys are progtammed with the keys, K, and KZ are deleted so no record of their values are kept, meaning that there is no way to compromise K, and K2.
However no more car-keys can be made for that car without reprogramming the car's Authentication Chip. The second scettario is that the car manufacturer keeps K, and K2, and new keys can be made for the car. A compromise of K, and K2 means that someone could make a car-key specifically for a particular car. -"ihe keys and rendom data used in the Authentication Chips must therefore be generated by a means that is non-deterministic (a completely computer generated pseudo-random number cannot be used because it is deterministic -knowledge of the generator's seed gives all future numbers). K, and K2 should be generated by a physically random process, and not by a computer. However, random bit generators based on natural sources of randotnness are subject to influence by external factors and also to malfunction. It is imperative that such devices be tested periodically for statistical randomness.
A simpie yet useful source of random numbers is the Lavarand system from SGi. This generator uses a digital camera to photograph six lava lamps every few minutes. Lava lamps contain chaotic turbnlent systems. The resukattt digital images are fed into an SHA-1 implementation that produces a 7-way hash, resulting in a 160-bit value from every 7th bye from the digitized image. These 7 sets of 160 bits total 140 bytes. The 140 byte value is fed into a BBS
generator to position the start of the output bitstream_ The output 160 bits from the BBS would be the key or the Authentication chip 53_ An extreme example of a non-deterministic random process is someone flipping a coin 160 times for K, and 160 times for K2 in a clean room. With each head or tail, a I or 0 is entered on a panel of a Key Programmer Device. The process must be undertaken with several observers (for verification) in silence (someone may have a hidden microphone). The point to be made is that secure data entry and storage is not as simple as it sounds. The physical security of the Key Prograrnmer Device and accompanying Prog'amrning Station requires an entire document of its own. Once keys K, and KZ have been determined, they must be kept for as long as Authentication Chips need to be made that use the key.
In the first car/car-key scenario K, and K2 are destroyed after a single System chip and a few consumable chips have been programmed. In the case of the photocopier / toner cartridge, K, and K2 must be retained for as long as the toner-cartridges are being made for the photocopiers. The keys must be kept securely.
Sta~e 3: Determine MinTicks for Systems and Consumables The value of MinTicks depends on the operating clock speed of the Authentication Chip (System specific) and the notion of what constitutes a reasonable time between RD or TST function calls (application specific). The duration of a single tick depends on the operating clock speed. This is the maximum of the input clock speed and the Authentication Chip's clock-limiting hardware. For example, the Authentication Chip's clock-limiting hardware may be set at 10 MHz (it is not changeable), but the input clock is I MHz In this case, the value of 1 tick is based on I
MHz, not 10 MHz. If the input clock was 20 MHz instead of 1 MHz, the value of I tick is based on 10 MHz (since the clock speed is limited to 10 MHz). Once the duration of a tick is known, the MinTicks value can be seL The value for MinTicks is the minimum number of ticks required to pass between calls to RD
or RND key-based functions.
Suppose the input clock speed matches the maximum clock speed of 10 MHz. If we want a minimum of I second between calls to TST, the value for MinTicks is set to 10,000,000. Even a value such as 2 seconds might be a completely reasonable value for a System such as a printer (one authentication per page, and one page produced every 2 or 3 seconds).
Stage 4; Prooram Kevs. Random Seed, MinTicks and Unused M
Authentication Chips are in an unknown state after manufacture. Alternatively, they have already been used in one consumable, and must be reprogrammed for use in another. Each Authentication Chip must be cleared and programmed with new keys and new state data. Clearing and subsequent programming of Authentication Chips must take place in a secure Programming Station environment.
Proerammine a Trusted System Authentication Chin If the chip is to be a trusted System chip, a seed value for R must be generated. It must be a random number derived from a physica8y random process, and must not be 0. The following tasks must be undertaken, in the following order, and in a secure progranuning environment:
RESET the chip CLR[]
Load R (160 bit register) with physically random data SSI[K1, KZ, R]
SMT[MinTickss,..]
The Authentication Chip is now ready for insertion into a System. It has been completely programmed. If the System Authentication Chips are stolen at this point, a clone manufacturer could use them to generate R, FK,[R] pairs in order to launch a known text attack on K,, or to use for launching a partially chosen-text attack on Kz. This is no different to the purchase of a number of Systems, each containing a tnisted Authentication Chip. The security relies on the strength of the Authentication protocols and the randomness of K, and KZ.
Proaramminy, a Non-Tnuted Consumable Authentication Chin If the chip is to be a non-trusbed Consumable Authentication Chip, the progtatnmutg is slightly different to that of the trusted System Authentication Chip. Firstly, the seed value for R must be 0.
It must have additional programming for M and the AccessMode values. The future use M[n] must be programmed with 0, and the random M[n] must be programmed with random data. The following tasks must be undertaken, in the following order, and in a secure programming environment:
RESET the chip CLR[]
Load R(160 bit register) with 0 SSI[K,, KZ, R]
Load X (256 bit register) with 0 Set bits in X corresponding to appropriate M[n] with physically random data WRP]
Load Y (32 bit register) with 0 Set bits in Y corresponding to appropriate M[n] with Read Only Access Modes SAM[Y]
SMT[MinTicksc.,,,.,j The non-trusted consumable chip is now ready to be programmed with the generel state data. If the Authentication Chips are stolen at this point, an attacker could perform a timited chosen text attacic. In the best situation, parts of M are Read Only (0 and random data), with the remainder of M completely chosen by an attacker (via the WR command). A
number of RD calls by an attacker obtains FK2[MIR] for a iimited M. In the worst situation, M can be completely chosen by-an attacker (since all 256 bits are used fa state data). In both ta.tes however, the attacker cannot choose any value for R since it is supplied by calls to RND from a System Authentic,ation Chip. The only way to obtain a chosen R
is by a Btute Force attack. It should be noted that if Stages 4 and 5 are catried out on the same Programming Station (the preferred and ideal situation), Authentication Chips cannot be removed in between the stages. Hence there is no possibility of the Authentication Chips being stolen at this point The decision to program the Authentication Chips at one or two times depends on the nequit+anents of the Sysoem/Co sumable manufactturr.
Stap-e 5: Proeram State Data and Access Modes This stage is only required for consumable Authentication Chips, since M and AccessMode registers cannot be altered on System Authentication Chips. The fuhme use and random values of M[n] have already been ptvgratnmed in Stage 4. The remaining state data values need to be programmed and the associated Access Mode values need to be set Bear in mind that the speed of this stage will be limited by the value stored in the MinTicks n:gister. This stage is separated from Stage 4 on account of the differences either in physical location or in time between where/when Stage 4 is performed, and wherelwhen Stage 5 is performed. Ideally, Stages 4 and 5 are performed at the same time in the same Programming Station. Stage 4 produces valid Authentication Chips, but does not load them with initial state values (other than 0). This is to allow the programtning of the chips to coincide with production line runs of consumables.
Although Stage 5 can be run multiple times, each time setting a different state data value and Access Mode value, it is more likely to be run a single time, setting all the remaining state data values and setting all the remaining Access Mode values. For example, a production line can be set up where the batch number and serial number of the Authentication Chip is produced according to the physical consumable being produced. This is much harder to match if the state data is loaded at a physically different factory.
'il-e Stage 5 process involves first checking to ensure the chip is a valid consumable chip, which includes a RD to gather the data from the Authentication Chip, followed by a WR of the initial data values, and then a SAM to pertnanently set the new data values. 'Ilte steps are outlined here:
IsTrusted = GIT[]
If (IsTtnsted), exit with error (wrong kind of chip!) Call RND on a valid System chip to get a valid input pair Call RD on chip to be programmed, passing in valid input pair Load X(256 bit register) with results from a RD of Authentication Chip Call TST on valid System chip to ensure X and consumable chip are valid If (TST retums 0), exit with error (wrong consumable chip for system) Set bits of X to initial state values WR[XI
Load Y(32 bit register) with 0 Set bits of Y corresponding to Access Modes for new state values SAM[Y]
Of course the validation (Steps I to 7) does not have to occur if Stage 4 and 5 follow on from one another on the same Programming Station. But it should occur in all other situations where Stage 5 is run as a separate programming process from Stage 4. If these Authentication Chips are now stolen, they are already programmed for use in a particular consumable. An attacker could place the stolen chips into a clone consumable. Such a theft would limit the number of cloned products to the number of chips stolen. A single theft should not create a supply constant enough to provide clone manufacnu+ers with a cost-effective business_ The altemative use for the chips is to save the attacker from purchasing tite same number of consumables, each with an Authentication Chip, in order to launch a partially chosen text attack or brute force attack. There is no special security breach of the keys if such an attack were to occur.
Manufacture 'Ihe circuitry of the Authentication Chip must be resistant to physical attack. A sumtnary of manufacturing implementation guidelines is presented, followed by specification of the chip's physical defenses (ordered by attack).
Guidelines for Manufacduitte The following are general guidelines for implementation of an Authentication Chip in terms of manufacture:
Standard process Minimum size (if possible) Clock Filter Noise Generator Tamper Prevention and Detection circ.uitry Protected memory with tamper detection Boot circuitry for loading program code Special implementation of FETs for key data paths Data connections in polysilicon layers where possible OverUnderPower Detection Unit No test circuitry Standard Process The Authentication Chip should be implemented with a standard manufacturing process (such as Flash). This is necessary to:
Allow a great range of manufacturing k"tion options Take advantage of well-defined and well-known technology Reduce cost Note that the standard process still allows physical protection mechanisms.
Minimum si~c The Authentication chip 53 must have a low manufaeturing cost in order to be included as the authentication mechanism for low cost consumables. It is therefore desirable to keep the chip size as low as reasonably possible.
Each Authentication Chip requires 802 bits of non-volatile memory. In addition, the storage ttquired for optimized HMAC-SHAI is 1024 bits. The remainder of the chip (state machine, processor, CPU or whatever is chosen to implement Protocol3) must be kept to a minimum in order that the number of transistors is minimized and thus the cost per chip is minimized. The circuit areas that process the secret key infonnation or could reveal information about the key should also be minimized (see Non-Flashing CMOS below for special data paths).
Clock Filtcs The Authentication Chip circuitry is designed to operate within a specific clock speed range. Since the user directly supplies the clock signai, it is possible for an attacker to attempt to introduce race-conditions in the circuitry at specific times during processing. An example of this is whene a high clock speed (higher than the cincuitry is designed for) may prevent an XOR from working properly, and of the two inputs, the fnst may always be returned. These styles of transient fault attacks can be very efficient at recovering sect+et key information. The lesson to be leamed from this is that the input clock signal cannot be trusted. Since the input clock signal cannot be trusted, it must be limited to operate up to a maximum frequency. 'Ibis can be achieved a number of ways. One way to filter the clock signal is to use an edge detea unit passing the edge on to a delay, which in turtt enables the input clock signal to pass through.
Fig. 174 shows clock signal flow within the Clock Filter. The delay should be set so that the maximum clock speed is a particular fieptency (e.g. about 4 MHz). Note that this delay is not progn;mmable - it is fixed. The filtered clock signal would be further divided intemally as required.
Noise Generator Each Authentication Chip should contain a noise generator that generates continuous circuit noise. The noise will interfere with other electromagnetic emissions from the chip's regular activities and add noise to the l,M signal.
Placement of the noise generator is not an issue on an Authentication Chip due to the length of the emission wavelengths. The noise generator is used to generate electronic noise, multiple state changes each clock cycie, and as a source of pseudo-random bits for the Tamper Prevention and Detection circuitry. A simple implementation of a noise generator is a 64-bit LFSR seeded with a non-zero number. The clock used for the noise generator should be nuuting at the maximum clock rate for the chip in order to generate as much noise as possible.
Tamper Prevention and Detection cQCOitrv A set of circuits is required to test for and prevent physical attacks on the Authentication Chip. However what is actually detected as an attack may not be an intentional physical attadc. It is therefore important to distinguish between these two types of attacks in an Authentication Chip:
where you can be certain that a physical attack has occutred.
whene you cannot be certain that a physical attack has occutred.
The two types of detection differ in what is perfotmed as a result of the deteotion. In the first case, where the circuitry can be certain that a true physical attack has occutred, erasure of Flash memory key information is a sensible action. In the second case, where the circuitry cannot be sure if an attack has occutred, there is still certainly something wrong.
Action must be taken, but the action should not be the erasure of secret key infocmation. A suitable action to take in the second case is a chip RESET. If what was detected was an attack that has permanently damaged the chip, the same conditions will occur next time and the chip will RESET again. If, on the other hand, what was detected was part of the nonnal operating environment of the chip, a RESET will not hann the key.
A good example of an event that circuitry cannot have knowledge about, is a power glitch. The glitch may be an intentional attack, attempting to reveal information about the key. It may, however, be the result of a faulty connection, or simply the start of a power-down sequence. It is therefore best to only RESET the chip, and not erase the key. If the chip was powering down, nothing is lost. If the System is faulty, repeated RESETs will cause the consumer to get the System repaired. In both cases the consumable is still intact.A good example of an event that circuitry can have knowledge about, is the cutting of a data line within the chip. If this attack is somehow detected, it could only be a result of a faulty chip (manufaciuring defect) or an attack In either case, the erasure of the secret information is a sensible step to take.
Consequently each Authentication Chip should have 2 Tamper Detection Lines as illustrated in Fig - one for deftnite attacks, and one for posstble attacks. Connected to these Tamper Deteetion Lines would be a number of Tamper Detection test units, eaoh testing for different fonns of tampering. In addition, we want to ensure tfiat the Tamper Detection Lines and Circuits themselves cannot also be tampered with.
At one end of the Tamper Detection Line is a source of pseudo-rattdom bits (clocking at high speed compared to the general opecating circuitry). The Noise Generator circuit described above is an adequate source. The generated bits pass through two different paths - one catries the originai data, and the other carries the inverse of the data. The wires canying these bits are in the layer above the general chip ciratitry (for example, the memory, the key manipulation circuitry ete). The wires must also cover the random bit genetator. The bits are recombined at a number of places via an XOR gate. If the bits are different (they should be), a I is output, and used by the particular unit (for example, each output bit from a memory read should be ANDed with this bit value). The lines fmally come togefher at the Flash memory Erase circuit, where a complete erasure is triggered by a 0 from the XOR Attached to the line is a number of triggers, each detecting a physical attack on the chip. Each trigger has an oversize nMOS transistor attached to GND.
"I'he Tamper Detection Line physically goes through this nMOS transistor. If the test fails, the trigger causes the Tamper Detect Line to become 0. The XOR test will therefore fail on either this clock cycle or the next one (on average), thus RESETing or erasing the chip. Fig. 175 illustrates the basic principle of a Tamper Detection Line in terms of tests and the XOR connected to either the Erase or RESET circuitry.
The Tamper Detection Line must go through the drain of an output transistor for each test, as illustrated by the oversize nMOS transistor layout of Fig. 176. :It is not possible to break the Tamper Detect Line since this would stop the flow of ls and Os from the random source. The XOR tests would therefore fail. As the Tamper Detect Line physically passes ttu+ough each test, it is not possible to eliminate any particular test without breaking the Tamper Detect Line. It is important that the XORs take values from a variety of places along the Tamper Detect Lines in order to reduce the chances of an attack. Fig. 177 illustrates the taking of multiple XORs from the Tamper Detect Line to be used in the different parts of the chip. Each of these XORs can be considered to be generating a ChipOK bit that can be used within each unit or sub-unit.
A sample usage would be to have an OK bit in each unit that is ANDed with a given ChipOK bit each cycle. The OK
bit is loaded with 1 on a RESET. If OK is 0, that unit will fail until the next RESET. If the Tamper Detect Line is functioning correctly, the chip will either RESET or erase all key information. If the RESET or erase circuitry has been destroyed, then this unit will not function, thus thwarting an attacker. The destination of the RESET and Erase line and associated circuitry is very context sensitive. It needs to be protected in much the same way as the individual tamper tests. There is no point generating a RESET pulse if the attacker can simply cut the wire leading to the RESET
circuitry. The actual implementation will depend very much on what is to be cleared at RESET, and how those items are cleared. Finally, Fig. 178 shows how the Tamper Lines cover the noise generator circuitry of the chip. The generator and NOT gate are on one level, while the Tamper Detect Lines nu- on a level above the generator.
Protected memory with tamner detection It is not enough to simply store secret information or program code in Flash memory. The Flash memory and RAM
must be protected from an attacker who would attempt to modify (or set) a particular bit of program code or key infonnation. The mechanism used must conform to being used in the Tamper Detection Circuitry (described above).
The first part of the solation is to ensure that the Tamper Detection Line passes directly above each Flash or RAM bit.
This ensures that an attacker cannot probe the contents of Flash or RAM. A
breach of the covering wire is a break in the Tamper Detection Line. The breach causes the Erase signal to be set, thus deleting any contents of the memory.
The high frequency noise on the Tamper Detection Line also obscures passive observation.
The second part of the solution for Flash is to use multi-level data storage, but only to use a subset of those muttiple levels for valid bit representations. Normally, when multi-level Flash storage is used, a single floating gate holds more than one bit. For example, a 4-voltage-state tcansistor can represent two bits. Assuming a minimum and maximum voltage representing 00 and I 1 respectively, the two middle voltages represent 01 and 10. In the Authentication Chip, we can use the two middle voltages to represent a single bit, and consider the two extremes to be invalid states. If an attacker attempts to force the state of a bit one way or the other by closing or cutting the gate's circuit, an invalid voltage (and hence invalid state) results.
The second part of the solution for RAM is to use a parity bit. The data part of the register can be checked against the parity bit (which will not match after an attack). The bits coming from Flash and RAM can therefore be validated by a number of test units (one per bit) connected to the common Tamper Detection Line. The Tamper Detection circuitry would be the first circuitry the data passes through (thus stopping an attacker from cutting the data lines).
Boot circuitry for loading proaram code Program code should be kept in multi-level Flash instead of ROM, since ROM is subject to being altered in a non-testable way. A boot mechanism is therefore required to load the program code into Flash memory (Flash memory is in an indetera-inate state after manufacture). The boot circuitry must not be in ROM - a small state-machine would suffice. Otherwise the boot code could be modified in an undetectable way. The boot circuitry must erase all Flash memory, check to ensure the erasure worked, and then load the program code.
Flash memory must be erased before loading the program code. Otherwise an attacker could put the chip into the boot state, and then load program code that simply extracted the existing keys. The state machine must also check to ensure that all Flash memory has been cleared (to ensure that an attacker has not cut the Erase line) before loading the new program code. The loading of program code must be undertaken by the secure Programming Station before secret information (such as keys) can be loaded.
Special implementation of FETs for key data aaths The normal situation for FET implementation for the case of a CMOS Inverter (which involves a pMOS transistor combined with an nMOS transistor) is shown in Fig. 179. During the transition, there is a small period of time where both the nMOS transistor and the pMOS transistor have an intermediate resistance. The resultant power-ground short circuit causes a temporary increase in the current, and in fact accounts for the majority of current consumed by a CMOS device. A small amount of infiared light is emitted during the short circuit, and can be viewed through the silicon substrate (silicon is transparent to infrared light). A small amount of light is also emitted during the charging and discharging of the transistor gate capacitance and transmission line capacitance.
For circuitry that manipulates secret key information, such information must be kept hidden. An alternative non-flashing CMOS implementation should therefore be used for all data paths that manipulate the key or a partially calculated value that is based on the key. The use of two non-overlapping clocks ~1 and ~2 can provide a non-flashing mechanism. ~l is connected to a second gate of all nMOS transistors, and 02 is connected to a second gate of all pMOS transistors. The transition can only take place in combination with the clock. Since 01 and 02 are non-overlapping, the pMOS and nMOS trsnsistors will not have a simultaneous intermediate resistance. The setup is shown in Fig. 180.
Finally, regular CMOS inverters can be positioned near critical non-Flashing CMOS components. These inverters should take their input signal from the Tamper Detection Line above. Since the Tamper Detection Line operates multiple times faster than the regular operating circuitry, the net effect will be a high rate of light-bursts next to each non-Flashing CMOS component. Since a brigbt light overwhehns observation of a nearby faint light, an observer will not be able to detect what switching operations are occun-ing in the chip proper. These regular CMOS inverters will also effectively increase the amount of circuit noise, reducing the SNR and obscuring useful EMI.
There are a number of side effects due to the use of non-Flashing CMOS:
The effective speed of the chip is reduced by twice the rise time of the clock per clock cycle. This is not a problem for an Authentication Chip.
The amount of cuirent drawn by the non-Flashing CMOS is reduced (since tlte short circuits do not occur).
However, this is offset by the use of regular CMOS inverters.
Routing of the clocks increases chip area, especially since multiple versions of 01 and 02 are required to cater for different levels of propagation. The estimation of chip area is double that of a regular implementation.
Design of the non-Flashing areas of the Authentication Chip are slightly more complex than to do the same with a with a regular CMOS design. In particular, standard cell components cannot be used, making these areas full custom. This is not a problem for something as small as an Authentication Chip, particularly when the entire chip does not have to be protected in this manner.
Connections in polysilicon layers where possible Wherever possible, the connections along which the key or secret data flows, should be made in the polysilicon layers.
Where necessary, they can be in metal 1, but must never be in the top metal layer (containing the Tamper Detection Lines).
OverUnderPower Detection Unit Each Authentication Chip requires an OverUnderPower Detection Unit to prevent Power Supply Attacks. An OverUnderPower Detection Unit detects power glitches and tests the power level against a Voltage Reference to ensure it is within a certain tolerance. The Unit contains a single Voltage Reference and two comparators. The OverUnderPower Detection Unit would be connected into the RESET Tamper Detection Line, thus causing a RESET
when triggered_ A side effect of the OverUnderPower Detection Unit is that as the voltage drops during a power-down, a RESET is triggered, thus erasing any work registers.
No Test Circuitrv Test hardware on an Authentication Chip could very easily introduce vulnerabilities. As a result, the Authentication Chip should not contain any BIST or scan paths. The Authentication Chip must therefore be testable with external test vectors. This should be possible since the Authentication Chip is not complex.
Readine ROM
This attack depends on the key being stored in an addressable ROM. Since each Authentication Chip stores its authentication keys in intemal Flash memory and not in an addressable ROM, this attack is irrelevant.
Reverse Engineering the Chio Reverse engineering a chip is only useful when the security of authentication lies in the algorithm alone. However our Authentication Chips rely on a secret key, and not in the secrecy of the algorithm. Our authentication algorithm is, by contrast, public, and in any case, an attacker of a high volume consumable is assumed to have been able to obtain detailed plans of the intemals of the chip. In light of these factors, reverse engineering the chip itself, as opposed to the stored data, poses no threat.
UsuroinQ the Authentication Process There are several forms this attack can take, each with varying degrees of success. In all cases, it is assumed that a clone manufacturer will have access to both the System and the consumable designs. An attacker may attempt to build a chip that tricks the System into retuming a valid code instead of generating an authentication code. This attack is not possible for two reasons. The first reason is that System Authentication chips and Consumable Authentication Chips, although physically identical, are programmed differently. In particular, the RD opcode and the RND opcode are the same, as are the WR and TST opcodes. A System authentication Chip cannot perform a RD command since every call is interpreted as a call to RND instead. The second reason this attack would fail is that separate serial data lines are provided from the System to the System and Consumable Authentication Chips.
Consequently neither chip can see what is being transmitted to or received from the other. If the attacker builds a clone chip that ignores WR commands (which decrement the consumable remaining), Protocol 3 ensures that the subsequent RD will detect that the WR did not occur. The System will therefore not go ahead with the use of the consumable, thus thwarting the attacker. The same is true if an attacker simulates loss of contact before authentication -since the authentication does not take place, the use of the consumable doesn't occur. An attacker is therefore limited to modifying each System in order for clone consumables to be accepted Modification of System The simplest method of modification is to replace the System's Authentication Chip with one that simply reports success for each call to TST. This can be thwarted by System calling TST
several times for each authentication, with the first few times providing false values, and expecting a fail from TST. The final call to TST would be expected to succeed. The number of false calls to TST could be determined by some part of the retumed result from RD or from the system clock. Unfortunately an attacker could simply rewire System so that the new System clone authentication chip 53 can monitor the retumed result from the consumable chip or clock. The clone System Authentication Chip would only return success when that monitored value is presented to its TST
function. Clone consumables could then return any value as the hash result for RD, as the clone System chip would declare that value valid. There is therefore no point for the System to call the System Authentication Chip multiple times, since a rewiring attack will only work for the System that has been rewired, and not for all Systems. A similar form of attack on a System is a replacement of the System ROM. The ROM program code can be altered so that the Authentication never occurs. There is nothing that can be done about this, since the System remains in the hands of a consumer. Of course this would void any watranty, but the consumer may consider the alteration worthwhile if the clone consumable were extremely cheap and more readily available than the original item.
The System/consumable manufacturer must therefore determine how ldcely an attack of this nature is. Such a study must include given the pricing structure of Systems and Consumables, frequency of System service, advantage to the consumer of having a physical modification perfortned, and where consumers would go to get the modification performed. The limit case of modifying a system is for a clone manufacturer to provide a completely clone System which takes clone consumables. This may be simple competition or violation of patents. Either way, it is beyond the scope of the Authentication Chip and depends on the technology or service being cloned.
Direct viewing of chip operation by conventional probing In order to view the chip operation, the chip must be operatittg. However, the Tatnper Prevention and Detection circuitry covers those sections of the chip that process or hold the key. It is not possible to view those sections through the Tamper Prevention lines. An attacker cannot simply slice the chip past the Tamper Prevention layer, for this will break the Tamper Detection Lines and cause an erasure of all keys at power-up.
Simply destroying the erasure circuitry is not sufficient, since the multiple ChipOK bits (now all 0) feeding into multiple units within the Authentication Chip will cause the chip's regular operating circuitry to stop functioning. To set up the chip for an attack, then, requires the attacker to delete the Tamper Detection lines, stop the Etasure of Flash memory, and somehow rewire the components that relied on the ChipOK lines. Even if all this could be done, the act of slicing the chip to this level will most likely destroy the charge pattems in the non-volatile memory that holds the keys, making the process fiuidess.
Direct viewine of the non-volatile memorv If the Authentication Chip were sliced so that the floating gates of the Flash memory were exposed, without discharging them, then the keys could probably be viewed directly using an STM
or SKM. However, slicing the chip to this level without discharging the gates is probably impossible_ Using wet etching, plasma etching, ion milling, or chemical mechanical polishing will almost certainly discharge the small charges present on the floating gates. This is true of regular Flash memory, but even more so of multi-level Flash memory.
Viewing the li t bursts caused by state chanees All sections of circuitry that manipulate secret key information are implemented in the non-Flashing CMOS described above. This prevents the emission of the majority of light bursts. Regular CMOS inverters placed in close proximity to the non-Flashing CMOS will hide any faint emissions caused by capacitDr charge and discharge. The inverters are connected to the Tamper Detection circuitry, so they change state many times (at the high clock rate) for each non-Flashing CMOS state change.
Monitorina EMI
The Noise Generator described above will cause circuit noise. The noise will interfere with other electromagnetic emissions from the chip's regular activities and thus obscure any meaningful reading of intemal data transfers.
Viewine L. fluctuations The solution against this kind of attack is to decrease the SNR in the Idd signal. This is accomplished by increasing the amount of circuit noise and decreasing the amount of signal. The Noise Generator circuit (which also acts as a defense against EMI attacks) will also cause enough state changes each cycle to obscure any meaningfiul information in the I&
signal. tn addition, the special Non-Flashing CMOS implementation of the key-carrying data paths of the chip prevents cun-ent from flowing when state changes occur. This has the benefit of reducing the amount of signal.
Differential Fault Anaiysis Differential fault bit errors are introduced in a non-targeted fashion by ionization, microwave radiation, and environmental stress. The most likely effect of an attack of this nature is a change in Flash memory (causing an invalid state) or RAM (bad parity). Invalid states and bad parity are detected by the Tamper Detection Circuitry, and cause an erasure of the key. Since the Tamper Detection Lines cover the key manipulation circuitry, any error introduced in the key manipulation circuitry will be mitrored by an error in a Tamper Detection Line. If the Tamper Detection Line is affected, the chip will either continually RESET or simply erase the key upon a power-up, rendering the attack fruitless. Rather than relying on a non-targeted attack and hoping that "just the right part of the chip is affected in just the right way", an attacker is better off trying to inaroduce a targeted fault (such as overwrite attacks, gate destruction etc). For information on these targeted fault attacks, see the relevant sections below.
Clock Glitch Attacks . q The Clock Filter (described above) eliminates the possibility of clock glitch attacks.
Power Supply Attadcs The OverUnderPower Detection Unit (described above) eliminates the possibility of power supply attacks.
Overwriting ROM
Authentication Chips store Program code, keys and secret information in Flash memory, and not in ROM. This attack is therefore not possible.
Modifying EEPROM/Flash Authentication Chips store Program code, keys and secret infotmation in Flash memory. However, Flash memory is covered by two Tamper Prevention and Detection L'ntes. If either of these lines is broken (in the process of destroying a gate) the attack will be detected on power-up, and the chip will either RESET (continually) or erase the keys from Flash memory. However, even if the attacker is able to somehow access the bits of Flash and destroy or short out the gate holding a particular bit, this will force the bit to have no charge or a full charge. These are both invalid states for the Authentication Chip's usage of the multi-level Flash memory (only the two middle states are valid). When that data value is transferred from Flash, detection circuitry will cause the Erasure Tamper Detection Line to be triggered -thereby erasing the remainder of Flash memory and RESETing the chip. A Modify EEPROM/Flash Attack is therefore fivitless.
Gate Destruction Attacks Gate Destruction Attacks rely on the ability of an attacker to modify a single gate to cause the chip to reveal information during operation. However any circuitry that manipulates secret information is covered by one of the two Tamper Prevention and Detection lines. If either of these lines is broken (in the process of destroying a gate) the attack will be detected on power-up, and the chip will either RESET (continually) or erase the keys from Flash memory. To launch this kind of attack, an attacker must fust reverse-engineer the chip to determine which gate(s) should be targeted. Once the location of the target gates has been determined, the attacker must break the covering Tamper Detection line, stop the Erasure of Flash memory, and somehow rewire the components that rely on the ChipOK lines.
Rewiring the circuitry cannot be done without slicing the chip, and even if it could be done, the act of slicing the chip to this level will most likely destroy the charge pattems in the non-volatile memory that holds the keys, making the process fruitless.
Overwrite Attacks An Overwrite Attack relies on being able to set individual bits of the key without knowing the previous value. It relies on probing the chip, as in the Conventional Probing Attack and destroying gates as in the Gate Destruction Attack.
Both of these attacks (as explained in their respective sections), will not succeed due to the use of the Tamper Prevention and Detection Circuitry and ChipOK lines. However, even if the attacker is able to somehow access the bits of Flash and destroy or short out the gate holding a particular bit, this will force the bit to have no charge or a full charge. These are both invalid states for the Authentication Chip's usage of the multi-level Flash memory (only the two middle states are valid). When that data value is transferred from Flash detection circuitry will cause the Erasure Tamper Detection Line to be triggered - thereby erasing the remainder of Flash memory and RESETing the chip. In the same way, a parity check on tampered values read from RAM will cause the Erasure Tamper Detection Line to be triggered. An Overwrite Attack is therefore fiuitless.
Memory Remanence Attack Any working registers or RAM within the Authentication Chip may be holding part of the authentication keys when power is removed. The working registers and RAM would continue to hold the infotmation for some time after the removal of power. If the chip were sliced so that the gates of the registers/RAM were exposed, without discharging them, then the data could probably be viewed directly using an sTM. The first defense can be found above, in the description of defense against Power Glitch Attacks. When power is removed, all registers and RAM are cleared, just as the RESET condition causes a clearing of memory. The chances then, are less for this attack to succeed than for a reading of the Flash memory. RAM charges (by nature) are more easily lost than Flash memory. The slicing of the chip to reveal the RAM will certainly cause the charges to be lost (if they haven't been lost simply due to the memory not being refreshed and the time taken to perform the slicing). This attack is therefore fruitless.
Chip Theft Attack There are distinct phases in the lifetime of an Authentication Chip. Chips can be stolen when at any of these stages:
After manufacture, but before programming of key After programming of key, but before programming of state data After progranuning of state data, but before insertion into the consumable or system After insertion into the system or consumable A theft in between the chip manufacturer and programming station would only provide the clone manufacturer with blank chips. This merely compromises the sale of Authentication chips, not anything authenticated by the Authentication chips. Since the programming station is the only mechanism with consumable and system product keys, a clone manufacturer would not be able to program the chips with the correct key. Clone manufacturers would be able to program the blank chips for their own Systems and Consumables, but it would be difficult to place these items on the market without detection. The second forrn of theft can only happen in a situation where an Authentication Chip passes through two or more distinct programming phases. This is possible, but unlikely. In any case, the worst situation is where no state data has been progratnmed, so all of M is read/write. If this were the case, an attacker could attempt to launch an Adaptive Chosen Text Attack on the chip. The I-IMAC-SHAI algorithm is resistant to such attacks. The third fortn of theft would have to take place in between the programming station and the installation factory. The Authentication chips would already be programmed for use in a particular system or for use in a particular consumable.
The only use these chips have to a thief is to place them into a clone System or clone Consumable. Clone systems are irrelevant - a cloned System would not even require an authentication chip 53.
For clone Consumables, such a theft would limit the number of cloned products to the number of chips stolen. A
single theft should not create a supply constant enough to provide clone manufacturers with a cost-effective business.The fmal form of theft is where the System or Consumable itself is stolen. When the theft occurs at the manufacturer, physical security protocols must be enhanced. If the theft occurs anywhere else, it is a matter of concem only for the owner of the item and the police or insurance company. The security mechanisms that the Authentication Chip uses assume that the consumables and systems are in the hands of the public. Consequently, having them stolen makes no difference to the security of the keys.
Authentication Chip Desi~tt The Authentication Chip has a physical and a logical external interface. The physical interface defines how the Authentication Chip can be connected to a physical System, and the logical interface determines how that System can communicate with the Authentication Chip.
Physical Interface The Authentication Chip is a small 4-pin CMOS package (actual intemal size is approximately 0.30 mm' using 0.25 m Flash process). The 4 pins are GND, CLK, Power, and Data. Power is a nominal voltage. If the voltage deviates from this by more than a fixed amount, the chip will RESET. The recommended clock speed is 4-10 MHz Intemal circuitry filters the clock signal to ensure that a safe maximum clock speed is not exceeded. Data is transmitted and received one bit at a time along the serial data line. The chip performs a RESET upon power-up, power-down. In addition, tamper detection and prevention circuitry in the chip will cause the chip to either RESET or erase Flash memory (depending on the attack detected) if an attack is detected. A special Programming Mode is enabled by holding the CLK voltage at a particular level. This is defuied further in the next section.
Logical Interface The Authentication Chip has two operating modes - a Normal Mode and a Programming Mode. The two modes are required because the operating program code is stored in Flash memory instead of ROM (for security reasons). The Programming mode is used for testing purposes after manufacture and to load up the operating program code, while the normal mode is used for all subsequent usage of the chip.
Prouamming Mode The Programming Mode is enabled by holding a specific voltage on the CLK line for a given amount of time. When the chip enters Programming Mode, all Flash memory is erased (including all secret key infonnation and any program code). The Authentication Chip then validates the erasure. If the erasure was successful, the Authentication Chip receives 384 bytes of data corresponding to the new program code. The bytes are transfecred in order byteo to byte383.
The bits are transferred from bita to bit7. Once all 384 bytes of program code have been loaded, the Authentication Chip hangs. If the erasure was not successful, the Authentication Chip will hang without loading any data into the Flash memory. After the chip has been programmed, it can be restarted. When the chip is RESET with a normal voltage on the CLK line, Normal Mode is entered.
Notmal Mode Whenever the Authentication Chip is not in Programming Mode, it is in Normal Mode. When the Authentication Chip starts up in Normal Mode (for example a power-up RESET), it executes the program currently stored in the program code region of Flash memory. The program code implements a communication mechanism between the System and Authentication Chip, accepting commands and data from the System and producing output values. Since the Authentication Chip communicates serially, bits are transfen-ed one at a time.The System communicates with the Authentication Chips via a simple operation command set. Each command is defined by 3-bit opcode. The interpretation of the opcode depends on the current value of the IsTntsted bit and the Is Written bit.
The following operations are defmed:
Op T W Mn Input Output Description 000 - - CLR - Clear 001 0 0 SSI [160, 160, 160] Set Secret Information 010 0 1 RD [160, 160] [256, 160] Read M securely 010 1 1 RND - [ 160, 160] Random 011 0 1 WR [256] - Write M
01 l 1 1 TST [256, 160] [1] Test 100 0 1 SAM [32] [32] Set Access Mode 101 - 1 G IT - [ 1] Get Is Trusted 110 - 1 SMT [32] - Set MinTicks Op = Opcode, T = IsTrusted value, W= IsWritten value, Mn = Mnemonic, [n] = number of bits required for parameter Any command not defined in this table is interpreted as NOP (No operation).
Examples include opcodes 110 and 1 I 1 (regardless of IsTrusted or IsWritten values), and any opcode other than SSI
when IsWritten = 0. Note that the opcodes for RD and RND are the same, as are the opcodes for WR and TST. The actual command run upon receipt of the opcode will depend on the current value of the IsTrusted bit (as long as IsWritten is 1). Where the IsTrusted bit is clear, RD and WR functions will be called. Where the IsTrusted bit is set, RND
and TST functions will be called. The two sets of commands are mutually exclusive between trusted and non-trusted Authentication Chips. In order to execute a command on an Authentication Chip, a client (such as System) sends the command opcode followed by the required input parameters for that opcode. The opcode is sent least significant bit through to most significant bit. For example, to send the SSI command, the bits 1, 0, and 0 would be sent in that order. Each input parameter is sent in the same way, least significant bit first through to most significant bit last.
Retum values are read in the same way - least significant bit first and most significant bit last. The client must know how many bits to retrieve.
In some cases, the output bits from one chip's command can be fed directly as the input bits to another chip's command. An example of this is the RND and RD commands. The output bits from a call to RND on a trusted Authentication Chip do not have to be kept by System. Instead, System can transfer the output bits directly to the input of the non-trusted Authentication Chip's RD command. The description of each command points out where this is so_ Each of the commands is examined in detail in the subsequent sections. Note that some algorithms are specifically designed because the permanent registers are kept in Flash memory.
Registers The memory within the Authentication Chip contains some non-volatile memory to store the variables required by the Authentication Protocol. The following non-volatile (Flash) variables are defined:
Size Variable Name (in bits) Description M[0..15] 256 16 words (each 16 bits) containing state data such as serial numbers, media remaining etc_ K, 160 Key used to transform R during authentication.
K2 160 Key used to transform M during authentication.
R 160 Current random number AccessMode[0..15] 32 The 16 sets of 2-bit AccessMode values for M[n].
MinTicks 32 The minimum number of clock ticks between calls to key-based functions SlWritten I If set, the secret key information (KI, K2, and R) has been written to the chip. If clear, the secret information has not been written yet.
IsTrusted 1 If set, the RND and TST functions can be called, but RD
and WR functions cannot be called.
If clear, the RND and TST functions cannot be called, but RD and WR functions can be called.
Total bits 802 Architecture Overview This section chapter provides the high-level defmition of a purpose-built CPU
capable of implementing the functionality required of an Authentication Chip. Note that this CPU is not a general purpose CPU. It is tailor-made for implementing the Authentication logic. The authentication commands that a user of an Authentication Chip sees, such as WRITE, TST, RND etc are all implemented as small programs written in the CPU instruction set. The CPU
contains a 32-bit Accumulator (which is used in most operations), and a number of registers. The CPU operates on 8-bit instructions specifically tailored to implementing authentication logic.
Each 8-bit instruction typically consists of a 4-bit opcode, and a 4-bit operand.
Operatine Speed An internal Clock Frequency Limiter Unit prevents the chip from operating at speeds any faster than a predetermined frequency. The frequency is built into the chip during manufacture, and cannot be changed. The frequency is recommended to be about 4-10 MHz.
Composition and Block Diagram The Authentication Chip contains the following components:
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Ouartz crystal 58 A quartz crysta158 is used as a frequency reference for the system clock. As the system clock is very high, the ACP 31 includes a phase locked loop clock circuit to increase the frequency derived from the crysta158.
ImaQe Sensine Area image sensor 2 The area image sensor 2 convetts an image through its lens into an elecarical signal. It can either be a charge coupled device (CCD) or an active pixel sensor (APS)CMOS image sector. At present, available CCD's nonmally have a higher image quality, however, there is cutrently much development occurring in CMOS imagers. CMOS
imagers arc eventually expected to be substantially cheaper than CCD's have smaUer pixel areas, and be able to incorporate drive circuitry and signal processing. They can also be made in CMOS fabs, which are transitioning to 12"
wafers. CCD's are usually built in 6" wafer fabs, and economics may not allow a conversion to 12" fabs. T7herefore, the diffaeme in fabrication cost between CCD's and CMOS imagers is likely to increase, prognessively favoring CMOS imagers. However, at present, a CCD is probably the best option.
The Artcam unit will produce suitable results with a 1,500 x 1,000 area image sensor. However, smaller sensors, such as 750 x 500, will be adequate for many markets. The Artcam is less sensitive to image sensor resolution than are conventional digital cameras. This is because many of the styles contained on Artcards 9 process the image in such a way as to obscure the lack of resolution. For example, if the image is distorted to simulate the effect of being converted to an itttpressionistic painting, low source intage resolution can be used with minimal effect. Ftmher examples for which low resolution input images will typically not be noticed include image warps which produce high distorted images, multiple miniature copies of the of the image (eg. passport photos), textural processing such as bump mapping for a base relief metal look, and photo-compositing into structured scenes.
This tolerance of low resolution image sensors may be a significant factor in reducing the manufacturing cost of an Artcam unit I camera. An Artcam with a low cost 750 x 500 image sensor will often produce superior results to a conventional digital camera with a much more expensive 1,500 x 1,000 image sensor.
Qptional stereosconic 3D image sensor 4 The 3D versions of the Artcam unit 1 have an additional image sensor 4, for stereoscopic operation. This image sensor is identical to the main image sensor. The circuitry to drive the optional image sensor may be included as a standard part of the ACP chip 31 to reduce incremental design cost.
Alternatively, a separate 3D Art.cam ACP can be designed. This option will reduce the manufacturing cost of a mainstream single sensor Artcam.
Print roll authentication chip 53 A small chip 53 is included in each print roll 42. This chip replaced the functions of the bar code, optical sensor and wheel, and ISO/ASA sensor on other forms of camera film units such as Advanced Photo Systems film carQidges.
The authentication chip also provides other features:
i. The storage of data rather than that which is mechanically and optically sensed from APS rolls 2. A remaining media length indication, accurate to high resolution.
3. Authentication Information to prevent inferior clone print roll copies.
The authentication chip 53 contains 1024 bits of Flash memory, of which 128 bits is an authentication key, and 512 bits is the authentication information. Also included is an encryption circuit to ensure that the authentication key cannot be accessed directly.
Print-head 44 The Artcam unit I. can utilize any color print technology which is stnall enough, low enough power, fast enough, high onough quality, attd low enough cost, and is compatible with the print roll. Relevant printheads will be specifically discussed hereinafter.
The specifications of the ink jet head are:
Image type Bi-level, dithered Color CMY Process Color Resolution 1600 dpi Print head length 'Page-width' (]00mm) Print speed 2 seconds per photo Ontional ink m+essure Controller (not shown) The function of the ink pressure controller depends upon the type of ink jet print head 44 incorporated in the Artcam. For some types of ink jet, the use of an ink pressure controller can be eliminated, as the ink pressure is simply atmospheric pressure. Other types of print head require a regulated positive ink ptessure. In this case, the in pressure controller consists of a pump and pressure transducer.
Other print heads may require an ultrasonic transducer to cause regular oscillations in the ink pressure, typically at frequencies around 100KHz. In the case, the ACP 31 controls the frequency phase and amplitude of these oscillations.
Paocr tran_port motor 36 'Ilie paper transport motor 36 moves the paper from within the print roll 42 past the print head at a relatively constant rate. The motor 36 is a miniature motor geared down to an appropriate speed to drive rollers which move the paper. A high quality motor and mechanical gears are required to achieve high image quality, as mechanical rumble or other vibrations will affect the printed dot row spacing.
Pe,per transnort motor driver 60 The motor driver 60 is a smail circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor 36.
Paper Pull sensor A paper pull sensor 50 detects a user's attempt to pull a photo from the camera unit during the printing process. The APC 31 reads this sensor 50, and activates the guillotine 41 if the condition oocuts. The paper pull sensor 50 is incorporated to make the camera more 'foolproof in operation.
Were the user to pull the paper out forcefully during printing, the print mechanism 44 or print roll 42 may (in extreme cases) be damaged. Since it is acceptable to pull out the 'pod' from a Polaroid type cautera before it is fully ejected, the public has been 'trained' to do this. Therefore, they are unlikely to heed printed instructions not to pull the paper.
The Artcam preferably restaru the photo print process after the guillotine 41 has cut the paper after pull sensing.
The pull sensor can be implemented as a strain gauge sensor, or as an optical sensor detecting a small plastic flag which is deflected by the torque that occurs on the paper drive rollers when the paper is pulled. The latter impletwntation is rccoRUnendation for low cost.
Pgper tnxiilotine actuator 40 Tlta paper guillotitte actuator 40 is a small actuator which causes the guillotine 41 to cut the paper either at the end of a photograph, or when the paper pull sensor 50 is activated.
The guillotine actuator 40 is a small circuit which amplifies a guillotine control signal from the APC tot the level required by the actuator 41.
Artcwd 9 The Artcard 9 is a program storage medium for the Artcam unit. As noted previously, the programs are in the form of Vark scripts. Vark is a powerful image processing language especially developed for the Artcam unit. Each Artcard 9 contains one Vark script, and thereby defines one image processing style.
Preferably, the VARK languagc is highly image processing specific. By being highly image processing specific, the atrwunt of storage required to store the details on the card are substantially reduced. Further, the ease with which new programs can be created, including enhanced effects, is also substantially increased. Preferably, the language includes facilities for handling many image processing functions ittcluding image warping via a warp map, convolution, color lookup tables, posterizing an image, adding noise to an image, image enhancement filters, painting algorithms, brush jiuering and manipulation edge detection filters, tiling, iilumination via light sources, bump maps, text. face detection and object detection attributes, fonts, including three dimensional fonts, and arbitrary complexity pre-rendered icons. Further details of the operation of the Vark language interpreter are contained hereinafter.
Hence, by utilizing the language constructs as defined by the created language, new affects on arbitrary images can be created and constructed for inexpensive storage on Artcard and subsequent distribution to camera owners. Further, on one surface of the card can be provided an example illustrating the effect that a particular VARK
script, stored on t}he other surface of the card, will have on an arbitrary captured image.
By utilizing such a system, camera technology can be distributed without a great fear of obsolescence in that, provided a VARK interpreter is incorporated in the cantera device, a device independent scenario is provided whereby the underlying technology can be completely varied over time. Further, the VARK scripts can be updated as new filters are created and distributed in an inexpensive manner, such as via simple cards for card reading.
The Artcard 9 is a piece of thin white plastic with the same format as a credit card (86mm long by 54mm wide). The Artcard is printed on both sides using a high resolution ink jet printer. The inkjet printer technology is assumed to be the same as that used in the Artcam, with 1600 dpi (63dpmm) resolution. A major feature of the Arteard 9 is low manufacturing cost. Artcards can be manufactured at high speeds as a wide web of plastic film. The plastic web is coated on both sides with a hydrophilic dye fixing layer. The web is printed simultaneously on both sides using a'pagewidth' color ink jet printer. The web is then cut and punched into individual cards. On one face of the card is printed a human readable representation of the effect the Artcard 9 will have on the sensed image. This can be simply a standard image which has been processed using the Vark script stored on the back face of the card.
On the back face of the card is printed an array of dots which can be decoded into the Vark script that defines the image processing sequence. The print area is 80mm x 50mm, giving a total of 15,876,000 dots. This array of dots could represent at least 1.89 Mbytes of data. To achieve high reliability, extensive error detection and correction is incorporated in the array of dots. This allows a substantial portion of the card to be defaced, worn, creased, or dirty with no effect on data integrity. The data coding used is Reed-Solomon coding, with half of the data devoted to error correction. This allows the storage of 967 Kbytes of error corrected data on each Artcard 9.
Linear image sensor 34 The Artcard linear sensor 34 converts the aforementioned Attcard data intage to electrical signals. As with the area image sensor 2,4, the linear image sensor can be fabricated using either CCD or APS CMOS technology. The active length of the image sensor 34 is 50mm, equal to the width of the data array on the Mcard 9. To satisfy Nyquist's sampling theorem, the resolution of the linear image sensor 34 must be at least twice the highest spatial frequency of the Artcard optical image reaching the image sensor. In practice, data detection is easier if the image sensor resolution is substantially above this. A resolution of 4800 dpi (189 dptnm) is chosen, giving a total of 9,450 pixels. This resolution requires a pixel sensor pitch of 5.3pm. This can readily be achieved by using four staggered rows of 20pm pixel sensors.
The linear image sensor is mounted in a special package which includes a LED
65 to illuminate the Artcard 9 via a Gght-pipe (not shown).
"I'he Ancard reader light-pipe can be a moided light-pipe which has several function:
1. It diflirses the light from the LED over the width of the card using total internal reflection facets.
2. It focuses the light onto a l6pm wide strip of the Artcard 9 using an integrated cylindrical lens.
3. It focuses light reflected from the Artcard onto the linear image sensor pixels using a molded array of microlenses.
The operation of the Artcard reader is explained further hereinafter.
Artcard reader motor 37 The Artcard reader motor propels the Artcard past the linear intage sensor 34 at a relatively constant rate. As it may not be cost effective to include extreme precision mechanical components in the Artcard reader, the motor 37 is a standard miniature motor geared down to an appropriate speed to drive a pair of rollets which move the Artcard 9.
The speed variations, rtunble, and other vibtations will affect the raw image data as circuitry within the APC 31 includes extensive compensation for these effects to reliably read the Artcard data.
The motor 37 is driven in reverse when the Artcard is to be ejected.
Artcar+d niotor driver 61 The Artcard motor driver 61 is a small circuit which amplifies the digital motor control signals from the APC
31 to levels suitable for driving the motor 37.
Card Insertion sensor 49 The card insertion sensor 49 is an optical sensor which detects the presence of a card as it is being inserted in the cani reader 34. Upon a signal from this sensor 49, the APC 31 initiates the card reading process, including the activation of the Artcard reader motor 37.
Card e1ect button 16 A card eject button 16 (Fig. 1) is used by the user to eject the current Artcard, so that another Artcard can be inserted. The APC 31 detects the pressing of the button, and reverses the Artcard reader motor 37 to eject the card.
Card status indicator 66 A card status indicator 66 is provided to signal the user as to the status of the Artcard reading process. This can be a standard bi-color (redlgreen) LED. When the card is successfully read, and data integrity has been verified, the LED lights up green continually. If the card is faulty, then the LED
lights up red.
If the camera is powered from a 1S V instead of 3V battery, then the power supply voltage is less than the forward voltage drop of the greed LED, and the LED will not light. In this case, red LEDs can be used, or the LED
can be powered from a voltage pump which also powers other circuits in the Artcam which require higher voltage.
64 Mbit DRAM 33 To perform the wide variety of image processing effects, the camera utilizes 8 Mbytes of tnemory 33. This can be provided by a single 64 Mbit memory chip. Of course, with changing memory technology increased Dram storage sizes may be substituted.
High speed access to the memory chip is required. This can be achieved by using a Rambus DRAM (burst access rat,e of 500 Mbytes per second) or chips using the new open standards such as double data rate (DDR) SDRAM
or Synclink DRAM.
Carnera authentication chiQ
The camera authentication chip 54 is identical to the print roll authentication chip 53, except that it has different information stored in it The camera authentication chip 54 has threo main purposes:
1. To provide a secure means of comparing authentication codes with the print roll authentication chip;
2. To provide storage for manufacturing infortttation, such as the serial number of the catnera;
3. To provide a small amount of non-volatile memory for storage of user information.
D~snlavs The Artcam includes an optional color display 5 and small status display 15.
Lowest cost consumer cameras may include a color image display, such as a small TFT LCD 5 similar to those found on some digital cameras and camcorders. The color display 5 is a major cost element of these versions of Artcam, and the display 5 plus back light are a major power consumption drain.
Status displav 15 The status display 15 is a small passive segment based LCD, sinular to those currently provided on silver halide and digital cameras. Its main function is to show the number of prints remaining in the print roll 42 and icons for various standard camera features, such as flash and bauery status.
Color disolav 5 Tlte color display 5 is a full motion image display which operates as a viewfinder, as a verification of the image to be printed, and as a user interface display. The cost of the display 5 is approximately proportional to its area, so large displays (say 4" diagonal) unit will be restricted to expensive versions of the Artcam unit. Smaller displays, such as color catncorder viewfinder'fFT's at around I", may be effective for mid-range Artcams.
Zoom lens (not shown) The Artcam can include a zoom lens. This can be a standard electronically controlled zoom lens, identical to one which would be used on a standard electronic camera, and similar to pocket camera zoom lenses. A referred version of the Artcazn unit may include standard interchangeable 35tnm SLR
lenses.
Autofocus motor 39 The autofocus motor 39 changes the focus of the zoom lens. The motor is a miniature motor geared down to an appropriate speed to drive the autofocus mechanism.
Autofocus motor driver 63 The autofocus motor driver 63 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor 39.
Zoom motor 38 The zoom motor 38 moves the zoom front lenses in and out. The motor is a miniature motor geared down to an appropriate speed to drive the zoom mechanism.
Zoom motor driver 62 The zoom motor driver 62 is a small circuit which amplifies the digital motor control signals from the APC 31 to levels suitable for driving the motor.
Communications The ACP 31 contains a universal serial bus (USB) interface 52 for communication with personal computers.
Not all Artcam models are intended to include the USB connector. However, the silicon area required for a USB
circuit 52 is smalt, so the interface can be included in the standard ACP.
4otional Keyboard 57 The Artcam unit may include an optional miniature keyboard 57 for customizing text specified by the Artcard. Any text appearing in an Artcard image may be editable, even if it is in a complex metallic 3D font. The miniature keyboatd includes a single line alphanumeric LCD to display the original text and editetl texL The keyboatd may be a standard accessory.
'Ihe ACP 31 contains a serial communications circuit for ttansferring data to and from the miniature keyboard.
Power Sunolv The Artcam unit uses a battery 48. Depending upon the Artcam options, this is either a 3V Lithium cell, 1.5 V AA alkaline cells, or other battery an-angement.
Power Managenient Unit 51 Power consumption is an important design constraint in the Artcam. It is desirable that either standard camera batteries (such as 3V lithium batters) or standard AA or AAA alkaline cells can be used. While the eleeunnic complexity of the Artcam unit is dramatically higher than 35mm photographic cameras, the power consumption need not be comrnensurately higher. Power in the Artcam can be carefully managed with all unit being turned off when not in use.
The most significant current drains are the ACP 31, the area image sensors 2,4, the printer 44 various motors, the flash unit 56, and the optional color display 5 dealing with each part separately:
1. ACP: If fabricated using 0.25 m CMOS, and running on 1.5V, the ACP power consumption can be quite low. Clocks to various parts of the ACP chip can be quite low. Clocks to various parts of the ACP chip can be turned off when not in use, virtually eliminating standby current consumption.
The ACP will only fully used for approximately 4 seconds for each photograph printed.
2. Area image sensor. power is only, supplied to the area image sensor when the user has their finger on the button.
3. 'Ihe printer power is only supplied to the printer when actually printing.
This is for around 2 seconds for each photograph. Even so, suitably lower power consumption printing shouid be used.
4. The motors required in the Artcam are all low power miniature motors, and are typically only activated for a few seconds per photo.
5. The flash unit 45 is only used for some photographs. Its power consumption can readily be provided by a 3V lithium battery for a reasonably battery life.
6. The optional color display 5 is a major current drain for two reasons: it must be on for the whole time that the camera is in use, and a backlight will be required if a liquid crystal display is used. Cameras which incorporate a color display will require a larger battery to achieve acceptable batter life.
F1ash unit 56 The flash unit 56 can be a standard miniature electronic flash for consumer cameras.
Overview of the ACP 31 Fig. 3 illustrates the Artcam Central Processor (ACP) 31 in more detail. The Artcam Central Prnoessor provides all of the processing power for Artcam. It is designed for a 0.25 micron CMOS
process, with approximately 1.5 million tt ansistors and an area of around 50 mm2. The ACP 31 is a complex design, but design effmt can be teduced by the use of datapath compilation techniques, macrocells, and IP cores. 'Ilte ACP 31 contains:
A RISC CPU core 72 A 4 way parallel VLIW Vector Processor 74 A Direct RAMbus interface 81 A CMOS image sensor interface 83 A CMOS linear image sensor interface 88 A USB serial interface 52 An infrared keyboard interface 55 A numeric LCD interface 84, and A color TFI' LCD interface 88 A 4Mbyte Flash tnemory 70 for program storage 70 The RISC CPU, Direct RAMbus interface 81, CMOS sensor interface 83 and USB
serial interface 52 can be vendor supplied cores. The ACP 31 is intended to run at a clock speed of 200 MHz on 3V externally and 1.5V internally to nrinimize power consumption. The CPU core needs only to run at 100 MHz. The following two block diagrams give two views of the ACP 3 1:
A view of tlte ACP 31 in isolation An example Artcam showing a high-level view of the ACP 31 connected to the rest of the Artcam hardware.
Access Image As stated previously, the DRAM Interface 81 is responsible for interfacing between other client portions of the ACP chip and the RAMBUS DRAM. In effect, each module within the DRAM
Interface is an address generator.
There are three logical types of images manipulated by the ACP. They are:
-CCD Itnage, which is the Input Inuige captured from the CCD.
-Internal Image format - the Image fomtat utilised intetnally by the Artcam device.
Print Image - the Output Image format printed by the Art,cam These images are typically different in color space, resolution, and the output & input color spaces which can vary from caniera to camera. For example, a CCD image on a low-end camera may be a different resolution, or have different color characteristics from that used in a high-end camera. However all internal image formats are the same format in tetms of color space across all cameras.
In addition, the three image types can vary with respect to which direction is 'up'_ The physical orientation of the camera causes the notion of a portrait or landscape itnage, and this must be maintained throughout processing. For this reason, the intemal image is always oriented correcdy, and rotation is performed on intages obtained from the CCD and during the print operation.
CPU Core (CPU) 71 The ACP 31 incorporates a 32 bit RISC CPU 72 to run the Vark image processing language interpreter and to perform Artcam's general operating system duties. A wide variety of CPU cores are suitable: it can be any processor core with sufScient processing power to perform the required core calculadons and control functions fast enough to met consumer expxtations. Examples of suitable cores are_ MIPS R4000 core from LSI
Logic, StrongARM core. There is no need to maintain instruction set continuity between different Artcam models. Artcard compatibility is maintained irrespective of future processor advances and changes, because the Vark interpreter is simply re-compiled for each new instruction set. The ACP 31 architecture is therefore also free to evolve.
Different ACP 31 chip designs may be fabricated by different manufacturers, without requiring to license or port the CPU core. This device independence avoids the chip vendor lock-in such as has occurred in the PC market with Intel. 'Ihe CPU operates at 1001vIHz, with a single cycle time of l0ns. It must be fast enough to run the Vark interpreter, although the VLIW Vector Processor 74 is responsible for most of the time-critical operations.
PtoSam cache 72 Although the program code is stored in on-chip Flash memory 70, it is unlikely that well packed Flash metnory 70 will be able to operate at the lOns cycle tinie required by the CPU. Consequently a smali cache is required for good perfotmance. 16 cache lines of 32 bytes each are sufficient, for a total of 512 bytes. The program cache 72 is defined in the chapter entitled Program cache 72.
Data cache 76 A small data cache 76 is required for good performance. This requirement is mostly due to the use of a RAMbus DRAM, which can provide high-speed data in bursts, but is inefficient for single byte accesses. The CPU has access to a memory caching system that allows flexible manipulation of CPU data cache 76 sizes. A minimum of 16 cache lines (5 12 bytes) is recommended for good perfortnance.
CPU Memory Model An Arteam's CPU memory model consists of a 32MB area. It consists of 8MB of physical RDRAM off-chip in the base model of Artcam, with provision for up to 16MB of off-chip memory. 'Ihcre is a 4MB Flash memory 70 on the ACP 31 for program st.orage, and finally a 4MB address space mapped to the various registers and controls of the ACP
31. The memory map then, for an Artcam is as follows:
Contents Size Base Artcam DRAM 8 MB
Extended DRAM 8 MB
Program memory (on ACP 31 in Flash memory 70) 4 MB
Reserved for extension of program memory 4 MB
ACP 31 registers and memory-mapped UO 4 MB
Resenied 4 MB
A straightforward way of decoding addresses is to use addwss bits 23-24:
If bit 24 is ckar, the address is in the lower 16-MB range, and =hence can be satisfied from DRAM and the Data cache 76. In most cases the DRAM will only be 8 MB, but 16 MB is allocated to cater for a higher memory model Artcams.
If bit 24 is set, and bit 23 is clear, then the address represents the Flash memory 70 4Mbyte range and is satisfied by the Pt+ogram cache 72.
If bit 24 = 1 and bit 23 = 1, the address is translated into an access over the low speed bus to the requested component in the AC by the CPU Memory Decoder 68.
Flash memory 70 The ACP 31 contains a 4Mbyte Plaslt memory 70 for storing the Artcam program.
It is envisaged that Flash memory 70 will have denser packing coefficients than masked ROM, and allows for greater flexibility for tesdng camera progratn code. The downside of the Flash memory 70 is the access time, which is unlikely to be fast enough for the 100 MHz operating speed (IOns cycle time) of the CPU. A fast Program Instruction cache 77 therefore acu as the interface between the CPU and the slower Flash memory 70.
Proeram cache 72 A small cache is required for good CPU performance. This requirement is due to the slow speed Flash memory 70 which stores the Progtam code. 16 cache lines of 32 bytes each are sufficient, for a total of 512 bytes. The PAogram cache 72 is a read only cache. The data used by CPU programs comes through the CPU Memory Decoder 68 and if the addttss is in DRAM, through the general Data cache 76. The separation allows the CPU to operate independently of the VLIW Vector Processor 74. If the data requirements are low for a given process, it can consequently operate completely out of cache.
Finally, the Program cache 72 can be read as data by the CPU rather than purely as program instructions. This allows tables, microcode for the VLIW etc to be loaded from the Flash memory 70.
Addresses with bit 24 set and bit 23 clear are satisfied from the Progtam cache 72.
CPU Memory Decoder 68 The CPU Memory Decoder 68 is a simple decoder for satisfying CPU data accesses. The Decoder translates data addresses into internal ACP register accesses over the internal low speed bus, and therefore allows for memory mappod 1/O of ACP registers. The CPU Memory Decoder 68 only interprets addresses that have bit 24 set and bit 23 clear. There is no caching in the CPU Memory Decoder 68.
DRAM interface81 The DRAM used by the Artcam is a single channel 64Mbit (8MB) RAMbus RDRAM
operating at 1.6GB/sec.
RDRAM accesses are by a single channel (16-bit data path) controller. The RDRAM also has several useful operating modes for low power operation. Although the Rambus specification describes a system with random 32 byte ttansfers as capable of achieving a greater than 95% efficiency, this is not true if only part of the 32 bytes are used. Two reads followed by two writes to the same device yields over 86% efficiency. The primary latency is required for bus turn-around going from a Write to a Read, and since there is a Delayed Write mechanism, efficiency can be further improved. With regards to writes, Write Masks allow specific subsets of bytes to be written to. These write masks would be set via intetnal cache "dirty bits". The upshot of the Rambus Direct RDRAM is a throughput of >1 GB/sec is easily achievable, and with multiple reads for every write (most processes) combined with intelligent algorithms making good use of 32 byte ttansfer knowledge, traasfer rates of >1.3 GB/sec ane expected. Every l Ons, 16 bytes can be ttansferred to or from the core.
DRAM Organization The DRAM organization for a base model (8MB RDRAM) Artcam is as follows:
Contents Size Program scratch RAM 0.50 MB
Artcard data 1.00 MB
Photo Image, captured from CMOS Sensor 0.50 MB
Print Image (compressed) 2.25 MB
I Channel of expanded Photo Image 1.50 MB
I Image Pyramid of single channel 1.00 MB
Intermediate Image Processing 1.25 MB
Notes:
the Print lmage requires 4.5MB (ISMB per channel). To accommodate other objects in the 8MB
model, the Print Image needs to be compressed. If the chrominance channel.s are compressed by 4:1 they require only 0.375MB each).
The memory model described here assumes a single 8 MB RDRAM. Other models of the Artcam niay have more memory, and thus not require compression of the Print Image. In addition, with more memory a larger part of the final image can be worlced on at once, potentially giving a speed improvement.
Note that ejecting or inserting an Artcard invalidates the 5.5MB area holding the Print Image, 1 channel of expanded phot.o image, and ihe image pyramid. This space may be safely used by the Artcard Interface for decoding the Artcard data.
Data cache 76 The ACP 31 contains a dedicated CPU instruction cache 77 and a general data cache 76. The Data cache 76 handles all DRAM requests (reads and writes of data) from the CPU, the Vi.IW Vector Processor 74, and the Display Controlkr 88. '17tese requests may have very different profiles in terms of inemory usage and algorithmic timing requiremonts.
For example, a VLIW process may be processing an image in linear mcmory, and lookup a value in a table for each value in the image. There is little need to cache much of the image, but it may be desirable to cache the entire lookup table so that no real memory access is required. Because of these differing requiretnents, the Data cache 76 allows for an intelligent definition of caching.
Although the Ranibus DRAM interface 81 is capable of very high-speed memory access (an avaage ihroughput of 32 bytes in 25ns), it is not efficient dealing with single byte requests. In order to reduce effective memory latency, the ACP 31 contains 128 cache lines. Each cache line is 32 bytes wide. Thus the total amount of data cache 76 is 4096 bytes (4KB). The 128 cache lines are configured into 16 progranunable-sized groups. Each of the 16 groups must be a contiguous set of cache lines. The CPU is responsible for determining how many cache lines to allocate to each group.
Within each group cache lines are filled according to a simple Least Recently Used algorithm. In tetms of CPU data requests, the Data cache 76 handles tnemory access requests that have address bit 24 clear. If bit 24 is clear, the address is in the lower 16 MB range, and hence can be satisfied from DRAM and the Data cache 76. In Tnost cases the DRAM
will only be 8 MB, but 16 MB is allocated to cater for a higher memory model Attcam If bit 24 is set, the address is ignored by the Data cache 76.
All CPU data requests are satisfied from Cache Group 0. A nanimum of 16 cache lines is recommended for good CPU
perfor,atance, although the CPU can assign any number of cache lines (except none) to Cache Group 0. The remaining Cache Groups (1 to 15) are allocated according to the curnent requirements.
This could mean allocation to a VLIW
Vector Processor 74 progtam or the Display Conttnller 88. For example, a 256 byte lookup table tecptired to be permanently available would require 8 cache lines. Writing out a sequential image would only require 2-4 cache lines (depending on the size of reoord being generated and whether write requests are being Write Delayed for a significant number of cycles). Associated with each cache line byte is a dirty bit, used for creating a Write Mask when writing memory to DRAM. Associated with each cache line is another dirty bit, which indicates whether any of the cache line bytes has been written to (and therefore the cache line must be written back to DRAM before it can be reused). Note that it is possible for two different Cache Groups to be accessing the same address in memory and to get out of sync.
The VLIW program writer is responsible to ensure that this is not an issue. It could be perfectly reasonable, for example, to have a Cache Group responsible for reading an image, and another Cache Group responsible for writing the changed image back to tnemory again. If the images are read or written sequentially there may be advantages in allocating cache iines in this manner. A total of 8 buses 182 connect the VL1W
Vector Processor 74 to the Data cache 76. Each bus is connected to an 1/O Address Generator. (There are 21/0 Address Generators 189, 190 per Processing Unit 178, and there are 4 Processing Units in the VLIW Vector Processor 74.
The total number of buses is therefore 8.) In any given cycle, in addition to a single 32 bit (4 byte) access to the CPU's cache group (Group 0), 4 simultaneous accesses of 16 byts (2 bytes) to remaining cache groups are petmitted on the 8 VLIW Vector Processor 74 buses. The Data cache 76 is responsible for fairly processing the requests. On a given cycle, no more than 1 request to a specific Cache Group will be processed. Given dtat there are 8 Address Generators 189, 190 in the VI.IW Vector Processor 74, each one of thesc has the potential to nafer to an individual Cache Group.
However it is possible and occasionally reasonable for 2 or more Address Generators 189, 190 to access the same Cache Group. The CPU is tesponsible for ensuring that the Cache Groups have been allocated the correct number of cache lines, and that the various Address Generators 189, 190 in the VLIW Vector Procassor 74 reference the specific Cache Groups eoerectly.
The Data cache 76 as descn'bed allows for the Display Controller 88 and VLIW
Vector Processor 74 to be active simultaueously. If the operation of these two components were deemed to never occur simultaneously, a total9 Cache Groups wottld suffice. Itie CPU would use Cache Group 0, and the VLIW Vector Processor 74 and the Display Controller 88 would share the mmaining 8 Cache Groups, requiring only 3 bits (tather than 4) to define which Cache Group would satisfy a particular request.
JTAG Intuface 85 A standard JTAG (Joint Test Action Group) Interface is included in the ACP 31 for testing purposes. Due to the con-plexity of the chip, a variety of testing techniques are required, including BIST (Built In Self Test) and functional block isolation. An overhead of 1096 in chip area is assumed for ovetall chip testing circuitry. The test circuitry is beyond the scope of this docament.
SerialInterfaces USB serial aort interface 52 This is a standard USB serial port, which is connected to the internal chip low speed bus, thereby allowing the CPU to control iL
Kevboard interface 65 This is a standard low-speed serial port, which is connected to the internal chip low speed bus, thereby allowing the CPU to control it. It is designed to be optionally connected to a keyboard to allow simple data input to customize prints.
Authentication chip serial interfaces 64 Those are 2 standard low-speed seriai porls, which are connected to the internal chip low speed bus, thereby allowing the CPU to control them. The reason for having 2 ports is to connect to both the on-camera Authentication chip, and to the print-roll Authentication chip using sepacate lines. Only using 1 line may make it possible for a clone print-roll manufacturer to design a chip which, instead of generating an authentication code, tricks the camera into using the code generated by the authentication chip in the camera.
Parallel Interface 67 The parallel interface connects the ACP 31 to individual static electrical signals. The CPU is able to control each of these connections as memory-mapped I/O via the low speed bus The following table is a list of connections to the parallel interface:
Connection Direction Pins Paper transpoct stepper motor Out 4 Artcard stepper motor Out 4 Zoom stepper motor Out 4 Guillotine motor Out 1 Flash trigger Out 1 Status LCD segment drivers Out 7 Status LCD common drivers Out 4 Artcard illumination LED Out 1 Artcard status LED (red/green) In 2 ~d sensor In I
Paper pull sensor In I
Orientation sensor In 2 Buttons In 4 VLIW Inout and Output FIFOs 78,79 The VLIW Input and Output FIFOs are 8 bit wide FIFOs used for communicating between processes and the VLIW
Vector Processor 74. Both FIFOs are under the control of the VLIW Vector Processor 74, but can be cleared and queried (e.g. for status) etc by the CPU.
VLIW n wt FII 0 78 A client writes 8-bit data to the VLIW Iwut FIFO 78 in order to have the data processed by the VLIW Vector Processor 74. Clients include the Image Sensor Interface, Artcard Interface, and CPU. Each of these processes is able to offload processing by simply writing the data to the FIFO, and letting the VLIW Vector Processor 74 do all the hard work. An example of the use of a client's use of the VLIW Input FIFO 78 is the Image Sensor Intetfaee (ISI 83). The ISI 83 takes data from the Image Sensor and writes it to the FIFO. A VLIW
process takes it from the FIFO, transforming it into the oorrect image data format, and writing it out to DRAM. The ISI 83 becomes much simpler as a result.
VLIW Output FIFO 79 The VLIW Vector Processor 74 writes 8-bit data to the VLIW Output FIFO 79 where clients can read it. Ciients include the Print Head Interface and the CPU. Both of these clients is able to offload processing by simply rrading the already processed data from the FiFO, and leaing the VLIW Vector Processor 74 do all the hard work. The CPU can also be intertupted whenever data is placed into the VLIW Output FIFO 79, allowing it to only process the data as it becomes available rather than polling the FIFO continuously. An example of the use of a client's use of the VLIW
Output FIFO 79 is the Print Head Interface (PHI 62). A VLIW proeGSS takes an image, rotates it to the cocrect orientation, color converts it, and dithers the resulting image according to the print head requirements. The PHI 62 reads the dithered fortnatted 8-bit data from the VLIW Output FIFO 79 and simply passes it on to the Print Head external to the ACP 31. The PHI 62 becomes much simpler as a result.
VLIW Vector Processor 74 To achieve the high processing requirements of Artcam, the ACP 31 contains a VLIW (Very Long Instntction Word) Vector Processor. The VLIW processor is a set of 4 identical Processing Units (PU e.g 178) working in parallel, connected by a crossbar switch 183. Each PU e.g 178 can perform four 8-bit multiplications, eight 8-bit additions, tlme 32-bit additions, UO processing, and various logical operations in each cycle. The PUs e.g 178 are niicrocoded, and each has two Address Generators 189, 190 to allow full use of available cycles for data processing. The four PUs e.g 178 are nomutly synchronized to provide a tightty interacting VLIW
processor. Clocldng at 200 MHz, the VLIW
Vector Processor 74 taas at 12 Gops (12 biliion operations per second).
Instructions are tuned for image processing functions such as warping, artistic brushing, complex synthetic illumination, color transfornts, image filtering, and compositing.lhese are accelerated by two orders of magnitude over desktop computers.
As shown in more detail in Fig. 3(a), the VLIW Vector Processor 74 is 4 PUs e.g 178 connected by a crossbar switch 183 such that each PU e.g 178 provides two inputs to, and takes two outputs from, the crossbar switch 183. Two comnton regisOers fotm a control and syncluonizadon mechanism for the PUs e.g 178. 8 Cache buses 182 allow connectivity to DRAM via the Data cache 76, with 2 buses going to each PU e.g 178 (1 bus per I/O Address Gettetator).
Each PU e.g 178 consists of an ALU 188 (containing a number of registers &
some arithmetic logic for processing data), some microcode RAM 196, and connections to the outside world (including other ALUs). A local PU state machine runs in microcode and is the means by which the PU e.g 178 is controlled. Each PU e.g 178 contains two 1/O
Address Generators 189, 190 controlling data flow between DRAM (via the Data cache 76) and the ALU 188 (via lnput FIFO and Output FIFO). The address genetator is able to read and write data (specifically iniages in a variety of formats) as well as tables and simulated FIFOs in DRAM. The formats are customizable under software control, but are not microcoded. Data taken from the Data cache 76 is iransferred to the ALU 188 via the 16-bit wide Input FIFO.
Output data is written to the 16-bit wide Output FIFO and from there to the Data cache 76. Finally, all PUs e.g 178 share a single 8-bit wide VLIW Input FIFO 78 and a single 8-bit wide VLIW
Output FIFO 79. The low speed data bus connection allows the CPU to read and write registers in the PU e.g 178, update mictocode, as well as the common registers shared by all PUs e.g 178 in the VLIW Vector Processor 74. Turning now to Fig. 4, a closer detail of the intetnals of a single PU e.g 178 can be seen, with components and control signals detailed in subsequent hereinafter:
Micxocade Each PU e.g 178 contains a microcode RAM 196 to hold the program for that particular PU e.g 178. Rather than have the microcode in ROM, the microcode is in RAM, with the CPU responsible for loading it up. For the same space on chip, this tradeoff reduces the maximum size of any one function to the size of the RAM, but allows an unlinated number of functions to be written in microcode. Functions implemented using microcode include Vark acceleration, ARcard reading, and Printing. The VLIW Vector Processor 74 scheme has several advantages for the case of the ACP
31:
Hardware design complexity is reduced Hardware risk is reduced due to reduction in complexity Hardware design tinte does not depend on all Vark functionality being implemented in dedicated silicon Space on chip is reduced overall (due to large number of processes able to be implemented as microcode) Functionality can be added to Vark (via microcode) with no impact on hardware design time Size and Content The CPU loaded microcode RAM 196 for controlling each PU e.g 178 is 128 words, with each word being 96 bits wide. A summary of the microcode size for control of various units of the PU
e.g 178 is listed in the following table:
Prucess Block Size (bits) Status Output 3 Branching (microcode control) 11 In 8 Out 6 Registers 7 Read 10 Write 6 Barrel Shifter 12 Adder/Logical 14 Multiply/Interpolate 19 With 128 instruction words, the total microcode RAM 196 per PU e.g 178 is 12,288 bits, or 1 SKB exactly. Since the VI.IW Vector Processor 74 consists of 4 identical PUs e.g 178 this equates to 6,144 bytes, exactly 6KB. Some of the bits in a microcode word ate directiy used as control bits, while others are decoded. See the various unit descriptions that detail the interpretation of each of the bits of the microcode word.
Svnchronization Between PUs e.,R 178 Each PU e.g 178.contains a 4 bit Synchronvation Register 197. It is a mask used to determine which PUs e.g 178 work together, and has one bit set for each of the cornsponding PUs e.g 178 that are functioning as a single process. For example, if all of the PUs e.g 178 were functioning as a single process, each of the 4 Synchronization Register 197s would have all 4 bits set. If there were two asynchronous processes of 2 PUs e.g 178 each, two of the PUs e.g 178 would have 2 bits set in their Synchronization Register 197s (corresponding to themselves), and the other two would have the other 2 bits set in their Synchronization Register 197s (corresponding to themselves).
The Synchronization Register 197 is used in two basic ways:
Stopping and starting a given process in synchrony Suspending execution within a process StoppinQ and Starting Processes The CPU is responsible for loading the microcode RAM 196 and loading the execution address for the first instruction (usually 0). When the CPU starts executing microcode, it begins at the specified address.
Fatectuion of niicrocode only occurs when all the bits of the Synchronization Register 197 are also set in the Common Synchronization Register 197. The CPU therefore sets up all the PUs e.g 178 and then starts or stops processes with a single write to the Common Synchronization Register 197.
This synchronization scheme. allows tnultiple processes to be running asynchronously on the PUs e.g 178, being stopped and started as processes rather than one PU e.g 178 at a time.
SuspQndjng Execution within a Process In a given eycle, a PU e.g 178 may need to read from or write to a FIFO (based on the opcode of the current microcode instruction). If the FIFO is empty on a read request, or full on a wtite request, the FIFO request cannot be completed.
The PU e.g 178 will therefore assert its SuspendProcess control signal 198.
The SuspendProcess signals from all PUs e.g 178 are fed back to all the PUs e.g 178. The Synchronization Register 197 is ANDed with the 4 SuspendProcess bits, and if the result is non-zero, none of the PU e.g 178's register WriteEnables or FIFO strobes will be seL
Consequently none of the PUs e.g 178 that form the same prooess group as the PU e.g 178 that was unable to complete its task will have their registers or FIFOs updated during that cycle. This simple technique keeps a given process group in syncitronization. Each subsequent cycle the PU e.g 178's state machine will attempt to re-execute the nucrocode instruction at the same address, and will continue to do so until successful.
Of course the Common Synchronization Register 197 can be written to by the CPU to stop the entire process if necessary. This synchronization scheme allows any combinations of PUs e.g 178 to work together, each group only affecting its co-workers with regards to suspension due to data not being ready for reading or writing.
Controi and Branchine During each cycle, each of the four basic input and calculation units within a PU e.g 178's ALU 188 (Read, Adder/Logic, Multiply/Interpolate, and Barrel Shifter) produces two status bits: a Zero flag and a Negative flag indicating whether the result of the operation during that cycle was 0 or negative. Each cycle one of those 4 status bits is chosen by nucrocode instructions to be output from the PU e.g 178. The 4 status bits (i per PU e.g 178's ALU 188) are combined into a 4 bit Convnon Status Register 200. During the next cycle, each PU e.g 178's niicrocode program can select one of the bits from the Conunon Status Register 200, and branch to another mlcrocode address dependant on the value of the status bit_ Status bit F.ach PU e.g 178's ALU 188 contains a number of input and calculation units.
Each unit produces 2 status bits - a negative flag and a zero flag. One of these status bits is output from the PU
e.g 178 when a particular unit asserts the value on the 1-bit tri-state status bit bus. The single status bit is output from the PU e.g 178, and then combined with the other PU e.g 178 status bits to update the Common Status Register 200. The microcode for determining the output status bit takes the following fotmv.
# Bits Description 2 Select unit whose status bit is to be output 00 = Adder unit 01 = Multiply/Logic unit = Barrel Shift unit 11 = Reader unit 1 0=Zeroflag i = Negative flag Within the ALU 188, the 2-bit Select Processor Block value is decoded into four 1-bit enable bits, with a different enable bit sent to each processor unit block. The status select bit (choosing Zero or Negative) is passed into all units to determine which bit is to be output onto the status bit bus.
Btanching Within Microcode Each PU e.g 178 contains a 7 bit Program Counter (PC) that holds the current microcode address being executed.
Normal program execution is linear, moving from address N in one cycle to address N+1 in the next cycle. Every cycle however, a microcode program has the ability to branch to a different location, or to test a status bit from the Common Status Register 200 and branch. The microcode for determining the next execution address takes the following form:
# Bits Description 2 00 = NOP (PC = PC+1) 01 = Branch always 10 = Branch if status bit clear II - Branch if status bit set 2 Select status bit from status word 7 Address to branch to (absolute address, 00-7F) Fig. 5 illustrates the ALU 188 in more detail. Inside the ALU 188 are a nttmber of specialized processing blocks, tmtrolled by a microcode ptngram. The specialized processing blocks include:
Read Block 202, for accepting data from the input FIFOs Write Block 203, for sending data out via the output FIFOs Adder/i..ogical block 204, for addition & subttaction, comparisons and logical operations Multiply/Interpolate block 205, for multiple types of interpolations and multiply/accumulates Barrel Shift block 206, for shifting data as required In block 207, for accepting data from the external crossbar switch 183 Out block 208, for sending data to the external crossbar switch 183 Registers block 215, for holding data in temporary storage Four specialized 32 bit registers hold the results of the 4 main processing blocks:
M register 209 holds the result of the Multiply/Interpolate biock L register 209 holds the result of the Adder/Logic block S register 209 holds the result of the Baael Shifter block R register 209 holds the result of the Read Block 202 In addition there are two internal crossbar switches 213m 214 for data transport. The various process blocks are further expanded in the following sections, together with the microcode definitions that pertain to each block. Note that the nticrocode is decoded within a block to provide the control signals to the vatious units within.
Data Transfers Between PUs e.g 178 Each PU e.g 178 is able to exchange data via the external crossbar. A PU e.g 178 takes two inputs and outputs two values to the external crossbar. In this way two operands for processing can be obtained in a single cycle, but cannot be actually used in an operation until the following cycle.
In 207 This block is illustrated in Fig. 6 and contains two registers, In, and In2 that accept data from the extemal crossbar. The registers can be loaded each cycle, or can remain unchanged. The selection bits for choosing from among the 8 inputs are output to the extemal crossbar switch 183. The microcode takes the following form:
# Bits Description 1 0 = NOP
1= Load In, from crossbar 3 Select Input 1 from external crossbar 1 0 = NOP
1= Load In2 from crossbar 3 Select Input 2 from external crossbar Out 208 Complementing In is Out 208. The Out block is illustrated in more detail in Fig. 7. Out contains two registers, Out, and Out2, both of which are output to the external crossbar each cycle for use by other PUs e.g 178. The Write unit is also able to write one of Out, or Out2 to one of the output FIFOs attached to the ALU 188. Finally, both registers are available as inputs to Crossbarl 213, which therefore makes the register values available as inputs to other units within the ALU 188. Each cycle either of the two registers can be updated according to microcode selection. The data loaded into the specified register can be one of Do - D3 (select,ed from Crossbarl 213) one of M, L, S, and R (selected from Crossbar2 214), one of 2 progratnmable constants, or the fixed values 0 or 1.
Tlte microcode for Out takes the following form:
# Bits Description 1 0 = NOP
I = Load Register I Select Register to load [Outt or Out2]
4 Select input [In1,In2,Outl,Outz,Da,D1,D2,D3,M,L,S,R,K1 ,KZ,0,1]
Local Registers and Data Transfers within ALU 188 As noted previously, the ALU 188 contains four specialized 32-bit registers to hold the results of the 4 main processing blocks:
M register 209 holds the result of the Multiply/Interpolate block L register 209 holds the result of the Adder/Logic block S register 209 holds the result of the Barrel Shifter block R register 209 holds the result of the Read Block 202 The CPU has direct access to these registers, and other units can select them as inputs via Crossbar2 214. Sometimes it is necessary to delay an operation for one or more cycles. The Registers block contains four 32-bit registers Da - D3 to hold temporary variables during processing. Each cycle one of the registers can be updated, while all the registers are output for other units to use via Crossbarl 213 (which also includes In,, In,, Out, and Out,). The CPU has direct access to these registers. The data loaded into the specified register can be one of Do - Di (selected from Crossbarl 213) one of M, L, S, and R (selected from Crossbar2 214), one of 2 programmable constants, or the fixed values 0 or 1. The Registers block 215 is illustrated in more detail in Fig. 8. The microcode for Registers takes the following form:
# Bits Description 1 0 = NOP
1 = Load Register 2 Select Register to load [Do - D3]
4 Select input [1n,,In2,Outt,Out2,Do,D,,D2,D3,M,L,S,R,K,,K2,0,1 ]
Crossbar] 213 Crossbarl 213 is illustrated in more detail in Fig. 9. Crossbarl 213 is used to select from inputs In,, In2, Outt, Out2, Do-I);. 7 outputs are generated from Crossbarl 213: 3 to the Multiply/Interpolate Unit, 2 to the Adder Unit, I to the Registers unit and 1 to the Out unit. The control signals for Crossbarl 213 come from the various units that use the Crossbar inputs. There is no specific microcode that is separate for Crossbarl 213.
Crossbar2 214 Crossbar2 214 is illustrated in more detail in Fig. 10.Crossbat2 214 is used to select from the general ALU 188 registers M, L, S and R. 6 outputs are generated from Crossbarl 213: 2 to the Multiply/Interpolate Unit, 2 to the Adder Unit, I to the Registers unit and I to the Out unit. The control signals for Crossbar2 214 come from the various units that use the Crossbar inputs. There is no specific microcode that is separate for Crossbar2 214.
Data Transfers Between PUs e.e 178 and DRAM or External Processes Returning to Fig. 4, PUs e.g 178 share data with each other directly via the external crossbar. They also transfer data to and from external processes as well as DRAM. Each PU e.g 178 has 2 UO Address Generators 189, 190 for transfetring data to and from DRAM. A PU e.g 178 can send data to DRAM via an I/O Address Generator's Output FIFO e.g. 186, or accept data from DRAM via an I/O Address Generator's Input FIFO 187. These F1FOs are local to the PU e.g 178. There is also a mechanism for transferring data to and from external processes in the form of a common VLIW Input FIFO 78 and a common VLIW Output FIFO 79, shared between all ALUs_ The VLIW Input and Output FIFOs are only 8 bits wide, and are used for printing, Artcard reading, transferring data to the CPU etc. The local Input and Output FIFOs are 16 bits wide.
Read The Read process block 202 of Fig. 5 is responsible for updating the ALU 188's R register 209, which represents the external input data to a VLIW microcoded process. Each cycle the Read Unit is able to read from either the common VLIW Input FIFO 78 (8 bits) or one of two local Input FIFOs (16 bits). A 32-bit value is generated, and then all or part of that data is transferred to the R register 209. The process can be seen in Fig. 11. The microcode for Read is described in the following table. Note that the interpretations of some bit patterns are deliberately chosen to aid decoding.
# Bits Description 2 00 = NOP
01 = Read from VL1W Input FIFO 78 = Read from Local FIFO I
I i= Read from Local FIFO 2 1 How many significant bits 0= 8 bits (pad with 0 or sign extend) 1= 16 bits (only valid for Local FIFO reads) 1 0 = Treat data as unsigned (pad with 0) 1= Treat data as signed (sign extend when reading from FIFO)r 2 How much to shift data left by:
00 = 0 bits (no change) 01 = 8 bits 10 = 16 bits 11=24bits 4 Which bytes of R to update (hi to lo order byte) Each of the 4 bits represents I byte WriteEnable on R
Write The Write process block is able to write to either the common VLIW Output FIFO
79 or one of the two local Output FIF.Os each cycle. Note that since only I FIFO is written to in a given cycle, only one 16-bit value is output to all FIFOs, with the low 8 bits going to the VLIW Output FIFO 79. The microcode controls which of the FIFOs gates in the value. The process of data selection can be seen in more detail in Fig.
12_ The source values Out, and Out-, come from the Out block. They are simply two registers. The nticrocode for Write takes the following form:
# Bits Description 2 00=NOP
01 = Write VLIW Output FIFO 79 = Write local Output FIFO I
11 = Write local Output FIFO 2 I. Select Output Value [Outt or Out2j 3 Select part of Output Value to write (32 bits = 4 bytes ABCD) 000=0D
001 = OD
010 = 0B
011 =0A
100=CD
101 = BC
110 = AB
I11=0 Cotnputational Biocks Each ALU 188 has two computational process blocks, namely an Addcr/Logic process block 204, and a Multiply/Interpolate process block 205. In addition there is a Barrel Shifter block to provide help to these cotnputational blocks. Registers from the Registers block 215 can be used for temporary storage during pipelined operations.
Batrel Shifter The Batrel Shifter process block 206 is shown in more detail in Fig. 13 and takes its input from the output of Adder/Logic or Multiply/Interpolate process blocks or the previous cycle's results from those blocks (ALU registers L
and M). The 32 bits selected are barrel shifted an arbitrary number of bits in either direction (with sign extension as necessary), and output to the ALU 188's S register 209. The tnicrocode for the Batrel Shift process block is described in the following table. Note that the intetpretations of some bit pattertu are deliberately chosen to aid decoding.
# Bits Description 3 000 = NOP
001 = Shift Left (unsigned) 010 = Reserved 011 = Shift Left (signed) 100 = Shift right (unsigned, no rounding) 101 = Shift right (unsigned, with rounding) I 10 = Shift right (signed, no rounding) 111 = Shift right (signed, with rounding) 2 Select Input to barrel shift:
00 = Multiply/Interpolate result 01 =M
= Adder/Logic result 11=L
5 # bits to shift 1 Ceiling of 255 1 Floor of 0 (signed data) Adder/Log'tc 204 The Adder/Logic process block is shown in more detail in Fig_ 14 and is designed for simple 32-bit addition/subtraction, comparisons, and logical operations. In a single cycle a single addition, comparison, or logical operation can be performed, with the result stored in the ALU 188's L register 209. There are two primary operands, A
and B, which are selected from either of the two crossbars or from the 4 constant registers. One crossbar selection allows the results of the previous cycle's arithmetic operation to be used while the second provides access to operands previously calculated by this or another ALU 188. The CPU is the only unit that has write access to the four constants (IKt-S4). In cases where an operation such as (A+B) x 4 is desired, the direct output from the adder can be used as input to the Barrel Shifter, and can thus be shifted left 2 places without needing to be latched into the L register 209 first. The output from the adder can also be made available to the multiply unit for a multiply-accumulate operation.
The microcode for the Adder/Logic process block is described in the following table. The interpretations of some bit pattertts are deliberately chosen to aid decoding. Microcode bit interpretation for Adder/Logic unit # Bits Description 4 0000=A+B (carry in=0) 0001 = A+B (carry in = carry out of previous operation) 0010 = A+B+1 (caey in = 1) 0011 = A+l (increments A) 0100 = A-B-1 (carry in = 0) 0101 = A-B (carry in = carry out of previous operation) 0110 = A-B (carry in = 1) 0111 = A-1 (decrements A) 1000=NOP
1001 = ABS(A-B) 1010 = MIN(A, B) 1011 = MAX(A, B) 1100 = A AND B (both A & B can be inverted, see below) 1101 = A OR B(both A& B can be inverted, see below) 1110 = A XOR B (both A & B can be inverted, see below) IIII = A (A can be inverted, see below) 1 If logical operation:
0 = A=A
1 = A=NOT(A) If Adder operation:
0 = A is unsigned 1 = A is signed If logical operation:
0=B=B
I = B=NOT(B) If Adder operation 0 = B is unsigned 1 = B is signed 4 Select A [In1,In2,Out1,Out2,Do,D,,D2,Dj,M,L,S,R,K1,KZ,K3,K4]
4 Select B [In,,In2,Out1,Out2,Do,D1 ,DZ,D3,M,L,S,R,K1,KZ,K3,K4]
Multiply/Interoolate 205 The Multiply/Interpolate process block is shown in more detail in Fig. 15 and is a set of four 8 x 8 interpolator units that are capable of performing four individual 8 x 8 interpolates per cycle, or can be combined to perform a single 16 x 16 multiply. This gives the possibility to perform up to 4 linear interpolations, a single bi-linear interpolation, or half of a tri-linear interpolation in a single cycle. The result of the interpolations or multiplication is stored in the ALU 188's M register 209. There are two primary operands, A and B. which are selected from any of the general registers in the ALU 188 or from four programmable constants internal to the Multiply/[nterpolate process block. Each interpolator block functions as a simple 8 bit interpolator [result = A+(B-A)f] or as a simple 8 x 8 multiply [result = A * B]. When the operation is interpolation, A and B are treated as four 8 bit numbers Aa thru A3 (Ao is the low order byte), and Bo thru B3. Agen, Bgen, and Fgen are responsible for ordering the inputs to the Interpolate units so that they match the operation being performed. For example, to perform bilinear interpolation, each of the 4 values must be multiplied by a different factor & the result summed, while a 16 x 16 bit multiplication requires the factors to be 0. The microcode for the Adder/Logic process block is described in the following table. Note that the interpretations of some bit patterns are deliberately chosen to aid decoding.
# Bits Description 4 0000=(A,o*B,o)+V
0001 =(AO * B0) +(A 1* B 1) + V
0010=(A,o*B,o)-V
0011=V-(A,o*B,o) 0100 = Interpolate Ao,Bo by fo 0101 = Interpolate Ao,Bo by fo, A,,B, by f, 0110 = Interpolate Ao,Bo by fo, A,,B, by f,, AZ,B, by f, 0111 = Interpolate Ao,Bo by fo, A,,B, by f,, A,,BZ by f,, A3,B3 by f3 1000 = Interpolate 16 bits stage 1[M = A,o * f,o]
1001 = Interpolate 16 bits stage 2 [M = M+(A,o * f,o)]
1010 = Tri-linear interpolate A by f stage I[M=Aofo+A, f,+A,f,+A3f3]
101 ]= Tri-linear interpolate A by f stage 2[M=M+Aafo+A,f,+A,f,+A3f3]
1100 = Bi-linear interpolate A by f stage 1[M=Aofo+A,f,]
1101 = B i-linear interpolate A by f stage 2[M=M+Aofo+A,f,]
1110 = Bi-linear interpolate A by f complete (M=Aofo+A,f,+AZf2+A3f3]
1111 =NOP
4 Select A [In1 ,In,,Out1 ,Out2,Do,D1,DZ,D3,M,L,S,R,Ki,K,,K3,K4]
4 Select B [In1 ,InZ,Out1,Out2,Do,D1,D,,D3,M,L,S,R,K1,K,,K3,K4]
If Mult:
4 Select V[In,,InZ,Out,,Out2,Do,D,,DZ,D3,K1,K,,K3,Ka,Adder result,M,O, I]
1 Treat A as signed 1 Treat B as signed 1 Treat V as signed If Interp:
4 Select basis for f(In,,In2,Out,,OutZ,Do,D,,D,,D3,K,,KZ,K3,Ka,X,X,X,X]
1 Select interpolation f generation from P, or P2 P. is interpreted as # fractional bits in f If Põ=0, f is range 0..255 representing 0..1 2 Reserved The same 4 bits are used for the selection of V and f, although the last 4 options for V don't generally make sense as f values. Interpolating with a factor of I or 0 is pointless, and the previous multiplication or current result is unlikely to be a meaningful value for f.
I/O Address GeneratorS 189. 190 The I/O Address Generators are shown in more detail in Fig. 16. A VLIW process does not access DRAM directly.
Access is via 2 1/0 Address Generators 189, 190, each with its own Input and Output FIFO. A PU e.g 178 reads data from one of two local Input FIFOs, and writes data to one of two local Output FIFOs. Each 1/0 Address Generator is responsible for reading data from DRAM and placing it into its Input FIFO, where it can be read by the PU e.g 178, and is responsible for taking the data from its Output FIFO (placed there by the PU e.g 178) and writing it to DRAM.
The I/O Address Generator is a state machine responsible for generating addresses and control for data retrieval and storage in DRAM via the Data cache 76. It is customizable under CPU software control, but cannot be microcoded.
The address generator produces addresses in two broad categories:
Image Iterators, used to iterate (reading, writing or both) through pixels of an image in a variety of ways Table 1/0, used to randomly access pixels in images, data in tables, and to simulate FIFOs in DRAM
Each of the 1/0 Address Generators 189, 190 has its own bus connection to the Data cache 76, making 2 bus connections per PU e.g 178, and a total of 8 buses over the entire VLIW Vector Processor 74. The Data cache 76 is able to service 4 of the maximum 8 requests from the 4 PUs e.g 178 each cycle_ The Input and Output FIFOs are 8 entry deep 16-bit wide FIFOs. The various types of address generation (Image Iterators and Table 1/0) are described in the subsequent sections.
e' e The I/O Address Generator has a set of registers for that are used to control address generation. The addressing mode also determines how the data is formatted and sent into the local Input FIFO, and how data is interpreted from the local Output FIFO. The CPU is able to access the registers of the I/O Address Generator via the low speed bus. The first set of registers define the housekeeping parameters for the 1/0 Generator:
Register Name # bits Description Reset 0 A write to this register halts any operations, and writes Os to all the data registers of the I/O Generator. The input and output FIFOs are not cleared.
Go 0 A write to this register restarts the counters according to the current setup. For example, if the 1/0 Generator is a Read Iterator, and the Iterator is currently halfway through the image, a write to Go will cause the reading to begin at the start of the image again. While the 1/0 Generator is performing, the Active bit of the Status register will be set.
Halt 0 A write to this register stops any current activity and clears the Active bit of the Status register. If the Active bit is already cleared, writing to this register has no effect.
Continue 0 A write to this register continues the 1/0 Generator from the current setup. Counters are not reset, and FIFOs are not cleared. A write to this register while the I/O Generator is active has no effect.
ClearFlFOsOnGo 1 0= Don't clear FIFOs on a write to the Go bit_ 1= Do clear FIFOs on a write to the Go bit.
Status 8 Status flags The Status register has the following values Register Name # bits Description Active 1 0= Currently inactive 1 = Currently active Reserved 7 -Cachine Several registers are used to control the caching mechanism, specifying which cache group to use for inputs, outputs etc. See the section on the Data cache 76 for more infotmation about cache groups.
Register Name # bits Description CacheGroupl 4 Defines cache group to read data from CacheGroup2 4 Defines which cache group to write data to, and in the case of the ImagePyramidLookup 1/0 mode, defines the cache to use for reading the Level Information Table.
Image Iterators = Seouential Automatic Access to pixels The primary image pixel access method for software and hardware algorithms is via Image Iterators. Image iterators perform all of the addressing and access to the caches of the pixels within an ima.ge channel and read, write or read &
write pixels for their client Read Iterators read pixels in a specific order for their clients, and Write Iterators write pixels in a specific order for their clients. Clients of Iterators read pixels from the local Input FIFO or write pixels via the local Output FIFO.
Read Image Iterators read through an image in a specific order, placing the pixel data into the local Input FIFO.
Every time a client reads a pixel from the Input FIFO, the Read Iterator places the next pixel from the image (via the Data cache 76) into the FIFO.
Write Iatage Iterators write pixels in a specific order to write out the entire image. Clients write pixels to the Output FIFO that is in turn read by the Write Image Iterator and written to DRAM via the Data cache 76.
Typically a VLIW process will have its input tied to a Read Iterator, and output tied to a corresponding Write Iterator.
From the PU e.g 178 microcode program's perspective, the FIFO is the effective interface to DRAM. The actual method of carrying out the storage (apart from the logical ordering of the data) is not of concern. Although the FIFO is perceived to be effectively unlimited in length, in practice the FIFO is of limited length, and there can be delays storing and retrieving data, especially if several niemory accesses are competing. A
variety of Image Iterators exist to cope with the most common addressing requirements of image processing algorithms.
In most cases there is a corresponding Write Iterator for each Read Iterator. The different Iterators are listed in the following table:
Read Iterators Write Iterators Sequential Read Sequential Write Box Read Vertical Strip Read Vertical Strip Write The 4 bit Address Mode Register is used to determine the Iterator type:
Bit # Address Mode 3 0= This addressing mode is an Iterator 2 to 0 Iterator Mode 001 = Sequential Iterator 010 = Box [read only]
100 = Vertical Strip remaining bit pattems are reserved The Access Specific registers are used as follows:
Register Name LocalName Description AccessSpecific, Flags Flags used for reading and writing AccessSpecificz XBoxSize Determines the size in X of Box Read. Valid values are 3. 5, and 7.
AccessSpecific3 YBoxSize Determines the size in Y of Box Read. Valid values are 3, 5, and 7.
AccessSpecific4 BoxOffset Offset between one pixel center and the next during a Box Read only.
Usual value is l, but other useful values include 2, 4, 8...
See Box Read for more details.
The Flags register (AccessSpecificl) contains a number of flags used to determine factors affecting the reading and writing of data. The Flags register has the following composition:
Label #bits Description ReadEnable I Read data from DRAM
WriteEnable 1 Write data to DRAM [not valid for Box model PassX 1 Pass X (pixel) ordinate back to Input FIFO
PassY I Pass Y (row) ordinate back to Input FIFO
Loop 1 0= Do not loop through data I = Loop through data Reserved 1 I Must be 0 Notes on ReadEnable and WriteEnable:
When ReadEnable is set, the 1/O Address Generator acts as a Read Iterator, and therefore reads the image in a particular order, placing the pixels into the Input FIFO.
When WriteEnable is set, the I/O Address Generator acts as a Write Iterator, and then:fore writes the image in a particular order, taking the pixels from the Output FIFO.
When both ReadEnable and WriteEnable are set, the 110 Address Generator acts as a Read Iterator and as a Write Iterator, reading pixels into the Input FIFO, and writing pixels from the Output FIFO. Pixels are only written after they have been read - i.e. the Write Iterator will never go faster than the Read Iterator. Whenever this mode is used, care should be taken to ensure balance between in and out processing by the VLIW microcode. Note that separate cache groups can be specified on reads and writes by loading different values in CacheGroupl and CacheGroup2.
Notes on PassX and PassY:
If PassX and PassY are both set, the Y ordinate is placed into the Input FIFO
before the X ordinate.
PassX and PassY are only intended to be set when the ReadEnable bit is clear.
Instead of passing the ordinates to the address generator, the ordinates are placed directly into the Input FIFO. The ordinates advance as they are removed from the FIFO.
If WriteEnable bit is set, the VLIW program must ensure that it balances reads of ordinates from the Input FIFO with writes to the Output FIFO, as writes will only occur up to the ordinates (see note on ReadEnable and WriteEnable above).
Notes on Looo-If the Loop bit is set, reads will recommence at [StartPixel, StartRowj once it has reached [EndPixet, EndRowl. This is ideal for processing a structure such a convolution kernel or a dither cell matrix, where the data must be read repeatedly.
Looping with ReadEnable and WriteEnable set can be useful in an environment keeping a single line history, but only where it is useful to have reading occur before writing. For a FIFO effect (where writing occurs before reading in a length constrained fashion), use an appropriate Table 1/0 addressing mode instead of an Intage Iterator.
Looping with only WriteEnable set creates a written window of the last N
pixels. This can be used with an asynchronous process that reads the data from the window. The Artcard Reading algorithm makes use of this mode.
Sequential Read and Write Iterators Fig. 17 illustrates the pixel data format. The simplest Image Iterators are the Sequential Read Iterator and corresponding Sequential Write Iterator. The Sequential Read Iterator presents the pixels from a channel one line at a time from top to bottom, and within a line, pixels are presented left to right. The padding bytes are not presented to the client. It is most useful for algorithtns that must perform some process on each pixel from an intage but don't care about the order of the pixels being processed, or want the data specifically in this order. Complementing the Sequential Read Iterator is the Sequential Write Iterator. Clients write pixels to the Output FIFO. A Sequential Write Iterator subsequently writes out a valid image using appropriate caching and appropriate padding bytes. Each Sequential Iterator requires access to 2 cache lines. When reading, while 32 pixels are presented from one cache line, the other cache line can be loaded from memory. When writing, while 32 pixels are being filled up in one cache line, the other can be being written to memory.
A process that perforins an operation on each pixel of an itnage independently would typically use a Sequential Read Itetator to obtain pixels, and a Sequential Write Iterator to write the new pixel values to their cotresponding locations within the destination image. Such a prooess is shown in Fig. 18.
In most cases, the source and destination images are different, and are represented by 2 1/0 Address Generators 189, 190. However it can be valid to have the source image and destination image to be the same, since a given input pixel is not read more than once. In that case, then the same Iterator can be used for both input and output, with both the ReadEnable and WriteEnable registers set appropriately. For maximum efficiency, 2 different cache groups should be used - one for reading and the other for writing. If data is being created by a VLIW process to be written via a Sequential Write Iterator, the PassX and PassY flags can be used to generate coordinates that are then passed down the Input FIFO. The VLIW process can use these coordinates and create the output data appropriately.
Box Read Iterator The Box Read Iterator is used to present pixels in an order most useful for perfortning operations such as general-purpose filters and convolve. The Iterator presents pixel values in a square box around the sequentially read pixels. The box is limited to being 1, 3, 5, or 7 pixels wide in X and Y (set XBoxSize and YBoxSize- they must be the same value or I in one dimension and 3, 5, or 7 in the other). The process is shown in Fig. 19:
BoxOffset: This special purpose register is used to determine a sub-sampling in terms of which input pixels will be used as the center of the box. The usual value is 1, which means that each pixel is used as the center of the box. The value "2" would be useful in scaling an image down by 4:1 as in the case of building an image pyramid. Using pixel addresses from the previous diagram, the box would be centered on pixel 0, then 2, 8, and 10. The Box Read Iterator requires access to a maximum of 14 (2 x 7) cache lines. While pixels are presented from one set of 7 lines, the other cache lines can be loaded from memory.
Box Write Iterator There is no corresponding Box Write Iterator, since the duplication of pixels is only required on input. A process that uses the Box Read Iterator for input would most likely use the Sequential Write Iterator for output since they are in sync. A good example is the convolver, where N input pixels are read to calculate I output pixel. The process flow is as illustrated in Fig. 20. The source and destination images should not occupy the same memory when using a Box Read Iterator, as subsequent lines of an image require the original (not newly calculated) values.
Vertical-Strip Read and Write Iterators In some instances it is necessary to write an image in output pixel order, but there is no knowledge about the direction of coherence in input pixels in relation to output pixels. An example of this is rotation. If an image is rotated 90 degrees, and we process the output pixels horizontally, there is a complete loss of cache coherence_ On the other hand, if we process the output image one cache line's width of pixels at a time and then advance to the next line (rather than advance to the next cache-line's worth of pixels on the same line), we will gain cache coherence for our input image pixels. It can also be the case that there is known 'block' coherence in the input pixels (such as color coherence), in which case the read governs the processing order, and the write, to be synchronized, must follow the same pixel order.
The order of pixels presented as input (Vertical-Strip Read), or expected for output (Vertical-Strip Write) is the same.
The order is pixels 0 to 31 from Iine 0, then pixels 0 to 31 of line I etc for all lines of the image, then pixels 32 to 63 of line 0, pixels 32 to 63 of line I etc. In the final vertical strip there may not be exactly 32 pixels wide. In this case only the actual pixels in the image are presented or expected as input. This process is illustrated in Fig. 21.
process that requires only a Vertical-Strip Write Iterator will typically have a way of mapping input pixel coordinates given an output pixel coordinate. It would access the input image pixels according to this mapping, and coherence is determined by having sufficient cache lines on the 'random-access' reader for the input image. The coordinates will typically be generated by setting the PassX and PassY flags on the VerticalStripWrite Iterator, as shown in the process overview illustrated in Fig. 22.
It is not meaningful to pair a Write Iterator with a Sequential Read Iterator or a Box read Iterator, but a Vertical-Strip Write Iterator does give significant improvements in performance when there is a non trivial mapping between input and output coordinates.
It can be meaningful to pair a Vertical Strip Read Iterator and Vertical Strip Write Iterator. In this case it is possible to assign both to a single ALU 188 if input and output images are the same. If coordinates are required, a further Iterator must be used with PassX and PassY flags set_ The Vertical Strip Read/Write Iterator presents pixels to the Input FIFO, and accepts output pixels from the Output FIFO. Appropriate padding bytes will be inserted on the write. Input and output require a minimum of 2 cache lines each for good performance.
Table UO Addressing Modes It is often necessary to lookup values in a table (sttch as an image). Table I/O addressing modes provide this functionality, requiring the client to place the index/es into the Output FIFO. The I/O Address Generator then processes the index/es, looks up the data appropriately, and rettutts the looked-up values in the Input FIFO for subsequent processing by the VLIW client.
ID, 2D and 3D tables are supported, with particular modes targeted at interpolation. To reduce complexity on the VLIW client side, the index values are treated as fixed-point numbers, with AccessSpecific registers defining the fixed point and therefore which bits should be treated as the integer portion of the index. Data formats are restricted forms of the general Image Characteristics in that the PixelOPfset register is ignored, the data is assumed to be contiguous within a row, and can only be 8 or 16 bits (I or 2 bytes) per data element.
The 4 bit Address Mode Register is used to detem-iine the 1/0 type:
Bit # Address Mode 3 1 = This addressing mode is Table I/O
2 to 0 000 = 1 D Direct Lookup 001 = 1D Interpolate (linear) 010=DRAMFIFO
011 = Reserved 100 = 2D Interpolate (bi-linear) 101 = Reserved 110 = 3D Interpolate (tri-linear) III = Image Pyramid Lookup The access specific registers are:
Register Name LocalName #bits Description -AccessSpecifict Flags 8 General flags for reading and writing.
See below for more information.
AccessSpecific2 FractX 8 Number of fractional bits in X index AccessSpecific3 FractY 8 Number of fractional bits in Y index AccessSpecific4 FractZ 8 Number of fractional bits in Z index (low 8 bits / next 12 or 24 ZOffset 12 or See below bits)) 24 FractX, FractY, and FractZ are used to generate addresses based on indexes, and interpret the format of the index in terms of significant bits and integer/fractional components. The various parameters are only defined as required by the number of dimensions in the table being indexed. A 1D table only needs FractX, a 2D table requires FractX and FractY. Each Fract value consists of the number of fractional bits in the corresponding index. For example, an X
index may be in the format 5:3. This would indicate 5 bits of integer, and 3 bits of fraction. FractX would therefore be set to 3. A simple 1 D lookup could have the format 8:0, i.e. no fractional component at all. FractX would therefore be 0. ZOffset is only required for 3D lookup and takes on two different interpretations. It is described more fully in the 3D-table lookup section. The Flags register (AccessSpecificl) contains a number of flags used to determine factors affecting the reading (and in one case, writing) of data. The F1ags register has the following composition:
Label #bits Description ReadEnable I Read data from DRAM
WriteEnable 1 Write data to DRAM [only valid for 1 D direct lookup]
DataSize 1 0 = 8 bit data 1 = 16 bit data Reserved 5 Must be 0 With the exception of the ID Direct Lookup and DRAM FIFO, all Table 1/O modes only supjort readinQ, and not writing- Therefore the ReadEnable bit will be set and the WriteEnable bit will be clear for all 1/0 modes other than these two modes. The 1 D Direct Lookup supports 3 modes:
Read only, where the ReadEnable bit is set and the WriteEnable bit is clear Write only, where the ReadEnable bit is clear and the WriteEnable bit is clear Read-Modify-Write, where both ReadEnable and the WriteEnable bits are set The different modes are described in the 1D Direct Lookup section below. The DRAM FIFO mode supports only I
mode:
Write-Read mode, where both ReadEnable and the WriteEnable bits are set This mode is described in the DRAM FIFO section below. The DataSize flag detenmines whether the size of each data elentents of the table is 8 or 16 bits. Only the two data sizes are supported. 32 bit elements can be created in either of 2 ways depending on the requiretnents of the process:
Reading from 2 16-bit tables simultaneously and combining the result. This is convenient if timing is an issue, but has the disadvantage of consuming 2 1/0 Address Generators 189, 190, and each 32-bit element is not readable by the CPU as a 32-bit entity.
Reading from a 16-bit table twice and combining the result. This is convenient since only I lookup is used, although different indexes must be generated and passed into the lookup.
I Dimensional Structures Direct Lookuo A direct lookup is a simple indexing into a 1 dimensional lookup table.
Clients can choose between 3 access modes by setting appropriate bits in the Flags register:
Read only Write only Read-Modify-Write Read Only A client passes the fixed-point index X into the Output FIFO, and the 8 or 16-bit value at Table[Int(X)] is returned in the Input FIFO. The fractional component of the index is completely ignored.
If the index is out of bounds, the DuplicateEdge flag determines whether the edge pixel or ConstantPixel is returned. The address generation is straightforward:
If DataSize indicates 8 bits, X is barrel-shifted right FractX bits, and the result is added to the table's base address ImageStart.
If DataSize indicates 16 bits, X is barrel-shifted right FractX bits, and the result shifted left I bit (bitO
becomes 0) is added to the table's base address limageStart.
The 8 or 16-bit data value at the resultant address is placed into the Input FIFO. Address generation takes I cycle, and transferring the requested data from the cache to the Output FIFO also takes I
cycle (assuming a cache hit)_ For example, assume we are looking up values in a 256-entry table, where each entry is 16 bits, and the index is a 12 bit fixed-point format of 8:4. FractX should be 4, and DataSize 1. When an index is passed to the lookup, we shift right 4 bits, then add the result shifted left I bit to ImageStatt.
Write Only A client passes the fixed-point index X into the Output FIFO followed by the 8 or 16-bit value that is to be written to the specified location in the table. A complete transfer takes a minimum of 2 cycles. I cycle for address generation, and I cycle to transfer the data from the FIFO to DRAM. There can be an arbitrary number of cycles between a VLIW
process placing the index into the FIFO and placing the value to be written into the FIFO. Address generation occurs in the same way as Read Only mode, but instead of the data being read from the address, the data from the Output FIFO
is written to the address. If the address is outside the table range, the data is removed from the FIFO but not written to DRAM.
Read-Modify-Write A client passes the fixed-point index X into the Output FIFO, and the 8 or 16-bit value at Table[Int(X)] is returned in the Input FIFO. The next value placed into the Output FIFO is then written to Table[Int(X)], replacing the value that had been returned earlier. The general processing loop then, is that a process reads from a location, modifies the value, and writes it back. The overall time is 4 cycles:
Getierate address from index Return value from table Modify value in some way Write it back to the table Tha+e is no specific read/write mode where a client passes in a flag saying "read from X" or "write to X". Clients can simulate a "read from X" by writing the original value, and a"write to X" by simply ignoring the returned value.
However such use of the mode is not encouraged since each action consumes a minimum of 3 cycles (the modify is not required) and 2 data accesses instead of I access as provided by the specific Read and Write modes_ Interpolate table This is the same as a Direct Lookup in Read mode except that two values are returned for a given fixed-point index X
instead of one. The values returned are Table[Int(X)], and Table[Int(X)+l ]_ If either index is out of bounds the DuplicateEdge flag detennines whether the edge pixel or ConstantPixel is retutned. Address generation is the same as Direct Lookup, with the exception that the second address is simply Addressl+ 1 or 2 depending on 8 or 16 bit data.
Transferring the requested data to the Output FIFO takes 2 cycles (assuming a cache hit), although two 8-bit values may actually be returned from the cache to the Address Generator in a single 16-bit fetch.
DRAM FIFO
A special case of a read/write 1D table is a DRAM FIFO. It is often necessary to have a simulated FIFO of a given length using DRAM and associated caches. With a DRAM FIFO, clients do not index explicitly into the table, but write to the Output FIFO as if it was one end of a FIFO and read from the Input FIFO as if it was the other end of the same logical FIFO. 2 counters keep track of input and output positions in the simulated FIFO, and cache to DRAM as needed. Clients need to set both ReadEnable and WriteEnable bits in the Flags register.
An example use of a DRAM FIFO is keeping a single line history of some value.
The initial history is written before processing begins. As the general process goes through a line, the previous line's value is retrieved from the FIFO, and this line's value is placed into the FIFO (this line will be the previous line when we process the next line). So long as input and outputs match each other on average, the Output FIFO should always be full_ Consequently there is effectively no access delay for this kind of FIFO (unless the total FIFO
length is very small - say 3 or 4 bytes, but that would defeat the purpose of the FIFO).
2 Dimensional Tables Direct Lookup A 2 dimensional direct lookup is not supported. Since all cases of 2D lookups are expected to be accessed for bi-linear interpolation, a special bi-linear lookup has been implemented.
Bi-Linear lookup This kind of lookup is necessary for bi-linear interpolation of data from a 2D
table. Given fixed-point X and Y
coordinates (placed into the Output FIFO in the order Y, X), 4 values are returned after lookup. The values (in order) are:
Table[Int(X), Int(Y)]
Table[Int(X)+1, Int(Y)]
Table[Int(X), Int(Y)+1 I
Table[Int(X)+1, Int(Y)+l]
The order of values returned gives the best cache coherence. If the data is 8-bit, 2 values are returned each cycle over 2 cycles with the low order byte being the first data eiement. If the data is 16-bit, the 4 values are returned in 4 cycles, 1 entry per cycle. Address generation takes 2 cycles. The first cycle has the index (Y) barrel-shifted right FractY bits being multiplied by RowOffset, with the result added to ImageStart. The second cycle shifts the X index right by FractX bits, and then either the result (in the case of 8 bit data) or the result shifted left I bit (in the case of 16 bit data) is added to the result from the first cycle. This gives us address Adr =
address of Table[Int(X), Int(Y)):
Adr = ImageStart + ShiftRight(Y, FractY)* RowOffset) + ShiftRight(X, FractX) We keep a copy of Adr in AdrOld for use fetching subsequent entries.
If the data is 8 bits, the timing is 2 cycles of address generation, followed by 2 cycles of data being returned (2 table entries per cycle).
If the data is 16 bits, the tinung is 2 cycles of address generation, followed by 4 cycles of data being returned (1 entry percycle) The following 2 tables show the method of address calculation for 8 and 16 bit data sizes:
Cycle Calculation while fetching 2 x 8-bit data entries from Adr I Adr = Adr + RowOffset 2 <preparing next lookup>
Cycle Calculation while fetching 1 x 16-bit data entry from Adr 1 Adr = Adr + 2 2 Adr = AdrOld + RowOffset 3 Adr=Adr+2 4 <preparing next lookup>
In both cases, the first cycle of address generation can overlap the insertion of the X index into the FIFO, so the effective timing can be as low as I cycle for address generation, and 4 cycles of return data. If the generation of indexes is 2 steps ahead of the results, then thete is no effective address generation time, and the data is simply produced at the appropriate rate (2 or 4 cycles per set).
3 Dimensional Lookur) Direct Lookuo Since all cases of 2D lookups are expected to be accessed for tri-linear interpolation, two special tri-linear lookups have been implemented. The first is a straightforward lookup table, while the second is for tri-linear interpolation from an Image Pyramtd.
Tri-linear lookuo This type of lookup is useful for 3D tables of data, such as color conversion tables. The standard image parameters define a single XY plane of the data - i.e. each plane consists of LoageHeight rows, each row containing RowOffset bytes. In most circumstances, assuming contiguous planes, one XY plane will be LnageHeight x RowOH'set bytes after another. Rather than assume or calculate this offset, the software via the CPU must provide it in the form of a 12-bit ZOffset register. In this form of lookup, given 3 fixed-point indexes in the order Z, Y. X, 8 values are returned in order from the lookup table:
Table[Int(X), Int(Y), Int(Z)]
Table[Int(X)+1, Int(Y), Int(Z)]
Table(Int(X), Int(Y)+1, Int(Z)1 Table(Int(X)+1, Int(Y)+1, Int(Z)]
Table[Int(X), Int(Y), Int(Z)+1]
Table[Int(X)+1, Int(Y), Int(Z)+1]
Table[Int(X), Int(Y)+1, Int(Z)+l]
Table[Int(X)+1, Int(Y)+1, Int(Z)+l]
The order of values returned gives the best cache coherence. If the data is 8-bit, 2 values are returned each cycle over 4 cycles with the low order byte being the first data element. If the data is 16-bit, the 4 values are returned in 8 cycles, I
entry per cycle. Address generation takes 3 cycles. The first cycle has the index (Z) barrel-shifted right FractZ bits being multiplied by the 12-bit ZOffset and added to ImageStart. The second cycle has the index (Y) barrel-shifted right FractY bits being multiplied by RowOffset, with the result added to the result of the previous cycle. The second cycle shifts the X index right by FractX bits, and then either the result (in the case of 8 bit data) or the result shifted left I bit (in the case of 16 bit data) is added to the result from the second cycle. This gives us address Adr = address of Table[Int(X), Int(Y), Int(Z)]:
Adr = ImageStart + (ShiftRight(Z, FractZ) * ZOffset) + (ShiftRight(Y, FractY)* RowOffset) + ShiftRight(X, FractX) We keep a copy of Adr in AdrOld for use fetching subsequent entries.
If the data is 8 bits, the timing is 2 cycles of address generation, followed by 2 cycles of data being returned (2 table entries per cycle).
If the data is 16 bits, the timing is 2 cycles of address generation, followed by 4 cycles of data being returned (1 entry per cycle) The following 2 tables show the method of address calculation for 8 and 16 bit data sizes:
Cycle Calculation while fetching 2 x 8-bit data entries from Adr I Adr = Adr + RowOffset 2 Adr = AdrOld + ZOffset 3 Adr = Adr + RowOffset 4 <preparing next lookup>
Cycle Calculation while fetching 1 x 16-bit data entries from Adr t Adr = Adr + 2 2 Adr = AdrOld + RowOffset 3 Adr = Adr + 2 4 Adr, AdrOld =AdrOld + Zoffset Adr=Adr+2 6 Adr = AdrOld + RowOffset 7 Adr = Adr + 2 8 <preparing next lookup>
In both cases, the cycles of address generation can overlap the insertion of the indexes into the FIFO, so the effective timing for a single one-off lookup can be as low as I cycle for address generation, and 4 cycles of return data. If the generation of indexes is 2 steps ahead of the results, then there is no effective address generation time, and the data is simply produced at the appropriate rate (4 or 8 cycles per set).
Image Pyramid LookuR
During brushing, tiling, and warping it is necessary to compute the average color of a particular area in an image.
Rather than calculate the value for each area given, these functions make use of an image pyramid. The description and construction of an image pyramid is detailed in the section on Internal Image Formats in the DRAM interface 81 chapter of this docunient This section is concerned with a method of addressing given pixels in the pyramid in terms of 3 fixed-point indexes ordered: level (Z), Y, and X. Note that Image Pyramid lookup assumes 8 bit data entries, so the DataSize flag is completely ignored. After specification of Z, Y, and X, the following 8 pixels are returned via the Input FIFO:
The pixel at [Int(X), Int(Y)], level Int(Z) The pixel at [Int(X)+I, Int(Y)], level Int(Z) The pixel at [Int(X), Int(Y)+l J, level Int(Z) The pixel at [Int(X)+1, Int(Y)+I], level Int(Z) The pixel at [Int(X), Int(Y)], level Int(Z)+1 The pixel at [Int(X)+1, Int(Y)], level Int(Z)+1 The pixel at [Int(X), Int(Y)+1], level Int(Z)+1 The pixel at [Int(X)+I, Int(Y)+11, level Iat(Z)+I
The 8 pixels are returned as 4 x 16 bit entries, with X and X+I entries combined hi/lo. For example, if the scaled (X, Y) coordinate was (10.4, 12.7) the fust 4 pixels retumed would be: (10, 12), (11, 12), (10, 13) and (11, 13). When a coordinate is outside the valid range, clients have the choice of edge pixel duplication or returning of a constant color value via the DuplicateEdgePixels and Constant.Pixel registers (only the low 8 bits are used)_ When the Image Pyramid has been constructed, there is a simple mapping from level 0 coordinates to level Z coordinates. The method is simply to shift the X or Y coordinate right by Z bits. This must be done in addition to the number of bits already shifted to retrieve the integer portion of the coordinate (i.e. shifting right FractX and FractY bits for X and Y
ordinates respectively). To find the ImageStart and RowOffset value for a given level of the image pyraniid, the 24-bit ZOffset register is used as a pointer to a Level Information Table. The table is an array of records, each representing a given level of the pyramid, ordered by level number. Each record consists of a 16-bit offset ZOffset from ImageStart to that level of the pyramid (64-byte aligned address as lower 6 bits of the offset are not present), and a 12 bit ZRowOffset for that level. Element 0 of the table would contain a ZOffset of 0, and a ZRowOffset equal to the general register RowOffset, as it simply points to the full sized image. The ZOffset value at element N of the table should be added to ImageStart to yield the effective ImageStart of level N of the image pyramid. The RowOffset value in element N of the table contains the RowOffset value for ievel N. The software running on the CPU must set up the table appropriately before using this addressing mode. The actual address generation is outlined here in a cycle by cycle description:
Load From Cycle Register Address Other Operations 0 - - ZAdr = ShiftRight(Z, FractZ) + ZOffset Zlnt = ShiftRight(Z, FractZ) 1 ZOffset Zadr ZAdr += 2 Ylnt = ShiftRight(Y, FractY) 2 ZRowOffset ZAdr ZAdr += 2 Ylnt = ShiftRight(YInt, Zlnt) Adr = ZOffset + ImageStart 3 ZOffset ZAdr ZAdr += 2 Adr += ZrowOffset * Ylnt Xlnt = ShiftRight(X, FractX) 4 ZAdr ZAdr Adr += ShiftRight(Xlnt, Zlnt) ZOffset += ShiftRight(Xlnt, 1) FIFO Adr Adr += ZrowOffset ZOffset += ImageStart 6 FIFO Adr Adr = (ZAdr * ShiftRight(Yint,1)) + ZOffset 7 FIFO Adr Adr += Zadr 8 FIFO Adr < Cycle 0 for next retrieval>
The address generation as described can be achieved using a single Barrel Shifter, 2 adders, and a single 16x16 multiply/add unit yielding 24 bits. Although some cycles have 2 shifts, they are either the same shift value (i.e. the output of the Barrel Shifter is used two times) or the shift is I bit, and can be hard wired. The following internal registers are required: ZAdr, Adr, Zlnt, Ylnt, XInt, ZRowOffset, and ZlmageStart. The _Int registers only need to be 8 bits maximum, while the others can be up to 24 bits. Since this access method only reads from, and does not write to image pyramids, the CacheGroup2 is used to lookup the Image Pyramid Address Table (via ZAdr). CacbeGroupl is used for lookups to the image pyramid itself (via Adr). The address table is around 22 entries (depending on original image size), each of 4 bytes. Therefore 3 or 4 cache lines should be allocated to CacheGroup2, while as many cache lines as possible should be allocated to CacheGroupl. The timing is 8 cycles for retuming a set of data, assuming that Cycle 8 and Cycle 0 overlap in operation - i.e. the next request's Cycle 0 occurs during Cycle 8. This is acceptable since Cycle 0 has no memory access, and Cycle 8 has no specific operations.
Generation of Coordinates usinz VLIW Vector Processor 74 Sotne functions that are linked to Write Iterators require the X and/or Y
coordinates of the current pixel being processed in part of the processing pipeline. Particular processing may also need to take place at the end of each row, or column being processed. In most cases, the PassX and PassY flags should be sufficient to completely generate all eoordinates. However, if there are special requirements, the following functions can be used. The calculation can be spread over a number of ALUs, for a single cycle generation, or be in a single ALU 188 for a multi-cycle generation Generate Seauential fX, Yl When a process is processing pixels in sequential order according to the Sequential Read Iterator (or generating pixels and writing them out to a Sequential Write Iterator), the following process can be used to generate X. Y coordinates instead of PassX/PassY flags as shown in Fig. 23.
The coordinate generator counts up to ImageWidth in the X ordinate, and once per ImageWidth pixels increments the Y ordinate. The actual process is illustrated in Fig. 24, where the following constants are set by software:
Constant Value K, lmageWidth K2 ImageHeight (optional) The following registers are used to hold temporary variables:
Variable Value Reg, X (starts at 0 each line) Reg, Y (starts at 0) The r+aquirements are summarized as follows:
Requirements *+ + R K LU Iterators General 0 3/4 2 1/2 0 0.
Genetate Vertical Strip X Y) When a process is processing pixels in order to write them to a Venical Strip Write Iterator, and for some reason cannot use the PassX/PassY flags, the process as illustrated in Fig. 25 can be used to gener=ate X, Y coordinates. The coordinate generator simply counts up to ImageWidth in the X ordinate, and once per ImageWidth pixels increments the Y ordinate. The actual process is illustrated in Fig. 26, where the following constants are set by software:
Constant Value Kt 32 K2 ItnageWidth K3 ImageHeight The following registers are used to hold temporary variables:
Variable Value Reg, StartX (starts at 0, and is incremented by 32 once per vertical strip) RegZ X
Reg3 EndX (starts at 32 and is incremented by 32 to a maximum of ImageWidth) once per vertical strip) Reg4 Y
The requirements are summarized as follows:
Requirements *+ + R K LU Iterators General 0 4 4 3 0 0 TOTAL 0 . 4 4 3 0 0 The calculations that occur once per vertical strip (2 additions, one of which has an associated MIN) are not included in the general timing statistics because they are not really part of the per pixel timing. However they do need to be taken into account for the programming of the microcode for the particular function.
Inutee Sensor Interface (ISI 83) The Image Sensor Interface (ISI 83) takes data from the CMOS Image Sensor and makes it available for storage in DRAM. The image sensor has an aspect ratio of 3:2, with a typical resolution of 750 x 500 samples, yielding 375K (8 bits per pixel). Each 2x2 pixel block has the configuration as shown in Fig.
27. The ISI 83 is a state machine that sends control information to the Image Sensor, including frame sync pulses and pixel clock pulses in order to read the image.
Pixels are read from the image sensor and placed into the VLIW Input FIFO 78.
The VLIW is then able to process and/or store the pixels. This is illustrated further in Fig. 28_ The ISI 83 is used in conjunction with a VLIW program that stores the sensed Photo Image in DRAM. Processing occurs in 2 steps:
A small VLIW program reads the pixels from the FIFO and writes them to DRAM
via a Sequential Write Iterator.
The Photo Image in DRAM is rotated 90, 180 or 270 degrees according to the orientation of the camera when the photo was taken.
If the rotation is 0 degrees, then step I merely writes the Photo Iniage out to the final Photo Image location and step 2 is not performed. If the rotation is other than 0 degrees, the image is written out to a temporary area (for example into the Print Image memory area), and then rotated during step 2 into the final Photo Image location. Step I is very simple microcode, taking data from the VLIW Input FIFO 78 and writing it to a Sequential Write Iterator. Step 2's rotation is accomplished by using the accelerated Vark Affine Transform function. The processitig is perfontted in 2 steps in order to reduce design complexity and to re-use the Vark aff ne transform rotate logic already required for images. This is acceptable since both steps are completed in approximately 0.03 seeonds, a time imperceptible to the operator of the Artcam. Even so, the read proccss is sensor speed bound, taking 0_02 seconds to read the full frame, and approxintatety 0.01 seconds to rotate the image.
The orientation is intportant for converting between the sensed Photo Image and the internal fotmat image, since the relative positioning of R, G, and B pixels changes with orientation_. The processed image may also have to be rotated during the Print process in order to be in the correct orientation for printing. The 3D model of the Artcam has 2 image sensors, with their inputs multiplexed to a single ISI 83 (different microcode, but same ACP 31). Since each sensor is a frame store, both images can be taken simultaneously, and then transferred to memory one at a time.
Disolav Controller 88 When the "Take" button on an Artcam is half depressed, the TFT will display the current image from the image sensor (converted via a simple VLIW process). Once the Take button is fully depressed, the Taken Image is displayed. When the user presses the Print button and image processing begins, the TFT is turned off. Once the image has been printed the TFT is turned on again. The Display Controller 88 is used in those Artcam models that incorporate a flat panel display. An example display is a TFT LCD of resolution 240 x 160 pixels. The structure of the Display Controller 88 isi illustrated in Fig. 29. The Display Controller 88 State Machine contains registers that control the tinvng of the Sync Generation, where the display image is to be taken from (in DRAM via the Data cache 76 via a specific Cache Group), and whether the TFT should be active or not (via TFT Enable) at the moment. The CPU can write to these registers via the low speed bus. Displaying a 240 x 160 pixel image on an RGB
TFT requires 3 components per pixel.
The image taken from DRAM is displayed via 3 DACs, one for each of the R, G, and B output signals. At an image refresh rate of 30 frames per second (60 fields per second) the Display Controller 88 requires data transfer rates of:
240x160x3x30=3.5MBpersecond This data rate is low compared to the rest of the system. However it is high enough to cause VLIW programs to slow down during the intensive image processing. The general principles of TFT
operation should reflect this.
Image Data Formats As stated previously, the DRAM Interface 81 is responsible for interfacing between other client portions of the ACP chip and the RAMBUS DRAM. In effect, each module within the DRAM
Interface is an address generator.
There are three logical types of images manipulated by the ACP_ They are:
-CCD Image, which is the Input Image captured from the CCD.
-Internal Image fotmat - the Image format utilised internally by the Artcam device.
Print Image - the Output Itnage format printed by the Artcam These images are typically different in color space, resolution, and the output & input color spaces which can vary from camera to camera. For example, a CCD image on a low-end camera may be a different resolution, or have different color characteristics from that used in a high-end camera However all internal image formats are the same format in tertns of color space across all canteras.
In addition, the three image types can vary with respect to which direction is 'up'. The physical orientation of the camera causes the notion of a portrait or landscape image, and this must be maintained throughout processing. For this reason, the internal image is always oriented correctly, and rotation is performed on iniages obtained from the CCD and during the print opetaiion.
CCD ImaQe Orzattization Although many different CCD image sensors could be utilised, it will be assumed that the CCD itself is a 750 x 500 image sensor, yielding 375,000 bytes (8 bits per pixel). Each 2x2 pixel block having the configuration as depicted in Fig. 30.
A CCD httage as stored in DRAM has consecutive pixels with a given line contiguous in tnemory. Each line is stored one after the other. The image sensor Interface 83 is responsible for taking data from the CCD and storing it in the DRAM correctly oriented. Thus a CCD image with rotation 0 degrees has its first line G, R. G, R, G, R... and its second line as B, G, B, G. B, G.... If the CCD image should be portrait, rotated 90 degrees, the first line will be R, G, R, G, R, G and the second line G, B, G, B, G, B...etc.
Pixels are stored in an interleaved fashion since all color components are required in order to convert to the internal image fotmat.
It should be noted that the ACP 31 makes no assumptions about the CCD pixel format, since the actual CCDs for imaging may vary from Artcam to Arccam, and over time. All processing that takes place via the hardware is controlled by major microcode in an attempt to extend the usefulness of the ACP 31.
Internal Imaee Organization Internal images typically consist of a number of channels. Vark images can include, but are not limited to:
Lab Laba LabA
aA
L
L, a and b correspond to components of the Lab color space, a is a matte channel (used for compositing), and A is a bump-map channel (used during brushing, tiling and illuminating).
The VLIW processor 74 requires images to be organized in a planar configuration. Thus a Lab image would be stored as 3 separate blocks of memory:
one block for the L channel, one block for the a channel, and one block for the b channel Within each channel block, pixels are stored contiguously for a givcn row (plus some optional padding bytes), and rows are stored one after the other.
Turning to Fig. 31 there is illustrated an example form of storage of a logical itnage 100. The logical image 100 is stored in a piatuv fashion having L 101, a 102 and b 103 color components stored one after another.
Alternatively, the logical image 100 can be stored in a compressed format having an uncompressed L component 101 and compressed A and B components 105, ]06.
Turning to Fig. 32, the pixels of for line n 110 are stored together before the pixels of for line and n + 1(111).
With the image being stored in contiguous memory within a single channel.
In the 8MB-ntenmry model, the final Print Image after all processing is finished, needs to be compressed in the chrominance channels. Compression of chrominance channels can be 4:1, causing an overall compression of 12:6, or 2:1.
Other than the final Print Image, images in the Artcam are typically not compressed. Becaase of tnemory constraints, software may choose to comptess the final Print hnage in the chrominance channels by scaling each of these channels by 2:1. If this has been done, the PRIWT Vark function call utilised to print an image must be told to treat the specified chrominance channels as compressed. The PRINT function is the only function that knows how to deal with compressed chrominance, and even so, it only deals with a fixed 2:1 compression ratio.
Although it is possible to compress an image and then operate on the compressed image to create the final print image, it is not recommended due to a loss in resolution. In addition, an image should only be compressed once -as the final stage before printout. While one compression is virtually undetectable, multiple compressions may cause substantial image degradation.
Clip image Organization Clip images stored on Artcards have no explicit support by the ACP 31 _ Software is responsible for taking any images from the current Artcard and organizing the data into a form known by the ACP. If images are stored compressed on an Artcard, software is responsible for decompressing them, as there is no specific hardware support for decompression of Artcard images.
Imaee Pyramid Organization During brushing, tiling, and warping prmesses utilised to manipulate an image it is often necessary to compute the average color of a particular area in an image. Rather than calculate the value for each area given, these functions make use of an image pyramid. As illustrated in Fig. 33, an image pyramid is effectively a multi-resolutionpixel- map. The original image 115 is a 1:1 representation. Low-pass fiitering and sub-sampling by 2:1 in each dimension produces an image Ni the original size 116. This process continues until the entire image is represented by a single pixel. An image pyramid is constructed from an original internal format image, and consumes 1/3 of the size taken up by the original image (1/4 + 1/16 + 1/64 + ...). For an original image of 1500 x 1000 the cotresponding image pyramid is approximately rhMB. An image pyramid is constructed by a specific Vark function, and is used as a parameter to other Vark functions.
Print Image Organization 'fhe entire processed image is required at the same time in order to print it.
However the Print Image output can comprise a CMY dithered image and is only a transient image format, tucd within the Print Image functionality.
However, it should be noted that color conversion will need to take place from the internal color space to the print color space. In addition, color conversion can be tuned to be different for different print rolls in the camera with different ink characteristics e.g. Sepia output can be accomplished by using a specific sepia toning Aricard, or by using a sepia tone print-roll (so all Artcards will work in sepia tone).
Color Spaces As noted previously there are 3 color spaces used in the Artcam, corresponding to the different image types.
The ACP has no direct knowledge of specific color spaces. Instead, it relies on client color space conversion tables to convert between CCD, intecnal, and printer color spaces:
CCD:RGB
Internal:Lab Printer.CMY
Removing the color space conversion from the ACP 31 allows:
-Different CCDs to be used in different cameras -Different inks (in different print rolls over time) to be used in the same camera -Separation of CCD selection from ACP design path -A well defined interoal color space for accurate color processing Artcard Interface 87 The Artcaid Interfxe (AI) takes data from the linear image Sensor while an Artcard is passing under it, and makes that data available for storage in DRAM. The image sensor produces 11,000 8-bit samples per scanline, sampling the Artcard at 4800 dpi. The AI is a state machine that sends control information to the linear sensor, including LineSync pulses and PixelClock pulses in order to read the intage. Pixels are read from the linear sensor and placed into the VLIW Input FIFO 78. The VLIW is then able to process and/or store the pixels.
The Al has only a few registers:
Register Name Description NumPixels The number of pixels in a sensor line (approx 'I 1,000) Status The Print Head Interface's Status Register PixeisRemaining The number of bytes remaining in the current line Actions Reset A write to this register resets the Al, stops any scanning, and loads all registers with 0.
Scan A write to this register with a non-zero value sets the Scanning bit of the Status register, and causes the Artcard Interface Scan cycle to start.
A write to this register with 0 stops the scanning process and clears the Scanning bit in the Status register.
The Scan cycle causes the AI to transfer NumPixels bytes from the sensor to the VLIW Input FIFO 78, producing the PixelClock signals appropriately. Upon completion of NumPixels bytes, a LineSync putse is given and the Scan cycle restarts.
The PixelsRemaining register holds the number of pixels remaining to be read on the current scanline.
Note that the CPU should clear the VLIW Input FIFO 78 before initiating a Scan. The Status register has bit interpretations as follows:
Bit Name Bits Description Scanning 1 If set, the Al is currently scanning, with the number of pixels remaining to be transferred from the current line recorded in PixelsRemaining.
If clear, the Al is not currently scanning, so is not transferring pixels to the VLIW Input FIFO 78.
Artcard Interface (AIl 87 The Artcard Interface (Al) 87 is responsible for taking an Artcard image from the Artcard Reader 34 , and decoding it into the original data (usually a Vark script)_ Specifically, the Al 87 accepts signals from the Artcard scanner linear CCD 34, detects the bit pattern printed on the card, and converts the bit pattern into the original data, correcting read errors.
With no Artcard 9 inserted, the image printed from an Artcam is simply the sensed Photo Iinage cleaned up by any standard image processing routines. The Artcard 9 is the means by which users are able to modify a photo before printing it out. By the simple task of inserting a specific Artcard 9 into an Artcam, a user is able to define complex image processing to be performed on the Photo Image.
With no Artcard inserted the Photo Image is processed in a standard way to create the Print Image. When a single Artcard 9 is inserted into the Artcam, that Artcard's effect is applied to the Photo Image to generate the Print lmage.
When the Artcard 9 is removed (ejected), the printed image reverts to the Photo Image processed in a standard way.
When the user presses the button to eject an Artcard, an event is placed in the event queue maintained by the operating system running on the Artcam Central Processor 31. When the event is processed (for example after the current Print has occurred), the following things occur.
If the current Artcard is valid, then the Print Image is marked as invalid and a'Process Standard' event is placed in the event queue. When the event is eventually processed it will perform the standard image processing operations on the Photo Image to produce the Print Image.
The motor is started to eject the Artcard and a time-specific 'Stop-Motor' Event is added to the event queue.
Insertingan Artcand When a user inserts an Artcard 9, the Artcard Sensor 49 detects it notifying the ACP72. This results in the software inserting an 'Artcard Inserted' event into the event queue. When the event is processed several things occur The current Artcard is marked as invalid (as opposed to 'none').
The Print Image is marked as invalid.
The Artcard motor 37 is started up to load the Artcard The Artcard Interface 87 is instructed to read the Artcard The Artcard Interface 87 accepts signals from the Artcard scanner linear CCD
34, detects the bit pattem printed on the cand, and cotrects errors in the detected bit pattern, producing a valid Artcard data block in DRAM.
Reading Data from the Artcard CCD - General Considerations As illusttaied in Fig. 34, the Data Card reading process has 4 phases operated while the pixel data is read from the card. The phases are as follows:
Phase 1. Detect data area on Artcard Phase 2. Detect bit pattern from Artcard based on CCD pixels, and write as bytes.
Phase 3. Descramble and XOR the byte-pattern Phase 4. Decode data (Reed-Solomon decode) As illustrated in Fig. 35, the Artcard 9 must be sampled at least at double the printed resolution to satisfy Nyquist's Theorem. In practice it is better to sample at a higher rate than this. Preferably, the pixels are sampled 230 at 3 times the resolution of a printed dot in each dimension, requiring 9 pixels to define a single dot. Thus if the resolution of the Artcard 9 is 1600 dpi, and the resolution of the sensor 34 is 4800 dpi, then using a 50tnm CCD image sensor results in 9450 pixels per column. Therefore if we require 2MB of dot data (at 9 pixels per dot) then this requires 2MB*8*9/9450 = 15,978 columns = approxitnately 16,000 columns. Of course if a dot is not exactly aligned with the sampling CCD the worst and most likely case is that a dot will be sensed over a 16 pixel area (4x4) 231.
An Artcard 9 may be slightly warped due to heat damage, slightly rotated (up to, say I degree) due to differences in insertion into an Ancard reader, and can have slight differences in true data rate due to fluctuations in the speed of the reader motor 37. These changes will cause columns of data from the card not to be read as corresponding colutnns of pixel data. As illustrated in Fig. 36, a I degree rotation in the Artcard 9 can cause the pixels from a column on the card to be read as pixels across 166 columns:
Finally, the Artcard 9 should be read in a reasonable amount of time with respect to the human operator. The data on the Artcard covers most of the Artcard surface, so timing concems can be limited to the Aitcard data itself. A
reading time of 1.5 seconds is adequate for Artcard reading.
The Artcard should be loaded in 1.5 seconds. Therefore all 16,000 columns of pixel data must be read from the CCD 34 in 1.5 second, i.e. 10,667 columns per second. Therefore the time available to read one column is 1/10667 seconds, or 93,747ns. Pixel data can be written to the DRAM one column at a time, completely independently from any processes that are reading the pixel data.
The time to write one column of data (9450/2 bytes since the reading can be 4 bits per pixel giving 2 x 4 bit pixels per byte) to DRAM is reduced by using 8 cache lines. If 4lines were written out at one time, the 4 banks can be written to independenUy, and thus overlap latency reduced. Thus the 4725 bytes can be written in I 1,840ns (4725/128 * 320ns). Thus the time taken to write a given column's data to DRAM uses just under 13% of the available bandwidth.
DecodinQ an Artcard A simple look at the data sizes shows the impossibility of fitting the process into the 8MB of inemory 33 if the entire Artcard pixel data (140 MB if each bit is read as a 3x3 array) as read by the linear CCD 34 is kept. For this reason, the reading of the linear CCD, decoding of the bitmap, and the un-bitmap process should take place in real-time (while the Artcard 9 is traveling past the linear CCD 34), and these processes must effectively work without having entire data stores available.
When an Artcard 9 is inserted, the old stored Print image and any expanded Photo Image becomes invalid.
The new Artcard 9 can contain directions for creating a new image based on the currendy r.aptured Photo Image. The old Print Image is invalid, and the area holding expanded Photo Image data and image pyramid is invalid, leaving more than 5MB that can be used as scratch memory during the read process. Strictiy speaking, the iMB area whete the Artcard raw data is to be written can also be used as scratch data during the Artcard read process as long as by the time the final Reed-Solomon decode is to occur, that 1MB area is free again. The reading process described here does not make use of the extra 1MB area (except as a final destination for the data).
It should also be noted that the unscrambling process requires two sets of 2MB
areas of memory since unscrambling cannot occur in place. Fortunately the 5MB scratch area contains enough space for this process.
Turning now to Fig. 37, there is shown a flowchart 220 of the steps necessary to decode the Artcard data.
These steps include reading in the Artcard 221, decoding the read data to produce corresponding encoded XORed scrambled bitmap data 223. Next a checkerboard XOR is applied to the data to produces encoded scrambled data 224.
This data is then unscrambled 227 to produce data 225 before this data is subjected to Reed-Solomon decoding to produce the original raw data 226. Alternatively, unscrambling and XOR process can take place together, not requiring a separate pass of the data. Each of the above steps is discussed in further detail hereinafter. As noted previously with reference to Fig. 37, the Artcard Interface, therefore, has 4 phases, the first 2 of which are time-critical, and must take place while pixel data is being read from the CCD:
Phase I. Detect data area on Artcard Phase 2. Detect bit pattern from Artcard based on CCD pixels, and write as bytes.
Phase 3. Descramble and XOR the byte-pattern Phase 4. Decode data (Reed-Solomon decode) The four phases are deseribed in more detail as foliows:
Phase 1. As the Artcard 9 moves past the CCD 34 the Al must detect the start of the data area by robustly detecting special targets on the Artcard to the left of the data area. If these cannot be detected, the card is marked as invalid. The detection must occur in real-time, while the Artcard 9 is moving past the CCD 34.
If necessary, rotation invariance can be provided. In this case, the targets are repeated on the right side of the Artcard, but relative to the bottom right corner instead of the top corncr. In this way the targets end up in the correct orientation if the card is inserted the "wrong" way. Phase 3 below can be altered to detect the orientation of the data, and account for the potential rotation.
Phase 2. Once the data area has been determined, the main read process begins, placing pixel data from the CCD into an 'Artcard data window', detecting bits from this window, assembling the detected bits into bytes, and constructing a byte-image in DRAM. This must all be done while the Artcard is moving past the CCD.
Phase 3. Once all the pixels have been read from the Artcard data area, the Artcard motor 37 can be stopped, and the byte image descrambled and XORed. Although not requiring real-time performance, the process should be fast enough not to annoy the human operator. The process must take 2 MB of scrambled bit-image and write the unscrambled/XORed bit-image to a separate 2MB image.
Phase 4. The final phase in the Artcard read process is the Reed-Solomon decoding process, where the 2MB
bit-image is decoded into a IMB valid Arteard data area. Again, while not requiring real-titne performance it is still necessary to decode quickly with regard to the hurnan operator. If the decode process is valid, the card is niarked as valid. If the decode failed, any duplicates of data in the bit-image are attempted to be decoded, a process that is repeated until success or until there are no more duplicate images of the data in the bit image.
The four phase process described requires 4.5 MB of DRAM. 2MB is reserved for Phase 2 output, and 0.5MB
is reserved for scratch data during phases 1 and 2. The remaining 2MB of space can hold over 440 columns at 4725 byes per column. In practice, the pixel data being read is a few columns ahead of the phase I algorithm, and in the worst case, about 180 columns behind phase 2, comfortably inside the 440 column limit_ A description of the actual operation of each phase will now be provided in greater detail_ Phase 1- Detect data area on Artcard This phase is concerned with robustly detecting the left-hand side of the data area on the Artcard 9. Accurate detection of the data area is achieved by accurate detection of special targets printed on the left side of the card. These targets are especially designed to be easy to detect even if rotated up to I
degree.
Turning to Fig_ 38, there is shown an enlargetnent of the left hand side of an Artcard 9. The side of the card is divided into 16 bands, 239 with a target eg. 241 located at the center of each band. The bands are logical in that there is no line drawn to separate bands. Turning to Fig. 39, there is shown a single target 241. The target 241, is a printed black square containing a single white dot. The idea is to detect firstly as many targets 241 as possible, and then to join at least 8 of the detected white-dot locations into a single logical straight line. If this can be done, the start of the data area 243 is a fixed distance from this logical line. If it cannot be done, then the card is rejected as invalid.
As shown in Fig. 38, the height of the card 9 is 3150 dots. A target (TargetO) 241 is placed a fixed distance of 24 dots away from the top left corner 244 of the data area so that it falls well within the first of 16 equal sized regions 239 of 192 dots (576 pixels) with no target in the final pixel region of the card. The target 241 must be big enough to be easy to detect, yet be small enough not to go outside the height of the region if the card is rotated 1 degree. A
suitable size for the target is a 31 x 31 dot (93 x 93 sensed pixels) black square 241 with the white dot 242.
At the worst rotation of I degree, a I column shift occurs every 57 pixels.
Therefore in a 590 pixel sized band, we cannot place any part of our symbol in the top or bottom 12 pixels or so of the band or they could be detected in the wrong band at CCD read time if the card is worst case rotated.
Therefore, if the black part of the rectangle is 57 pixels high (19 dots) we can be sure that at least 9.5 black pixels will be read in the same column by the CCD (worst case is half the pixels are in one column and half in the next). To be sure of reading at least 10 black dots in the same column, we must have a height of 20 dots. To give room for erroneous detection on the edge of the start of the black dots, we increase the number of dots to 31, giving us 15 on either side of the white dot at the target's local coordinate (15, 15). 31 dots is 91 pixels, which at tnost suffers a 3 pixel shift in column, easily within the 576 pixel band.
Thus each target is a block of 31 x 31 dots (93 x 93 pixels) each with the composition:
15 columns of 31 black dots each (45 pixel width columns of 93 pixels).
I column of 15 black dots (45 pixels) followed by I white dot (3 pixels) and tben a further 15 black dots (45 pixels) 15 columns of 31 black dots each (45 pixel width columns of 93 pixels) Detect targets Targets are detected by reading columns of pixels, one column at a time rather than by detecting dots. It is necessary to look within a given band for a number of columns consisting of large numbers of contiguous black pixels to btrild up the left side of a targeL Next, it is expected to see a white region in the center of further black columns, and finally the black columns to the left of the target center.
Eight cache lines are required for good cache performance on the reading of the pixels. Each logical read fills 4 cache lines via 4 sub-reads while the other 4 cache-lines are being used.
This effectively uses up 13% of the available DRAM bandwidth.
As illustrated in Fig. 40, the detection mechanism FIFO for detecting the targets uses a filter 245, run-length encoder 246, and a FIFO 247 that requires special wiring of the top 3 elenients (S1, S2, and S3) for random access.
The columns of input pixels are processed one at a time until either all the targets are found, or until a specified number of columns have been processed. To process a column, the pixels are read from DRAM, passed dvough a filter 245 to detect a 0 or 1, and then run length encoded 246. The bit value and the number of contiguous bits of the same value are placed in FIFO 247. Each entry of the FIFO 249 is in 8 bits, 7 bits 250 to hold the run-length, and I bit 249 to hold the value of the bit detected.
The run-length encoder 246 only encodes contiguous pixels within a 576 pixel (192 dot) region.
The top 3 elements in the FIFO 247 can be accessed 252 in any random order.
The run lengths (in pixels) of these entries are filtered into 3 values: short, mediunr, and long in accordance with the following table:
Short Used to detect white dot. RunLength < 16 Medium Used to detect runs of black above or below the 16<= RunLength < 48 white dot in the center of the target.
Long Used to detect run lengths of black to the left and RunLength >= 48 right of the center dot in the target.
I.ooking at the top three entries in the FIFO 247 there are 3 specific cases of interest:
Case I S1 = white long We have detected a black column of the target to S2 = black long the left of or to the right of the white center dot.
S3 = white medium/long Case 2 S I= white long If we've been processing a series of columns of S2 = black medium Case Is, then we have probably detected the S3 = white short white dot in this column_ We know that the next Previous 8 columns were Case I entry will be black (or it would have been included in the white S3 entry), but the number of black pixels is in question. Need to verify by checking after the next FIFO advance (see Case 3).
Case 3 Prev = Case 2 We have detected part of the white dot. We S3 = black med expect around 3 of these, and then some more columns of Case 1.
Preferably, the following information per region band is kept:
TargetDetected I bit BlackDetectCount 4 bits WhiteDetectCount 3 bits PrevColumnStartPixel 15 bits TargetColumn ordinate 16 bits (15:1) TargetRow ordinate 16 bits (15:1) TOTAL 7 bytes (rounded to 8 bytes for easy addressing) Given a total of 7 bytes. It makes address generation easier if the total is assumed to be 8 bytes. Thus 16 entries requires 16 * 8 = 128 bytes, which fits in 4 cache lines_ The address range should be inside the scratch 0.5MB
DRAM area since other phases make use of the remaining 4MB data area.
When beginning to process a given pixel column, the register value S2StartPixel 254 is reset to 0. As entries in the FIFO advance from S2 to S1, they are also added 255 to the existing S2StartPixel value, giving the exact pixel position of the run currently defined in S2. Looking at each of the 3 cases of interest in the FIFO, S2StartPixei can be used to determine the start of the black area of a target (Cases I and 2), and also the start of the white dot in the center of the target (Case 3). An algorithm for processing columns can be as follows:
1 TargetDetected[0-15] := 0 BlackDetectCount{0-151 := 0 WhiteDetectCount[0-15] := 0 TargetRow[0-15] := 0 TargetColumn[0-151 := 0 PrevColStartPixel[0-15] := 0 CurrentColumn = 0 2 Do ProcessColumn 3 CurrentColumn++
4 If (CurrentColumn <= LastValidColumn) Goto 2 The steps involved in the processing a column (Process Column) are as follows:
I S2StartPixel := 0 FIFO := 0 BlackDetectCount := 0 WhiteDetectCount 0 ThisColumnDetected := FAISE
PrevCaseWasCase2 := FALSE
2 If (! TargetDetected[Target]) & (! ColumnDetected[Target]) ProcessCases Endlf 3 PrevCaseWasCase2 := Case=2 4 Advance FIFO
The processing for each of the 3 (Process Cases) cases is as follows:
Case 1:
BlackDetectCount[target] < 8 ABS(S2StartPixel - PrcvColStartPixel[Target]) OR If (0<== < 2) WhiteDetectCount[Target] = 0 BlackDetectCount[Targct]++ (max value =8) Else BlackDetectCount[Target] I
WhiteDetectCount[Target) := 0 Endif PrevCo]StartPixel[Target] = S2StartPixel ColumnDetected[Target] := TRUE
BitDetected = 1 BlackDetectCount(target] >= 8 PrevColStartPixel[Target) := S2StartPixel WhiteDetectCount[Target] != 0 ColumnDetected[Target] := TRUE
BitDetected = I
TargetDetected[Target] := TRUE
TargetColumn[Target] := CurrentColumn - 8 -(WhiteDetectCount[Target]/2) Case 2:
No special processing is recorded except for setting the 'PrevCaseWasCase2' flag for identifying Case 3 (see Step 3 of processing a column described above) Case 3:
PrevCaseWasCase2 = TRUE If (WhiteDetectCount[Target] < 2) BlackDetectCount[Target] >= 8 TargetRow[Target) = S2StartPixel +
(S2R,,,,L~r&/2) WhiteDetectCount=l Endif := ABS(S2StartPixel - PrevColStartPixel[Target)) If (0<=- < 2) WhiteDetectCount[Target)++
Else WhiteDetectCount[Targetj := I
Endif PrevColStartPixel[Target] := S2StartPixel ThisColumnDetected := TRUE
BitDetected = 0 At the end of processing a given column, a comparison is made of the current column to the maximum number of columns for target detection. If the number of columns allowed has been exceeded, then it is necessary to check how many targets have been found. If fewer than 8 have been found, the card is considered invalid.
Process targets After the targets have been detected, they should be processed_ All the targets may be available or rnerely some of them. Some targets niay also have been erroneously detected.
This phase of processing is to determine a mathematical line that passes through the center of as many targets as possible. The more targets that the line passes through, the more confident the target position has been found_ The limit is set to be 8 targets. If a line passes through at least 8 targets, then it is taken to be the right one.
It is all right to take a brute-force but straightforward approach since there is the time to do so (see below), and lowering complexity makes testing easier. It is necessary to determine the line between targets 0 and 1(if both targets are considered valid) and then determine how many targets fall on this line.
Then we determine the line between targets 0 and 2, and repeat the process. Eventually we do the same for the line between targets 1 and 2, 1 and 3 etc. and finally for the line between targets 14 and 15. Assuming all the targets have been found, we need to perform 15+14+13+ ...= 90 sets of calculations (with each set of calculations requiring 16 tests = 1440 actual calculations), and choose the line which has the maxirnum number of targets found along the line.
The algorithm for target location can be as follows:
TargetA := 0 MaxFound := 0 BestLine := 0 While (TargetA < 15) If (TargetA is Valid) Target8 = TargetA + 1 While (TargetB<= 15) If (TargetB is valid) CurrentLine :=1ine between TargetA and TargetB
TargetC := 0;
While (TargetC <= 15) If (TargetC valid AND TargetC on line AB) TargetsHit++
Endlf If (TargetsHit > MaxFound) MaxFound := TargetsHit BestLine CurrentLine Endif TargetC++
EndWhile Endlf TargetB ++
EndWhile Endlf TargetA++
EndWhile If (MaxFound < 8) Card is Invalid Else Stote expected centroids for rows based on BestLine Endlf As illustrated in Fig. 34, in the algorithm above, to determine a CurrentLine 260 from Target A 261 and target B. it is necessary to calculate Arow (264) & Acolumn (263) between targets 261, 262, and the location of Target A. It is then possible to move from Target 0 to Target I etc. by adding Orow and Ocolumn. The found (if actually found) location of target N can be compared to the calculated expected position of Target N on the line, and if it falls within the tolerance, then Target N is determined to be on the line.
To calculate Arow & Acolumn:
Arow = (rowTwA - row Tvs)/(B-A) Acolumn = (columnT.,1,~,A- columtrrõwd3)/(B-A) Then we calculate the position of Target0:
row = rowTargetA - (A * Mow) column = columnTargetA - (A * Acolunm And compare (row, column) against the actual rowT.,o and columnT,,.D. To move from one expected target to the next (e.g_ from TargetO to Targetl ), we simply add Arow and Acolumn to row and column respectively. To check if each target is on the line, we must calculate the expected position of Target0, and then perform one add and one comparison for each target ordinate_ At the end of comparing all 16 targets against a maximum of 90 lines, the result is the best line through the valid targets. If that line passes through at least 8 targets (i.e. MaxFound >= 8), it can be said that enough targets have been found to form a line, and thus the card can be processed. If the best line passes through fewer than 8, then the card is considered invalid.
The resulting algorithm takes 180 divides to calculate Arow and Acolumn, 180 multiply/adds to calculate targetO position, and then 2880 adds/comparisons. The time we have to perform this processing is the time taken to read 36 columns of pixel data = 3,374,892ns. Not even accounting for the fact that an add takes less time than a divide, it is necessary to perform 3240 mathematical operations in 3,374,892ns. That gives approximately I040ns per operation, or 104 cycles. The CPU can therefore safely perfonm the entire processing of targets, reducing complexity of design.
Update centroids based on data edge border and clockmarks Step 0: Locate the data area From Target 0(241 of Fig. 38) it is a predetermined fixed distance in rows and columns to the top left border 244 of the data area, and then a further I dot column to the vertical clock marks 276. So we use TargetA, Arow and Acolumn found in the previous stage (Arow and Acolumn refer to distances between targets) to calculate the centroid or expected location for TargetO as described previously.
Since the fixed pixel offset from TargetO to the data area is related to the distance between targets (192 dots between targets, and 24 dots between TargetO and the data area 243), simply add Arow/8 to TargetO's centroid column coordinate (aspect ratio of dots is 1: I). Thus the top co-ordinate can be defined as:
(columnD.c.,,,,,,,,T%, = columnTõ,,a + (Arow/8) (rowp,,,cd,,,,,,,Tw = rowT~,,O + (Acolumn /8) Next Arow and Acolumn are updated to give the number of pixels between dots in a single column (instead of between targets) by dividing them by the number of dots between targets:
Arow = Arow/192 Acolutntt = Ocolutnn /192 We also set the currentColutnn register (see Phase 2) to be -1 so that after=
step 2, when phase 2 begins, the cutretttColutnn register will increment from -1 to 0.
Step 1: Write out the initial centroid deltas (A) and bit history This simply involves writing setup infotmation required for Phase 2.
This can be achieved by writing Os to all the Arow and Acolumn entries for each row, and a bit history. The bit history is actually an expected bit history since it is known that to the left of the clock mark column 276 is a border column 277, and before that, a white area. The bit history therefore is 011, 010, 011, 010 etc.
Steo 2: Undate the centroids based on actual pixels read.
The bit history is set up in Step 1 according to the expected clock marks and data border_ The actual centroids for each dot row can now be more accurately set (they were initially 0) by comparing the expected data against the actual pixel values. The centroid updating mechanism is achieved by simply performing step 3 of Phase 2.
Phase 2- Detect bitpattern from Artcard based on pixels read, and write as bytes.
Since a dot from the Artcard 9 requires a minimum of 9 sensed pixels over 3 columns to be represented, there is little point in performing dot detection calculations every sensed pixel column. It is better to average the time required for processing over the average dot occurrence, and thus make the most of the available processing titne. This allows processing of a column of dots from an Artcard 9 in the time it takes to read 3 columns of data from the Artcard.
Although the most likely case is that it takes 4 columns to represent a dot, the 4~' column will be the last column of one dot and the first column of a next dot. Processing should therefore be limited to only 3 columns.
As the pixels from the CCD are written to the DRAM in 13% of the time available, 83% of the time is available for processing of I column of dots i.e. 83% of (93,747*3) = 83% of 281,241 ns = 233,430ns.
In the available time, it is necessary to detect 3150 dots, and write their bit values into the raw data area of memory. The processing therefore requires the following steps:
For each coltunn of dots on the Artcard:
Step 0: Advance to the next dot eofumn Step 1: Detect the top and bottom of an Artcard dot column (check clock marks) Step 2: Process the dot column, detecting bits and storing them appropriately Step 3: Update the centroids Since we are processing the Artcard's logical dot columns, and these may shift over 165 pixels, the worst case is that we cannot process the first column until at least 165 columns have been read into DRAM. Phase 2 would therefore finish the same amount of time after the read process had terminated. The worst case time is: 165 * 93,747ns 15,468,255ns or 0.015 seconds.
Step 0: Advance to the next dot coltunn In order to advance to the next column of dots we add Arow and t,column to the dotColumnTop to give us the centroid of the dot at the top of the column. The fust time we do this, we are currently at the clock marks column 276 to the left of the bit image data area, and so we advance to the first column of data. Since Arow and Acolumn refer to distance between dots within a column, to move between dot columns it is necessary to add Orow to colurrtn&w-t,,,,,,,Tp and Acolumn to rowdc.I,,,,,,,T,.
To keep track of what column number is being processed, the column number is recorded in a register called CurrentColumn. Every time the sensor advances to the next dot column it is necessary to increment the CurrentColumn register. The first time it is incremented, it is incremented from -1 to 0 (see Step 0 Phase I). The CurrentColumn register determines when to terminate the read process (when reaching maxColumns), and also is used to advance the DataOut Pointer to the next column of byte information once all 8 bits have been written to the byte (once every 8 dot columns). The lower 3 bits determine what bit we're up to within the cun-ettt byte. It will be the sanie bit being written for the whole colttmrt.
Step 1: Detect the tqp and bottom of an Artcard dot column.
In order to process a dot column from an Artcard, it is necessary to detect the top and bottom of a colutttn_ The column should fotm a straight line between the top and bottom of the column (except for local warping etc.).
Initially dotColumnTop points to the clock mark column 276. We simply toggle the expected value, write it out into the bit history, and move on to step 2, whose first task will be to add the Arow and Acolumn values to dotColumnTop to arrive at the first data dot of the column.
Stea 2: Process an Artcard's dot column Given the centroids of the top and bottom of a column in pixel coordinates the column should form a straight line between them, with possible minor variances due to warping etc_ Assuming the processing is to start at the top of a column (at the top centroid coordinate) and move down to the bottom of the column, subsequent expected dot centroids are given as:
rowmx, = row + Orow column. = colutnn + Acolumn This gives us the address of the expected centroid for the next dot of the column However to account for local warping and error we add another Arow and Acolumn based on the last time we found the dot in a given row. In this way we can account for small drifts that accumulate into a maximum drift of some percentage from the straight line joining the top of the column to the bottom.
We therefore keep 2 values for each row, but store them in separate tables since the row history is used in step 3 of this phase.
* Arow and Acolumn (2 @ 4 bits each = I byte) =
* row history (3 bits per row, 2 rows are stored per byte) For each row we need to read a Arow and Acolumn to determine the change to the centroid. Tfte read process takes 5% of the bandwidth and 2 cache lines:
76*(3150/32) + 2*3150 = 13,824ns = 5% of bandwidth Once the centroid has been detertnined, the pixels around the centroid need to be examined to detect the status of the dot and hence the value of the bit. In the worst case a dot covers a 4x4 pixel area. However, thanks to the fact that we are sampling at 3 times the resolution of the dot, the number of pixels required to detect the status of the dot and hence the bit value is much less than this. We only require access to 3 columns of pixel columns at any one time.
In the worst case of pixel drift due to a 1% rotation, centroids will shift I
column every 57 pixel rows, but since a dot is 3 pixels in diameter, a given column witl be valid for 171 pixel rows (3*57). As a byte contains 2 pixels, the number of bytes valid in each buffered read (4 cache lines) will be a worst case of 86 (out of 128 read).
Once the bit has been detected it must be written out to DRAM. We store the bits from 8 columns as a set of contiguous bytes to mininuze DRAIvi delay. Since all the bits from a given dot column will correspond to the next bit position in a data byte, we can read the old value for the byte, shift and OR
in the new bit, and write the byte back.
The read / shift&OR I write process requires 2 cache lines.
We need to read and write the bit history for the given row as we update it We only require 3 bits of history per row, ailowing the storage of 2 rows of history in a single byte. The read / shift&OR / write process requires 2 cache lines.
The total bandwidth required for the bit detection and storage is summarised in the following table:
Read centroid A 5%
Read 3 columns of pixel data 19%
Read/Write detected bits into byte buffer 10%
Read/Write bit history 5%
TOTAL 39%
Detecting a dot The process of detecting the value of a dot (and hence the value of a bit) given a centroid is accomplished by examining 3 pixel values and getting the result from a lookup table. The process is fairly simple and is illustrated in Fig. 42. A dot 290 has a radius of about 1.5 pixels. Therefore the pixel 291 that holds the centroid, regardless of the actual position of the centroid within that pixel, should be 100g'~ of the dot's value. If the centroid is exactly in the center of the pixel 291, then the pixels above 292 & below 293 the centroid's pixel, as well as the pixels to the left 294 & right 295 of the centroid's pixel will contain a majority of the dot's value. The further a centroid is away from the exact center of the pixel 295, the more likely that more than the center pixel will have 100% coverage by the dot.
Although Fig. 42 only shows centroids differing to the left and below the center, the same relationship obviously holds for centroids above and to the right of center. center. In Case 1, the centroid is exactly in the center of the middle pixel 295. The center pixel 295 is completely covered by the dot, and the pixels above, below, left, and right are also well covered by the dot. In Case 2, the centroid is to the left of the center of the middle pixel 291. The center pixel is still completely covered by the dot, and the pixel 294 to the left of the center is now completely covered by the dot The pixels above 292 and below 293 are still well covered. In Case 3, the centroid is below the center of the middle pixel 291. The center pixel 291 is still completely covered by the dot 291, and the pixel below center is now completely covered by the dot. The pixels left 294 and right 295 of center are still well covered. In Case 4, the centroid is left and below the center of the middle pixel. The center pixel 291 is still completely covered by the dot, and both the pixel to the left of center 294 and the pixel below center 293 are completely covered by the dot.
The algorithm for updating the centroid uses the distance of the centroid from the center of the middle pixel 291 in order to select 3 representative pixels and thus decide the value of the dot:
Pixel 1: the pixel containing the centroid Pixel 2: the pixel to the left of Pixel I if the centroid's X coordinate (column value) is <'h, otherwise the pixel to the right of Pixel 1.
Pixel 3: the pixel above pixel 1 if the centroid's Y coordinate (row value) is < th., otherwise the pixel below Pixel 1.
As shown in Fig. 43, the value of each pixel is output to a pre-calculated lookup table 301. T7te 3 pixels are fed into a 12-bit lookup table, which outputs a single bit indicating the value of the dot - on or off. The lookup table 301 is constructed at chip definition time, and can be compiled into about 500 gates. The lookup table can be a simple threshold table, with the exception that the center pixel (Pixel 1) is weighted more heavily.
Step 3: U ate the centroid ds for each row in the column The idea of the As processing is to use the previous bit history to generate a 'perfect' dot at the expected centroid location for each row in a current column. The actual pixels (from the CCD) are compared with the expected 'perfect' pixels. If the two match, then the actual centroid location must be exactly in the expected position, so the centroid As must be valid and not need updating. Otherwise a process of changing the centroid As needs to occur in order to best fit the expected centroid location to the actual data. The new centroid As will be used for processing the dot in the next column.
Updating the centroid As is done as a subsequent process from Step 2 for the following reasons:
to reduce complexity in design, so that it can be perfonned as Step 2 of Phase I there is enough bandwidth remaining to allow it to allow reuse of DRAM buffers, and to ensure that all the data required for centroid updating is available at the start of the process without special pipelining.
The centroid A are processed as Acolumn Arow respectively to reduce complexity.
Although a given dot is 3 pixels in diameter, it is likely to occur in a 4x4 pixei area. However the edge of one dot will as a result be in the same pixel as the edge of the next dot. For this reason, centroid updating requires more than simply the information about a given single dot.
Fig. 44 shows a single dot 310 from the previous column with a given centroid 311. In this example, the dot 310 extend A over 4 pixel columns 312-315 and in fact, part of the previous dot column's dot (coordinate =
(Prevcolumn, Current Row)) has entered the current column for the dot on the current row. If the dot in the current row and column was white, we would expect the rightmost pixel column 314 from the previous dot column to be a low value, since there is only the dot information from the previous column's dot (the current column's dot is white). From this we can see that the higher the pixel value is in this pixel column 315, the more the centroid should be to the right Of course, if the dot to the right was also black, we cannot adjust the centroid as we cannot get infotmation sub-pixel.
The same can be said for the dots to the left, above and below the dot at dot coordinates (PrevColtunn, CurrentRow).
From this we can say that a maximum of 5 pixel columns and rows are required.
It is possible to simplify the situation by taking the cases of row and column centroid As separately, treating them as the same problem, only rotated 90 degrees.
Taking the horizontal case first, it is necessary to change the column centroid As if the expected pixels don't match the detected pixels. From the bit history, the value of the bits found for the Current Row in the current dot column, the previous dot coltmm, and the (previous-1)th dot column are known.
The expected centroid location is also known. Using these two pieces of inforntation, it is possible to generate a 20 bit expected bit pattern should the read be 'perfect'. The 20 bit bit-pattern reptrsertts the expected A values for each of the 5 pixels across the horizontal dimension. The first nibble would represent the tightmost pixel of the leftmost dot. The next 3 nibbles represent the 3 pixels across the center of the dot 310 from the previous column, and the last nibble would be the leftmost pixel 317 of the rightmost dot (from the current column).
If the expected centroid is in the center of the pixel, we would expect a 20 bit pattern based on the following table:
Bit history Expected pixels I I I DDFDD
The pixels to the left and right of the center.dot are either 0 or D depending on whether the bit was a 0 or I
respectively. The center three pixels are either 000 or DFD depending on whether the bit was a 0 or I respectively_ These values are based on the physical area taken by a dot for a given pixel.
Depending on the distance of the centroid from the exact center of the pixel, we would expect data shifted slightly, which realiy only affects the pixels either side of the center pixel. Since there are 16 possibilities, it is possible to divide the distance from the center by 16 and use that amount to shift the expected pixels.
Once the 20 bit 5 pixel expected value has been determined it can be compared against the actual pixels read.
This can proceed by subtracting the expected pixels from the actual pixels read on a pixel by pixel basis, and finally adding the differences together to obtain a distance from the expected A
values.
Fig. 45 illustrates one form of implementation of the above algorithm which includes a look up table 320 which receives the bit history 322 and central fractional component 323 and outputs 324 the cotresponding 20 bit number which is subtracted 321 from the central pixel input 326 to produce a pixel difference 327.
This process is carried out for the expected centroid and once for a shift of the centroid left and right by I
amount in Acolumn. The centroid with the smallest difference from the actual pixels is considered to be the 'winner' and the Acolumn updated accordingly (which hopefully is 'no change'). As a result, a Acolumn cannot change by more than I each dot column.
The process is repeated for the vertical pixels, and Arow is consequentially updated.
There is a large amount of scope here for parallelism. Depending on the rate of the clock chosen for the ACP
unit 31 these units can be placed in series (and thus the testing of 3 different A could occur in consecutive clock cycles), or in parallel where all 3 can be tested simultaneously. If the clock rate is fast enough, there is less need for parallelism.
Bandwidth utilization It is necessary to read the old 0 of the As, and to write them out again. This takes 10% of the bandwidth:
2 * (76(3150/32) + 2*3150) = 27,648ns = 10% of bandwidth It is necessary to read the bit history for the given row as we update its As.
Each byte contains 2 row's bit histories, thus taking 2.596 of the bandwidth:
76((315012)/32) + 2*(3150J2) = 4,085ns = 2.5% of bandwidth In the worst case of pixel drift due to a 1% rotation, centroids will shift I
column every 57 pixel rows, but since a dot is 3 pixels in diameter, a given pixel colutnn will be valid for 171 pixel rows (3*57). As a byte contains 2 pixels, the number of bytes valid in cached reads will be a worst case of 86 (out of 128 read). The worst case timing for columns is therefore 31 % bandwidth_ 5*(((9450/(128 * 2)) * 320) * 128/86) = 88, 112ns = 3195 of bandwidth.
The total bandwidth required for the updating the centroid A is summarised in the following table:
Read/Write centroid A 10%
Read bit history 2S5To Read 5 columns of pixel data 31%
TOTAL 43.5%
Memorv usaQe for Phase 2:
The 2MB bit-image DRAM area is read from and written to during Phase 2 processing. The 2MB pixel-data DRAM area is read.
The 0.5MB scratch DRAM area is used for storing row data, namely:
Centroid array 24bits (16:8) * 2 * 3150 = 18,900 byes Bit History array 3 bits * 3150 entries (2 per byte) = 1575 bytes Phase 3 -Unscramble and XOR the raw data Returning to Fig. 37, the next step in decoding is to unscramble and XOR the raw data. The 2MB byte image, as taken from the Artcard, is in a scrambled XORed form. It must be unscrambled and re-XORed to retrieve the bit intage necessary for the Reed Solomon decoder in phase 4.
Tuming to Fig. 46, the unscrambling process 330 takes a 2MB scrambled byte image 331 and writes an unscrambled 2MB image 332. The process cannot reasonably be perfotmed in-place, so 2 sets of 2MB areas are utilised. The scrambled data 331 is in symbol block order arranged in a 16x16 array, with symbol block 0(334) having all the symbol 0's from all the code words in random order. Symbol block 1 has all the symbol 1's from all the code words in random order etc. Since there are only 255 symbols, the 256h symbol block is currentiy unused.
A linear feedback shift register is used to determine the relationship between the position within a symbol block eg. 334 and what code word eg. 355 it came from. This works as long as the same seed is used when generating the original Artcard images. The XOR of bytes from altemative source lines with OxAA and 0x55 respectively is effectively free (in time) since the bottleneck of time is waiting for the DRAM to be ready to read/write to non-sequential addresses.
The timing of the unscrambling XOR process is effectively 2MB of random byte-reads, and 2MB of random byte-writes i.e. 2 *(2MB * 76ns + 2MB * 2ns) = 327,155,712ns or approximately 0.33 seconds. This timing assumes no caching.
Phase 4- Reed Solomon decode This phase is a loop, iterating through copies of the data in the bit image, passing them to the Reed-Solomon decode module until either a successful decode is made or until there are no more copies to attempt decode from.
The Reed-Solomon decoder used can be the VLIW processor, suitably programmed or, alternatively, a separate hardwired core such as LSI Logic's L64712. 'Ile L64712 has a throughput of SOMbits per second (around 6.25MB per second), so the time may be bound by the speed of the Reed-Solomon decoder rather than the 2MB read and 1 MB write memory access time (500MB/sec for sequential accesses). The time taken in the worst case is thus 2/6.25s = approximately 0.32 seconds.
Phase 5 Running the Vark script The overall time taken to read the Artcard 9 and decode it is therefore approximately 2.15 seconds. The apparent delay to the user is actually only 0.65 seconds (the total of Phases 3 and 4), since the Artcard stops moving after 1.5 seconds.
Once the Artcard is loaded, the Artvark script must be interpreted, Rather than run the script immediateiy, the script is only run upon the pressing of the 'Print' button 13 (Fig. 1). The taken to mn the script will vary depending on the complexity of the script, and must be taken into account for the perceived delay between pressing the print button and the actual print button and the actual printing.
Alternative Artcard Fomat Of course, other artcard formats are possible. Tltere will now be described one such alternative artcard format with a number of preferable feature. Described hereinafter will be the alterttative Artcard data format, a mechanism for mapping user data onto dots on an alternative Artcard, and a fast alternative Artcard reading algorithm for use in embedded systems where resources are scarce.
Alternative Artcard Overview The Alternative Artcards can be used in both embedded and PC type applications, providing a user-friendly interface to large amounts of data or configuration information.
While the back side of an altemative Artcard has the same visual appearance regardless of the application (since it stores the data), the front of an atternative Artcard can be application dependent. It must make sense to the user in the context of the application.
Alternative Artcard technology can also be independent of the printing resolution. The notion of storing data as dots on a card simply means that if it is possible put more dots in the sante space (by increasing resolution), then tltose dots can represent more data The prefetTed etnbodiment assumes utilisation of 1600 dpi printing on a 86 mm x 55 mm card as the sample Artcard, but it is simple to determine alternative equivalent layouts and data sizes for other card sizes and/or other print resolutions. Regardless of the print resolution, the reading technique remain the same.
After all decoding and other overhead has been taken into account, alternative Artcards are capable of storing up to 1 Megabyte of data at print resolutions up to 1600 dpi. Altemative Artcards can store megabytes of data at print resolutions greater than 1600 dpi. The following two tables summarize the effective alt.ernative Artcard data storage capacity for certain print resolutions:
Format of an alternative Artcard The structure of data on the alternative Artcard is therefore specifically designed to aid the recovery of data_ This section describes the format of the data (back) side of an alternative Artcard.
Dots The dots on the data side of an alternative Artcard can be monochrome. For example, black dots printed on a white background at a predetermined desired print resolution. Consequently a "black dot" is physically different from a "white dot". Fig. 47 illustrates various examples of magnified views of black and white dots. The monochromatic scheme of black dots on a white background is preferably chosen to maximize dynamic range in blurry reading environments. Although the black dots are printed at a particular pitch (eg.
1600 dpi), the dots themselves are slightly larger in order to create continuous lines when dots are printed contiguously. In the example images of Fig. 47, the dots are not as merged as they may be in reality as a result of bleeding.
There would be more smoothing out of the black indentations. Although the alternative Artcard system described in the preferred embodiment allows for flexibly different dot sizes, exact dot sizes and ink/printing behaviour for a particular printing technology should be studied in more detail in order to obtain best results.
In describing this artcard embodiment, the term dot refers to a physical printed dot (ink, thermal, electro-photographic, silver-halide etc) on an alternative Artcard. When an alternative Artcard reader scans an alternative Artcard, the dots must be sampled at least double the printed resolution to satisfy Nyquist's Theorem The term pixel refers to a sample value from an alternative Artcard reader device. For example, when 1600 dpi dots are scanned at 4800 dpi there are 3 pixels in each dimension of a dot, or 9 pixels per dot.
The sampling process will be further explained hereinafter.
Turning to Fig. 48, there is shown the data surface 1101 a sample of alternative Artcard. Each alternative Artcard consists of an "active" region 1102 surrounded by a white border region 1103. The white border 1103 contains no data information, but can be used by an alternative Artcard reader to calibrate white levels. The active region is an array of data blocks eg. 1104, with each data block separated from the next by a gap of 8 white dots eg.
1106. Depending on the print resolution, the number of data blocks on an alternative Artcard will vary. On a 1600 dpi alternative Artcard, the array can be 8 x 8. Each data block 1104 has dimensions of 627 x 394 dots. With an inter-block gap 1106 of 8 white dots, the active area of an alternative Artcard is therefore 5072 x 3208 dots (8.lnun x S.lmm at 1600 dpi).
Data blocks Turning now to Fig. 49, there is shown a single data block 1107. The active region of an alternative Artcard consists of an array of identically structured data blocks 1107. Each of the data blocks has the following structure: a data region 1108 sutrounded by clock-marks 1109, borders 11 10, and targets 1 I 11. The data region holds the encoded data proper, while the clock-marks, borders and targets are present specifically to help locate the data region and ensure accurate recovery of data from within the region.
Each data block 1107 has dimensions of 627 x 394 dots. Of this, the central area of 595 x 384 dots is the data region 1108. The surrounding dots are used to hold the clock-marks, borders, and targets.
Borders and Clockmarks Fig. 50 illustrates a data block with Fig. 51 and Fig. 52 illustrating magnified edge portions thereof. As illustrated in Fig. 51 and Fig. 52, there are two 5 dot high border and clockmark regions 1170, 1177 in each data block:
one above and one below the data region. For example, The top 5 dot high region consists of an outer black dot border line 1112 (which stretches the length of the data block), a white dot separator line 1113 (to ensure the border line is independent), and a 3 dot high set of clock marks 1114. The clock marks alternate between a white and black row, starting with a black clock mark at the 8th column from either end of the data block. There is no separation between clockmark dots and dots in the data region.
The clock marks are symmetric in that if the alternative Artcard is inserted rotated 180 degrees, the same relative border/clockmark regions will be encountered. The border 1112, 1113 is intended for use by an alternative Artcard reader to keep vertical tracking as data is read from the data region.
The clockmarks 1114 are intended to keep horizontal tracking as data is read from the data region. The separation between the border and clockmarks by a white line of dots is desirable as a result of blurring occurring during reading.
The border thus becomes a black line with white on either side, making for a good frequency response on reading. The clockmarks alternating between white and black have a similar result, except in the horizontal rather than the vertical dimension. Any aiternative Artcard reader must locate the clockmarks and border if it intends to use them for tracking.
The next section deals with targets, which are designed to point the way to the clockmarks, border and data.
Targets in the Target region As shown in Fig. 54, there are two 15-dot wide target regions 1116, 11 17 in each data block: one to the left and one to the right of the data region. The target regions are separated from the data region by a single column of dots used for orientation. The purpose of the Target Regions 1116, 1117 is to point the way to the clockmarks, border and data regions. Each Target Region contains 6 targets eg. 1 118 that are designed to be easy to find by an alternative Artcard reader. Turning now to Fig. 53 there is shown the structure of a single target 1120. Each target 1120 is a 15 x 15 dot black square with a center saructure 1121 and a run-length encoded target number 1122. The center structure 1121 is a simple white cross, and the target number component 1122 is simply two columns of white dots, each being 2 dots long for each part of the target number. Thus target number 1's target id 1 122 is 2 dots long, target number 2's target id 1122 is 4 dots wide etc.
As shown in Fig. 54, the targets are arranged so that they are rotation invariant with regards to card insertion.
This means that the left targets and right targets are the same, except rotated 180 degrees. In the left Target Region 1116, the targets are arranged such that targets 1 to 6 are located top to bottom respectively. In the right Target Region, the targets are arranged so that target numbers I to 6 are located bottom to top. The target number id is always in the half closest to the data region. The magnified view portions of Fig. 54 reveals clearly the how the right targets are simply the same as the left targets, except rotated 180 degrees.
As shown in Fig. 55, the targets 1124, 1125 are specifically placed within the Target Region with centers 55 dots apart. In addition, there is a distance of 55 dots from the center of target 1(1124) to the first clockmark dot 1126 in the upper clockmark region, and a distance of 55 dots from the center of the target to the first clockmark dot in the lower clocktnark region (not shown). The first black clockmark in both regions begins directly in line with the target center (the 8th dot position is the center of the 15 dot-wide target).
The simplified schematic illustrations of Fig. 55 illustrates the distances between target centers as well as the distance from Target 1(1124) to the first dot of the first black clockmark (1126) in the upper border/clockmark region.
Since there is a distance of 55 dots to the clockmarks from both the upper and lower targets, and both sides of the altemative Artcard are sytnmetrical (rotated through 180 degrees), the card can be read left-to-right or right-to-left.
Regardless of reading direction, the orientation does need to be determined in order to extract the data from the data region.
Orientation colonuis As illustrated in Fig. 56, there are two 1 dot wide Orientation Columns 1127, 1128 in each data block: one directly to the left and one directly to the right of the data region. The Orientation Columns are present to give orientation infonnation to an alternative Artcard reader: On the left side of the data region (to the right of the Left Targets) is a single column of white dots 1127. On the right side of the data region (to the left of the Right Targets) is a single column of black dots 1128. Since the targets are rotation invariant, these two columns of dots allow an alternative Artcard reader to determine the orientation of the alternative Artcard - has the card been inserted the right way, or back to front. From the alternative Artcard reader's point of view, assuming no degradation to the dots, there are two possibilities:
* If the column of dots to the left of the data region is white, and the column to the right of the data region is black, then the reader will know that the card has been inserted the same way as it was written.
* If the column of dots to the left of the data region is black, and the column to the right of the data region is white, then the reader will know that the card has been inserted backwards, and the data region is appropriately rotated. The reader must take appropriate action to correctly recover the information from the alternative Artcard.
Data Region As shown in Fig. 57, the data region of a data block consists of 595 columns of 384 dots each, for a total of 228,480 dots_ These dots must be interpreted and decoded to yield the original data. Each dot represents a single bit, so the 228,480 dots represent 228,480 bits, or 28,560 bytes. The interpretation of each dot can be as follows:
Black White 0 The actual interpretation of the bits derived from the dots, however, requires understanding of the mapping from the original data to the dots in the data regions of the alternative Artcard_ Mapping original data to data region dots There will now be described the process of taking an original data file of maximum size 910,082 bytes and mapping it to the dots in the data regions of the 64 data blocks on a 1600 dpi alternative Artcatd. An alternative Artcard reader would reverse the process in order to extract the original data from the dots on an alternative Artcard.
At first glance it seems trivial to map data onto dots: binary data is comprised of Is and Os, so it would be possible to simply write black and white dots onto the card. This scheme however, does not allow for the fact that ink can fade, parts of a card may be damaged with dirt, grime, or even scratches. Without error-detection encoding, there is no way to detect if the data retrieved from the card is correct. And without redundancy encoding, there is no way to correct the detected errors. The aim of the mapping process then, is to make the data recovery highly robust, and also give the alternative Artcard reader the ability to know it read the data cotrectly.
There are [hree basic steps involved in mapping an original data file to data region dots * Redundancy encode the original data * Shuffle the encoded data in a deterministic way to reduce the effect of localized alternative Artcard damage * Write out the shuffled, encoded data as dots to the data blocks on the alternative Artcard Each of these steps is examined in detail in the followine sections.
Redundancy encode using ReedSolomon encoding The mapping of data to altemative Artcard dots relies heavily on the method of redundancy encoding employed. Reed-Solomon encoding is preferably chosen for its ability to deal with burst errors and effectively detect and correct errors using a minimum of redundancy. Reed Solomon encoding is adequately discussed in the standard texts such as Wicker, S., and Bhargava, V., 1994, Reed-Solomon Codes and their Applications, IEEE Press.
Rorabaugh, C, 1996, Error Coding Cookbook, McGraw-Hill. Lyppens, H., 1997, Reed-Solomon Error Correction, Dr. Dobb's Journai, January 1997 (Volume 22, Issue 1).
A variety of different parameters for Reed-Solomon encoding can be used, including different symbol sizes and different levels of redundancy. Preferably, the following encoding parameters are used:
* m=8 s t=64 Having m=8 means that the symbol size is 8 bits (I byte). It also means that each Reed-Solomon encoded block size n is 255 bytes (28 - I symbols). In order to allow correction of up to t symbols, 2t symbols in the final block size must be taken up with redundancy symbols. Having t=64 means that 64 bytes (symbols) can be corrected per block if they are in error. Each 255 byte block therefore has 128 (2 x 64) redundancy bytes, and the remaining 127 bytes (k=127) are used to hold original data. Thus:
* n=255 * k=127 The practical result is that 127 bytes of original data are encoded to become a 255-byte block of Reed-Solomon encoded data. The encoded 255-byte blocks are stored on the alternative Artcard and later decoded back to the original 127 bytes again by the alternative Artcard reader. The 384 dots in a single column of a data block's data region can hold 48 bytes (384/8). 595 of these columns can hold 28,560 bytes.
This amounts to 112 Reed-Solomon blocks (each block having 255 bytes). The 64 data blocks of a complete alternative Artcard can hold a total of 7168 Reed-Solomon blocks (1,827,840 bytes, at 255 bytes per Reed-Solomon block).
Two of the 7,168 Reed-Solomon blocks are reserved for control infomtation, but the remaining 7166 are used to store data. Since each Reed-Solomon block holds 127 bytes of actual data, the total amount of data that can be stored on an altemative Artcard is 910,082 bytes (7166 x 127). If the original data is less than this amount, the data can be encoded to fit an exact number of Reed-Solomon blocks, and then the encoded blocks can be replicated until all 7,166 are used. Fig. 58 illustrates the overall form of encoding utilised.
Each of the 2 Control blocks 1132, 1133 contain the sanie encoded information required for decoding the remaining 7,166 Reed-Solomon blocks:
The number of Reed-Solomon blocks in a full n-tessage (16 bits stored lo/hi), and The number of data bytes in the last Reed-Solomon block of the message (8 bits) These two numbers are repeated 32 tintes (consutning. 96 bytes) with the remaining 31 bytes reserved and set to 0. Each control block is then Reed-Solomon encoded, tuming the 127 bytes of control information into 255 bytes of Reed-Solomon encoded data.
The Conttnl Block is stored twice to give greater chance of it surviving. In addition, the repetition of the data within the Control Block has particular significance when using Reed-Solomon encoding. In an uncorrupted Reed-Solomon encoded block, the first 127 bytes of data are exactly the original data, and can be looked at in an attempt to recover the original message if the Control Block fails decoding (niore than 64 symbols are cotrupted). Thus, if a Control Block fails decoding, it is possible to examine sets of 3 bytes in an effort to determine the most likely vaiues for the 2 decoding parameters. It is not guaranteed to be recoverable, but it has a better chance through redundancy.
Say the last 159 bytes of the Control Block are destroyed, and the first 96 bytes are perfectly ok. Looking at the first 96 bytes will show a repeating set of numbers. These numbers can be sensibly used to decode the remainder of the message in the remaining 7,166 Reed-Solomon blocks.
By way of example, assume a data file containing exactly 9,967 bytes of data.
The number of Reed-Solomon blocks trquired is 79. The first 78 Reed-Solomon blocks are completely utilized, consunting 9,906 bytes (78 x 127).
The 79th block has only 61 bytes of data (with the remaining 66 bytes all Os).
The alternative Artcard would consist of 7,168 Reed-Solomon blocks. The first 2 blocks would be Control Blocks, the next 79 would be the encoded data, the next 79 would be a duplicate of the encoded data, the next 79 would be another duplicate of the encoded data, and so on. After storing the 79 Reed-Solomon blocks 90 times, the remaining 56 Reed-Solomon blocks would be another duplicate of the first 56 blocks from the 79 blocks of encoded data (the final 23 blocks of encoded data would not be stored again as there is not enough room on the alternative Artcard). A hex representation of the 127 bytes in each Control Block data before being Reed-Solomon encoded would be as illustrated in Fig. 59.
Scramble the Encoded Data Assuming all the encoded blocks have been stored contiguously in memory, a maximum 1,827,840 bytes of data can be stored on the alternative Artcard (2 Control Blocks and 7,166 inforntation blocks, totalling 7,168 Reed-Solomon encoded blocks). Preferably, the data is not directly stored onto the alternative Artcard at this stage however, or all 255 bytes of one Reed-Solomon block will be physically together on the card. Any dirt, grime, or stain that causes physical damage to the card has the potential of damaging more than 64 bytes in a single Reed-Solomon block, which would make that block unrecoverable. If there are no duplicates of that Reed-Solomon block, then the entire altetnative Artcard cannot be decoded.
The solution is to take advantage of the fact that there are a large number of bytes on the alternative Artcard, and that the alternative Artcard has a reasonable physical size. The data can therefore be scrambled to ensure that symbols from a single Reed-Solomon block are not in close proximity to one another. Of course pathological cases of card degradation can cause Reed-Solomon blocks to be unrecoverable, but on average, the scrambiing of data makes the card much more robust. The scrambling scheme chosen is simple and is illustrated schematically in Fig 14. All the Byte Os from each Reed-Solomon block are placed together 1136, then all the Byte Is etc. There will therefore be 7,168 byte 0's, then 7,168 Byte 1's etc. Each data block on the alternative Artcard can store 28,560 bytes.
Consequently there are approximately 4 bytes from each Reed-Solomon block in each of the 64 data blocks on the alternative Artcard.
Under this scrambling scheme, complete damage to 16 entire data blocks on the alternative Artcard will result in 64 symbol errors per Reed-Solomon block. This tneans that if there is no other damage to the altetnative Artcard, the entire data is completely recoverable, even if there is no data duplication.
Write the scrambled encoded data to the alternative Artcard Once the original data has been Reed-Solomon encoded, duplicated, and scrambled, there are 1,827,840 bytes of data to be stored on the alternative Arteard. Each of the 64 data blocks on the alternative Artcard stores 28,560 bytes.
The data is simply written out to the alternative Artcard data blocks so that the first data block contains the first 28,560 bytes of the scrambled data, the second data block contains the next 28,560 bytes etc.
As illustrated in Fig. 61, within a data block, the data is written out column-wise left to right.'Chus the left-most column within a data block contains the first 48 bytes of the 28,560 bytes of scrambled data, and the last column contains the last 48 bytes of the 28,560 bytes of scrambled data. Within a column, bytes are written out top to bottom, one bit at a time, starting from bit 7 and finishing with bit 0. If the bit is set (1), a black dot is placed on the alternative Artcar+d, if the bit is clear (0), no dot is placed, leaving it the white background color of the card.
For example, a set of 1,827,840 bytes of data can be created by scrambling 7,168 Reed-Solomon encoded blocks to be stored onto an altetnative Artcard. The first 28,560 bytes of data are written to the first data block The first 48 bytes of the first 28,560 bytes are written to the fust column of the data block, the next 48 bytes to the next coltnnn and so on. Suppose the first two bytes of the 28,560 bytes are hex D3 5F. Those first two bytes will be stored in column 0 of the data block. Bit 7 of byte 0 will be stored first, then bit 6 and so on. Then Bit 7 of byte I will be stored through to bit 0 of byte 1. Since each "I" is stored as a black dot, and each "0" as a white dot, these two bytes will be represented on the altemative Artcard as the following set of dots:
* D3 (I 101 0011) becomes: black, black, white, black, white, white, black, black * 5F (0101 1111) becomes: white, black, white, black, black, black, black, black Decoding an alternative Artcard This section deals with extracting the original data from an alternative Artcard in an accurate and robust manner. Specifically, it assumes the alternative Artcard format as described in the previous chapter, and describes a tttetltod of extracting the original pre-encoded data from the alternative Artcard.
There are a number of general considerations that are part of the assumptions for decoding an alternative Artcard.
User The purpose of an alternative Artcard is to store data for use in different applications. A user inserts an altemative Artcard into an altetnative Artcard reader, and expects the data to be loaded in a "reasonable time". From the user's perspective, a motor transport moves the alternative Artcard into an alternative Artcard reader. This is not perceived as a problematic delay, since the alternative Artcard is in motion.
Any time after the alternative Artcard has stopped is perceived as a delay, and should be minimized in any alternative Artcard reading scheme. Ideally, the entire altemative Aruxrd would be read while in motion, and thus there would be no perceived delay after the card had stopped moving.
For the purpose of the preferred embodiment, a reasonable time for an alternative Artcard to be physically loaded is defined to be 1.5 seconds. There should be a minimization of time for additional decoding after the alternative Artcatd has stopped moving. Since the Active region of an alternative Artcard covers most of the altetnative Artcard surface we can limit our timing concerns to that region.
Sampling Dots The dots on an altemative Artcard must be sampled by a CCD reader or the like at least at double the printed resolution to satisfy Nyquist's Theorem. In practice it is better to sample at a higher rate than this. In the altetnative Artcard reader environment, dots are preferably sampled at 3 times their printed resolution in each dimension, requiring 9 pixels to define a single dot. If the resolution of the alternative Artcard dots is 1600 dpi, the alternative Artcard reader's image sensor must scan pixels at 4800 dpi. Of course if a dot is not exactly aligned with the sampling sensor, the worst and most likely case as illustrated in Fig. 62, is that a dot will be sensed over a 4x4 pixel area.
Each sampled pixel is I byte (8 bits). The lowest 2 bits of each pixel can contain significant noise. Decoding algorithms must therefore be noise tolerant.
Alignment/Rotation It is extremely unlikely that a user will insert an alternative Artcard into an alternative Artcard reader perfectly aligned with no rotation. Certain physical constraints at a reader entrance and motor aransport grips will help ensure that once inserted, an altemative Artcard will stay at the original angle of insertion relative to the CCD. Preferably this angle of rotation, as illustrated in Fig. 63 is a maximum of I degree. There can be some slight aberrations in angle due to jitter and motor rumble during the teading process, but these are assumed to essentially stay within the I-degree limit.
The physical dimensions of an alternative Artcard are 86mm x 55mm. A I degree rotation adds 1.5mm to the effective height of the card as 86mm passes under the CCD (86 sin 1 ), which will affect the required CCD length.
The effect of a I degree rotation on alternative Artcard reading is that a single scanline from the CCD will include a number of different columns of dots from the alternative Artcard.
This is illustrated in an exaggerated form in Fig. 63 which shows the drift of dots across the columns of pixels. Although exaggerated in this diagram, the actual drift will be a maximum 1 pixel column shift every 57 pixels.
When an altemative Artcard is not rotated, a single column of dots can be read over 3 pixel scanlines. The more an alternative Artcard is rotated, the greater the local effect. The more dots being read, the longer the rotation effect is applied. As either of these factors increase, the larger the number of pixel scanlines that are needed to be read to yield a given set of dots from a single column on an alternative Artcard.
The following table shows how many pixel scanlines are required for a single column of dots in a particular alternative Artcard structure.
Region Height 0 rotation 1 rotation Active region 3208 dots 3 pixel columns 168 pixel columns Data block 394 dots 3 pixel columns 21 pixel columns To read an entire alternative Artcard, we need to read 87 mm (86mm + Imm due to 1 rotation). At 4800 dpi this implies 16,252 pixel columns.
CCD (or other I.inear Image Sensor) Length The length of the CCD itself must accommodate:
the physical height of the alternative Artcard (55 mm), vertical slop on physical alternative Artcard insertion (lmm) insertion rotation of up to I degree (86 sin 1 = 1.5mm) These factors combine to form a total length of 57Smm.
When the alternative Artcard Image sensor CCD in an alternative Artcard reader scans at 4800 dpi, a single scanline is 10,866 pixels. For simplicity, this figure has been rounded up to 11,000 pixels. The Active Region of an alternative Artcard has a height of 3208 dots, which implies 9,624 pixels. A
Data Region has a height of 384 dots, which implies 1,152 pixels.
DRAM Size The amount of inemory tequined for alternative Artcard reading and decoding is ideally minimized. The typical placement of an altemative Artcand reader is an embedded system where memory resources are precious. This is made more problematic by the effects of rotation. As described above, the more an alternative Artcard is rotated, the more scanlines are requited to effectively tecover original dots.
There is a trade-off between algorithmic complexity, user perceived delays, robustness, and memory usage.
One of the sitnplest reader algorithms would be to simply scan the whole alternative Artcard, and then to process the whole data without real-time constraints. Not only would this require huge reserves of inemory, it would take longer than a reader algorithm that occurred concurrently with the alternative Artcard reading process.
The actual amount of memory required for reading and decoding an alternative Artcard is twice the amount of space required to hold the encoded data, together with a small amount of scratch space (1-2 KB). For the 1600 dpi alternative Artcard, this implies a 4 MB memory requirement. The actual usage of the memory is detailed in the following algorithm description.
Transfer rate DRAM bandwidth assumptions need to be made for timing considerations and to a certain extent affect algorithmic design, especially since alternative Artcard readers are typically part of an embedded system.
A standard Rambus Direct RDRAM architectute is assumed, as defined in Rambus Ine, Oct 1997, Direct Rambus Technolog), Disclosure, with a peak data transfer rate of 1.6GB/sec.
Assuming 75% efficiency (easily achieved), we have an average of 1.2GB/sec data transfer rate. The average tinte to access a block of 16 bytes is therefore 12ns.
Dirty Data Physically damaged alternative Artcards can be inserted into a reader.
Altennative Artcards tnay be scratched, or be stained with grime or dirt. A altettative Artcard reader can't assume to read everything perfeetly. The effect of dirty data is made worse by blurring, as the dirty data affects the surrounding clean dots.
Blurry Environment Tltere are two ways that blurring is inttodttced into the alternative Artcard reading environment:
* Natural blurring due to natttre of the CCD's distance from the alternative Artcard.
* Warping of alternative Artcand Natural blurring of an alternative Artcard image occurs when there is overlap of sensed data from the CCD.
Blutring can be useful, as the overlap ensures there are no high frequencies in the sensed data, and that there is no data missed by the CCD. However if the area covered by a CCD pixel is too latge, theie will be too much blurring and the sampling required to recover the data will not be tnet. Fig. 64 is a schematic illustration of the overlapping of sensed data.
Another fomt of blutring occurs when an alternative Artcard is slightly warped due to heat damage. When the watping is in the vertical dimension, the distance between the altetnative Artcard and the CCD will not be constant, and the level of blutring will vary across those areas.
Black and white dots were chosen for alternative Artcards to give the best dynanric range in blurry reading environments. Blurring can cause problems in attempting to detenmine whether a given dot is black or white.
As the blurring increases, the more a given dot is influenced by the surrounding dots. Consequently the dynamic range for a particular dot decreases. Consider a white dot and a black dot, each surrounded by all possible sets of dots. The 9 dots are blurred, and the center dot sampled. Fig. 65 shows the distribution of resultant center dot values for black and white dots.
The diagram is intended to be a representative blurring. The curve 1140 from 0 to around 180 shows the range of black dots. The curve 1141 from 75 to 250 shows the range of white dots.
However the greater the blurring, the more the two curves shift towards the center of the range and therefore the greater the intersection area, which nteans the more difficult it is to determine whether a given dot is black or white. A
pixel value at the center point of intersection is ambiguous - the dot is equally likely to be a black or a white.
As the blurring increases, the likelihood of a read bit error increases.
Fortunately, the Reed-Solomon decoding algorithm can cope with these gracefully up to t symbol errors. Fig. 65 is a graph of number predicted number of alternative Artcard Reed-Solomon blocks that cannot be recovered given a particular symbol error rate. Notice how the Reed-Solomon decoding scheme perfornu well and then substantially degrades. If there is no Reed-Solomon block duplication, then only 1 block needs to be in error for the data to be unrecoverable. Of course, with block duplication the chance of an alt.ernative Artcard decoding increases.
Fig. 66 only illustrates the symbol (byte) errors corresponding to the number of Reed-Solomon blocks in error. There is a trade-off between the amount of blurring that can be coped with, compared to the amount of damage that has been done to a card. Since all etror detection and correction is perfomied by a Reed-Solomon decoder, there is a finite number of errors per Reed-Solomon data block that can be coped with.
The more errors introduced through blutring, the fewer the number of etrors that can be coped with due to altemative Artcard damage.
Overview of alternative Artcard Decoding As noted previously, when the user inserts an alternative Artcard into an alternative Artcard reading unit, a motor transport ideally carries the alternative Artcard past a monochrome linear CCD image sensor. The card is sampled in each dimension at three times the printed resolution. Alternative Artcard reading hardware and software compensate for rotation up to 1 degree, jitter and vibration due to the motor transport, and blurring due to variations in alternative Artcard to CCD distance. A digital bit image of the data is extracted from the sampled image by a complex motltod described here. Reed-Solomon decoding corrects arbitrariiy distributed data corruption of up to 25% of the raw data on the alternative Artcard. Approximately 1 MB of corrected data is extracted from a 1600 dpi card.
The steps involved in decoding are so as indicated in Fig. 67.
= The decoding process requires the following steps:
* Scan 1144 the alternative Artcard at three times printed resolution (eg scan 1600 dpi alternative Artcard at 4800 dpi) * Extract 1145 the data bitmap from the scanned dots on the card.
* Reverse 1146 the bitmap if the alternative Artcard was inserted backwards.
* Unscramble 1147 the encoded data * Reed-Solomon 1148 decode the data from the bitmap Algorithmic Overview Phase 1- Real time bit itnage extraction A simple comparison between the available memory (4 MB) and the memory required to hold all the scanned pixels for a 1600 dpi alternative Artcatd (172.5 MB) shows that unless the card is read multiple titnes (not a realistic option), the extraction of the bitmap from the pixel data must be done on the fly, in real time, while the altemative Arocurl is moving past the CCD. Two tasks must be accomplished in this phase:
* Scan the alternative Artcard at 4800 dpi * Extract the data bitrnap from the scanned dots on the card The rotation and unscrambling of the bit image cannot occur until the whoie bit image has been extracted. It is therefore necessary to assign a memory region to hold the extracted bit image. The bit image fits easily within 2MB, leaving 2MB for use in the extraction process.
Rather than extracting the bit image while looking only at the current scanline of pixels from the CCD, it is possible to allocate a buffer to act as a window onto the alternative Artcard, storing the last N scanlines read. Memory requirements do not allow the entire altetnative Artcard to be stored this way (172.5MB would be required), but allocating 2MB to store 190 pixel columns (each scanline takes less than 11,000 bytes) makes the bit image extraction process simpler.
The 4MB memory is therefore used as follows:
* 2 MB for the extracted bit innage * -2 MB for the scanned pixels * 1.5 KB for Phase 1 scxatch data (as required by algorithm) The time taken for Phase I is 1.5 seconds, since this is the time taken for the alternative Artcard to travel past the CCD and physically load.
Phase 2- Data extraction from bit image Once the bit image has been extracted, it must be unscrambled and potentially rotated 180 . It must then be decoded. Phase 2 has no real-time requiretnents, in that the alternative Artcard has stopped moving, and we are only concerned with the user's perception of elapsed time. Phase 2 therefore involves the remaining tasks of decoding an alternative Artc:atd:
= Re-organize the bit image, reversing it if the alternative Artcard was inserted backwards * Unscramble the encoded data * Reed-Solomon decade the data trom the bit image The input to Phase 2 is the 2MB bit image buffer. Unscrambling and rotating cannot be performed in situ, so a second 2MB buffer is required. Tlte 2MB buffer used to hold scanned pixels in Phase I is no longer required and can be used to store the rotated unscrambled data.
The Reed-Solomon decoding task takes the unscrambled bit image and decodes it to 910,082 bytes. The decoding can be performed in situ, or to a specified location elsewhere. The decoding process does not require any additional memory buffers.
The 4MB metnory is therefore used as follows:
' 2 MB for the extracted bit image (from Phase 1) ' -2 MB for the unscrambled, potentially rotated bit image ~ < 1 KB for Phase 2 scratch data (as required by algorithm) The time taken for Phase 2 is hardware dependent and is bound by the time taken for Reed-Solomon decoding. Using a dedicated core such as LSI Logic's L64712, or an equivalent CPU/DSP combination, it is estimated that Phase 2 would take 032 seconds.
Phase 1- Extract Bit Image This is the real-time phase of the algorithm, and is concerned with extracting the bit image from the altetnative Artcard as scanned by the CCD.
As shown in Fig. 68 Phase I can be divided into 2 asynchronous process streams. The first of these streams is simply the real-time reader of alternative Artcard pixels from the CCD, writing the pixels to DRAM_ The second stream involves looking at the pixels, and extracting the bits_ The second process stream is itself divided into 2 processes. The first process is a global process, concerned with locating the start of the alternative Artcard. The second process is the bit image extraction proper.
Fig. 69 illustrates the data flow from a data/process perspective.
Timing For an entire 1600 dpi alternative Artcard, it is necessary to read a maximum of 16,252 pixel-colunuts. Given a total time of 1.5 seconds for the whole alternative Artcard, this implies a maximum time of 92,296ns per pixel column during the course of the various processes.
Process 1- Read pixels from CCD
The CCD scans the alternative Artcard at 4800 dpi, and generates 11,000 1-byte pixel samples per column.
This process simply takes the data from the CCD and writes it to DRAM, completely independently of any other process that is reading the pixel data from DRAM. Fig. 70 illustrates the steps involved.
The pixels are written contiguously to a 2MB buffer that can hold 190 full columns of pixels. The buffer always holds the 190 columns most recently read. Consequently, any process that wants to read the pixel data (such as Processes 2 and 3) must firstly know where to look for a given colurnn, and secondly, be fast enough to ensure that the data required is actually in the buffer.
Process 1 makes the current scanline number (CutrentScanl.ine) available to other processes so they can ensure they are not attempting to access pixels from scanlines that have not been read yet The time taken to write out a single column of data (11,000 bytes) to DRAM is:
11,000/16 * 12 = 8,256ns Process I therefore uses just under 9% of the available DRAM bandwidth (8256/92296).
Process 2- Detect start of alternative Artcard This process is concemed with locating the Active Area on a scanned alternative Artcard. The input to this stage is the pixel data from DRAM (placed there by Process 1). The output is a set of bounds for the first 8 data blocks on the altemative Artcard, required as input to Process 3. A high level overview of the process can be seen in Fig. 71.
An alternative Artcard can have vertical slop of lmttt upon insertion. With a rotation of I degree there is further vertical slop of 1 Smm (86 sin 1 ). Consequently there is a total vertical slop of 2.5mm. At 1600dpi, this equates to a slop of approximately 160 dots. Since a single data block is only 394 dots high, the slop is just under half a data block. To get a better estimate of where the data blocks are located the alternative Artcard itself needs to be detected.
Process 2 therefore consists of two parts:
' Locate the start of the alternative Artcard, and if found, ' Calculate the bounds of the first 8 data blocks based on the siart of the alternative Artcard.
Locate the Start of the alternative Artcard The scanned pixels outside the alternative Artcard area are black (the surface can be black plastic or sotne other non-reflective surface). The border of the alternative Artcard area is white. If we process the pixel columns one by one, and filter the pixels to either black or white, the transition point from black to white will mark the start of the altereative Artcard. The highest level process is as follows:
for (Column=0; Column < MAX COLUMN; Column++) {
Pixel = ProcessColutnn(Column) if (Pixel) return (Pixel, Column) success!
return failure // no alternative Artcard found The ProcessColumn function is simple. Pixels from two areas of the scanned column are passed through a threshold filter to determine if they are black or white. It is possible to then wait for a certain number of white pixels and announce the start of the alternative Artcard once the given number has been detected. The logic of processing a pixel column is shown in the following pseudocode. 0 is retumed if the alternative Artcard has not been detected during the column. Otherwise the pixel number of the detected location is returned.
// Try upper region first count=0 for (i=O; i<UPPER REGIOIV BOUND; i++) {
if (GetPixel(column, i) <'IHRF.SHOLD) {
count = 0 U pixel is black }
else count++ U pixel is white if (count > WHTIE ALTERNATIVE ARTCARD) return i // Try lower region next. Process pixels in reverse count = 0 for (i=MAX_PIXEL_BOUND; i>LOWER_REGION_BOUND; i-) {
if (GetPixel(column, i) <THRESHOLD) {
count = 0 pixel is black }
else {
count++ // pixel is white if (count > WHTTE_ALTERNATIVE ARTCARD) return i }
//Not in upper bound or in lower bound. Return failure return 0 Calculate Data Block Bounds At this stage, the alternative Artcard has been detected. Depending on the rotation of the alternative Artcard, either the top of the alternative Artcard has been detected or the lower part of the alternative Artcard has been detected.
The second step of Process 2 determines which was detected and sets the data block bounds for Phase 3 appropriately.
A look at Phase 3 reveals that it works on data block segment bounds: each data block has a StartPixel and an EndPixel to determine where to look for targets in order to locate the data block's data region.
If the pixel value is in the upper half of the card, it is possible to simply use that as the first StartPixel bounds.
If the pixel value is in the lower half of the card, it is possible to tnove back so that the pixel value is the last segment's EndPixel bounds. We step forwards or backwards by the atternative Artcard data size, and thus set up each segtttent with appropriate bounds. We are now ready to begin extracting data from the alternative Artcard.
// Adjust to become first pixel if is lower pixel if (pixel > LOWER_REGION BOUND) {
pixel -= 6 * 1152 if (pixel <0) pixel = 0 }
for (i=O; i<6; i++) {
endPixel = pixel + 1152 segment[i].MaxPixel= MAX PIXEI._BOLJND
segment(il.SetBounds(pixel, endPixel) pixel = endPixel The MaxPixel value is defined in Process 3, and the SetBounds function simply sets StartPixel and EndPixel clipping with respect to 0 and MaxPixel.
Process 3- Extract bit data from pixels This is the heart of the altetnative Artcard Reader algorithm. This process is concerned with extracting the bit data from the CCD pixel data. The process essentially creates a bit-image from the pixel data, based on scratch information created by Process 2, and maintained by Process 3. A high level overview of the process can be seen in Fig. 72.
Rather than simply read an alternative Artcard's pixel column and detemvne what pixels belong to what data block, Process 3 works the other way around. It knows where to look for the pixels of a given data block. It does this by dividing a logical altemative Artcard into 8 segments, each containing 8 data blocks as shown in Fig. 73.
The segments as shown match the logical alternative Ancard. Physically, the alternative Artcard is likely to be rotated by some amount. The segments remain locked to the logical altemative Artcard structure, and hence are rotation-independent. A given segment can have one of two states:
* LookingForTargets: where the exact data block position for this segment has not yet been determined. Targets are being located by scanning pixel column data in the bounds indicated by the segment bounds.
Once the data block has been located via the targets, and bounds set for black & white, the state changes to ExtractingBitlmage.
* ExtractingBitlmage: where the data block has been accurately located, and bit data is being extracted one dot column at a time and written to the alternative Artcard bit image. The following of data block clockmarks gives accurate dot recovery regardless of rotation, and thus the segment bounds are ignored. Once the entire data block has been extracted, new segment bounds are calculated for the next data block based on the current position. The state changes to LookingForTargers.
The process is complete when all 64 data blocks have been extracted, 8 from each region.
Each data block consists of 595 columns of data, each with 48 bytes.
Preferably, the 2 orientation columns for the data block are each extracted at 48 bytes each, giving a total of 28,656 bytes extracted per data block. For simplicity, it is possible to divide the 2MB of memory into 64 x 32k chunks.
The nth data block for a given segment is stored at the location:
StartBuffer + (256k * n) Data Structure for Segments Each of the 8 segments has an associated data structure. The data structure defining each segment is stored in the scratch data area. The structure can be as set out in the following table:
DataName Comment CurrentState Defines the cutrent state of the segment. Can be one of:
LookingForTargets F.xiractingBitJmage Initial value is LookingForTargets Used during LookingForTargets:
StartPixel Upper pixel bound of segment. Initially set by Process 2.
EndPixel Lower pixel bound of segment. Initially set by Process 2 MaxPixel The maximum pixel number for any scanline.
It is set to the same value for each segment: 10,866.
CurrentColumn Pixel column we're up to while looking for targets.
FinalColumn Defines the last pixel column to look in for targets.
LocatedTargets Points to a list of located Targets_ PossibleTargets Points to a set of pointers to Target structures that represent currently investigated pixel shapes that may be targets AvailableTargets Points to a set of pointers to Target structures that are currently unused.
TargetsFound The number of Targets found so far in this data block.
PossibleTargetCount The number of elements in the PossibleTargets list AvailabletargetCount The number of elements in the AvailableTargets list Used during ExtractingBitJmage:
BitImage The start of the Bit Image data area in DRAM where to store the next data block:
Segment 1= X, Segment 2 = X+32k etc Advances by 256k each time the state changes from ExtractingBitImageData to Looking ForTargets CurrentByte Offset within BitImage where to store next extracted byte CurrentDotColumn Holds current clockmarkJdot column number.
Set to -8 when transitioning from state LookingForTarget to ExtractingBitImage.
UpperClock Coordinate (column/pixel) of current upper clockmarkJborder LowerClock Coordinate (column/pixel) of current lower clockmark/border CurrentDot The center of the current data dot for the current dot column.
Initially set to the center of the first (topmost) dot of the data column.
DataDelta What to add (column/pixel) to CurrentDot to advance to the center of the next dot.
BlackMax Pixel value above which a dot is definitely white WhiteMin Pixel value below which a dot is definitely black MidRange The pixel value that has equal likelihood of coming from black or white.
When all smarts have not determined the dot, this value is used to determine it. Pixels below this value are black, and above it are white.
High Level of Process 3 Process 3 simply iterates through each of the segments, performing a single line of processing depending on the segment's current state. The pseudocode is straightforward:
blockCount = 0 while (blockCount < 64) for (i=0; i<8; i++) {
finishedBlock = segment[i].ProcessState() if (finishedBlock) blockCount++
Process 3 must be halted by an external controlling process if it has not terminated after a specified amount of time. This wiU only be the case if the data cannot be exttacted. A simple niechanism is to start a countdown after Process I has finished reading the altemative Artcard. If Process 3 has not finished by that time, the data from the altetnative Artcard cannot be recovered.
GtirraitState = LooldngForTargets Targets are detected by reading columns of pixels, one pixel-column at a time rather than by detecting dots within a given band of pixels (between StartPixel and EndPixel) eertain patterns of pixels are detected. The pixel columns are processed one at a time until either all the targets are found, or until a specified number of columns have been processed. At that time the targets can be processed and the data area located via clockmarks. The state is changed to ExtractingBitlmage to signify that the data is now to be extracted.
If enough valid targets are not located, then the data block is ignored, skipping to a column definitely within the missed data block, and then beginning again the process of looking for the targets in the next data block. This can be seen in the following pseudocode:
finishedBlock = FALSE
if(CurrentColumn < Processl.CurrentScanlrne) [
ProcessPixelColumn() CutrentColtunn++
if ((TargetsFound = 6) II (CurrentColumn > LastColumn)) {
if (TargetsFound >= 2) ProcessTargets() if (TargetsFound >= 2) {
BuildClockmarkEstimates() SetB lackAndWhiteBoundsQ
CurrentState = ExtractingBitImage CumentDotColutnn = -8 }
else {
// data block cannot be recovered. Look for // next instead. Must adjust pixel bounds to // take account of possible 1 degree rotation.
finishedBlock = TRUE
SetBounds(StartPixel-12, EndPixel+12) Bitlmage += 256KB
CurrentByte = 0 LastColumn += 1024 TargetsFound = 0 }
}
return finishedBlock ProcessPixelColumn Each pixel column is processed within the specified bounds (between StartPixel and EndPixel) to search for certain patterns of pixels which will identify the targets. The structure of a single target (target number 2) is as previously shown in Fig. 54:
From a pixel point of view, a target can be identified by:
Left black region, which is a number of pixel columns consisting of large numbers of contiguous black pixels to build up the first part of the target.
* Target center, which is a white region in the center of further black columns * Second black region, which is the 2 black dot columns after the targot center * Target number, which is a black-surrounded white region that defines the target number by its length * Third black region, which is the 2 black coiumns after the target number An overview of the required process is as shown in Fig. 74.
Since identification only relies on black or white pixels, the pixels 1150 from each column are passed through a filter 1151 to detect black or white, and then run length encoded 1152. The run-lengths are then passed to a state machine 1153 that has access to the last 3 run lengths and the 4th last color.
Based on these values, possible targets pass through each of the identification stages.
The GatherMin&Max process 1155 simply keeps the minimum & maximum pixel values encountered during the processing of the segment These are used once the targets have been located to set BlackMax, WhiteMin, and MidRange values.
Each segment keeps a set of target structutr,s in its search for targets.
While the target structures themselves don't move around in memory, several segment variables point to lists of pointers to these target structures. The three pointer lists are repeated here:
LocatedTargets Points to a set of Target structures that represent located targets.
PossibleTargets Points to a set of pointers to Target structures that represent currently investigated pixel shapes that may be targets.
AvailableTargets Points to a set of pointers to Target structures that are currently unused.
There are counters associated with each of these list pointers: TargetsFound, PossibleTargetCount, and AvailableTargetCount respectively.
Before the alternative Artcard is loaded, TargetsFound and PossibleTargetCount are set to 0, and AvailableTargetCount is set to 28 (the maximum number of target structures possible to have under investigation since the minimum size of a target border is 40 pixels, and the data area is approximately 1152 pixels). An example of the target pointer layout is as illustrated in Fig. 75.
As potential new targets are found, they are taken from the AvailableTargets list 1157, the target data structure is updated, and the pointer to the structure is added to the PossibleTargets tist 1158. When a target is completely verified, it is added to the LocatedTargets list 1159. If a possible target is found not to be a target after all, it is placed back onto the AvailableTargets list 1157. Consequently there are always 28 target pointers in circulation at any time, moving between the lists.
The Target data structure 1160 can have the following form:
DataName Comment CurrentState The current state of the target search DetectCount Counts how long a target has been in a given state StartPixel Where does the target start? All the lines of pixels in this target should start within a tolerance of this pixel value.
TargetNumber Which target number is this (according to what was read) Column Best estimate of the target's center column ordinate Pixel Best estimate of the target's center pixel ordinate The ProcessPixelColumn function within the find targets module 1162 (Fig. 74) then, goes through all the run lengths one by one, comparing the runs against existing possible targets (via StartPixel), or creating new possible targets if a potential target is found where none was previously known. In all cases, the comparison is only made if SO.color is white and Sl.oolor is black.
The pseudocode for the ProcessPixelColumn set out hereinafter. When the first target is positively identified, the last column to be checked for targets can be determined as being within a maximum distance from it. For 1 rotation, the maximum distance is 18 pixel cohmtmm pixel = StartPixel t=O
target=PossibleTarget[t]
while ((pixel < EndPixel) && (Targetsi'-ound < 6)) {
if ((SO.Color = white) && (S I.Color = black)) {
do {
keepTrying = FALSE
if ( (target != NULL) &&
(target >AddToTarget(Column, pixel, S 1, S2, S3)) ) {
if (target->CurrentState = IsATarget) {
Remove target from PossibleTargets List Add target to LocatedTargets List TargetcFound++
if (TargetsFound - I ) FinalColumn = Column + MAX TARGET DELTA }
}
else if (target->CurrentState = NotATarget) {
Remove target from PossibleTargets List Add target to AvailableTargets List keepTrying = TRUE
}
else {
t++ // advance to next target target = PossibleTarget[t]
else {
tmp = AvailableTargets{0]
if (tmp->AddToTarget(Column,pixel,S 1,S2,S3) Remove tmp from AvailableTargets list Add tmp to PossibleTargets list t++ target t has been shifted right }
} while (keepTrying) pixel += S i .RunLength Advance SO/S 1/S2/S3 }
AddToTarget is a function within the find targets module that determines whether it is possible or not to add the specific run to the given target:
* If the run is within the tolerance of target's starting position, the run is directly related to the current target, and can therefore be applied to it.
* If the run starts before the target, we assume that the existing target is still ok, but not relevant to the run. The target is therefore left unchanged, and a return value of FALSE tells the caller that the run was not applied.
The caller can subsequenfly check the run to see if it starts a whole new target of its own.
* If the run starts after the target, we assume the target is no longer a possible target. The state is changed to be NotATarget, and a return value of TRUE is returaed.
If the run is to be applied to the target, a specific action is performed based on the current state and set of runs in S1, S2, and S3. The AddToTarget pseudocode is as follows:
IvIAX_TARGET_DELTA = 1 if (CurentState != NothingKnown) if (pixel > StartPixel) run starts after target {
diff = pixel - StartPixel if (diff> MAX_TARGET DELTA) {
CurrentState = NotATarget return TRiJE
}
}
else {
diff = StartPixel - pixel if (diff > MAX_TARGET_DELTA) return FALSE
}
}
runType = DetemtineRunType(S1, S2, S3) EvaluateState(runType) StartPixel = currentPixel retum TRUE
Types of pixel runs are identified in DetermineRunType is as follows:
Types of Pixel Runs Type How identified (Sl is always black) TargetBorder S 1= 40 < RunLength < 50 S2 = white run TargetCenter S I = 15 < RunLength < 26 S2 = white run with [RunLength < 12]
S3 = black run with [ 15 < RunLength < 26]
TargetNumber S2 = white run with [RunLength <= 40]
The EvaluateState procedure takes action depending on the current state and the run type.
The actions are shown as follows in tabular form:
CurrentState Type of Pixel Run Action NothingKnown TargetBorder DetectCount = I
CurrentState = LeftOfCenter LeftOfCenter TargetBorder DetectCount++
if (DetectCount > 24) CurrentState = NotATarget TargetCenter DetectCount = 1 CurrentState = InCenter Column = currentColumn Pixel = currentPixel + S I.RunLength CurrentState = NotATarget InCenter TargetCenter DetectCount++
tmp = currentPixel + S 1.RunLength if (tmp < Pixel) Pixel = tmp if (DetectCount > 13) CurrentState = NotATarget TargetBorder DetectCount = 1 CurrentState = RightOfCenter CurrentState = NotATarget RightOfCenter TargetBorder DetectCount++
if (DetectCount >= 12) CurrentState = NotATarget TargetNumber DetectCount = I
CurrentState = InTargetNumber TargetNumber = (S2.RunLength+ 2)/6 CurrentState = NotATarget InTargetNumber TargetNumber tmp = (S2.RunLength+ 2)/6 if (tmp > TargetNumber) TargetNumber = tmp DetectCount++
if (DetectCount >= 12) CurrentState = NotATarget CurrentState Type of Pixel Run Action TargetBorder if (DetectCount >= 3) CurrentState = IsATarget else CurrentState = NotATarget CurrentState = NotATarget IsATarget or -NotATarget Processing Targets he located targets (in the LocatedTargets list) are stored in the order they were located. Depending on alternative Artcard rotation these targets will be in ascending pixel order or descending pixel order. In addition, the target numbets recovered from the targets may be in error. We may have also have recovered a false target. Before the clockmark estimates can be obtained, the targets need to be processed to ensure that invalid targets are discarded, and valid targets have target numbers fixed if in error (e.g. a damaged target number due to dirt). Two main steps are involved:
* Sort targets into ascending pixel order * Locate and fix erroneous target numbers The first step is simple. The nature of the target retrieval means that the data should already be sorted in either ascending pixel or descending pixel. A simple swap sort ensures that if the 6 targets are already sorted con-ectly a maximum of 14 comparisons is made with no swaps. If the data is not sorted, 14 comparisons are made, with 3 swaps_ The following pseudocode shows the sorting process:
for (i = 0; i <TargetsFound-1; i++) oldTarget = LocatedTargets[i]
bestPixel = oldTarget->Pixel best = i j=i+1 while (jlTargetsFound) if (LocatedTargets[j]-> Pixel < bestPixel) best = j j++
if (best != i) // move only if necessary LocatedTargets[i] = LocatedTargets[best]
L.ocatedTargets[best] = oldTarget }
Locating and fixing erroneous target numbers is only slightly more complex_ One by one, each of the N
targets found is assumed to be con=t. The other targets are compared to this "cotrect" target and the number of targets that require change should target N be correct is counted. If the number of changes is 0, then all the targets must afready be cotrect. Otherwise the target that requires the fewest changes to the others is used as the base for change. A
change is registered if a given target's target number and pixel position do not correlate when compared to the "correct" target's pixel position and target number. The change may mean updating a target's target number, or it may mean elimination of the target. It is possible to assume that ascending targets have pixels in ascending order (since they have already been sorted).
kPixelFactor = I1(55 * 3) bestTarget = 0 bestChanges = TargetsFound + 1 for (i-0; i< TotalTargetsFound; i++) {
numberOfChanges = 0;
fromPixel = (LocatedTargets[i])->Pixel fromTargetNumber = LocatedTargets[i].TargetNumber for (j=1; j< TotalTargetsFound; j++) {
toPixel = LocatedTargets[j)->Pixel deltaPixel = toPixel - fromPixel if (deltaPixel >= 0) deltaPixel += PIXELS_BE'IWEEN TARGET_CENTRESrl else deltaPixel -= PIXELS_BEIWEEN TARGET CENTRES/2 targetNtumber =deltaPixel * kPixelFactor targetNumber += fromTargetNumber if (targetNumber < I )A(targetNumber > 6) II
(targetNumber != L.ocatedTargets[j]-> TargetNumber) numbetOiChanges++
if (numberOfChanges < bestChanges) {
bestTarget = i bestChanges = numberOfChanges }
if (bestChanges < 2) break;
}
In most cases this function will terminate with bestChanges = 0, which means no changes are required.
Otherwise the changes need to be applied. The functionality of applying the changes is identical to counting the changes (in the pseudocode above) until the comparison with targetNumber. The change application is:
if ((targetNumber < I )II(targetNumber > TARGETS_PER_BLOCK)) {
LocatedTargets(j] = NULL
TargetsFound--}
else {
LocatedTargets(j]-> TargetNumber = targetNumber At the end of the change loop, the LocatedTargets list needs to be compacted and all NULL targets removed.
At the end of this procedure, there may be fewer targets. Whatever targets remain may now be used (at least 2 targets are required) to locate the clockmarks and the data region.
Building Clockmark Estimates from Targets As shown previously in Fig. 55, the upper region's first clockmark dot 1126 is 55 dots away from the center of the first target 1124 (which is the same as the distance between target centers). The center of the clockmark dots is a further 1 dot away, and the black border line 1123 is a further 4 dots away from the first clockmark dot. The lower region's fust clocktnark dot is exactly 7 targets-distance away (7 x 55 dots) from the upper region's first clockmark dot 1126.
It cannot be assumed that Targets 1 and 6 have been located, so it is necessary to use the upper-most and lower-most targets, and use the target numbers to determine which targets are being used. It is necessary at least 2 targets at this point. In addition, the target centers are only estimates of the actual target centers. It is to locate the target center more accurately. The center of a target is white, surrounded by black. We Iherefore want to find the local maximum in both pixel & column dimensions. This involves reconstructing the continuous image since the maximum is unlikely to be aligned exactly on an integer boundary (our estimate).
Before the continuous image can be constructed around the target's center, it is necessary to create a better estimate of the 2 target centers. The existing target centers actually are the top left coordinate of the bounding box of the target center. It is a simple process to go through each of the pixels for the atea defining the center of the target, and find the pixel with the highest value. There may be more than one pixel with the same maximum pixel value, but the estimate of the center value only requires one pixel.
The pseudocode is straightforward, and is performed for each of the 2 targets:
CENTER_WIDTH = CENTER_MGHT = 12 maxPixel = Ox00 for (i=O; i<CBN'IER_WIDTH; i++) for (j=0; j<CEN'IER_MGHT; j++) t -p = GetPixel(colunut+i, pixel+j) if (p > maxPixel) maxPixel = p centerColumn = column + i centerPixel = pixel + j }
Target.Column = centerColumn Target.Pixel = centerPixel At the end of this process the target center coordinates point to the whitest pixel of the target, which should be within one pixel of the actual center. The process of building a more accurate position for the target center involves reconstructing the continuous signal for 7 scanline slices of the target, 3 to either side of the estimated target center.
The 7 maximum values found (one for each of these pixel dimension slices) are then used to reconstruct a continuous signal in the column dimension and thus to locate the maximum value in that dimension.
Given estimates column and pixel, determine a 1/ betterColumn and betterPixel as the center of // the target for (y=O; y<7; y++) for (x=O; x<7; x++) samples[x] = GetPixel(column-3+y, pixel-3+x) FindMax(samples, pos, maxVal) reSamples[y] = maxVal if(y-3) betterPixel = pos + pixel }
FindMax(reSamples, pos, maxVal) betterColumn = pos + column FindMax is a function that reconstructs the original I dimensional signal based sample points and returns the position of the maximum as well as the maximum value found. The method of signal reconsttuction/resampling used is the Lanczos3 windowed sinc function as shown in Fig. 76.
The Lanczos3 windowed sinc function takes 7 (pixel) samples from the dimension being reconstructed, centered around the estimated position Y. i.e. at X-3, X-2, X-1, X, X+1, X+2, X+3. We reconstruct points from X-1 to X+1, each at an interval of 0.1, and determine which point is the maximum. The position that is the maximum value becomes the new center. Due to the nature of the kernel, only 6 entries are required in the convolution kernel for points between X and X+I. We use 6 points for X-1 to X, and 6 points for X to X+1, requiring 7 points overall in order to get pixel values from X-1 to X+1 since sonte of the pixels required are the same.
Given accurate estimates for the upper-most target from and lower-most target to, it is possible to calculate the position of the fust clockmark dot for the upper and lower regions as follows:
TARGETS_PER_BLOCK = 6 numTargetsDiff = to.TargetNum - from.TargetNum deltaPixel = (to.Pixel - from.Pixel) / numTargetsDiff deltaColumn = (to.Column - from.Column) / numTargetsDiff UpperClock.pixel = from.Pixel - (from.TargetNum*deltaPixel) UpperClock.column = from.Column-(from.TargetNum*deltaColumn) 1/ Given the first dot of the upper clockmark, the // first dot of the lower clockmark is straightforward.
LowetClock.pixel = UpperClock.pixel +
((TARGETS_PER_ BLOCK+I) * deltaPixel) LowetClock.column = UpperClock.column +
((TARGETS_PER- BLOCK+I) * deltaColumn) This gets us to the first clockmark doL It is necessary move the column position a further I dot away from the data area to reach the center of the clockmark. It is necessary to also move the pixel position a further 4 dots away to reach the center of the border line. The pseudocode values for deltaColumn and deltaPixel are based on a 55 dot distance (the distance between targets), so these deltas must be scaled by 1/55 and 4/55 tespectively before being applied to the clockmark coordinates. "I7 s is represented as:
kDeltaDotFactor = 1/DOTS_BETWF.EN TARGET CENTRES
deltaColumn *= kDeltaDotFactor deltaPixel *= 4 * kDeltaDotFactor UpperClock.pixel -= deltaPixel UpperClock.column -= deltaColumn LowerClock.pixel += deltaPixel LowerClock.column += deltaColumn UpperClock and Lov/erClock are now valid clockmark estimates for the first clockmarks directly in line with the centers of the targets.
Setting Black and White Pixel/Dot Ranges Before the data can be extracted from the data area, the pixel ranges for black and white dots needs to be ascertained. The n nimum and maximum pixels encountered during the search for targets were stored in WhiteMin and BlackMax respectively, but these do not represent valid values for these variables with respect to data extraction.
They are merely used for storage convenience. The following pseudocode shows the method of obtaining good values for WhiteMin and BlackMax based on the min & max pixels encountered:
MinPixel = WhiteMin MaxPixel = BlackMax MidRange = (MinPixel + MaxPixel) / 2 WhiteMin = MaxPixel - 105 BlackMax = MinPixel + 84 CurrentState = ExtractingBitlmage The F.xtractingBitlnwge state is one where the data block has already been accurately located via the targets, and bit data is currently being extracted one dot column at a time and written to the alternative Artcard bit image. The following of data block clockmarks/borders gives accurate dot recovery regardless of rotation, and thus the segment bounds are ignored. Once the entire data block has been extracted (597 columns of 48 bytes each; 595 columns of data + 2 orientation columns), new segment bounds are calculated for the next data block based on the current position. The state is changed to LookingForTargets.
Processing a given dot column involves two tasks:
* The first task is to locate the specific dot column of data via the clockmarks.
* The second task is to run down the dot column gathering the bit values, one bit per dot.
These two tasks can only be undertaken if the data for the column has been read off the alternative Artcard and ttansfetred to DRAM. This can be determined by checking what scanline Process I is up to, and comparing it to the clockmark columns. If the dot data is in DRAM we can update the clockmarks and then extract the data from the column before advancing the clockmarks to the estimated value for the next dot column. The process overview is given in the following pseudocode, with specific functions explained hereinafter:
finishedBlock = FALSE
if((UpperClock.column < Process 1.CurrentScani.ine) &&
(LowerClock_coiumn < Process I.CurrentScanLine)) DetermineAccurateClockMarks() DetermineDataInfo() if (CurrentDotColumn >= 0) ExtractDataFromColumnO
AdvanceClockMarks() if (CurrentDotCoiumn = FINAL-COLUMN) {
finishedBlock = TRUE
currentState = LookingForTargets SetBounds(UpperClock.pixel, LowerClock.pixel) BitItnage += 256KB
CurrentByte = 0 TargetsFound = 0 }
return finishedB lock Locating the dot colunw A given dot column needs to be located before the dots can be read and the data extracted. This is accomplished by following the clockmarks/borderline along the upper and lower boundaries of the data block. A
software equivalent of a phase-locked-loop is used to ensure that even if the clockmarks have been damaged, good estimations of clockmark positions will be made. Fig. 77 illustrates an example data block's top left which corner reveals that there are clockmarks 3 dots high 1166 extending out to the target area, a white row, and then a black border line.
Initially, an estimation of the center of the first black clockmark position is provided (based on the target positions). We use the black border 1168 to achieve an accurate vertical position (pixel), and the clockmark eg. 1166 to get an accurate horizontal position (column). These are reflected in the UpperClock and LowerClock positions.
The clockmark estimate is taken and by looking at the pixel data in its vicinity, the continuous signal is reconstructed and the exact center is deterarined. Since we have broken out the two dimensions into a clockmark and border, this is a simple one-dimensional process that needs to be perfonnied twice. However, this is only done every second dot column, when there is a black clockmark to register against. For the white clockmarks we simply use the estimate and leave it at that. Alternatively, we could update the pixel coordinate based on the bonder each dot column (since it is always present). In practice it is sufficient to update both ordinates every other column (with the black clockmarks) since the resolution being worked at is so fine. The process therefore becomes:
// Tutn the estimates of the clockmarks into accurate positions only when there is a black clockmark /1(ie every 2nd dot coiumn, starting from -8) if (BitO(CurrentDotColumn) = 0) 1/ even column {
DetermineAccurateUpperpot{,enterQ
DetermineAccurateLowerpotCenterQ
If there is a deviation by more than a given tolerance (MAX_CLOCKMARK_DEVIATION), the found signal is ignored and only deviation from the estimate by the maximum tolerance is allowed. In this respect the functionality is similar to that of a phase-locked loop. Thus DetermineAccurateUpperDotCenter is implemented via the following pseudocode:
/! Use the estimated pixel position of // the border to determine where to look for // a more accurate clockmark center. The clockmark // is 3 dots high so even if the estimated position // of the border is wrong, it won't affect the // fixing of the clockmark position.
MAX-CLOCKMARK_DEVIATION = 0S
diff = GetAccurateColumn(UpperClock.column, UpperClock.pixel+(3*PD{ELS_PER_DOT)) diff = UpperClockcolumn if (diff> MAX_CLOCKMARK_DEVIATION) diff = MAX CLOCKMARIC DEVIATION
else if (diff < -MAX CLOCKMARK DEVIATION) diff = -MAX CLOCKMARK,-DEVIATION
UpperClock.column += diff // Use the newly obtained clockmark center to // determine a more accurate border position.
diff = GetAccuratePixel(UpperClockcoiumn, UpperClockpixel) diff -= UpperClock.pixel if (diff > MAX_CLOCKMARK_DEVIATION) diff = MAX CLOCKMARK_DEVIATION
else if (diff < -MAX_CLOCKMARK_DEVIATION) diff = -MAX_CLOCKMARK DEVIATION
UpperClockpixel += diff DetemtineAccurateLowerpotCenter is the same, except that the direction from the border to the clockmark is in the negative direction (-3 dots rather than +3 dots)_ GetAccuratePixel and GetAceurateColumn are functions that determine an accurate dot center given a coordinate, but only from the perspective of a single dimension. Determining accurate dot centers is a process of signal reeonstntction and then finding the location whete the minimum signal value is found (this is differcnt to locating a target oenter, which is locating the maximum value of the signal since the target center is white, not black). The method chosen for signal reconstruction/resampling for this application is the Lanezos3 windowed sinc function as previously discussed with reference to F'ig. 76.
It may be that the clockmark or border has been damaged in some way - perhaps it has been scratched. If the new center value retrieved by the resampling differs from the estimate by more than a tolerance amount, the center value is only moved by the maximum tolorartce. If it is an invalid position, it should be close enough to use for data retrieval, and future clockmarks will resynchronize the position.
Determining the center of the first data dot and the deltas to subsequent dots Once an accurate UppeaClock and LowerClock position has been determined, it is possible to calculate the center of the first data dot (CurrentDot), and the delta amounts to be added to that center position in order to advance to subsequent dots in the column (DataDelta).
The first thing to do is calculate the deltas for the dot column. This is achieved simply by subtracting the UpperClock from the LowerClock, and then dividing by the number of dots between the two points. It is possible to actually multiply by the inverse of the number of dots since it is constant for an alterttative Artcard, and multiplying is fister. It is possible to use different constants for obtaining the deltas in pixel and column dimensions_ The delta in pixels is the distance between the two borders, while the delta in columns is between the centers of the two cloclcmarks. Thus the funetion DetermineDatalnfo is two parts. The first is given by the pseudocode:
kDeltaColumnFactor = 1/(DOTS_PER_DATA_COLUMN + 2+ 2 - 1) kDeltaPixelFactor = 1/(DOTS PER DATA COLUMN + 5+ 5- 1) delta = LowerClockcolumn - UppeiClockcolumn DataDelta.column = delta * kDeltaColumnFactor delta = LowerClockpixel - UppetClockpixel DataDeltapixel = delta * kDeltaPixelFactor It is now possible to determine the center of the first data dot of the column. There is a distance of 2 dots from the center of the clockmark to the center of the first data dot, and 5 dots from the center of the border to the center of the first data dot. Thus the second part of the function is given by the pseudocode:
CutrentDot.coltunn = UppetClockcolutnn + (2*DataDeltacolumn) CtrrentDot.pixel = Upper(.'lockpixel + (5*DataDe1ta pixel) Running down a dot column Since the dot column has been located from the phase-locked loop tracking the clockmarks, all that remains is to sample the dot column at the ccnter of each dot down that column. The variable CurrentDot points is determined to the center of the first dot of the current column. We can get to the next dot of the column by simply adding DataDelta (2 additions: I for the column ordinate, the other for the pixel ordinate). A
sample of the dot at the given coordinate (bi-linear interpolation) is taken, and a pixel value representing the center of the dot is determined. The pixel value is then used to determine the bit value for that dot. However it is possible to use the pixel value in context with the center value for the two surrounding dots on the same dot line to make a better bit judgement.
We can be assured that all the pixels for the dots in the dot column being extracted are cun-ently loaded in DRAM, for if the two ends of the line (clockmarks) are in DRAM, then the dots between those two clockmarks must also be in DRAM. Additionally, the data block height is short enough (only 384 dots high) to ensure that simple deltas are enough to traverse the length of the line. One of the reasons the card is divided into 8 data blocks high is that we cannot make the same rigid guarantee across the entire height of the card that we can about a single data block.
The high level process of extracting a single line of data (48 bytes) can be seen in the following pseudocode.
The dataBuffer pointer increments as each byte is stored, ensuring that consecutive bytes and columns of data are stored consecutively.
bitCount = 8 curr = Ox00 // definitely black next = GetPixel(CurrentDot) for (i=0; i < DOTS_PER DATA_COLUMN; i++) {
CurrentDot += DataDelta prev = curr curr = next next = GetPixel(CurrentDot) bit = DetermineCenterpot(prev, curr, next) byte = (byte 1) 1 bit bitCount-if (bitCount = 0) {
*(Bitimage I CurrentByte) = byte CurrentByte++
bitCount = 8 }
}
The GetPixel function takes a dot coordinate (ftxed point) and samples 4 CCD
pixels to ariive at a center pixel value via bilinear interpolation_ The DetermineCenterDot function takes the pixel values representing the dot centers to either side of the dot whose bit value is being determined, and attempts to intelligently guess the value of that center dot's bit value. From the generalized blutring curve of Fig. 64 there are three conunon cases to consider:
* The dot's center pixel value is lower than WhiteMin, and is therefore definitely a black dot. The bit value is therefore definitely 1.
* The dot's center pixel value is higher than BlackMax, and is therefore definitely a white doL The bit value is therefore definitely 0.
* The dot's center pixel value is sontewhere between BlackMax and WhiteMin.
The dot may be black, and it may be white. The value for the bit is therefore in question. A number of schemes can be devised to make a reasonable guess as to the value of the bit. "Iltese schemes must balance complexity against accuracy, and also take into account the fact that in some cases, there is no guaranteed solution. In those cases where we make a wrong bit decision, the bit's Reed-Solomon symbol will be in error, and must be coirected by the Reed-Solomon decoding stage in Phase 2.
The scheme used to detennine a dot's value if the pixel value is between BlackMax and WhiteMin is not too complex, but gives good results. It uses the pixel values of the dot centers to the left and right of the dot in question, using their values to help detenn-kine a more likely value for the center dot:
* If the two dots to either side are on the white side of MidRange (an average dot value), then we can guess that if the center dot were white, it would likely be a "definite"
white. The fact that it is in the not-sure region would indicate that the dot was black, and had been affected by the surrounding white dots to make the value less sure.
The dot value is therefore assumed to be black, and hence the bit value is I.
* If the two dots to either side are on the black side of MidRange, then we can guess that if the center dot were black, it would likely be a "definite" black. The fact that it is in the not-sure region would indicate that the dot was white, and had been affected by the surrounding black dots to make the value less sure. The dot value is therefore assumed to be white, and hence the bit value is 0.
* If one dot is on the black side of MidRange, and the other dot is on the white side of MidRange, we simply use the center dot value to decide. If the center dot is on the black side of MidRange, we choose black (bit value 1). Otherwise we choose white (bit value 0).
The logic is represented by the following:
if (pixel < WhiteMin) definitely black bit = Ox01 else if (pixel > BlackMax) definitely white bit = Ox00 else if ((prev > MidRange) && (next> MidRange)) //prob black bit - OxOl else if ((prev < MidRange) && (next < MidRange)) //prob white bit = OxOO
else if (pixel < MidRange) bit = Ox01 else bit = OxOO
From this one can see that using surrounding pixel values can give a good indication of the value of the center dot's state. The scheme described here only uses the dots from the same row, but using a single dot line history (the previous dot line) would also be straightforward as would be alternative arrangements.
Updating dockroarlts for the next column Once the center of the first data dot for the column has been determined, the clockmark values are no longer needed. They are conveniently updated in readiness for the next column after the data has been retrieved for the column. Since the clockmark direction is perpendicular to the traversal of dots down the dot column, it is possible to use the pixel delta to update the column, and subtract the column delta to update the pixel for both clocks:
UpperClock.column += DataDelta.pixel LowerClockcolumn += DataDeltapixel UpperClock.pixel -= DataDeltacoiumn LowetCtock.pixel -= DataDelta.column These are now the estimates for the next dot column.
'lmmng The timing requirement will be met as long as DRAM utilization does not exceed 100%, and the addition of parallel algorithm timing multiplied by the algorithm DRAM utiGzation does not exceed 100%. DRAM utilization is specified relative to Processl, which writes each pixel once in a consecutive manner, consuming 99'0 of the DRAM
bandwidth.
The timing as described in this section, shows that the DRAM is easily able to cope with the demands of the alternative Artcard Reader algotithm. The timing bottleneck will therefore be the implementation of the algorithm in terms of logic speed, not DRAM access. The algorithms have been designed however, with simple architectures in mind, requiring a minimum number of logical operations for every memory cycle.
From this point of view, as long as the implementation state machine or equivalent CPU/DSP architecutre is able to perform as described in the following sub-sections, the target speed will be met.
Locating the brgets Targets are located by reading pixels within the bounds of a pixel column.
Each pixel is read once at most.
Assuming a run-length encoder that operates fast enough, the bounds on the location of targets is memory access. The accesses will therefore be no worse than the timing for Process 1, which means a 9% utiii7ation of the DRAM
bandwidth.
The total utilization of DRAM during target location (including Processl) is therefore 18%, meaning that the target locator will always be catching up to the alternative Artcard image sensor pixel reader.
Processing the targets The timing for sorting and checking the target numbers is trivial. The finding of better estimates for each of the two target centers involves 12 sets of 12 pixel reads, taking a total of 144 reads. However the fixing of accurate target centers is not trivial, requiring 2 sets of evaluations_ Adjusting each target center requires 8 sets of 20 different 6-entry convolution ketnels. Thus this totals 8 x 20 x 6 multiply-accumulates = 960. In addition, there ane 7 sets of 7 pixels to be retrieved, requiring 49 memory accesses. The total number per target is therefore 144 + 960 + 49 = 1153, which is approximately the same number of pixels in a column of pixels (1152).
Thus each target evaluation consumes the tiate taken by otherwise processing a row of pixels. For two targets we effectively consume the time for 2 columns of pixels.
A target is positively identified on the first pixel column after the target number. Since there are 2 dot columns before the orientation column, there are 6 pixel columns. The Target Location process effectively uses up the ftrst of the pixel columns, but the remaining 5 pixel columns are not processed at all.
Therefore the data area can be located in 2/5 of the time- available without impinging on any other process time.
The remaining 3/5 of the time available is ample for the trivial task of assigning the ranges for black and white pixels, a task that may take a couple of machine cycles at most.
Extracti;ng data There are two parts to consider in terms of timing:
* Getting accurate clockmarks and border values * Extracting dot values Clockmarks and border values are only gathered every second dot column.
However each time a clockmark estimate is updated to become more accurate, 20 different 6-entry convolution kernels must be evaluated. On average thete ate 2 of these per dot column (there are 4 every 2 dot-columns).
Updating the pixel ordinate based on the border only requires 7 pixels from the same pixel scanline. Updating the column ordinate however, requires 7 pixels from different columns, hence different scanlines. Assuming worst case scenario of a cache miss for each scanline entry and 2 cache misses for the pixels in the same scanGne, this totals 8 cache misses.
Extracting the dot information involves only 4 pixel reads per dot (rather than the average 9 that define the dot). Considering the data area of 1152 pixels (384 dots), at best this will save 72 cache reads by only reading 4 pixel dots instead of 9. The worst case is a rotation of 1 which is a single pixel translation every 57 pixets, which gives only slightly worse savings.
It can then be safely said that at worst, we will be reading fewer cache lines less than that consumed by the pixels in the data area. The accesses will thetefore be no worse than the tinting for Process I, which implies a 9%
utilization of the DRAM bandwidth.
The total utilization of DRAM during data extraction (including Process 1) is therefore 18%, meaning that the data extractor will always be catching up to the alternative Artcard intage sensor pixel nader. This has implications for the Process Targets process in that the processing of targets can be performed by a relatively inefficient method if necessary, yet sdll catch up quickly during the extracting data prooess-Phase 2- Decode Bit Image Phase 2 is the non-real-time phase of alternative Artcard data recovery algorithm. At the start of Phase 2 a bit image has been extracted from the alternative Artcard_ It represents the bits read from the data regions of the alternative Artcard. Some of the bits will be in error, and perhaps the entire data is rotated 180 because the alternative Artcard was rotated when inserted. Phase 2 is concerned with reliably extracting the original data from this encoded bit image.
There are basically 3 steps to be carried out as illustrated in Fig. 79:
* Reorganize the bit image, reversing it if the alternative Artcard was inserted backwards * Unscramble the encoded data * Reed-Solomon decode the data from the bit image Each of the 3 steps is defined as a separate process, and performed consecutively, since the output of one is required as the input to the next. It is straightforward to combine the first two steps into a single process, but for the purposes of clarity, they are treated separately here.
From a data/process perspective, Phase 2 has the structure as illustrated in Fig. 80.
The timing of Processes I and 2 are likely to be negligible, consuming less than 1/1000t' of a second between them. Process 3 (Reed Solomon decode) consumes approximately 0.32 seconds, making this the total time required for Phase 2.
Reorganize the bit image, reversing it if necessary The bit map in DRAM now represents the retrieved data from the alternative Artcard. However the bit image is not contiguous. It is broken into 64 32k chunks, one chunk for each data block.
Each 32k chunk contains only 28,656 useful bytes:
48 bytes from the leftmost Orientation Column 28560 bytes from the data region proper 48 bytes from the rightmost Orientation Column 4112 unused bytes The 2MB buffer used for pixel data (stored by Process 1 of Phase 1) can be used to hold the reorganized bit image, since pixel data is not required during Phase 2. At the end of the reorganization, a correctly oriented contiguous bit image will be in the 2MB pixel buffer, ready for Reed-Solomon decoding.
If the card is correctly oriented, the leftmost Orientation Column will be white and the rightmost Orientation Column will be black. If the card has been rotated 180 , then the leftmost Orientation Column will be black and the rightmost Orientation Column will be white.
A simple method of determining whether the card is correctly oriented or not, is to go through each data block, checking the first and last 48 bytes of data until a block is found with an overwhelming ratio of black to white bits. The following pseudocode demonstrates ihis, returning TRUE if the card is correctly oriented, and FALSE if it is not totalCountL = 0 totalCountR = 0 for (i=O; i<64; i++) blackCountL = 0 blackCountR = 0 currBuff = dataBuffer for (j=0; j<48; j++) blackCountL += CountBits(*currBufl) currBuff++
}
currBuff += 28560 for (j_0; j<48; j++) blackCountR += CountBits(*cuirBuff) currBuff++
}
dataBuffer += 32k if (blackCountR > (blackCountL * 4)) return TRUE
if (btackCountL> (blackCountR * 4)) return FALSE
totalCountL += blackCountL
totalCountR += blackCountR
}
return (totalCountR > totalCountL) The data must now be reorganized, based on whether the card was oriented correctly or not. The simplest case is that the card is correctly oriented. In this case the data only needs to be moved around a little to remove the orientation columns and to make the entire data contiguous. This is achieved very simply in situ, as described by the following pseudocode:
DATA_BYTES_pER_pATA BLOCK=28560 to = dataBuffer from = dataBuffer + 48) // left orientation column for (i=0; i<64; i++) I
BlockMove(from, to, DATA Bl''IFS_YER-DATA BI:OCK) from += 32k to += DATA BYIES_PER DATA_BLOCK
}
The other case is that the data actually needs to be reversed. The atgoritfim to reverse the data is quite simple, but for simplicity, requires a 256-byte table Reverse where the value of Reverse[N] is a bit-reversed N.
DATA_BYTE.S_PER_DATA_BLOCK = 28560 to = outBuffer for (i=O; i<64; i++) {
from = dataBuffer + (i * 32k) from += 48 /1 skip orientation column from += DATA_Bl'TF.S_PER_DATA_BLOCK - 1 // end of block for (j=0; j < DATA_BYTF.S_PER_DATA_BLOCK; j++) [
*to++ = Reverse[*from]
from--The tiniing for either process is negligible, consuming less than 1/1000'" of a second:
* 2MB contiguous reads (2048/16 x 12ns = 1,536ns) * 2MB effectively contiguous byte writes (2048/16 x 12ns = 1,536ns) Unscramble the encoded intage Tbe bit image is now 1,827,840 contiguous, comectly oriented, but scrambled bytes. The bytes must be unscrambled to create the 7,168 Reed-Solomon blocks, each 255 bytes long. The unscrambling process is quite straightforward, but requires a separate output buffer since the unscrambling cannot be performed in situ. Fig. 80 illustrates the unscrambling process conducted memory The following pseudocode defines how to perform the unscrambling process:
groupSize = 255 numBytes = 1827840;
inBuffer = sctambledButf'er.
outBuffer = unscrambledBuffer;
for (i=0; i<groupSize; i++) for (j=i; j<numBytes; j+=groupSize) outBuffer[j] = *inBuffer++
The tinring for this process is negligible, consuniing less than 1/10006 of a second:
* 2MB contiguous reads (2048/16 x 12ns = 1,536ns) * 2MB non-contiguous byte writes (2048 x 12ns = 24,576ns) At the end of this process the unscrambled data is ready for Reed-Solomon decoding.
Reed Solomon decode The final part of reading an alternative Artcard is the Reed-Solomon decode process, where approximately 2MB of unscrambled data is decoded into approximately 1 MB of valid alternative Artcard data.
The algorithm performs the decoding one Reed-Solomon block at a time, and can (if desired) be performed in situ, since the encoded block is larger than the decoded block, and the redundancy bytes are stored after the data bytes_ The first 2 Reed-Solomon blocks are control blocks, containing information about the size of the data to be extracted from the bit image. This meta-information must be decoded first, and the resultant information used to decode the data proper. The decoding of the data proper is simply a case of decoding the data blocks one at a time.
Duplicate data blocks can be used if a particular block fails to decode.
The highest level of the Reed-Solomon decode is set out in pseudocode:
// Constants for Reed Solomon decode sourceBlockL.ength = 255;
destBlockl.ength = 127;
numControlBlocks = 2;
O Decode the control information if (! GetControlData(source, destB locks, lastBlock)) return error destBytes = ((destBlocks-1) * destBlockL.ength) + lastBlock offsetToNextDuplicate = destBlocks * sourceBlockLength A Slcip the control blocks and position at data source += numControlBlocks * sourceBlockLength !1 Decode each of the data blocks, trying U duplicates as necessary blocksInEiror = 0;
for (i=O; i<destBlocks; i++) {
found = DecodeBlock(sottrce, dest);
if (! found) {
duplicate = source + offsetToNextDuplicate while ((! found) && (duplicate<sourceEnd)) found = DecodeBlock(dupticate, dest) duplicate += offsetToNextDuplicate }
if (! found) blocksInError++
source += sourceBlockLength dest += destBlockLength }
return destBytes and blocksInEn-or DecodeBlock is a standard Reed Solomon block decoder using m=8 and t=64.
The GetControlData function is straightforward as long as there are no decoding errors. The function simply calls DecodeB lock to decode one control block at a tinie until successful.
The control parameters can then be extracted from the first 3 bytes of the decoded data (destBlocks is stored in the bytes 0 and 1, and lastBlock is stored in byte 2). If there are decoding errors the function must traverse the 32 sets of 3 bytes and decide which is the most likely set value to be correct. One simple method is to find 2 consecutive equal copies of the 3 bytes, and to declare those values the correct ones_ An alternative method is to count occurrences of the different sets of 3 bytes, and announce the most common occurrence to be the correct one.
The time taken to Reed-Solomon decode depends on the implementation. While it is possible to use a dedicated core to perform the Reed-Solomon decoding process (such as LSI
Logic's L64712), it is preferable to select a CPU/DSP combination that can be more generally used throughout the embedded system (usually to do something with the decoded data) depending on the application. Of course decoding time must be fast enough with the CPU/DSP
combination.
The L64712 has a throughput of 50Mbits per second (around 6.25MB per second), so the time is bound by the speed of the Reed-Solomon decoder rather than the maximum 2MB read and 1 MB
write memory access time. The time taken in the worst case (all 2MB requires decoding) is thus 2/6.25s =
approximately 0.32 seconds. Of course, many further refinements are possible including the following:
The blurrier the reading environment, the more a given dot is influenced by the surrounding dots. The current reading algorithm of the preferred embodiment has the ability to use the surrounding dots in the same column in order to make a better decision about a dot's value. Since the_previous column's dots have already been decoded, a previous column dot history could be useful in detertitining the value of those dots whose pixel values are in the not-sure range.
A different possibility with regard to the initial stage is to remove it entirely, make the initial bounds of the data blocks larger than necessary and place greater intelligence into the ProcessingTargets functions. This may reduce overall complexity. Care must be taken to maintain data block independence.
Furiher the control block mechanism can be made more robust:
' The control block could be the first and last blocks rather than make them contiguous (as is the case now). This may give greater protection against certain pathological damage scenarios.
* The second refinement is to place an additional kvel of redundancy/error detection into the control block structure to be used if the Reed-Solomon decode step fails. Something as simple as parity might improve the likelihood of control information if the Reed-Solomon stage fails.
Phase 5 Running the Vark scriQt The overall time taken to read the Artcard 9 and decode it is therefore approximately 2_ 15 seconds. The apparent delay to the user is actually only 0.65 seconds (the total of Phases 3 and 4), since the Artcard stops moving after 1.5 secotids.
Once the Artcard is loaded, the Artvark script must be intetpreted, Rather than run the script immediately, the script is only run upon the pressing of the 'Print' button 13 (Fig. 1). The taken to run the script will vary depending on the complexity of the script, and must be taken into account for the perceived delay between pressing the print button and the actual print button and the actual printing.
As noted previously, the VLIW processor 74 is a digital processing system that accelerates computationally expensive Vark functions. The balance of functions perfotmed in software by the CPU core 72, and in hardware by the VLIW processor 74 will be implementation dependent. The goal of the VLIW
processor 74 is to assist all Artcard styles to execute in a time that does not seem too slow to the user. As CPUs become faster and more powerful, the number of functions requiring hardware acceleration becomes less and less. The VLIW processor has a microcoded ALU sub-system that allows general hardware speed up of the following time-critical functions.
1) Image access mechanisms for general software processing 2) Image convolver.
3) Data driven iniage warper 4) Image scaling 5) Image tessellation 6) Affine transform 7) Image compositor 8) Color space transform 9) Histogram collector 10) Illumination of the Image 11) Brush stamper 12) Histogram collector 13) CCD image to internal image conversion 14) Construction of image pyramids (used by warper & for brushing) The following table summarizes the time taken for each Vark operation if implemented in the ALU model.
The method of implementing the function using the ALU model is described hereinafter.
Operation Speed of Operation 1500 * 1000 image 1 channel 3 channels Image composite I cycle per output pixel 0.015 s 0.045 s Image convolve k/3 cycles per output pixel (k = kernel size) 3x3 convolve 0.045 s 0.135 s 5x5 convolve 0.125 s 0.375 s 7x7 convolve 0.245 s 0.735 s Image warp 8 cycles per pixel 0.120 s 0.360s Histogram collect 2 cycles per pixel 0.030 s 0.090 s Image Tessellate 1/3 cycle per pixel 0.005 s 0.015 s Image sub-pixel Translate I cycle per output pixel -Color lookup replace 'h cycle per pixel 0.008 s 0.023 Color space transform 8 cycles per pixel 0.120 s 0.360 s Convert CCD image to 4 cycles per output pixel 0.06 s 0.18 s internal itnage (including color convert & scale) Construct image pyramid 1 cycle per input pixel 0.015 s 0.045 s Scale Maximum of: 0.015 s 0.045 s (minimum) 2 cycles per input pixel (fftinimum) 2 cycles per output pixel 2 cycles per output pixel (scaled in X only) Affine transform 2 cycles per output pixel 0.03 s 0.09 s Brush rotatekranslate and ?
composite Tile Image 4-8 cycles per output 0.015 s to 0.030 s 0.060 s to 0.120 s to for pixel 4 channels (Lab, texture) Illuminate image Cycles per pizel Ambient only 0.008 s 0.023 s Directional light l 0.015 s 0.045s Directional (bm) 6 0.09 s 0.27 s Omni light 6 0.09 s 0.27 s Omni (bm) 9 0.137 s 0.41 s Spotlight 9 0.137 s 0.41 s Spotlight (bm) 12 0.18 s 0.54 s (bm) = bumpmap For example, to convert a CCD image, collect histogram & perform lookup-color replacement (for image enhancement) takes: 9+2+05 cycles per pixel, or 11.5 cycles. For a 1500 x 1000 image that is 172,500,000, or approximately 0.2 seconds per component, or 0.6 seconds for all 3 components.
Add a simple warp, and the total comes to 0.6 + 0.36, almost 1 second.
ImaQe Convolver A convolve is a weighted average around a center pixel. The average may be a simple sum, a sum of absolute values, the absolute value of a sum, or sums truncated at 0.
The image convolver is a general-purpose convolver, allowing a variety of functions to be implement.ed by varying the values within a variable-sized coefficient kemel. The kernel sizes supported are 3x3, 5x5 and 7x7 only.
Turning now to Fig. 82, there is illustrated 340 an example of the convolution process. The pixel component values fed into the convolver process 341 come from a Box Read Iterator 342.
The Iterator 342 provides the image data row by row, and within each row, pixel by pixel. The output from the convolver 341 is sent to a Sequential Write Iterator 344, which stores the resultant image in a valid image format.
A Coefficient Kernel 346 is a lookup table in DRAM. The kemel is arranged with coefficients in the same order as the Box Read Iterator 342. Each coefficient entry is 8 bits. A simple Sequential Read Iterator can be used to index into the kerne1346 and thus provide the coefficients. It simulates an image with ImageWidth equal to the kernel size, and a Loop option is set so that the kernel would continuously be provided.
One form of implementation of the convolve process on an ALU unit is as illustrated in Fig. 81.The following constants are set by software:
Constant Value Ki Kernel size (9, 25, or 49) The control logic is used to count down the number of multiply/adds per pixel.
When the count (accumulated in Latch2) reaches 0, the control signal generated is used to write out the current convolve value (from Latch,) and to reset the count. In this way, one control logic block can be used for a number of parallel convolve streams.
Each cycle the multiply ALU can perform one multiply/add to incorporate the appropriate part of a pixel. The number of cycles taken to sum up all the values is therefore the number of entries in the kernel. Since this is compute bound, it is appropriate to divide the image into multiple sections and process them in parallel on different ALU units.
On a 7x7 kernel, the time taken for each pixel is 49 cycles, or 490ns. Since each cache line holds 32 pixels, the time available for memory access is 12,740ns. ((32-7+1) x 490ns). The time taken to read 7 cache lines and write I
is worse case 1,120ns (8*140ns, all accesses to same DRAM bank). Consequendy it is possible to process up to 10 pixels in parallel given unlimited resources. Given a limited number of ALUs it is possible to do at best 4 in parallel.
The time taken to therefore perform the convolution using a 7x7 kernel is 0.18375 seconds (1500*1000 * 490ns / 4 183,750,000ns).
On a 5x5 kernel, the time taken for each pixel is 25 cycles, or 250ns. Since each cache line holds 32 pixels, the time available for memory access is 7,000ns. ((32-5+1) x 250ns). The time taken to read 5 cache lines and write I
is worse case 840ns (6 * 140ns, all accesses to same DRAM bank). Consequently it is possible to process up to 7 pixels in parallel given unlimited resources. Given a limited number of ALUs it is possible to do at best 4. The time taken to therefore perform the convolution using a 5x5 kernel is 0.09375 seconds (1500*
1000 * 250ns / 4= 93,750,000ns).
On a 3x3 kernel, the time taken for each pixel is 9 cycles, or 90ns. Since each cache line holds 32 pixels, the time available for memory access is 2,700ns. ((32-3+1) x 90ns). The time taken to read 3 cache lines and write I is worse case 560ns (4 * 140ns, all accesses to same DRAM bank). Consequently it is possible to process up to 4 pixels in parallel given unlimited resources. Given a limited number of ALUs and Read/Write Iterators it is possible to do at best 4. The time taken to therefore perform the convolution using a 3x3 kemel is 0.03375 seconds (1500*1000 * 90ns /
4 = 33,750,000ns).
Consequently each output pixel takes kernelsize/3 cycles to compute. The actual timings are summarised in the following table:
Kernel size Time taken to Time to process Time to Process calculate output pixel 1 channel at 1500x1000 3 channels at 1500x1000 3x3 (9) 3 cycles 0.045 seconds 0.135 seconds ig~ 8 1/3 cycles 0.125 seconds 0.375 seconds 16 1/3 cycles 0.245 seconds 0.735 seconds L7x Image Compositor Compositing is to add a foreground image to a background image using a matte or a channel to govern the appropriate proportions of background and foreground in the final image. Two styles of compositing are preferably supported, regular compositing and associated compositing. The rules for the two styles are:
Regular composite: new Value = Foreground + (Background - Foreground) a Associated composite: new value = Foreground + (1- a) Background The difference then, is that with associated compositing, the foreground has been pre-multiplied with the matte, while in regular compositing it has not. An example of the compositing process is as illustrated in Fig. 83.
The alpha channel has values from 0 to 255 corresponding to the range 0 to 1.
Reeular Composite A regular composite is implemented as:
Foreground + (Background - Foreground) * = = / 255 The division by 3{255 is approximated by 257X/65536. An implementation of the compositing process is shown in more detail in Fig. 84, where the following constant is set by software:
Constant Value K, 257 Since 4 Iterators are required, the composite process takes I cycle per pixel, with a utilization of only half of the ALUs. The composite process is only run on a single channel. To composite a 3-channel image with another, the compositor must be run 3 times, once for each channel.
The time taken to composite a full size single channel is 0.015s (1500 * 1000 * I* lOns), or 0.045s to composite all 3 channels.
To approximate a divide by 255 it is possible to multiply by 257 and then divide by 65536. It can also be achieved by a single add (256 * x + x) and ignoring (except for rounding purposes) the final 16 bits of the result.
As shown in Fig. 42, the compositor process requires 3 Sequential Read Iterators 351-353 and I Sequential Write Iterator 355, and is implemented as microcode using a Adder ALU in conjunction with a multiplier ALU.
Composite time is I cycle (IOns) per-pixel. Different microcode is required for associated and regular compositing, although the average time per pixel composite is the same.
The composite process is only run on a single channel. To composite one 3-channel image with another, the compositor must be run 3 times, once for each channel. As the a channel is the same for each composite, it must be read each time. However it should be noted that to transfer (read or write) 4 x 32 byte cache-lines in the best case takes 320ns. The pipeline gives an average of 1 cycle per pixel composite, taking 32 cycles or 320ns (at 100MHz) to composite the 32 pixels, so the a channel is effectively read for free. An entire channel can therefore be composited in:
1500/32 * 1000 * 320ns = 15,040,000ns = 0.015seconds.
The time taken to composite a full size 3 channel image is therefore 0.045 seconds.
Constrect Image Pvramid Several functions, such as warping, tiling and brushing, require the average value of a given area of pixels.
Rather than calculate the value for each area given, these functions preferably make use of an image pyramid. As illustrated previously in Fig. 33, an image pyramid 360 is effectively a multi-resolution pixelmap. The original image is a 1:1 representation. Sub-sampling by 2:1 in each dimension produces an image 1/4 the original size. This process continues until the entire image is represented by a single pixel.
An image pyramid is constructed from an original image, and consumes 1/3 of the size taken up by the original image (1/4 + 1/16 + 1/64 + ...). For an original image of 1500 x 1000 the corresponding image pyramid is approximately th MB
The image pyramid can be constructed via a 3x3 convolve performed on I in 4 input image pixels advancing the center of the convolve kernel by 2 pixels each dimension. A 3x3 convolve results in higher accuracy than simply averaging 4 pixels, and has the added advantage that coordinates on different pyramid levels differ only by shifting I
bit per level.
The construction of an entire pyramid relies on a software loop that calls the pyramid level construction function once for each level of the pyramid.
The timing to produce I level of the pyramid is 9/4 * 1/4 of the resolution of the input image since we are generating an image 1/4 of the size of the original. Thus for a 1500 x 1000 image:
T'tming to produce level I of pyramid = 9/4 * 750 * 500 = 843, 750 cycles Timing to produce level 2 of pyramid = 9/4 * 375 * 250 = 210,938 cycles Timing to produce level 3 of pytamid = 9/4 * 188 * 125 = 52. 735 cycles Etc.
The total time is 3/4 cycle per original image pixel (image pyramid is 1/3 of original image size, and each pixel takes 9/4 cycles to be calculated, i.e. 1/3 * 9/4 = 3/4). In the case of a 1500 x 1000 image is 1,125,000 cycles (at 100MHz), or 0.011 seconds. This timing is for a single color channel, 3 color channels require 0.034 seconds processing time.
General Data Driven Ima eg Watper The ACP 31 is able to carry out image warping manipulations of the input image. The principles of image warping are well-known in theory. One thorough text book reference on the process of warping is "Digital Image Warping" by George Wolberg published in 1990 by the IEEE Computer Society Press, Los Afamitos, California. The warping process utilizes a warp map which forms part of the data fed in via Artcard 9_ The warp map can be arbitrarily dimensioned in accordance with requirements and provides information of a mapping of input pixels to output pixels.
Unfortunately, the utilization of arbitrarily sized warp maps presents a number of problems which must be solved by the image warper.
Turning to Fig. 85, a warp map 365, having dimensions AxB comprises array values of a certain magnitude (for example 8 bit values from 0 - 255) which set out the coordinate of a theoretical input image which maps to the cotresponding "theoretical" output image having the same array coordinate indices. Unfortunately, any output image eg. 366 will have its own dimensions CxD which may further be totally different from an input image which niay have its own dimensions ExF. Hence, it is necessary to facilitate the remapping of the warp map 365 so that it can be utilised for output image 366 to determine, for each output pixel, the corresponding area or region of the input image 367 from which the output pixel color data is to be constructed. For each output pixel in output image 366 it is necessary to first determine a corresponding warp map value from warp map 365.
This may include the need to bilinearly interpolate the surrounding warp map values when an output image pixel maps to a fractional position within warp map table 365. The result of this process will give the location of an input image pixel in a "theoretical" image which will be dimensioned by the size of each data value within the warp map 365. These values must be re-scaled so as to map the theoretical image to the corresponding actual input image 367.
In order to determine the actual value and output image pixel should take so as to avoid aliasing effects, adjacent output image pixels should be examined to determine a region of input image pixels 367 which will contribute to the final output image pixel value. In this respect, the image pyramid is utilised as will become more apparent hereinafter.
The image warper perfotms several tasks in order to warp an image_ Scale the warp map to match the output image size.
Detemune the span of the region of input image pixels represented in each output pixel.
- Calculate the final output pixel value via tri-linear interpolation from the input image pyramid Scale warro map As noted previously, in a data driven warp, there is the need for a warp map that describes, for each output pixel, the center of a corresponding input image map. Instead of having a single warp map as previously described, containing interleaved x and y value information, it is possible to treat the X and Y coordinates as separate channels.
Consequently, preferably there are two warp maps: an X warp map showing the warping of X coordinates, and a Y warp map, showing the warping of the Y coordinates. As noted previously, the warp map 365 can have a different spatial resolution than the image they being scaled (for example a 32 x 32 warp-map 365 may adequately describe a warp for a 1500 x 1000 image 366). In addition, the warp maps can be represented by 8 or 16 bit values that correspond to the size of the image being warped.
There are several steps involved in producing points in the input image space from a given warp map:
1. Detetmining the corresponding position in the warp map for the output pixel 2. Fetch the values from the warp map for the next step (this can require scaling in the resolution domain if the warp map is only 8 bit values) 3. Bi-linear interpolation of the warp map to determine the actual value 4. Scaling the value to correspond to the input image domain The first step can be accomplished by multiplying the current X/Y coordinate in the output image by a scale factor (which can be different in X & Y). For example, if the output image was 1500 x 1000, and the warp map was 150 x 100, we scale both X & Y by 1/10.
Fetching the values from the warp map requires access to 2 Lookup tables. One Lookup table indexes into the X warp-tnap, and the other indexes into the Y warp-map. The lookup table either reads 8 or 16 bit entries from the lookup table, but always returns 16 bit values (clearing the high 8 bits if the original values are only 8 bits).
The next step in the pipeline is to bi-linearly interpolate the looked-up warp map values.
Finally the result from the bi-linear interpolation is scaled to place it in the same domain as the image to be warped. Thus, if the warp map range was 0-255, we scale X by 1500/255, and Y
by 1000/255.
The interpolation process is as illustrated in Fig. 86 with the following constants set by software:
Constant Value Ki Xscale (scales 0-ImageWidth to 0-WarpmapWidth) K2 Yscale (scales 0-ImageHeight to O-WarpmapHeight) K3 XrangeScale (scales warpmap range (eg 0-255) to 0-ImageWidth) Ka YrangeScale (scales warpmap range (eg 0-255) to 0-ImageHeight) The following lookup table is used:
Lookup Size Details LUt and WarpmapWidth x Warpmap lookup.
LU2 WarpmapHeight Given [X,Y] the 4 entries required for bi-linear interpolation are returned. Even if entries are only 8 bit, they are returned as 16 bit (high 8 bits 0).
Transfer time is 4 entries at 2 bytes per entry.
Total time is 8 cycles as 2 lookups are used.
Span calculation The points from the warp map 365 locate centers of pixel regions in the input image 367. The distance between input image pixels of adjacent output image pixels will indicate the size of the regions, and this distance can be approximated via a span calculation.
Turning to Fig. 87, for a given current point in the warp map P1, the previous point on the same line is called P0, and the previous line's point at the same position is called P2. We determine the absolute distance in X & Y
between PI and P0, and between P1 and P2. The maximum distance in X or Y
becomes the span which will be a square approximation of the actual shape.
Preferably, the points are processed in a vertical strip output order, PO is the previous point on the same line within a strip, and when P 1 is the first point on line within a strip, then PO refers to the last point in the previous strip's corresponding line. P2 is the previous line's point in the same strip, so it can be kept in a 32-entry history buffer. The basic of the calculate span process are as illustrated in Fig. 88 with the details of the process as illustrated in Fig. 89.
The following DRAM FIFO is used:
Lookup Size Details FIFO8 8 ImageWidth bytes. P2 history/lookup (both X & Y in same FIFO) [ImageWidth x 2 entries at Pl is put into the FIFO and taken out again at the same 32 bits per entry] pixel on the following row as P2.
Transfer time is 4 cycles (2 x 32 bits, with I cycle per 16 bits) Since a 32 bit precision span history is kept, in the case of a 1500 pixel wide image being warped 12,000 bytes temporary storage is required.
Calculation of the span 364 uses 2 Adder ALUs (1 for span calculation, I for looping and counting for PO and P2 histories) takes 7 cycles as follows:
Cycle Action I A=ABS(Pl~-P2,) Store Pl. in P2. history 2 B = ABS(Pl. - P0,) Store P1õ in P0, history 3 A=MAX(A,B) 4 B=ABS(Ply-P2y) Store Ply in P2y history A = MAX(A, B) 6 B=ABS(Pty-P0y) Store Ply in P0y history 7 A = MAX(A, B) The history buffers 365, 366 are cached DRAM. The 'Previous Line' (for P2 history) buffer 366 is 32 entries of span-precision. The 'Previous Point' (for P0 history). Buffer 365 requires L register that is used most of the time (for calculation of points I to 31 of a line in a strip), and a DRAM buffered set of history values to be used in the calculation of point 0 in a strip's line.
32 bit precision in span history requires 4 cache lines to hold P2 history, and 2 for P0 history. P0's history is only written and read out once every 8 lines of 32 pixels to a temporary storage space of (ImageHeight*4) bytes. Thus a 1500 pixel high image being warped re,quitrs 6000 bytes temporary storage, and a total of 6 cache lines.
'Iri-linear intetpolation Having determined the center and span of the area from the input image to be averaged, the final part of the warp process is to determine the value of the output pixel. Since a single output pixel could theoretically be represented by the entire input image, it is potentially too time-consuming to actually read and average the specific area of the input image contributing to the output pixel. Instead, it is possible to approximate the pixel value by using an image pyranud of the input intage.
If the span is I or less, it is necessary only to read the original image's pixels around the given coordinate, and perform bi-linear interpolation. If the span is greater than l, we must read two appropriate levels of the image pyramid and perform tri-linear interpolation. Performing linear interpolation between two levels of the image pyramid is not sttietly conect, but gives acceptable results (it errs on the side of bluning the resultant image).
Turning to Fig. 90, generally speaking, for a given span 's', it is necessary to read image pyramid levels given by lnZs (370) and ln2s+l (371). Ln2s is simply decoding the highest set bit of s. We must bi-linear interpolate to determine the value for the pixel value on each of the two levels 370,371 of the pyramid, and then interpolate between levels.
As shown in Fig. 91, it is necessary to first interpolate in X and Y for each pyrantid level before interpolating between the pyratnid levels to obtain a final output value 373.
The image pyramid address mode issued to generate addresses for pixel coordinates at (x, y) on pytamid level s & s+l. Each level of the image pyramid contains pixels sequential in x.
Hence, reads in x are likely to be cache hits.
Reasonable cache coherence can be obtained as local regions in the output image are typically locally coherent in the input image (perhaps at a different scale however, but coherent within the scale)_ Since it is not possible to know the relationship between the input and output images, we ensure that output pixels are written in a vertical strip (via a Vertical-Strip Iterator) in order to best make use of cache coherence.
Tri-linear interpolation can be completed in as few as 2 cycles on average using 4 multiply ALUs and all 4 adder ALUs as a pipeline and assunring no menwry access required. But since all the interpolation values are derived from the image pyramids, interpolation speed is completely dependent on cache coherence (not to mention the other units are busy doing warp-map scaling and span calculations). As many cache lines as possible should therefore be available to the image-pyramid reading. The best speed will be 8 cycles, using 2 Multiply ALUs.
The output pixels are written out to the DRAM via a Vertical-Strip Write Iterator that uses 2 cache lines. The speed is therefore limited to a minimum of 8 cycles per output pixel. If the scaling of the warp map requires 8 or fewer cycles, then the overall speed will be unchanged. Otherwise the throughput is the time taken to scale the warp map. In most cases the warp map will be scaled up to match the size of the photo.
Assuming a warp map that requires 8 or fewer cycles per pixel to scale, the time taken to convert a single color component of image is therefore 0.12s (1500 * 1000 * 8 cycles * l Ons per cycle).
Histogram Collector The histogram collector is a microcode program that takes an image channel as input, and produces a histogram as output. Each of a channel's pixels has a value in the range 0-255. Consequently there are 256 entries in the histogram table, each entry 32 bits - large enough to contain a count of an entire 150ox 1000 image.
As shown in Fig. 92, since the histogram represents a summary of the entire image, a Sequential Read Iterator 378 is sufficient for the input. The histogram itself can be completely cached, requiring 32 cache lines (1 K).
The microcode has two passes: an initialization pass which sets all the counts to zero, and then a "count" stage that increments the appropriate counter for each pixel read from the image.
The first stage requires the Address Unit and a single Adder ALU, with the address of the histogram table 377 for initialising.
Relative Microcode Address Unit Adder Unit 1 Address A = Base address of histogram 0 Write 0 to Out 1= A
A+(Adderl.Outl 2) A = A - 1 1 Rest of processing Rest of processing The second stagc processes the actual pixels from the image, and uses 4 Adder ALUs:
Adder 1 Adder 2 Adder 3 Adder 4 Address Unit I A=O A=-I
2 Out 1= A A= Adder l.Out 1 A= A= A+ 1 Out 1= Read 4 bytes BZ A pixel Z = pixel - Adr.Outl from: (A +
2 Adderl.Outl (Adderl.Outl 2)) 3 Outl = A Outl = A Outl = A Write Adder4.Out1 to:
A = (A + (Adder 2.Out 2) Adder3.Out 1 4 Write Adder4.Out1 to:
(A + (Adder 2.Out 2) Flush caches The Zero flag from Adder2 cycle 2 is used to stay at microcode address 2 for as long as the input pixel is the same. When it changes, the new count is written out in mierocode address 3, and processing resumes at microcode address 2. Microcode address 4 is used at the end, when there are no more pixels to be mad.
Stage 1 takes 256 cycles, or 2560ns. Stage 2 varies according to the values of the pixels. The worst case time for lookup table replacement is 2 cycles per image pixel if every pixel is not the same as its neighbor. The time taken for a single color lookup is 0.03s (1500 x 1000 x 2 cycle per pixel x l Ons per cycle = 30,000,000ns). The time taken for 3 color components is 3 times this amount, or 0.09s.
Color Transform Color transfotmation is achieved in two main ways:
Lookup table replacetnent Color space conversion LookuD Table Realacement As illustrated in Fig. 86, one of the simplest ways to transform the color of a pixel is to encode an arbitrarily complex transform function into a lookup table 380. The component color value of the pixel is used to lookup 381 the new component value of the pixel. For each pixel read from a Sequential Read Itetator, its new value is read from the New Color Table 380, and written to a Sequential Write Iterator 383. The input image can be processed simultaneously in two halves to make effective use of memory bandwidth. The following lookup table is used:
Lookup Size Details LU, 256 entries Replacetnent(X]
8 bits per entry Table indexed by the 8 highest significant bits of X.
Resultant 8 bits treated as fixed point 0:8 The total process requires 2 Sequential Read Iterators and 2 Sequential Write iterators. The 2 New Color Tables require 8 cache lines each to hold the 256 bytes (256 entries of 1 byte).
The average tinie for lookup table replacement is therefore 44 cycle per image pixel. The time taken for a single color lookup is 0.0075s (1500 x 1000 x SFi cycle per pixel x lOns per cycle = 7,500,000ns). The time taken for 3 color components is 3 times this amount, or 0.0225s. Each color component has to be processed one after the other under control of software.
Color Space Conversion Color Space conversion is only required when moving between color spaces. The CCD images are captured in RGB color space, and printing occurs in CMY color space, while clients of the ACP 31 likely process images in the Lab color space. All of the input color space channels are typically required as input to deterntine each output channel's component value. Thus the logical process is as illustrated 385 in Fig. 94.
Simply, conversion between Lab, RGB, and CMY is fairly straightforward.
However the individual color profile of a particular device can vary considerably. Consequently, to allow future CCDs, inks, and printers, the ACP
31 performs color space conversion by means of tri-linear interpolation from color space conversion lookup tables.
Color coherence tends to be area based rather than line based. To aid cache coherence during tri-linear interpolation lookups, it is best to process an image in vertical strips. Thus the read 386-388 and write 389 iterators would be Vertical-Strip Iterators.
Tri-linear color space conversion For each output color component, a single 3D table mapping the input color space to the output color component is required. For example, to convert CCD images from RGB to Lab, 3 tables calibrated to the physical characteristics of the CCD are required:
RGB->L
RGB->a RGB->b To convert from Lab to CMY, 3 tables calibrated to the physical characteristics of the ink/printer are required:
Lab->C
Lab->M
Lab->Y
The 8-bit input color components are treated as fixed-point numbers (3:5) in order to index into the conversion tables. The 3 bits of integer give the index, and the 5 bits of ftaction are used for interpolation. Since 3 bits gives 8 values, 3 dimensions gives 512 entries (8 x 8 x 8). The size of each entry is I byte, requiring 512 bytes per table.
The Convert Color Space process can therefore be implemented as shown in Fig.
95 and the following lookup table is used:
Lookup Size Details LU, 8 x 8 x 8 entries ConveR(X, Y. Z]
512 entries Table indexed by the 3 highest bits of X. Y, and Z.
8 bits per entry 8 entries returned from Tri-linear index address unit Resultant 8 bits treated as fixed point 8:0 Transfer time is 8 entries at I byte per entry Tri-linear interpolation returns interpolation between 8 values. Each 8 bit value takes I cycle to be returned from the lookup, for a total of 8 cycles_ The tri-linear interpolation also takes 8 cycles when 2 Multiply ALUs are used per cycle. General tri-linear interpolation information is given in the ALU
section of this document. The 512 bytes for the lookup table fits in 16 cache lines.
Tlte time taken to convert a single color component of image is therefore 0.
105s (1500 * 1000 * 7 cycles *
l Ons per cycle). To convert 3 components takes 0.415s. Fortunately, the color space conversion for printout takes place on the fly during printout itself, so is not a perceived delay.
If color components are converted separately, they must not overwrite their input color space components since alI color components from the input color space are required for converting each component.
Since only 1 multiply unit is used to perform the interpolation, it is alternatively possible to do the entire Lab->CMY conversion as a single pass. This would require 3 Vertical-Strip Read Iterators, 3 Vertical-Strip Write Iterators, and access to 3 conversion tables simultaneously. In that case, it is possible to write back onto the input image and thus use no extra tnemory. However, access to 3 conversion tables equals 1/3 of the caching for each, that could lead to high latency for the overall process.
Affine Transfotm Prior to compositing an image with a photo, it may be necessary to rotate, scale and translate it. If the image is only being translated, it can be faster to use a direct sub-pixel translation function. However, rotation, scale-up and translation can all be incorporated into a single affine transform.
A general affine transform can be included as an accelerated function. Affine transfotms are limited to 2D, and if scaling down, input images should be pre-scaled via the Scale function.
Having a general affine transform function allows an output image to be constructed one block at a time, and can reduce the tinie taken to perform a number of transformations on an image since all can be applied at the same time.
A transformation matrix needs to be supplied by the client - the matrix should be the inverse matrix of the transformation desired i.e. applying the matrix to the output pixel coordinate will give the input coordinate.
A 2D matrix is usually represented as a 3 x 3 atray:
a b 0 c d 0 e f 1 Since the 3d column is always[0, 0, 11 clients do not need to specify it.
Clients instead specify a, b, c, d, e, and f.
Given a coordinate in the output image (x, y) whose top left pixel coordinate is given as (0, 0), the input coordinate is specified by: (ax + cy + e, bx + dy + f). Once the input coordinate is determined, the input image is sampled to arrive at the pixel value. Bi-littear interpolation of input image pixels is used to determine the value of the pixel at the calculated coordinate. Since affine transforms preserve parallel lines, images are processed in output vertical strips of 32 pixels wide for best average input image cache coherence.
11uee Multiply ALUs are required to perform the bi-linear interpolation in 2 cycles. Multiply ALUs I and 2 do linear interpolation in X for lines Y and Y+1 respectively, and Multiply ALU 3 does linear interpolation in Y
between the values output by Multiply ALUs I and 2.
As we move to the right across an output line in X, 2 Adder ALUs calculate the actual input image coordinates by adding 'a' to the current X value, and 'b' to the current Y
value respectively. When we advance to the next line (either the next line in a vertical strip after processing a maximum of 32 pixels, or to the first line in a new vertical strip) we update X and Y to pre-calculated start coordinate values constants for the given block The process for calculating an input coordinate is given in Fig. 96 where the following constants are set by software:
Calculate Pixel Once we have the input image coordinates, the input image must be sampled. A
lookup table is used to retum the values at the specified coordinates in readiness for bilinear interpolation. The basic process is as indicated in Fig.
97 and the following lookup table is used:
Lookup Size Details LU, Image Bilinear Image lookup [X, Y]
width by Table indexed by the integer part of X and Y.
Image 4 entries returned from Bilinear index address unit. 2 per cycle.
height Each 8 bit entry treated as fixed point 8:0 8 bits per Transfer time is 2 cycles (2 16 bit entries in FIFO hold the 4 8 bit entries) entry The affine transform requires all 4 Multiply Units and all 4 Adder ALUs, and with good cache coherence can perform an affine transfotrn with an average of 2 cycles per output pixel.
This timing assumes good cache coherence, which is true for non-skewed images. Worst case timings are severely skewed images, which meaningful Vark scripts are unlikely to contain.
The time taken to transform a 128 x 128 image is therefore 0.00033 seconds (32,768 cycles). If this is a clip image with 4 channels (including a channel), the total time taken is 0.00131 seconds (131,072 cycles).
A Vertical-Strip Write Iterator is required to output the pixels. No Read Iterator is required. However, since the affine transfotm accelerator is bound by time taken to access input image pixefs, as tnatty cache lines as possible should be allocated to the read of pixels from the input image. At least 32 should be available, and preferably 64 or inore.
Sc ' Scaling is essentially a re-sampling of an image. Scale up of an image can be performed using the Affine Ttansfotm function. Generalized scaling of an image, including scale down, is performed by the hardware acccletated Scale function. Scaling is performed independently in X and Y, so different scale factors can be used in each ditnension.
The generalized scale unit must match the Affine Transfotm scale function in tettns of registration. The generalized scaling process is as illustrated in Fig. 98. The scale in X is accomplished by Fant's re-sampling algorithm as illustrated in Fig. 99.
Where the following constants are set by software:
Constant Value K, Number of input pixels that contribute to an output pixel in X
KZ 1/K, The following tegisters are used to hold temporary variables:
Variable Value Latch, Amount of input pixel remaining unused (starts at I and decrements) Latch2 Amount of input pixels remaining to contribute to current output pixel (starts at K, and decrements) Latch3 Next pixel (in X) Latch4 Current pixel Latchs Accumulator for output pixel (unscaled) Latch6 Pixel Scaled in X (output) The Scale in Y process is illustrated in Fig. 100 and is also accomplished by a sliehtlv altered version of Fant's re-sampling algorithm to account for processing in order of X pixels.
Where the following constants are set by software:
Constant Value K, Number of input pixels that contribute to an output pixel in Y
K2 l /K, The following registers are used to hold'temporary variables:
Variable Value Latch, Amount of input pixel remaining unused (starts at l and decrements) Latch2 Amount of input pixels remaining to contribute to current output pixel (starts at K, and decrements) Latch3 Next pixel (in Y) Latch4 Curtent pixel Latchs Pixel Scaled in Y(output) The following DRAM FIFOs are used:
Lookup Size Details FIFO1 ImageWidthou-r entries 1 row of image pixels already scaled in X
8 bits per entry t cycle transfer time FIFO2 ImageWidthoUT entries I row of image pixels aiready scaled in X
16 bits per entry 2 cycles transfer time (I byte per cycle) Tessellate Image Tessellation of an image is a fonn of tiling. It involves copying a specially designed "tile" multiple times horizontally and vertically into a second (usually larger) image space. When tessellated, the small tile forms a seamless picture. One example of this is a small tile of a section of a brick wall. It is designed so that when tessellated, it forms a full brick wall. Note that there is no scaling or sub-pixel translation involved in t;essellation.
The most cache-coherent way to perform tessellation is to output the image sequentially line by line, and to repeat the same line of the input image for the duration of the line. When we finish the line, the input image must also advance to the next line (and repeat it multiple times across the output line).
An overview of the tessellation function is illustrated 390 in Fig_ 101. The Sequential Read Iterator 392 is set up to continuously read a single line of the input tile (StartLine would be 0 and EndLine would be 1). Each input pixel is written to all 3 of the Write lterators 393-395. A counter 397 in an Adder ALU counts down the number of pixels in an output line, terminating the sequence at the end of the line.
At the end of processing a line, a small software routine updates the Sequential Read Iterator's StartLine and EndLine registers before restaRing the microcode and the Sequential Read Iterator (which clears the FIFO and repeats line 2 of the tile). The Write Iterators 393-395 are not updated, and simply keep on writing out to their respective parts of the output image. The net effect is that the tile has one line repeated across an output line, and then the tile is repeated vertically too.
This ptncess does not fully use the memory bandwidth since we get good cache coherence in the input image, but it does allow the tessellation to function with tiles of any size. The process uses I Adder ALU. If the 3 Write Iterators 393-395 each write to 1/3 of the image (breaking the image on tile sized boundaries), then the entire tessellation process takes place at an average speed of 1/3 cycle per output image pixel. For an intage of 1500 x 1000, this equates to .005 seconds (5,000,000ns).
Sub-pixel Ttanslator Before compositing an image with a background, it may be necessary to translate it by a sub-pixel amount in both X and Y. Sub-pixel transforms can increase an image's size by I pixel in each dimension. The value of the region outside the image can be client determined, such as a constant value (e.g.
black), or edge pixel replication. Typically it will be better to use black.
The sub-pixel translation process is as illustrated in Fig. 102. Sub-pixel translation in a given dimension is defined by:
Pixel. = Pixe1;. * (1-Transiation) + Pixel., * Translation It can also be represented as a fonn of interpolation:
Pixel., = Pixel;,., + (Pixel;,, - Pixeli,,,)= Ttanslation Implementation of a single (on average) cycle interpolation engine using a single Multiply ALU and a single Adder ALU in conjunction is straightforward. Sub-pixel translation in both X &
Y requires 2 interpolation engines In order to sub-pixel translate in Y, 2 Sequential Read Iterators 400,401 are required (one is reading a line ahead of the other from the same image), and a single Sequential Write Iterator 403 is required.
The first intetpolation engine (interpolation in Y) accepts pairs of data from 2 streams, and linearly interpolates between them. The second inteipolation engine (intapolation in X) accepts its data as a single 1 dimensional stream and linearly interpolates between values. Both engines interpolate in I cycle on average.
Each interpolation engine 405, 406 is capable of performing the sub-pixel translation in I cycle per output pixel on average. The overall time is therefore I cycle per output pixel, with requirements of 2 Multiply ALUs and 2 Adder ALUs.
The time taken to output 32 pixels from the sub-pixel translate function is on average 320ns (32 cycles). This is enough time for 4 full cache-line accesses to DRAM, so the use of 3 Sequeatial Iterators is well within titning limits.
The total time taken to sub-pixel translate an image is therefore I cycle per pixel of the output image. A
typical image to be sub-pixel translated is a tile of size 128 * 128. The output image size is 129 * 129. The process takes 129 * 129 * l Ons = 166,410ns.
The Image Tiler function also makes use of the sub-pixel translation algorithm, but does not require the writing out of the sub-pixel-translated data, but rather processes it further.
ImaQe Tiler The high level algorithm for tiling an image is carried out in software. Once the placement of the tile has been detetmined, the appropriate colored tile must be composited. 'Ihe actual compositing of each tile onto an image is carried out in hardware via the microcoded ALUs. Compositing a tile involves both a texture application and a color application to a background image. In some cases it is desirable to compare the actual amount of texture added to the background in relation to the intended amount of texture, and use this to scale the color being applied. In these cases the texture must be applied first.
Since color application functionality and texture application functionality are somewhat independen[. they are separated into sub-functions.
The number of cycles per 4-channel tile composite for the different texture styles and coloring styles is summarised in the following table:
Constant Pixel color color Replace texture 4 4.75 25% background + tile texture 4 4.75 Average height algorithm 5 5.75 Average height algorithm with feedback 5.75 6.5 Tile Colorine and Comoositin~
A tile is set to have either a constant color (for the whole tile), or takes each pixel value from an input image.
Both of these cases may also have feedback from a texturing stage to scale the opacity (similar to thinning paint).
The steps for the 4 cases can be summarised as:
- Sub-pixel translate the tile's opacity values, - Optionally scale the tile's opacity (if feedback from texture application is enabled).
- Determine the color of the pixel (constant or from an image map).
- Composite the pixel onto the background image.
Each of the 4 cases is treated separately, in order to minimize the time taken to perform the function. The summary of time per color compositing style for a single color channel is described in the following table:
Tiling color style No feedback from Feedback from texture (cycles per texture pixel) (cycles per pixel) Tile has constant color per pixel 1 2 Tile has per pixel color from input image 1.25 2 Constant color In this case, the tile has a constant color, determined by software. While the ACP 31 is placing down one tile, the software can be determining the placement and coloring of the next tile.
The color of the tile can be determined by bi-linear interpolation into a scaled version of the image being tiled.
The scaled version of the image can be created and stored in place of the image pyramid, and needs only to be performed once per entire tile operation. If the tile size is 128 x 128, then the image can be scaled down by 128:1 in each dimension.
Without feedback When there is no feedback from the texturing of a tile, the tile is simply placed at the specified coordinates.
The tile color is used for each pixel's color, and the opacity for the composite comes from the tile's sub-pixel translated opacity channel. In this case color channels and the texture channel can be processed completely independently between tiling passes.
The overview of the process is illustrated in Fig. 103. Sub-pixel translation 410 of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the mask to be used in compositing 411 the constant tile color 412 with the background image from background sequential Read iterator.
Compositing can be performed using I Multiply ALU and 1 Adder ALU in an average time of 1 cycle per composite. Requirements are therefore 3 Multiply ALUs and 3 Adder ALUs. 4 Sequential Iterators 413-416 are n qttired, taking 320ns to read or write their contents. With an average number of cycles of I per pixel to sub-pixel translate and composite, there is sufficient time to read and write the buffers.
With feedback When there is feedback from the texturing of a tile, the tiie is placed at the specified coordinates. The tile color is used for each pixel's color, and the opacity for the composite comes from the tile's sub-pixel translated opacity channel scaled by the feedback parameter. Thus the texture values must be calculated before the color value is applied.
The overview of the process is illustrated in Fig. 97. Sub-pixel translation of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the tnask to be scaled according to the feedback read from the Feedback Sequential Read Iterator 420.
The feedback is passed it to a Scaler (I Multiply ALU) 421.
Compositing 422 can be performed using 1 Multiply ALU and I Adder ALU in an average time of 1 cycle per composite. Requirements are therefore 4 Multiply ALUs and al14 Adder ALUs.
Although the entire process can be accomplished in I cycle on avetage, the bottleneck is the memory access, since 5 Sequential Itenitors are n:quired.
With sufficient buffering, the average time is 1.25 cycles per pixel.
Color from Input Imaee One way of coloring pixels in a tile is to take the color from pixels in an input image. Again, there are two possibilities for compositing: with and without feedback from the texturing.
Without feedback In this case, the tile color simply comes from the relative pixel in the input image. 'Ilie opacity for compositing comes from the tile's opacity channel sub-pixel shi8ecl.
The overview of the process is illustrated in Fig. 105. Sub-pixel translation 425 of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the mask to be used in compositing 426 the tile's pixel color (read from the input image 428 ) with the background image 429.
Compositing 426 can be performed using I Multiply ALU and I Adder ALU in an average time of I cycle per composite. Requirements are therefore 3 Multiply ALUs and 3 Adder ALUs.
Although the entire process can be accomplished in I cycle on average, the bottleneck is the memory access, since 5 Sequential Iterators are required.
With sufficient buffering, the average time is 1.25 cycles per pixel.
With feedback In this case, the tile color still comes from the relative pixel in the input image, but the opacity for compositing is affected by the relative amount of texture height actually applied during the texturing pass. This process is as illustrated in Fig. 106.
Sub-pixel translation 431 of a tile can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from the sub-pixel translation is the mask to be scaled 431 according to the feedback read from the Feedback Sequential Read Iterator 432.
The feedback is passed to a Scaler (I
Multiply ALU) 431.
Compositing 434 can be performed using I Multiply ALU and I Adder ALU in an average time of 1 cycle per composite.
Requirements are therefore al14 Multiply ALUs and 3 Adder ALUs. Although the entire process can be accomplished in I cycle on average, the bottleneck is the memory access, since 6 Sequential Iterators are required.
With sufficient buffering, the average time is 1 S cycles per pixel.
Tile Texturine Each tile has a surface texture defined by its texwre chaonel. The texture must be sub-pixel translated and then applied to the output image. There are 3 styles of teacture compositing:
Replace texture 250% background + tile's texture Average height algorithm In addition, the Average height algorithm can save feedback parameters for color compositing.
The time taken per texture compositing style is summarised in the following table:
Tiling color style Cycles per pixel Cycles per pixel (no feedback from (feedback from texture) texture) Replace texture 1 -25% background + tile texture value 1 -Average height algorithm 2 2 Replace texture In this instance, the texture from the tile replaces the texture channel of the image, as illustrated in Fig. 107.
Sub-pixel translation 436 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from this sub-pixel translation is fed directiv to the Sequential Write lterator 437.
The time taken for replace texture compositing is 1 cycle per pixel. There is no feedback, since 100% of the texture value is always applied to the background. There is therefore no requirement for processing the channels in any particutar order.
25% Backeround + Tile's Texture In this instance, the texture from the tile is added to 25% of the existing texture value. The new value must be greater than or equal to the original value. In addition, the new texture value must be clipped at 255 since the texture channel is only 8 bits. The process utilised is iliustrated in Fig. 108.
Sub-pixel transiation 440 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. The output from this sub-pixel translation 440 is fed to an adder 441 where it is added to'/. 442 of the background texture value. Min and Max functions 444 are provided by the 2 adders not used for sub-pixel ttanslation and the output written to a Sequential Write Iterator 445.
The time taken for this style of texture compositing is 1 cycle per pixel.
There is no feedback, since 100% of the texture value is considered to have been applied to the background (even if clipping at 255 occurred). There is therefore no requirement for processing the channels in any particular order.
Averaee heisht aleorithm In this texture application algorithm, the average height under the tile is computed, and each pixel's height is compared to the average height. If the pixel's height is less than the average, the stroke height is added to the background height. If the pixel's height is greater than or equal to the average, then the stroke height is added to the average height. Thus background peaks thin the stroke. The height is constrained to increase by a minimum amount to prevent the background from thinning the stroke application to 0 (the minimum amount can be 0 however). 'Me height is also clipped at 255 due to the 8-bit resolution of the texture channel.
There can be feedback of the difference in texture applied versus the expected amount applied. The feedback amount can be used as a scale factor in the application of the tile's color.
In both cases. the average texture is provided by software, calculated by performing a bi-level interpolation on a scaled version of the texture map. Software detetmines the next tile's average textune height while the current tile is being applied. Software must also provide the minimum thickness for addition, which is typically constant for the entire tiling process.
Without feedback With no feedback, the texture is simply applied to the background texture, as shown in Fig. 109.
4 Sequential Iterators are required, which means that if the process can be pipelined for 1 cycle, the memory is fast enough to keep up.
Sub-pixel translation 450 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. Each Min & Max function 451,452 requires a separate Adder ALU in order to complete the entire operation in I cycle. Since 2 are already used by the sub-pixel translation of the texture, there are not enough remaining for a I cycle average time.
The average time for processing I pixel's texture is therefore 2 cycles. Note that there is no feedback, and hence the color channel order of compositing is irrelevant.
With feedback This is conceptually the same as the cate without feedback, except that in addition to the standard processing of the texture application algorithm, it is necessary to also record the proportion of the texture actually applied. The proportion can be used as a scale factor for subsequent compositing of the tile's color onto the background image. A
flow diagram is illustrated in Fig. I 10 and the following lookup table is used:
Lookup Size Details LU, 256 entries 1/N
16 bits per entry Table indexed by N (range 0-255) Resultant 16 bits treated as fixed point 0:16 Each of the 256 entries in the software provided 1IN table 460 is 16 bits, thus requiring 16 cache lines to hold continuously.
Sub-pixel translation 461 of a tile's texture can be accomplished using 2 Multiply ALUs and 2 Adder ALUs in an average time of I cycle per output pixel. Each Min 462 & Max 463 function requires a separate Adder ALU in order to complete the entire operation in I cycle. Since 2 are already used by the sub-pixel ttanslation of the texture, there are not enough remaining for a I cycle average time.
The average time for processing 1 pixel's texture is therefore 2 cycles.
Sufficient space must be allocated for the feedback data area (a tile sized image channel). The texture must be applied before the tile's color is applied, since the feedback is used in scaling the tile's opacity.
CCD Imaee Interuolator Images obtained from the CCD via the ISI 83 (Fig. 3) are 750 x 500 pixels.
When the image is captured via the ISI, the orientation of the camera is used to rotate the pixels by 0, 90, 180, or 270 degrees so that the top of the image cotresponds to 'up'. Since every pixel only has an R, G, or B color component (rather than all 3), the fact that these have been rotated must be taken into account when interpreting the pixel values. Depending on the orientation of the camera, each 2x2 pixel block has one of the configurations illustrated in Fig. i 11:
Several processes need to be performed on the CCD captured image in order to transform it into a useful form for processing:
Up-interpolation of low-sample rate color components in CCD image (interpreting correct orientation of pixels) Color conversion from RGB to the intemal color space Scaling of the intemal space image from 750 x 500 to 1500 x 1000.
Writing out the image in a planar fotmat The entire channel of an image is required to be available at the same time in order to allow warping. In a low memory model (8MB), there is only enough space to hold a single channel at full resolution as a temporary object.
Thus the color conversion is to a single color channel. The limiting factor on the process is the color conversion, as it involves tri-linear interpolation from RGB to the internal color space. a process that takes 0.026ns per channel (750 x 500 x 7 cycles per pixel x l Ons per cycle = 26:250,000ns).
It is important to perform the color conversion before scaling of the intemal color space image as this reduces the number of pixels scaled (and hence the overall process time) by a factor of 4.
The requirements for all of the transformations may not fit in the ALU scheme.
The transformations are therefore broken into two phases:
Phase 1: Up-interpolation of low-sample rate color components in CCD image (interpreting correct orientation of pixels) Color conversion from RGB to the intemal color space Writing out the image in a planar format Phase 2: Scaling of the intemal space image from 750 x 500 to 1500 x 1000 Separating out the scale function implies that the small color converted image must be in memory at the same time as the large one. The output from Phase 1 (0.5 MB) can be safely written to the memory area usually kept for the image pyramid (1 MB). The output from Phase 2 can be the general expanded CCD
image. Separation of the scaling also allows the scaling to be accomplished by the Affine Transform, and also allows for a different CCD resolution that may not be a simple 1:2 expansion.
Phase 1: Up-interpolation of low-sample rate color components.
Each of the 3 color components (R, G, and B) needs to be up interpolated in order for color conversion to take place for a given pixel. We have 7 cycles to perfotm the interpolation per pixel since the color conversion takes 7 cycles.
Interpolation of G is straightforward and is illustrated in Fig. 112.
Depending on orientation, tfie actual pixel value G altetnates between odd pixels on odd lines & even pixels on even lines, and odd pixels on even lines & even pixels on odd lines. In both cases, linear interpolation is all that is required. Interpolation of R and B components as illustrated in Fig. 113 and Fig. 113, is more complicated, since in the horizontal and vertical directions, as can be seen from the diagrams, access to 3 rows of pixels simultaneously is required, so 3 Sequential Read Iterators are required, each one offset by a single row. In addition, we have access to the previous pixel on the same row via a latch for each row.
Each pixel therefore contains one component from the CCD, and the other 2 up-interpolated. When one component is being bi-linearly interpolated, the other is being linearly interpolated. Since the interpolation factor is a constant 0.5, interpolation can be calculated by an add and a shift 1 bit right (in 1 cycle), and bi-linear int.erpolation of factor 0.5 can be calcuhtted by 3 adds and a shift 2 bits right (3 cycles).
The total number of cycles required is therefore 4, using a single multiply ALU.
Fig. 115 illusttates the case for rotation 0 even line even pixel (EL, EP), and odd line odd pixel (OL, OP) and Fig. 116 illustrates the case for rotation 0 even line odd pixel (EL, OP), and odd line even pixel (OL, EP). The other rotations are simply different fonns of these two expressions.
Color conversion Color space conversion from RGB to Lab is achieved using the same method as that descn"bed in the general Color Space Convert funetion, a process that takes 8 cycles per pixel. Phase I
processing can be described with reference to Fig. 117.
The up-interpolate of the RGB takes 4 cycles (1 Multiply ALU), but the conversion of the color space takes 8 cycles per pixel (2 Multiply ALUs) due to the lookup transfer time.
Phase 2 Scaline the image This phase is concemed with up-interpolating the image from the CCD resolution (750 x 500) to the working photo resolution (1500 x 1000). Scaling is accomplished by runtting the Affme transfontt with a scale of 1:2. The timing of a general affine transform is 2 cycles per output pixel, which in this case means an elapsed scating time of 0.03 seconds.
liluminate Imaee Once an image has been processed, it can be illuminated by one or more light sources. Light sources can be:
1_ Directional - is infmitely distant so it casts parallel light in a single direction 2. Omni - casts unfocused lights in ail directions.
3. Spot - casts a focused beam of light at a specific target point. There is a cone and penumbra associated with a spotlight.
The scene may also have an associated bump-map to cause reflection angles to vary. Ambient light is also optionally present in an illuminated scene.
In the process of acceletated illumination, we are concemed with illuminating one image channel by a single light source. Multiple light sources can be applied to a single image channel as multiple passes one pass per light source. Multiple channels can be processed one at a time with or without a bump-map.
The normal surfane vector (N) at a pixel is computed from the bump-map if pre.sent The default nomtal vector, in the absence of a bump-map, is perpendicular to the image plane i.e.
N=[0, 0, l].
The viewing vector V is always perpendicular to the image plane i.e. V = j0, 0, 1].
For a directional light source, the light source vector (L) from a pixel to the light source is constant across the entire image, so is computed once for the entire image. For an omni light source (at a finite distance), the light source vector is computed independently for each pixel.
A pixel's reflection of ambient light is computed according to: I,k,Od A pixel's diffuse and specular reflection of a light source is computed according to the Phong model:
f,alP[kaOe(1=1=L) + ksOs(R=V)"]
When the light source is at infmity, the light source intensity is constant across the image.
Each light source has three contributions per pixel Ambient Contribution Diffuse contribution Specular contribution The light source can be defined using the following variables:
dL Distance from light source f,a Attenuation with distance [f.,, = I / dL ]
R Normalised reflection vector [R = 2N(N.L )- L]
I. Ambient light intensity (p Diffuse light coefficient k. Ambient reflection coefficient kd Diffuse reflection coefficient k, Specular reflection coefficient kx Specular color coefficient L Normalised light source vector N Normalised surface normal vector n Specular exponent Od Object's diffuse color (i.e. image pixel color) O. Object's specular color (kuOd + (I- ku)lP) V Normalised viewing vector [V = [0, 0, 1]]
The same reflection coefficients (kõ k,, kd) are used for each color component.
A given pixel's value will be equal to the ambient contribution plus the sum of each light's difl'use and specular contribution.
Sub-Processes of Illumination Calculation In order to calculate diffuse and specular contributions, a variety of other calculations are required. These are calculations of:
N
L
N=L
R=V
fõ, f-P
Sub-processes are also defined for calculating the contributions of:
ambient diffuse specular The sub-processes can then be used to calculate the overall illumination of a light source. Since there are only 4 multiply ALUs, the microcode for a particular type of light source can have sub-processes intermingled appropriately for perfotmance.
Calculation of I/JX
The Vark lighting model uses vectors. In many cases it is important to calculate the inverse of the length of the vector for normalization purposes. Calculating the inverse of the length requires the calculation of I/SquareRoot[X]_ Logically, the process can be represented as a process with inputs and outputs as shown in Fig. 118.
Referring to Fig. 119, the calculation can be made via a lookup of the estimation, followed by a single iteration of the following function:
Vn+l -'/: Vn(3 - XV.2) The number of iterations depends on the accuracy required_ In this case only 16 bits of precision are required.
The table can therefore have 8 bits of precision, and only a single iteration is necessary. The following constant is set by software:
Constant Value K, 3 The following lookup table is used:
Lookup Size Details LU, 256 entries I/SquareRoot[XJ
8 bits per entry Table indexed by the 8 highest significant bits of X.
Resultant 8 bits treated as fixed point 0:8 Calculation of N
N is the surface normal vector. When 8tene is no bump-map, N is constant. When a bump-map is present, N
must be calculated for each pixeL
No bttmo-man When there is no bump-map, there is a fixed norma! N that has the following properties:
N=[XN, YN, ZNI -[0= 0, 11 lIMI = I
lnfmi =1 normalizsd N = N
These properties can be used instead of specifically calculating the notmal vector and 14INII and thus optimize other calculations.
With bump-map As illustrated in Fig. 120, when a bump-map is present, N is calculated by comparing bump-map values in X
and Y dimensions. Fig. 120 shows the calculation of N for pixel P1 in terms of the pixels in the same row and column, but not including the value at P I itself. The calculation of N is made resolution mdependent by multiplying by a scale factor (same scale factor in. X & Y). This process can be represented as a process having inputs and outputs (ZN is always 1) as illustrated in Fig. 121.
As ZN is always 1. Consequently XN and YN are not normalued yet (since ZN =
1). Normalization of N is delayed until after calculation of N.L so that there is only I multiply by l4jNJI instead of 3.
An actual process for calculating N is illustrated in Fig. 122.
The following constant is set by software:
Constant Value K, ScaleFactor (to make N resolution independent) Calculation of L
Directional liehts When a light source is infinitely distant, it has an effective constant light vector L. L is normalized and calculated by software such that:
L = [XL, YL, ZL]
IILII =1 l4Iu1 = I
These properties can be used instead of specifically calculating the L and 141LI) and thus optimize other calculations. This process is as illustrated in Fig. 123.
Omni liQhts and Spotlights When the light source is not infinitely distant, L is the vector from the current point P to the light source PL. Since P
[Xp, Yp, 0], L is given by:
L = [XL, YL, ZLl XL = XP - XPL
YL=YP-YeL
ZI. - -ZPL
We notmalize XL, YL and ZL by multiplying each by 141LIJ. The calcutation of 1AILf J (for later use in notmalizing) is accomplished by calculating V = XL2 + YL2+ ZL2 and then calculating V-' In this case, the calculation of L can be represented as a process with the inputs and outputs as indicated in Fig. 124.
Xp and YP are the coordinates of the pixel whose illumination is being calculated. Zp is always 0.
The actual process for calculating L can be as set out in Fig- 125.
Where the following constants are set by software:
Constant Value K, XPL
K3 ZPi (as ZP is 0) K4 I-zm Calculation ofN.L
Calculating the dot product of vectors N and L is defined as:
XNXL + YNYL + ZNZL
No bumn-mat) _ When there is no bump-map N is a constant [0, 0, 1]. N.L therefore reduces to ZL.
With bump-map When there is a bump-map, we must calculate the dot product directly. Rather than take in normalized N
components, we norinalize after taking the dot product of a non-normalized N
to a notmalized L. L is either normalized by software (if it is constant), or by the Calculate L process.
This process is as illustrated in Fig. 126.
Note that ZN is not required as input since it is defined to be 1. However 1fNIJ is required instead, in order to notmalize the result One actual process for calculating N.L is as illustrated in Fig. 127.
Calculation of R*V
R=V is required as input to specular contnbution calculations. Since V=[0, 0, 1], only the Z components are required. R= V therefore reduces to:
R=V = 2Zr,(N.L ) - ZL
In addition, since the un-normalized ZN = I, normalized ZN = 14INII
No bumo-mao The sitnplest implementation is when N is constant (i.e. no bump-map). Since N
and V are constant, N.L and R=V can be simplified:
V = [0, 0, 11 N = [0, 0, 1]
L a [Xt., Yi, ZLl N.L = ZL
R=V =2ZN(N.L)-ZL
x24_ZL
= ZL
When L is constant (Directional light source), a normalized ZL can be supplied by soRware in the form of a constant whenever R-V is t+equired. When L varies (Omni lights and Spotlights), nomialiaed ZL must be calcutated on the fly. It is obtained as output from the Calculate L process_ With bumtrmao When N is not constant, the process of calculating R=V is simply an implementation of the generalized formula:
R*V = 2ZN(N.L ) - ZL
The inputs and outputs are as shown in Fig. 128 with the an actual implementation as shown in Fig. 129.
Calculation of Attenuation Factor Directional lights When a light source is infinitely distant, the intensity of the light does not vary across the image. The attenuation factor f. is therefore 1. This constant can be used to optimize illumination calculations for infinitely distant light sources.
Omni liehts and Saotli~ltts When a light source is not infinitely distant, the intensity of the light can vary according to the following formula:
f. = fo + fi/d + f2/dZ
Appropriate settings of coefficients fo, fl, and f, allow light intensity to be attenuated by a constant, linearly with distance, or by the square of the distance.
Since d = JILIJ, the calculation of f. can be represented as a process with the following inputs and outputs as illustrated in Fig. 130.
The actual process for calculating f,a can be defined in Fig. 131.
Where the following constants are set by sofftware:
Constant Value K, F2 f~
K3 Fo Calculation of Cone and Penumbra Factor Directional lights and Omni lights These two light sources are not focused, and therefore have no cone or penumbra. The cone-penumbra scaling factor f, is therefore 1. This constant can be used to optimize iliutnination calculations for Directional and Omni light sources.
S tli ts A spotlight focuses on a particular target point (PT). The intensity of the Spotlight varies according to whether the particular point of the image is in the cone, in the penumbra, or outside the cone/penuttlbra region.
Turning now to Fig. 132, there is illustrated a gtaph of f, with respect to the penumbra position. Inside the cone 470, fW is 1, outside 471 the penumbra fW is 0. From the edge of the cone through to the end of the penumbra, the light intensity varies accotding to a cubic function 472.
The various vectors for penumbra 475 and cone 476 calculation are as illustrated in Fig. 133 and Fig_ 134.
Looking at the surface of the image in I dimension as shown in Fig. 134, 3 angles A, B, and C are defined. A
is the angle between the target point 479, the light source 478, and the end of the cone 480. C is the angle between the target point 479, light source 478, and the end of the penumbra 481 _ Both are fixed for a given light source. B is the angle between the target point 479, the light source 478, and the position being calculated 482, and therefore changes with every point being calculated on the image.
We normalize the range A to C to be 0 to 1, and find the distance that B is along that angle tange by the formula:
(B-A)/(C-A) The range is forcxd to be in the range 0 to 1 by ttuncation, and this value used as a lookup for the cubic approximation of f,.
The calculation of f.Q can therefore be represented as a ptvicess with the inputs and outputs as illusttated in Fig. 135 with an actual process for calculating fv is as shown in Fig. 136 where the following constants are set by software:
Constant Value K, XLT
K5 1/(C-A). [MAXNUM if no penumbra]
The following lookup tables are used:
Lookup Size Details LU, 64 entries Arcos(X) 16 bits per entry Units are same as for constants KS and KQ
Table indexed by highest 6 bits Result by linear interpolation of 2 entries Timing is 2 * 8 bits * 2 enaries = 4 cycles LU2 64 entries Light Response function f, 16 bits per entry F(l) = 0, F(0) = 1, others are according to cubic Table indexed by 6 bits (1:5) Result by linear interpolation of 2 entries Timing is 2* 8 bits = 4 cycles Calculation of Ambient Contnbution Regardless of the number of lights being applied to an image, the ambient light contribution is performed once for each pixel, and does not depend on the bump-map.
The ambient calculation process can be represented as a process with the inputs and outputs as illustrated in Fig. 131. The implementation of the process requires multiplying each pixel from the input image (Od) by a constant value (I,k,), as shown in Fig. 138 where the following constant is set by software:
Constant Value K, Ik.
Calculation of DitTuse Contribution Each light that is applied to a surface produces a diffuse illumination. The diffuse illumination is given by the formula:
diffuse = kdbd(N.L ) There are 2 different implementations to consider.
Implementation 1- constant N and L
When N and L are both constant (Directional light and no bump-map):
N.L =ZL
Therefore:
ditfitse = kdOdZL
Since Od is the only variable, the actual process for calculating the difl'use contribution is as illustrated in Fig.
139 where the following constant is set by software:
Constant Value Ki kd(N.L ) = kdZL
Implementation 2- non-constant N & L
When either N or L are non-constant (either a bump-map or illumination from an Omni light or a Spotlight), the diffuse calculation is performed directly according to the formula:
diffuse =1caOd(N.L ) The diffuse calculation process can be represented as a process with the inputs as illusttated in Fig. 140. N.L
can either be calculated using the Calculate N.L Process, or is provided as a constant. An actual process for calculating the ditl'use contribution is as shown in Fig. 141 where the following constants are set by software:
Constant Value Ki kd Calculation of 3cecular Contribution Each light that is applied to a surface produces a specular illumination. The specular illumination is given by the formula:
specular = kOs(R=V) where O, = kKOd + (l-ktt)lP
There are two implementations of the Calculate Specular process.
Implementation t- constant N and L
The first implementation is when both N and L are constant (Directional light and no bump-map). Since N, L
and V are constant, N.L and R=V are also constant:
V=[0,0, 1]
N = [0, 0, 1]
L[XL,1'L,ZL]
N.L = ZL
R=V = 2ZN(N.L ) - ZL
=2ZL-ZL
-ZL
The specular calculation can thus be reduced to:
specular = kOs ZL"
= kyZL"(k.Od + (1-1.)IP) = kJ(-ZL"Od + (1-k.)1PksZ( Since only Od is a variable in the specular calculation, the calculation of the specular contribution can therefore be represented as a process with the inputs and outputs as indicated in Fig. 142 and an actual process for calculating the specular contribution is illustrated in Fig. 143 where the following constants are set by software:
Constant Value K, kjcwZL"
K2 (1-ku)IpksZL"
lmnlementation 2- non constant N and L
This implementation is when either N or L are not constant (either a bump-map or illumination from an Omni light or a Spotlight). This implies that R=V must be supplied, and hence R=V"
must also be calculated.
The specular calculation process can be represented as a process with the inputs and outputs as shown in Fig.
144. Fig. 145 shows an actual process for calculating the specular contribution where the following constants are set by software:
Constant Value Ki l4 KZ kx K3 (I-ku)l:P
The following lookup table is used:
Lookup Size DetaiLs LU, 32 entries X"
16 bits per Table indexed by 5 highest bits of integer R=V
entry Result by linear interpolation of 2 entries using fraction of R.V.
Interpolation by 2 Multiplies.
The time taken to retrieve the data from the lookup is 2= 8 bits * 2 entries = 4 cycles.
When ambient light is the only illumination If the ambient contribution is the only light source, the process is very straightforward since it is not necessary to add the ambient light to anything with the overall process being as illustrated in Fig. 146. We can divide the image vertically into 2 sections, and process each half simultaneously by duplicating the ambient light logic (thus using a total of 2 Multiply ALUs and 4 Sequential Iterators). The timing is therefore'/~
cycle per pixel for ambient light application.
The typical illumination case is a scene lit by one or more lights. In these cases, because ambient light calculation is so cheap, the ambient calculation is included with the processing of each light source. The first light to be processed should have the cotrect I,k, setting, and subsequent lights should have an l,ka value of 0 (to prevent multiple ambient contributions).
If the ambient light is processed as a separate pass (and not the fust pass), it is necessary to add the ambient light to the current calculated value (requiring a read and write to the same address). The process overview is shown in Fig. 147.
The process uses 3 Image Iterators, I Multiply ALU, and takes I cycle per pixel on average.
Infinite LiQht Source In the case of the infinite light source, we have a constant light source intensity across the image. Thus both L
and f., are constant.
No Bumo Map When there is no bump-map, there is a constant normal vector N[0, 0, 1 J. The complexity of the illumination is greatly reduced by the constants of N, L, and f.. The process of applying a single Directional light with no bump-map is as illustrated in Fig. 147 where the following constant is set by software:
Constant Value K, IP
For a single infinite light source we want to perform the logical operations as shown in Fig. 148 where K, through Ka are constants with the following values:
Constant Value K, Kd(NsL) = Kd Lz KZ kK
K3 Ka(NsH)" = K. Hz2 The process can be simplified since K2, K3, and Ke are constants. Since the complexity is essentially in the calculation of the specular and diffuse contributions (using 3 of the Multiply ALUs), it is possible to safely add an ambient calculation as the 4'" Multiply ALU. The first infmite light source being processed can have the true ambient light parameter Ik; and all subsequent infmite lights can set Ik. to be 0. The ambient light calculation becomes effectively fi-ee.
If the infinite light source is the fust light being applied, there is no need to include the existing contributions made by other light sources and the situation is as illustrated in Fig. 149 where the constants have the following values:
Constant Value K, kd(LsN) = kdLz Ks (1- k,(NsH)")IP = (I - k,Hz")IP
IC6 kxks(NsH)" IP = kuksHz"Ip K7 I.k.
If the infinite light source is not the fust light being applied, the existing contribution made by previously processed lights must be included (the same constants apply) and the situation is as illustrated in Fig. 148.
In the first case 2 Sequential Iterators 490,491 are required, and in the second case, 3 Sequential Iterators 490, 491, 492 (the extra Iterator is required to read the previous light contributions). In both cases, the application of an infinite light source with no bump map takes I cycle per pixel, including optional application of the ambient light.
With Bump Map When there is a bump-map, the normal vector N must be calculated per pixel and applied to the constant light source vector L. 1AjNjj is also used to calculate R=V, which is required as input to the Calculate Specular 2 process.
The following constants are set by software:
Constant Value K, XL
K2 yL
K, ZL
Bump-map Sequential Read Iterator 490 is responsible for reading the current line of the bump-map. lt provides the input for determining the slope in X. Bump-map Sequential Read Iterators 491, 492 and are responsible for reading the line above and below the current line. They provide the input for determining the slope in Y.
Omni Liehts In the case of the Omni light source, the lighting vector L and attenuation factor fõ, change for each pixel across an image. Therefore both L and f,,,, must be calculated for each pixel.
No Bump Map When there is no bump-map, there is a constant normal vector N [0, 0, 1].
Although L must be calculated for each pixel, both N.L and R=V are simplified to ZL. When there is no bump-map, the application of an Omni light can be calculated as shown in Fig. 149 where the following constants are set by software:
Constant Value K, XP
KZ YP
The algorithm optionally includes the contributions from previous light sources, and aiso includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0.
The algorithm as shown requires a total of 19 multiply/accumulates. The times taken for the lookups are I
cycle during the calculation of L, and 4 cycles during the specular contribution. The processing time of 5 cycles is therefore the best that can be accomplished. The time taken is increased to 6 cycles in case it is not possible to optimally microcode the ALUs for the function. The speed for applying an Omni light onto an image with no associated bump-map is 6 cycles per pixel.
With Bumtrman When an Omni light is applied to an image with an associated a bump-map, calculation of N, L, N.L and R=V are all necessary. The process of applying an Omni light onto an image with an associated bump-map is as indicated in Fig.
150 where the following constants are set by software:
Constant Value K, XP
The algorithm optionally includes the contnbtttions from previous light sources, and also includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0.
The algorithm as shown requires a total of 32 multiply/accumulates. The times taken for the lookups are I
cycle each during the calculation of both L and N, and 4 cycles for the specular contribution. However the lookup required for N and L are both the same (thus 2 LUs implement the 3 LUs). The processing time of 8 cycles is adequate.
The time taken is extended to 9 cycles in case it is not possible to optimally microcode the ALUs for the function. The speed for applying an Omni light onto an image with an associated bump-map is 9 cycles per pixel.
S tli ts Spotlights are similar to Omni lights except that the attenuation factor fõ is modified by a cone/penumbra factor fp that effectively focuses the light around a target No bumn-map When there is no bump-map, there is a constant normal vector N [0, 0, 1].
Although L must be calculated for each pixel, both N.L and R=V are simplified to ZL. Fig. 151 illustrates the application of a Spotlight to an image where the following constants are set by software:
Constant Value K, X, K, IP
The algorithm optionally includes the contributions from previous light sources, and also includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0.
The algorithm as shown requires a total of 30 multiply/accumulates. The times taken for the lookups are I
cycle during the calculation of L, 4 cycles for the specular contribution, and 2 sets of 4 cycle lookups in the cone/penumbra calculation.
With bumo-map When a Spotlight is applied to an image with an associated a bump-map, calculation of N, L, N.L and R=V
are all necessary. The process of applying a single Spotlight onto an image with associated bump-map is illustrated in Fig. 152 where the following constants are set by software:
The algorithm optionally includes the contributions from previous light sources, and also includes an ambient light calculation. Ambient light needs only to be included once. For all other light passes, the appropriate constant in the Calculate Ambient process should be set to 0. The algorithm as shown requires a total of 41 multiply/accumulates.
Print Head 44 Fig. 153 illustrates the logical layout of a single print Head which logically consists of 8 segments, each printing bi-level cyan, magenta, and yellow onto a portion of the page.
Loading a seernent for printing Before anything can be printed, each of the 8 segments in the Print Head must be loaded with 6 rows of data corresponding to the following relative rows in the final output image:
Row 0 = Line N, Yellow, even dots 0, 2,4,6,8,...
Row I = Line N+8, Yellow, odd dots 1, 3, 5, 7, ...
Row 2= Line N+10, Magenta, even dots 0, 2, 4, 6, 8, ...
Row 3= Line N+18, Magenta, odd dots 1, 3, 5, 7, ...
Row 4= Line N+20, Cyan, even dots 0, 2, 4, 6, 8, ...
Row 5= Line N+28, Cyan, odd dots 1, 3, 5, 7, _-Each of the segments prints dots over different parts of the page. Each segment prints 750 dots of one color, 375 even dots on one row, and 375 odd dots on another. 71te 8 segments have dots corresponding to positions:
Segment First dot Last dot Each dot is represented in the Print Head segment by a single bit. The data must be loaded I bit at a time by placing the data on the segment's BitValue pin, and clocked in to a shift register in the segment according to a BitClock. Since the data is loaded into a shift register, the order of loading bits must be correct_ Data can be clocked in to the Print Head at a maximum rate of 10 MHz Once all the bits have been loaded, they must be transferred in parallel to the Print Head output buffer, ready for printing. The transfer is accomplished by a single pulse on the segment's ParallelXferClock pin_ Controlline the Print In order to conserve power, not all the dots of the Print Head have to be printed simultaneously. A set of control lines enables the printing of specific dots. An external controller, such as the ACP, can change the number of dots printed at once, as well as the duration of the print pulse in accordance with speed and/or power requirements.
Each segment has 5 NozzleSelect lines, which are decoded to select 32 sets of nozzles per row. Since each row has 375 nozzles, each set contains 12 nozzles. There are also 2 BankEnable lines, one for each of the odd and even rows of color. Finally, each segment has 3 ColorEnable lines, one for each of C, M, and Y colors. A pulse on one of the ColorEnable lines causes the specified noules of the color's specified rows to be printed. A pulse is typically about 2 s in duration.
If all the segments are controlled by the same set of NozzleSelect, BankEnable and ColorEnable lines (wired externally to the print head), the following is true:
If both odd and even banks print simuNaneously (both BankEnable bits are set), 24 nozzles fire simultaneously per segment, 192 nozzles in all, consuming 5.7 Watts.
If odd and even banks print independently, only 12 nozzles fire simultaneously per segment, 96 in all, consuming 2.85 Watts.
Print Head Interface 62 The Print Head Interface 62 connects the ACP to the Print Head, providing both data and appropriate signals to the external Print Head. The Print Head Interface 62 works in conjunction with both a VLIW processor 74 and a software algorithm running on the CPU in order to print a photo in approximately 2 seconds.
An overview of the inputs and outputs to the Print Head Interface is shown in Fig. 154. The Address and Data Buses are used by the CPU to address the various registers in the Print Head Interface. A single BitClock output line connects to all 8 segments on the print head. The 8 DataBits lines lead one to each segment, and are clocked in to the 8 segments on the print head simuhaneously (on a BitClock pulse). For example, dot 0 is transferred to segmenta, dot 750 is transfermd to segment,, dot 1500 to segment2 etc. simultaneously.
The VLIW Output FIFO contains the dithered bi-level C, M, and Y 6000 x 9000 resolution print image in the correct order for output to the 8 DataBits. The ParallelXferClock is connected to each of the 8 segments on the print head, so that on a single pulse, all segments Iransfer their bits at the same time. Finally, the NozzleSelect, BankEnable and ColorEnable lines are connected to each of the 8 segments, allowing the Print Head Interface to control the duration of the C, M, and Y drop pulses as well as how many drops are printed with each pulse. Registers in the Print Head Interface allow the specification of pulse durations between 0 and 6 s, with a typical duration of 2 s.
Printing an Image There are 2 phases that must occur before an image is in the hand of the Artcam user.
1. Preparation of the image to be printed 2. Printing the prepared image Preparation of an image only needs to be performed once. Printing the image can be performed as many times as desired_ Prenare the Image Preparing an image for printing involves:
I. Convert the Photo Image into a Print Image 2. Rotation of the Print Image (internal color space) to align the output for the orientation of the printer 3. Up-interpolation of compressed channels (if necessary) 4. Color conversion from the intemal color space to the CMY color space appropriate to the specific printer and ink At the end of image preparation, a 4.5MB correctly oriented 1000 x 1500 CMY
image is ready to be printed.
Convert Photo Image to Print Image The conversion of a Photo Image into a Print Image requires the execution of a Vark sa-ipt to perform image processing. The script is either a default image enhancement script or a Vark script taken from the cutrently inserted Artcard. The Vark script is executed via the CPU, accelerated by functions performed by the VLIW Vector Processor.
Rotate the Print Imaee The image in memory is originally oriented to be top upwards. This allows for straightforward Vark processing. Before the image is printed, it must be aligned with the print roll's orientation_ The re-alignment only needs to be done once. Subsequent Prints of a Print Image will already have been rotated appropriately.
The transformation to be applied is simply the inverse of that applied during capture from the CCD when the user pressed the "Image Capture" button on the Artcam. If the original rotation was 0, then no ttansformation needs to take place. If the original rotation was +90 degrees, then the rotation before printing needs to be -90 degrees (same as 270 degrees). The method used to apply the rotation is the Vark accelerated Affine Transform function. The Affine Transform engine can be called to rotate each color channel independently.
Note that the color channels carmot be rotated in place. Instead, they can make use of the space previously used for the expanded single channel (I.5MB).
Fig. 155 shows an example of rotation of a Lab image where the a and b channels are compressed 4:1. The L
channel is rotated into the space no longer required (the single channel area), then the a channel can be rotated into the space left vacant by L. and finally the b channel can be rotated. The total time to rotate the 3 channels is 0.09 seconds.
It is an acceptable period of time to elapse before the 5rst print image.
Subsequent prints do not incur this overhead.
Up Interpolate and color convert The Lab image must be converted to CMY before printing. Different processing occurs depending on whether the a and b channels of the Lab image is compressed. If the Lab image is compressed, the a and b channels must be decompressed before the color conversion occurs. If the Lab image is not compressed, the color conversion is the only necessary step. The Lab image must be up interpolated (if the a and b channels are compressed) and converted into a CMY image. A single VLIW process combining scale and color transform can be used.
The method used to perform the color conversion is the Vark accelerated Color Convert function. The Affine Transform engine can be called to rotate each color channel independently. The color channels cannot be rotated in place. Instead, they can make use of the space previously used for the expanded single channel (1.5MB).
Print the Image Printing an image is concerned with taking a correctly oriented 1000 x 1500 CMY image, and generating data and signals to be sent to the external Print Head. The process involves the CPU working in conjunction with a VLIW
process and the Print Head Interface.
The resolution of the image in the Artcam is 1000 x 1500. The printed image has a resolution of 6000 x 9000 dots, which makes for a very straightforward relationship: I pixel = 6 x 6 =
36 dots. As shown in Fig. 156 since each dot is 16.6 m, the 6 x 6 dot square is 100 m square. Since each of the dots is bi-level, the output must be dithered.
The image should be printed in approximately 2 seconds. For 9000 rows of dots this implies a time of 222 s time between printing each row. The Print Head Interface must generate the 6000 dots in this time, an average of 37ns per dot. However, each dot comprises 3 colors, so the Print Head Interface must generate each color component in approximately 12ns, or 1 clock cycle of the ACP (IOns at 100 MHz). One VLIW
process is responsible for calculating the next line of 6000 dots to be printed. The odd and even C, M, and Y dots are generated by dithering input from 6 different 1000 x 1500 CMY image lines. The second VLIW process is responsible for taking the previously calculated line of 6000 dots, and correctly generating the 8 bits of data for the 8 segments to be transferred by the Print Head Interface to the Print Head in a single transfer.
A CPU process updates registers in the fist VLIW process 3 times per print line (once per color component =
27000 times in 2 secondsO, and in the 2nd VLIW process once every print line (9000 times in 2 seconds). The CPU
works one line ahead of the VLIW process in order to do this.
Finally, the Print Head Interface takes the 8 bit data from the VLIW Output FIFO, and outputs it unchanged to the Print Head, producing the BitClock signals appropriately. Once all the data has been transfemed a ParallelXferClock signal is generated to load the data for the next print line. In conjunction with transferring the data to the Print Head, a separate ttmer is generating the signals for the different print cycles of the Print Head using the NozzleSelect, ColorEnable, and BankEnable lines a specified by Print Head Interface internal registers.
The CPU also controls the various motors and guillotine via the parallel interface during the print process.
Generate C. M. and Y Dots The input to this process is a 1000 x 1500 CMY image correctly oriented for printing. The image is not compressed in any way. As illustrated in Fig. 157, a VLIW microcode program takes the CMY image, and generates the C, M, and Y pixels required by the Print Head Interface to be dithered.
The process is run 3 times, once for each of the 3 color components. The process consists of 2 sub-processes run in parallel - one for producing even dots, and the other for producing odd dots. Each sub-process takes one pixel from the input image, and produces 3 output dots (since one pixel = 6 output dots, and each sub-process is concerned with either even or odd dots). Thus one output dot is generated each cycle, but an input pixel is only read once every 3 cycles.
The original dither cell is a 64 x 64 cell, with each entry 8 bits. This original cell is divided into an odd cell and an even cell, so that each is sti1164 high, but only 32 entries wide. The even dither cell contains original dither cell pixels 0, 2, 4 etc., while the odd contains original dither cell pixels 1, 3, 5 etc. Since a dither cell repeats across a line, a single 32 byte line of each of the 2 dither cells is required during an entire line, and can therefore be completely cached. The odd and even lines of a single process line are staggered 8 dot lines apart, so it is convenient to rotate the odd dither cell's lines by 8 lines. Therefore the same offset into both odd and even dither cells can be used.
Consequently the even dither cell's line corresponds to the even entries of line L in the original dither cell, and the even dither cell's line corresponds to the odd entries of line L+8 in the original dither cell.
"Me process is run 3 times, once for each of the color components. The CPU
software routine must ensure that the Sequential Read Iterators for odd and even lines are pointing to the con-ect image lines corresponding to the print heads. For example, to produce one set of 18,000 dots (3 sets of 6000 dots):
= Yellow even dot line = 0, therefore input Yellow image line = 0/6 = 0 = Yellow odd dot line = 8, therefore input Yellow image line = 8/6 = I
= Magenta even line = 10, therefore input Magenta image line = 10/6 = 1 = Magenta odd line = 18, therefore input Magenta image line = 18/6 = 3 = Cyan even line = 20, therefore input Cyan image line = 20/6 = 3 = Cyan odd line = 28, therefore input Cyan image line = 28/6 = 4 Subsequent sets of input image lines are:
= Y=[0, 1], M=[l, 3], C=[3, 4]
= Y=[0, 1], M=[I, 3], C=[3, 4]
= Y=[0, 1], M=[2, 3], C=[3, 5]
= Y=[0, 1], M=[2, 3], C=[3, 5]
= Y=[0, 2], M=[2, 3], C=[4, 5]
The dither cell data however, does not need to be updated for each color component The dither cell for the 3 colors becomes the same, but offset by 2 dot lines for each component The Dithered Output is written to a Sequential Write lterator, with odd and even dithered dots written to 2 separate outputs. The same two Write iterators are used for all 3 color components, so that they are contiguous within the break-up of odd and even dots.
While one set of dots is being generated for a print line, the previously generated set of dots is being merged by a second VLIW process as described in the next section.
Generate Merged 8 bit Dot Output This process, as illustrated in Fig. 158, takes a single line of dithered dots and generates the 8 bit data stream for output to the Print Head Interface via the VLIW Output FIFO. The process requires the entire line to have been prepared, since it requires semi-random access to most of the dithered line at once. The following constant is set by software:
Constant Value K, 375 The Sequential Read Iterators point to the line of previously generated dots, with the Iterator registers set up to limit access to a single color component The distance between subsequent pixels is 375, and the distance between one line and the next is given to be I byte. Consequently 8 entries are read for each "line". A single "line" corresponds to the 8 bits to be loaded on the print head. The total number of "lines" in the image is set to be 375. With at least 8 cache lines assigned to the Sequential Read Iterator, complete cache coherence is maintained_ Instead of counting the 8 bits, 8 Microcode steps count implicitly.
The generation process first reads all the entries from the even dots, combining 8 entries into a single byte which is then output to the VLIW Output FIFO. Once all 3000 even dots have been read, the 3000 odd dots are read and processed. A software routine must update the address of the dots in the odd and even Sequential Read Iterators once per color component, which equates to 3 times per line. The two VLIW
processes require all 8 ALUs and the VLIW Output FIFO. As long as the CPU is able to update the registers as described in the two processes, the VLIW
processor can generate the dithered image dots fast enough to keep up with the printer.
Data Card Reader Fig. 159, there is illustrated on form of card reader 500 which allows for the insertion of Artcards 9 for reading. Fig. 158 shows an exploded perspective of the reader of Fig. 159.
Cardreader is interconnected to a computer system and includes a CCD reading mechanism 35. The cardreader includes pinch rollers 506, 507 for pinching an inserted Artcard 9. One of the roller e.g. 506 is driven by an Artcard motor 37 for the advancement of the card 9 between the two rollers 506 and 507 at a uniformed speed. The Artcard 9 is passed over a series of LED lights 512 which are encased within a clear plastic mould 514 having a semi circular cross section. The cross section focuses the light from the LEDs eg 512 onto the surface of the card 9 as it passes by the LEDs 512. From the surface it is reflected to a high resolution linear CCD 34 which is constructed to a resolution of approximately 480 dpi. The surface of the Artcard 9 is encoded to the level of approximately 1600 dpi hence, the linear CCD 34 supetsamples the Artcard surface with an approximately three times multiplier. The Artcard 9 is further driven at a speed such that the linear CCD 34 is able to supersample in the direction of Artcard movement at a rate of approximately 4800 readings per inch. The scanned Artcard CCD data is forwarded from the Artcard reader to ACP 31 for processing. A sensor 49, which can comprise a light sensor acts to detect of the presence of the card 13.
The CCD reader includes a bottom subshate 516, a top substrate 514 which comprises a transparent molded plastic. In between the two substrates is inserted the linear CCD array 34 which comprises a thin long linear CCD
array constructed by means of semi-conductor manufacturing processes.
Tuming to Fig. 160, there is illustrated a side perspective view, partly in section, of an example construction of the CCD reader unit. The series of LEDs eg. 512 are operated to emit light when a card 9 is passing across the surface of the CCD reader 34. The emitted light is transmitted through a portion of the top substrate 523. The substrate includes a portion eg. 529 having a curved circumference so as to focus light emitted from LED 512 to a point eg. 532 on the surface of the card 9. The focused light is reflected from the point 532 towards the CCD atray 34.
A series of microlenses eg. 534, shown in exaggerated fotm, are formed on the surface of the top substrate 523. The microlenses 523 act to focus light received across the surface to the focused down to a point 536 which corresponds to point on the surface of the CCD reader 34 for sensing of light falling on the light sensing portion of the CCD array 34.
A number of refinements of the above arrangement are possible. For example, the sensing devices on the linear CCD 34 may be staggered. The corresponding microlenses 34 can also be correspondingly formed as to focus light into a staggered series of spots so as to correspond to the staggered CCD sensors.
To assist reading, the data surface area of the Artcard 9 is modulated with a checkerboard pattem as previously discussed with reference to Fig. 38. Other forms of high frequency modulation may be possible however.
It will be evident that an Artcard printer can be provided as for the printing out of data on storage Artcard.
Hence, the Artcard system can be utilized as a general form of information distribution outside of the Artcam device.
An Artcard printer can prints out Artcards on high quality print surfaces and multiple Artcards can be printed on same sheets and later separated. On a second surface of the Artcard 9 can be printed information relating to the files etc.
stored on the Artcard 9 for subsequent storage.
Hence, the Artcard system allows for a simplified form of storage which is suitable for use in place of other forms of storage such as CD ROMs, magnetic disks etc. The Artcards 9 can also be mass produced and thereby produced in a substantially inexpensive form for redistribution.
Print Rolls Turning to Fig. 162, there is illustrated the print roll 42 and print-head portions of the Artcam. The paper/film 611 is fed in a continuous "web-like" process to a printing mechanism 15 which includes further pinch rollers 616 - 619 and a print head 44 The pinch roller 613 is connected to a drive mechanism (not shown) and upon rotation of the print roller 613, "paper" in the form of film 611 is forced through the printing mechanism 615 and out of the picture output slot 6. A
rotary guillotine mechanism (not shown) is utilised to cut the roll of paper 611 at required photo sizes.
It is therefore evident that the ptinter roll 42 is responsible for supplying "papet" 611 to the print mechanism 615 for printing of photographically imaged pictures.
In Fig. 163, there is shown an exploded perspective of the print roll 42_ The printer roll 42 includes output printer paper 611 which is output under the operation of pinching rollers 612, 613.
Referring now to Fig. 164, there is illustrated a more fully exploded perspective view, of the print roll 42 of Fig. 163 without the "paper" film roll. The print roll 42 includes tlu ee main parts comprising ink reservoir section 620, paper roll sections 622, 623 and outer casing sections 626, 627.
Turning first to the ink reservoir section 620, which includes the ink reservoir or ink supply sections 633. The ink for printing is contained within three bladder type containers 630 - 632.
The printer roll 42 is assumed to provide full color output inks. Hence, a first ink reservoir or bladder container 630 contains cyan colored ink. A second reservoir 631 contains magenta colored ink and a third reservoir 632 contains yellow ink. Each of the reservoirs 630 -632, although having different volumetric dimensions, are designed to have substantially the same volumetric size.
The ink reservoir sections 621, 633, in addition to cover 624 can be made of plastic sections and are designed to be mated together by means of heat sealing, ultra violet radiation, etc.
Each of the equally sized ink reservoirs 630 -632 is connected to a corresponding ink channel 639 - 641 for allowing the flow of ink from the reservoir 630 - 632 to a corresponding ink output port 635 - 637. The ink reservoir 632 having ink channel 641, and output port 637, the ink reservoir 631 having ink channel 640 and output port 636, and the ink reservoir 630 having ink channel 639 and output port 637.
In operation, the ink reservoirs 630 - 632 can be filled with corresponding ink and the section 633 joined to the section 621. The ink reservoir sections 630 - 632, being collapsible bladders, allow for ink to traverse ink channels 639 - 641 and therefore be in fluid communication with the ink output ports 635 - 637. Further, if required, an air inlet port can also be provided to allow the pressure associated with ink channel reservoirs 630 - 632 to be maintained as required.
The cap 624 can be joined to the ink reservoir section 620 so as to form a pressurized cavity, accessible by the air pressure inlet port.
The ink reservoir sections 621, 633 and 624 are designed to be connected together as an integral unit and to be inserted inside printer roll sections 622, 623. The printer roll sections 622, 623 are designed to mate together by means of a snap fit by means of male portions 645 - 647 mating with corresponding female portions (not shown). Similarly, female portions 654 - 656 are designed to mate with corresponding male portions 660 - 662. The paper roll sections 622, 623 are therefore designed to be snapped together. One end of the film within the role is pinched between the two sections 622, 623 when they are joined together. The print film can then be rolled on the print roll sections 622, 625 as required.
As noted previously, the ink reservoir sections 620, 621, 633, 624 are designed to be inserted inside the paper roll sections 622, 623. The printer roll sections 622, 623 are able to be rotatable around stationery ink reservoir sections 621, 633 and 624 to dispense film on demand.
The outer casing sections 626 and 627 are further designed to be coupled around the print roller sections 622, 623. In addition to each end of pinch rollers eg 612, 613 is designed to clip in to a corresponding cavity eg 670 in cover 626, 627 with roller 613 being driven extemally (not shown) to feed the print film and out of the print roll.
Finally, a cavity 677 can be provided in the ink reservoir sections 620, 621 for the insertion and gluing of an silicon chip integrated circuit type device 53 for the storage of information associated with the print roll 42.
As shown in Fig. 155 and Fig. 164, the print roll 42 is designed to be inserted into the Artcam camera device so as to couple with a coupling unit 680 which includes connector pads 681 for providing a connection with the silicon chip 53. Further, the connector 680 includes end connectors of four connecting with ink supply ports 635 - 637. The ink supply ports are in tum to connect to ink supply lines eg 682 which are in turn interconnected to printheads supply ports eg. 687 for the flow of ink to print-head 44 in accordance with requirements.
The "media" 611 utilised to form the roll can comprise many different materials on which it is designed to print suitable images. For example, opaque rollable plastic material may be utilized, transparencies may be used by using transparent plastic sheets, metallic printing can take place via utilization of a metallic sheet film. Further, fabrics could be utilised within the printer roll 42 for printing images on fabric, although care must be taken that only fabrics having a suitable stiffness or suitable backing material are utilised.
When the print media is plastic, it can be coated with a layer which fixes and absorbs the ink. Further, several types of print media may be used, for example, opaque white matte, opaque white gloss, transparent film, frosted transparent film, lenticular array film for stereoscopic 3D prints, metallised film, film with the embossed optical variable devices such as gratings or holograms, media which is pre-printed on the reverse side, and media which includes a magnetic recording layer. When udlising a metallic foil, the metallic foil can have a polymer base, coated with a thin (several micron) evaporated layer of aluminum or other metal and then coated with a clear protective layer adapted to receive the ink via the ink printer mechanism.
In use the print roll 42 is obviously designed to be inserted inside a camera device so as to provide ink and paper for the printing of images on demand. The ink output ports 635 - 637 meet with corresponding ports within the camera device and the pinch rollers 672, 673 are operated to allow the supply of paper to the camera device under the control of the camera device.
As illustrated in Fig. 164, a mounted silicon chip 53 is insert in one end of the print roll 42. In Fig. 165 the authentication chip 53 is shown in more detail and includes four communications leads 680 - 683 for communicating details from the chip 53 to the con;esponding camera to which it is inserted.
Tuming to Fig. 165, the chip can be separately created by means of encasing a small integrated circuit 687 in epoxy and running bonding leads eg. 688 to the extemal communications leads 680 - 683. The integrated chip 687 being approximately 400 microns square with a 100 micron scribe boundary.
Subsequently, the chip can be glued to an appropriate surface of the cavity of the print roll 42. In Fig. 166, there is illustrated the integrated circuit 687 interconnected to bonding pads 681, 682 in an exploded view of the arrangement of Fig. 165.
Authentication Chin Authentication Chips 53 The authentication chip 53 of the prefen=ed embodiment is responsible for ensuring that only correctly manufactured print rolls are utilized in the camera system. The authentication chip 53 utilizes technologies that are generally valuable when utilized with any consumables and are not restricted to print roll system. Manufacturers of other systems that require consumables (such as a laser printer that requires toner cartridges) have struggled with the problem of authenticating consumables, to varying levels of success. Most have resorted to specialized packaging.
However this does not stop home refill operations or clone manufacture. The prevention of copying is important to prevent poorly manufactured substitute consumables from damaging the base system. For example, poorly filtered ink may clog print nozzles in an ink jet printer, causing the consumer to blame the system manufacturer and not admit the use of non-authorized consumables.
To solve the authentication problem, the Authentication chip 53 contains an authentication code and circuit specially designed to prevent copying. The chip is manufactured using the standard Flash memory manufacturing process, and is low cost enough to be included in consumables such as ink and toner cartridges. Once programmed, the Authentication chips as described here are compliant with the NSA export guidelines. Authentication is an extremely large and constantly growing field. Here we are concemed with authenticating consumables only.
Symbolic Nomenclature The following symbolic nomenclature is used throughout the discussion of this embodiment:
Symbolic Nomenclature Description F[X] Function F, taking a single parameter X
F[X, Y] Function F, taking two parameters, X and Y
X IY X concatenated with Y
X A Y Bitwise X AND Y
X v Y Bitwise X OR Y (inclusive-OR) X Y Bitwise X XOR Y (exclusive-OR) --X Bitwise NOT X (complement) X<- y X is assigned the value Y
X<- {Y, Z) The domain of assignment inputs to X is Y and Z.
X= Y X is equal to Y
X#Y X is not equal to Y
uX Decrement X by 1(floor 0) X Increment X by 1(with wrapping based on register length) Erase X Erase Flash memory register X
SetBits[X, Y] Set the bits of the Flash memory register X based on Y
Z F ShiftRight[X, Y] Shift register X right one bit position, taking input bit from Y and placing the output bit in Z
Basic Terms A message, denoted by M, is plaintext. The process of transforming M into cyphertext C, where the substance of M
is hidden, is called encryption. The process of transforming C back into M is called decryption. Referring to the encryption function as E, and the decryption function as D, we have the following identities:
E[M] = C
D[C] = M
Therefore the following identity is true:
D[E[M]] = M
Symmetric CryptoQraohy A symmetric encryption algorithm is one where:
the encryption function E relies on key Ki, the decryption function D relies on key K2, K2 can be derived from Ki, and Ki can be derived from K2.
In most symmetric algorithms, K, usually equals K2. However, even if K, does not equal K2, given that one key can be derived from the other, a single key K can suffice for the mathematical defmition. Thus:
EK[M] = C
DK[C] = M
An enormous variety of symmetric algorithms exist, from the textbooks of ancient history through to sophisticated modem algorithms. Many of these are insecure, in that modem cryptanalysis techniques can successfully attack the algorithm to the extent that K can be derived. The security of the particular symmetric algorithm is normally a function of two things: the strength of the algorithm and the length of the key. The following algorithms include suitable aspects for utilization in the authentication chip.
DES
Blowfish IDEA
DES
DES (Data Encryption Standard) is a US and international standard, where the same key is used to encrypt and decrypt. The key length is 56 bits. It has been implemented in hardware and software, although the original design was for hardware only. The original algorithm used in DES is described in US
patent 3,962,539. A variant of DES, called triple-DES is more secure, but requires 3 keys: Ki, K2, and K3.The keys are used in the following manner:
EK3[Dx2[EK1[M]11 = C
DK3[Ex2[Dxi[C]]l = M
The main advantage of triple-DES is that existing DES implementations can be used to give more security than single key DES. Specifically, triple-DES gives protection of equivalent key length of 112 bits. Triple-DES does not give the equivalent protection of a 168-bit key (3 x 56) as one might naively expect.
Equipment that performs triple-DES
decoding and/or encoding cannot be exported from the United States.
Blowfish Blowfish, is a symmetric block cipher fust presented by Schneier in 1994. It takes a variable length key, from 32 bits to 448 bits. In addition, it is much faster than DES. The Blowfish algorithm consists of two parts: a key-expansion part and a data-encryption part. Key expansion converts a key of at most 448 bits into several subkey arrays totaling 4168 bytes. Data encryption occurs via a 16-round Feistel network. All operations are XORs and additions on 32-bit words, with four index array lookups per round. It should be noted that decryption is the same as encryption except that the subkey arrays are used in the reverse order. Complexity of implementation is therefore reduced compared to other algorithms that do not have such symmetry.
Designed by Ron Rivest in 1995, RC5 has a variable block size, key size, and number of rounds. Typically, however, it uses a 64-bit block size and a 128-bit key. The RC5 algorithm consists of two parts: a key-expansion part and a data-encryption part. Key expansion converts a key into 2r+2 subkeys (where r= the number of rounds), each subkey being w bits. For a 64-bit blocksize with 16 rounds (w=32, r=16), the subkey arrays total 136 bytes. Data encryption uses addition mod 2', XOR and bitwise rotation.
IDEA
Developed in 1990 by Lai and Massey, the first incatnation of the IDEA cipher was called PES. After differential cryptanalysis was discovered by Biham and Shamir in 1991, the algorithm was strengthened, with the result being published in 1992 as IDEA. IDEA uses 128 bit-keys to operate on 64-bit plaintext blocks. The same algorithm is used for encryption and decryption. It is generally regarded to be the most secure block algorithm available today. It is described in US Patent No.5,214,703, issued in 1993.
Asymmetric Cryptoeraphy As altemative an asymmetric algorithm could be used. An asymmetric encryption algorithm is one where:
the encryption function E relies on key K,, the decryption function D relies on key K2, K2 cannot be derived from K, in a reasonable amount of time, and K, cannot be derived from K2 in a reasonable amount of time.
Thus:
EK,[M] = C
DK2[C] = M
These algorithms are also called public-key because one key K, can be made public. Thus anyone can encrypt a message (using K,), but only the person with the corresponding decryption key (K2) can decrypt and thus read the message. In most cases, the following identity also holds:
EK2[M] = C
DK, [C] = M
This identity is very important because it implies that anyone with the public key K, can see M and know that it came from the owner of K,. No-one else could have generated C because to do so would imply knowledge of K2. The property of not being able to derive K, from K2 and vice versa in a reasonable time is of course clouded by the concept of reasonable time. What has been demonstrated time after time, is that a calculation that was thought to require a long time has been made possible by the introduction of faster computers, new algorithms etc. The security of asymmetric algorithms is based on the difficulty of one of two problems: factoring large numbers (more specifically large numbers that are the product of two large primes), and the difficulty of calculating discrete logarithms in a finite field. Factoring large numbers is conjectured to be a hard problem given today's understanding of mathematics. The problem however, is that factoring is getting easier much faster than anticipated. Ron Rivest in 1977 said that factoring a 125-digit number would take 40 quadrillion years. In 1994 a 129-digit number was factored. According to Schneier, you need a 1024-bit number to get the level of security today that you got from a 512-bit number in the 1980's. If the key is to last for some years then 1024 bits may not even be enough. Rivest revised his key length estimates in 1990: he suggests 1628 bits for high security lasting until 2005, and 1884 bits for high security lasting until 2015. By contrast, Schneier suggests 2048 bits are required in order to protect against corporations and governments until 2015.
A number of public key cryptographic algorithms exist. Most are impractical to implement, and many generate a very large C for a given M or require enormous keys. Still others, while secure, are far too slow to be practical for several years. Because of this, many public-key systems are hybrid - a public key mechanism is used to transmit a symmetric session key, and then the session key is used for the actual messages. All of the algorithms have a problem in terms of key selection. A random number is simply not secure enough. The two large primes p and q must be chosen carefully -there are certain weak combinations that can be factored more easily (some of the weak keys can be tested for). But nonetheless, key selection is not a simple matter of randomly selecting 1024 bits for example. Consequently the key selection process must also be secure.
Of the practical algorithms in use under public scrutiny, the following may be suitable for utilization:
RSA
DSA
E1Gamal RSA
The RSA cryptosystem, named after Rivest, Shamir, and Adleman, is the most widely used public-key cryptosystem, and is a de facto standard in much of the world. The security of RSA is conjectured to depend on the difficulty of factoring large numbers that are the product of two primes (p and q). There are a number of restrictions on the generation of p and q. They should both be large, with a similar number of bits, yet not be close to one another (otherwise pq = 4pq). In addition, many authors have suggested that p and q should be strong primes. The RSA
algorithm patent was issued in 1983 (US patent number 4,405,829).
DSA
DSA (Digital Signature Standard) is an algorithm designed as part of the Digital Signature Standard (DSS). As defined, it cannot be used for generalized encryption. In addition, compared to RSA, DSA is 10 to 40 times slower for signature verification. DSA explicitly uses the SHA-1 hashing algorithm (see definition in One-way Functions below). DSA key generation relies on fmding two primes p and q such that q divides p-1.
According to Schneier, a 1024-bit p value is required for long term DSA
security. However the DSA standard does not permit values of p larger than 1024 bits (p must also be a multiple of 64 bits). The US Govemment owns the DSA
algorithm and has at least one relevant patent (US patent 5,231,688 granted in 1993).
ElGamal The ElGamal scheme is used for both encryption and digital signatures. The security is based on the difficulty of calculating discrete logarithms in a finite field. Key selection involves the selection of a prime p, and two random numbers g and x such that both g and x are less than p. Then calculate y = gx mod p. The public key is y, g, and p. The private key is x.
Crypto~raphic Challenge-Response Protocols and Zero Knowledae Proofs The general principle of a challenge-response protocol is to provide identity authentication adapted to a camera system.
The simplest form of challenge-response takes the form of a secret password. A
asks B for the secret password, and if B responds with the correct password, A declares B authentic. There are three main problems with this kind of simplistic protocol. Firstly, once B has given out the password, any observer C will know what the password is.
Secondly, A must know the password in order to verify it. Thirdly, if C
impersonates A, then B will give the password to C (thinking C was A), thus compromising B. Using a copyright text (such as a haiku) is a weaker alternative as we are assuming that anyone is able to copy the password (for example in a country where intellectual property is not respected). The idea of cryptographic challenge-response protocols is that one entity (the claimant) proves its identity to another (the verifier) by demonstrating knowledge of a secret known to be associated with that entity, without revealing the secret itself to the verifier during the protocol. In the generalized case of cryptographic challenge-response protocols, with some schemes the verifier knows the secret, while in others the secret is not even known by the verifier. Since the discussion of this embodiment specifically concerns Authentication, the actual cryptographic challenge-response protocols used for authentication are detailed in the appropriate sections. However the concept of Zero Knowledge Proofs will be discussed here. The Zero Knowledge Proof protocol, first described by Feige, Fiat and Shamir is extensively used in Smart Cards for the purpose of authentication.
The protocol's effectiveness is based on the assumption that it is computationally infeasible to compute square roots modulo a large composite integer with unknown factorization. This is provably equivalent to the assumption that factoring large integers is difficult. It should be noted that there is no need for the claimant to have significant computing power. Smart cards implement this kind of authentication using only a few modular multiplications. The Zero Knowledge Proof protocol is described in US Patent 4,748,668.
One-way Functions A one-way function F operates on an input X, and retums F[X] such that X
cannot be determined from F[X]. When there is no restriction on the format of X, and F[X] contains fewer bits than X, then collisions must exist. A collision is defined as two different X input values producing the same F[X] value - i.e.
X, and X, exist such that X, X, yet F[Xj = F[X2]. When X contains more bits than F[X], the input must be compressed in some way to create the output.
In many cases, X is broken into blocks of a particular size, and compressed over a number of rounds, with the output of one round being the input to the next. The output of the hash function is the last output once X has been consumed. A
pseudo-collision of the compression function CF is defined as two different initial values V i and V2 and two inputs X, and X2 (possibly identical) are given such that CF(Vi, Xi) = CF(V2, X2). Note that the existence of a pseudo-collision does not mean that it is easy to compute an X2 for a given X,.
We are only interested in one-way functions that are fast to compute. In addition, we are only interested in deterministic one-way functions that are repeatable in different implementations. Consider an example F where F[X] is the time between calls to F. For a given F[X] X cannot be determined because X
is not even used by F. However the output from F will be different for different implementations. This kind of F
is therefore not of interest.
In the scope of the discussion of the implementation of the authentication chip of this embodiment, we are interested in the following forms of one-way functions:
Encryption using an unknown key Random number sequences Hash Functions Message Authentication Codes Encryption Using an Unknown Kev When a message is encrypted using an unknown key K, the encryption function E
is effectively one-way. Without the key, it is computationally infeasible to obtain M from EK[MJ without K. An encryption function is only one-way for as long as the key remains hidden. An encryption algorithm does not create collisions, since E creates EK[M] such that it is possible to reconstruct M using function D. Consequently F[XJ contains at least as many bits as X (no information is lost) if the one-way function F is E. Symmetric encryption algorithms (see above) have the advantage over Asymmetric algorithms for producing one-way functions based on encryption for the following reasons:
The key for a given strength encryption algorithm is shorter for a symmetric algorithm than an asymmetric algorithm Symmetric algorithms are faster to compute and require less software/silicon The selection of a good key depends on the encryption algorithm chosen.
Certain keys are not strong for particular encryption algorithms, so any key needs to be tested for strength. The more tests that need to be performed for key selection, the less likely the key will remain hidden.
Random Number Seouences Consider a random number sequence Ra, Ri, ..., RI, R. We define the one-way function F such that F[X] returns the Xd' random number in the random sequence. However we must ensure that F[X] is repeatable for a given X on different implementations. The random number sequence therefore cannot be truly random. Instead, it must be pseudo-random, with the generator making use of a specific seed.
There are a large number of issues concerned with defming good random number generators. Knuth, describes what makes a generator "good" (including statistical tests), and the general problems associated with constructing them.
The majority of random number generators produce the i'h random number from the i-1& state - the only way to determine the ith number is to iterate from the 0 i number to the id. If i is large, it may not be practical to wait for i iterations. However there is a type of random number generator that does allow random access. Blum, Blum and Shub defme the ideal generator as follows:"... we would like a pseudo-random sequence generator to quickly produce, from short seeds, long sequences (of bits) that appear in every way to be generated by successive flips of a fair coin".
They defined the 2 mod n generator, more commonly refetred to as the BBS
generator. They showed that given certain assumptions upon which modem cryptography relies, a BBS generator passes extremely stringent statistical tests.
The BBS generator relies on selecting n which is a Blum integer (n = pq where p and q are large prime numbers, p;t q, p mod 4 = 3, and q mod 4 = 3). The initial state of the generator is given by a where o= Z mod n, and x is a random integer relatively prime to n. The io' pseudo-random bit is the least significant bit of x; where x; = xi_,Z mod n. As an extra property, knowledge of p and q allows a direct calculation of the i's number in the sequence as follows: x; = a'"
mod n, where y= 2' mod ((p-1)(q-1)) Without knowledge of p and q, the generator must iterate (the security of calculation relies on the difficulty of factoring large numbers). When first defined, the primary problem with the BBS generator was the amount of work required for a single output bit. The algorithm was considered too slow for most applications. However the advent of Montgomery reduction arithmetic has given rise to more practical implementations. In addition, Vazirani and Vazirani have shown that depending on the size of n, more bits can safely be taken from xi without compromising the security of the generator. Assuming we only take I bit per x;, N bits (and hence N iterations of the bit generator function) are needed in order to generate an N-bit random number. To the outside observer, given a particular set of bits, there is no way to detennine the next bit other than a 50/50 probability. If the x, p and q are hidden, they act as a key, and it is computationally unfeasible to take an output bit stream and compute x, p, and q. It is also computationally unfeasible to determine the value of i used to generate a given set of pseudo-random bits.
This last feature makes the generator one-way. Different values of i can produce identical bit sequences of a given length (e.g. 32 bits of random bits). Even if x, p and q are known, for a given F[i], i can only be derived as a set of possibilities, not as a certain value (of course if the domain of i is known, then the set of possibilities is reduced further).
However, there are problems in selecting a good p and q, and a good seed x. In particular, Ritter describes a problem in selecting x. The nature of the problem is that a BBS generator does not create a single cycle of known length. Instead, it creates cycles of various lengths, including degenerate (zero-length) cycles. Thus a BBS generator cannot be initialized with a random state - it might be on a short cycle.
Hash Functions Special one-way functions, known as Hash functions map arbitrary length messages to fixed-length hash values. Hash functions are referred to as H[M]. Since the input is arbitrary length, a hash function has a compression component in order to produce a fixed length output. Hash functions also have an obfuscation component in order to make it difficult to fmd collisions and to determine information about M from H[M]. Because collisions do exist, most applications require that the hash algorithm is preimage resistant, in that for a given Xi it is difficult to fmd X2 such that H[Xi] =
H[XZ]. In addition, most applications also require the hash algorithm to be collision resistant (i.e. it should be hard to find two messages Xi and X2 such that H[X,] = H[XZ]). It is an open problem whether a collision-resistant hash function, in the idealist sense, can exist at all. The primary application for hash functions is in the reduction of an input message into a digital "fingerprint" before the application of a digital signature algorithm. One problem of collisions with digital signatures can be seen in the following example.
A has a long message M, that says "I owe B $10". A signs H[Mi] using his private key. B, being greedy, then searches for a collision message M2 where H[M,] = H[M1] but where M2 is favorable to B, for example "I owe B$lmillion". Clearly it is in A's interest to ensure that it is difficult to find such an Mz.
Examples of collision resistant one-way hash functions are SHA-1, MD5 and RIPEMD-160, all derived from MD4.
Ron Rivest introduced MD4 in 1990. It is mentioned here because all other one-way hash functions are derived in some way from MD4. MD4 is now considered completely broken in that collisions can be calculated instead of searched for. In the example above, B could trivially generate a substitute message M2 with the same hash value as the original message Mi.
Ron Rivest introduced MD5 in 1991 as a more secure MD4. Like MD4, MD5 produces a 128-bit hash value.
Dobbertin describes the status of MD5 after recent attacks. He describes how pseudo-collisions have been found in MD5, indicating a weakness in the compression function, and more recently, collisions have been found. This means that MD5 should not be used for compression in digital signature schemes where the existence of collisions may have dire consequences. However MD5 can still be used as a one-way function. In addition, the HMAC-MD5 construct is not affected by these recent attacks.
SHA-1 is very similar to MD5, but has a 160-bit hash value (MD5 only has 128 bits of hash value). SHA-1 was designed and introduced by the NIST and NSA for use in the Digital Signature Standard (DSS). The original published description was called SHA, but very soon afterwards, was revised to become SHA-I, supposedly to correct a security fiaw in SHA (although the NSA has not released the mathematical reasoning behind the change). There are no known cryptographic attacks against SHA-1. It is also more resistant to brute-force attacks than MD4 or MD5 simply because of the longer hash result. The US Government owns the SHA-l and DSA algorithms (a digital signature authentication algorithm defined as part of DSS) and has at least one relevant patent (US patent 5,231,688 granted in 1993).
RIPEMD-160 is a hash function derived from its predecessor RIPEMD (developed for the European Community's RIPE project in 1992). As its name suggests, RIPEMD-160 produces a 160-bit hash result. Tuned for software implementations on 32-bit architectures, RIPEMD-160 is intended to provide a high level of security for 10 years or more. Although there have been no successful attacks on RIPEMD-160, it is comparatively new and has not been extensively cryptanalyzed. The original RIPEMD algorithm was specifically designed to resist known cryptographic attacks on MD4. The recent attacks on MD5 showed similar weaknesses in the RIPEMD 128-bit hash function.
Although the attacks showed only theoretical weaknesses, Dobbertin, Preneel and Bosselaers further strengthened RIPEMD into a new algorithm RIPEMD-160.
Message Authentication Codes The problem of message authentication can be summed up as follows:
How can A be sure that a message supposedly from B is in fact from B?
Message authentication is different from entity authentication. With entity authentication, one entity (the claimant) proves its identity to another (the verifier). With message authentication, we are concemed with making sure that a given message is from who we think it is from i.e. it has not been tampered en route from the source to its destination.
A one-way hash function is not sufficient protection for a message. Hash functions such as MD5 rely on generating a hash value that is representative of the original input, and the original input cannot be derived from the hash value. A
simple attack by E, who is in-between A and B, is to intercept the message from B, and substitute his own. Even if A
also sends a hash of the original message, E can simply substitute the hash of his new message. Using a one-way hash function alone, A has no way of knowing that B's message has been changed. One solution to the problem of message authentication is the Message Authentication Code, or MAC. When B sends message M, it also sends MAC[M] so that the receiver will know that M is actually from B. For this to be possible, only B must be able to produce a MAC of M, and in addition, A should be able to verify M against MAC[M]. Notice that this is different from encryption of M -MACs are useful when M does not have to be secret. The simplest method of constructing a MAC from a hash function is to encrypt the hash value with a symmetric algorithm:
Hash the input message H[M]
Encrypt the hash EK[H[M]]
This is more secure than first encrypting the message and then hashing the encrypted message. Any symmetric or asymmetric cryptographic function can be used. However, there are advantages to using a key-dependant one-way hash function instead of techniques that use encryption (such as that shown above):
Speed, because one-way hash functions in general work much faster than encryption;
Message size, because EK[H[M]] is at least the same size as M, while H[M] is a fixed size (usually considerably smaller than M);
Hardware/software requirements - keyed one-way hash functions are typically far less complexity than their encryption-based counterparts; and One-way hash function implementations are not considered to be encryption or decryption devices and therefore are not subject to US export controls.
It should be noted that hash functions were never originally designed to contain a key or to support message Use well-defined and well-behaved technology Reduce cost Regardless of the autiientication scheme used, the circuitry of the authentication part of the chip must be resistant to physical attack. Physical attack comes in four main ways, although the form of the attack can vary:
Bypassing the Authentication Chip altogether Physical examination of chip while in operation (destnuctive and non-destructive) Physical decomposition of chip Physical alteration of chip Ideally, the chip should be exportable from the U.S., so it should not be possible to use an Authentication chip 53 as a secure encryption device. This is low priority requirement since there are many companies in other countries able to manufacture the Authentication chips. In any case, the export restrictions from the U.S. may change.
Authentication Existing solutions to the problem of authenticating consumables have typically relied on physical patents on packaging. However this does not stop home refill operations or clone manufacture in countries with weak industrial property protection. Consequently a much higher level of protection is required. It is not enough to provide an authentication method that is secret, relying on a home-brew security method that has not been scrutinized by security experts. Security systems such as Netscape's original proprietary system and the GSM Fraud Prevention Netwotk used by cellular phones are examples where design secrecy caused the vulnerability of the security. Both security systems were broken by conventional means that would have been detected if the companies had followed an open design process. The solution is to provide authentication by means that have withstood the scrutiny of experts. A number of protocols that can be used for consumables authentication. We only use security methods that are publicly described, using known behaviors in this new way. For all protocols, the security of the scheme relies on a secret key, not a secret algorithm. All the protocols rely on a time-variant challenge (i_e. the challenge is different each time), where the response depends on the challenge and the secret. The challenge involves a random number so that any observer will not be able to gather useful information about a subsequent identification.
Two protocols are presented for each of Presence Only Authentication and Consumable Lifetime Authentication. Although the protocols differ in the number of Authentication Chips required for the authentication process, in all cases the System authenticates the consumable.
Certain protocols will wodc with either one or two chips, while other protocols only work with two chips. Whether one chip or two Authentication Chips are used the System is still responsible for making the authentication decision.
Sinp-le Chip Authentication When only one Authentication chip 53 is used for the authentication protocol, a single chip (referred to as ChipA) is responsible for proving to a system (refen-ed to as System) that it is authentic. At the start of the protocol, System is unsure of ChipA's authenticity. System undertakes a challenge-response protocol with ChipA, and thus determines ChipA's authenticity. In all protocols the authenticity of the consumable is directly based on the authenticity of the chip, i.e. if ChipA is considered authentic, then the consumable is considered authentic. The data flow can be seen in Fig. 167. In single chip authentication protocols, System can be software, hardware or a combmation of both. It is important to note that System is considered insecure - it can be easily reverse engineered by an attacker, either by examining the ROM or by examining circuitry. System is not specially engineered to be secure in itself.
Double Chip Authentication In other protocols, two Authentication Chips are required as shown in Fig.
168. A single chip (referred to as ChipA) is responsible for proving to a system (refen-ed to as System) that it is authentic. As part of the authentication process, System makes use of a trusted Authentication Chip (refertrd to as ChipT). In double chip authentication protocols, System can be software, hardware or a combination of both. However ChipT must be a physical Authentication Chip.
In some protocols ChipT and ChipA have the same intemal structure, while in others ChipT and ChipA have different internal structures.
Presence Only Authentication (Insecure State Data) For this level of consumable authentication we are only concerned about validating the presence of the Authentication chip 53. Although the Authattication Chip can contain state infonnation, the transmission of that state information would not be considered secure. Two protocols are presented. Protocol 1 requires 2 Authentication Chips, while Protocol2 can be impiemented using either I or 2 Authentication Chips.
Protocol I
Protocol I is a double chip protocol (two Authentication Chips are required).
Each Authentication Chip contains the following values:
K Key for FK[X]. Must be secret.
R Current random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each invocation of the Random function.
Each Authentication Chip contains the following logical functions:
Random[l Retums R, and advances R to next in sequence.
F[X] Retums FK[X], the result of applying a one-way fnnction F to X based upon the sectet key K.
The protocol is as follows:
System requests Random[] from ChipT;
ChipT retums R to System;
System requests F[R] from both ChipT and ChipA;
ChipT n'mnts Ficr[R] to System;
ChipA refums FKAR) to System;
System compares FKT[R] with FKA[R]. If they are equal, then ChipA is considered valid. If not, then ChipA is considered invalid.
11m data flow can be seen in Fig. 169. The System does not have to comprehend FK[R] messages. It must merely check that the responses from ChipA and ChipT are the same. The System therefore does not require the key. The security of Protocol 1 lies in two places:
The security of F[X], Only Authentication chips contain the seeret key, so anything that can produce an F[X] from an X that matches the F[X] generated by a tntsted Attthentiration chip 53 (ChipT) must be autttetttic.
The domain of R generated by all Authetnication chips must be Iatge and non-detenninistic. If the domain of R
generated by all Authentication chips is small, then there is no need for a clone manufactum to crack the key.
Instead, the clone manufacttmer could iacoaporate a ROM in their dtip that had a record of all of the responses from a genuine chip to the codes sent by the system. The Random function does not strictly have to be in the Autltentication Chip, since System can potentially generate the same tandom number sequence.
However it simplifies the design of System and ensures the security of the random number generator will be the same for all implementations that use the Authentication Chip, reducing possible error in system implementation.
Protocol I has several advantages:
K is not revealed during the authentication process Given X, a clone chip cannot generate FK[X] without K or access to a real Authentication Chip.
System is easy to design, especially in low cost systems such as ink-jet printers, as no enctyption or decryption is required by System itself.
A wide range of keyed one-way functions exists, including symmetric cryptography, random number sequences, and message authentication codes.
One-way functions require fewer gates and are easier to verify than asymmetric algoriduns).
Secure key size for a keyed one-way function does not have to be as large as for an asymmetric (public key) algorithm. A minimum of 128 bits can provide appropriate security if F[X] is a symmetric cryptographic function.
However there are problems with this protocol:
It is susceptible to chosen text attack An attacker can plug the chip into their own system, generate chosen Rs, and observe the output. In order to find the key, an attacker can also search for an R that will generate a specific F[Mj since multiple Authentication chips can be tested in paralleL
Depending on the one-way fitttction chosen, key generation can be complicated.
The method of selecting a good key depends on the algorithm being used. Certain keys are weak for a given algorithm.
Ihe choice of the keyed one-way functions itself is non-trivial. Some require licensing due to patent protection.
A man-in-the middle could take action on a plaintext message M before passing it on to ChipA - it would be preferable if the man-in-the-middle did not see M until after ChipA had seen it. It would be even more preferable if a man-in-the-middle didn't see M at all.
If F is symmetric encryption, because of the key size needed for adequate security, the chips could not be exported fivm the USA since they could be used as strong encryption devices.
If Protocol I is implemented with F as an asymmetric encryption algorithm, there is no advantage over the symmetric case - the keys needs to be longer and the encryption algorithm is more expensive in silicon. Protocol I must be itnplemented with 2 Authentication Chips in order to keep the key secure. This means that each System requires an Authentication Chip and each consumable requires an Authentication Chip.
Protocol 2 In some cases, System may contain a large amount of processing power.
Altematively, for instances of systems that are manufactured in large quantities, integtation of ChipT into System may be desirable. Use of an asymmetrical enctyption algorithm allows the ChipT portion of System to be insecure.
Protocol 2 therefore, uses asymmetric cryptography. For this protocol, each chip contains the following values:
K Key for FJX] and DKjXJ. Must be sec,ret in ChipA. Does not have to be secret in ChipT.
R Curnnt random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each utvocation of the Random function.
The following fimctions are defined:
EIXI ChipT only. Retums EK[X] where E is asymmetric encrypt fnnction E.
D[X] ChipA only. Retums DK[X) where D is asyrnmetric decrypt fanction D.
Random[] ChipT only. Retums R I EK[R], where R is random number based on seed S. Advances R to next in random number sequence_ The public key KT is in ChipT, while the secret key KA is in ChipA. Having KT
in ChipT has the advantage that ChipT
can be implemented in software or hardware (with the proviso that the seed for R is diffen:nt for each chip or system).
Protocol 2 therefore can be implemented as a Single Chip Protocol or as a Double Chip Protocol. The protocol for authentication is as follows:
System calls ChipT's Random function;
ChipT returns R I EKAR] to System;
System calls ChipA's D function, passing in FKT[R];
ChipA returns R, obtained by DKA[EKT[R]];
System compares R from ChipA to the original R generated by ChipT. If they are equal, then ChipA is considered valid. If not, ChipA is invalid.
The data flow can be seen in Fig. 170. Protocol 2 has the following advantages:
KA (the secret key) is not revealed during the authentication process Given EKT[X], a clone chip cannot generate X without KA or access to a real ChipA.
Since KT # Kk, ChipT can be implemented completely in software or in insecure hardware or as part of System.
Only ChipA (in the consumable) is required to be a sectue Authentication Chip.
If ChipT is a physical chip, System is easy to design.
There are a number of well-documented and cryptanalyzed asymmetric algorithms to chose from for implementation, including patent-free and license-free solutions.
However, Protocol 2 has a number of its own problems:
For satisfactory security, each key needs to be 2048 bits (compared to minimum 128 bits for synunetric ctyptography in Protocol 1). The associated intermediate memory used by the encryption and decryption algorithms is correspondingly latger.
Key generation is non-trivial. Random numbers are not good keys.
If ChipT is implemented as a core, there may be difficulties in linking it into a given System ASIC.
If QtipT is implemented as software, not only is the implementation of System open to programming error and non-rigorous testing, but the integrity of the compiler and mathematics primitives must be rigorously checked for each impiementation of System. This is more complicated and costly than simply using a well-tested chip.
Although many symmetric algorithms are specifically strongthened to be resistant to differential c yptanalysis (which is based on chosen text attacks), the private key K, is susceptible to a chosen text attack If ChipA and ChipT are instattces of the same Authentication Chip, each chip must contain both asymmetric encrypt and decrypt functionality. Consequently each chip is larger, more complex, and more expensive than the chip required for Protocol 1.
If the Authentication Chip is broken into 2 chips to save cost and reduce complexity of design/test, two chips still need to be manufactured, reducing the economies of scale. This is offset by the relative numbers of systems to consumables, but must still be taken into account.
Protocol 2 Authentication Chips could not be exported from the USA, since they would be considered strong enayption devices.
Even if the process of choosing a key for Protocol 2 was straightforward, Protocol 2 is impractical at the present time due to the high cost of silicon implementation (both key size and functional implementation). Therefore Protocol 1 is the protoeol of choice for Presence Only Authentication.
Clone Consumable usine Real Authentication Chio Protocols I and 2 only check that ChipA is a real Authentication Chip. They do not check to see if the consumable itself is valid. The fundamental assumption for authentication is that if ChipA is valid, the consumable is validd It is therefore possible for a clone manufaciurer to insert a real Authentication Chip into a clone consumable. There are two cases to consider.
In cases where state data is not written to the Authentication Chip, the chip is completely reusable. Clone manufacturers could therefore recycle a valid consumable into a clone consumable. This may be made more difficult by melding the Authentication Chip into the consumable's physical packaging, but it would not stop refill operators.
In cases where state data is written to the Authentication Chip, the chip may be new, partially used up, or completely used up. However this does not stop a clone manufacturer from using the Piggyback attack, where the clone manufacturer builds a chip that has a real Authentication Chip as a piggyback The Attacker's chip (ChipE) is therefore a man-in-the-middle. At power up, ChipE reads all the memory state values from the real Authentication chip 53 into its own memory. ChipE then examines requests from System, and takes different actions depending on the request Authentication requests can be passed direexly to the real Authentication chip 53, while read/write requests can be simulated by a memory that resembles real Authentication Chip behavior. In this way the Authentication chip 53 will always appear fresh at power-up. ChipE can do this because the data access is not authenticated.
In order to fool System into thinking its data accesses were successfiil, ChipE still requires a real Authentication Chip, and in the second case, a clone chip is required in addition to a real Authentication Chip. Consequently Protocols I and 2 can be useful in situations where it is not cost effective for a clone manufacturer to embed a real Authentication chip 53 into the consumable. If the consumable caanot be recycled or refilled easily, it may be protection enough to use Protocols 1 or 2. For a clone operation to be successful each clone consumable must include a valid Authentication Chip. The chips would have to be stolen en masse, or taken fivm old consumables. The quantity of these reclaimed chips (as well as the effort in reclaiming them) should not be enough to base a business on, so the added protection of secure data transfer (see Protocols 3 and 4) may not be useful.
Loneevitv of Kev A general problem of these two protocols is that once the authentication key is chosen, it cannot easily be changed. In sotne iostances a key-compromise is not a problem, while for others a key compromise is disastrous. For example, in a car/car-key Systeni/Consumable scenario, the customer has only one set of car/car-keys. Each car has a different authentication key. Consequently the loss of a car-key only compromises the individual car. If the owner considers this a problem, they must get a new lock on the car by replacing the System chip inside the car's electraucs. The owner's keys must be reprogrammed/replaced to work with the new car System Authentication Chip_ By conuast, a c.ompromise of a key for a high volume consumable market (for example ink cartridges in printers) would allow a clone ink cartridge manufacturer to make their own Authentication Chips. The only solution for existing systems is to update the System Authentication Chips, which is a costly and logistically difficult exercise. In any case, consumers' Systems already work - they have no incentive to hobble their existing equipment.
Consumable Lifetime Authentication In this level of consumable authentication we are concemed with validating the existence of the Authentication Chip, as well as ensuring that the Authentication Chip lasts only as long as the consumable. In addition to validating that an Authentication Chip is present, writes and reads of the Authentication Chip's memory space must be authenticated as well. In this section we assume that the Authentication Chip's data storage integrity is secure - certain parts of inemory are Read Only, others are ReadfWrite, while others are Decrement Only (see the chapter entitled Data Storage Integrity for more information). Two protocols are presented. Protocol 3 requires 2 Authentication Chips, while Protocol 4 can be implemented using either 1 or 2 Audtetttication Chips.
Protocol 3 This protocol is a double chip protocol (two Authentication Chips are required). For this protocol, each Authentication Chip contains the following values:
K, Key for calculating FKi[X]. Must be secret.
K2 Key for calculating FK2[X]. Must be secret.
R Cunent random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each successful authentication as defined by the Test function.
M Memory vector of Authentication chip 53. Part of this space should be different for each chip (does not have to be a random number).
Each Authentication Chip contains the following logical functions:
FIX[ Internal function only. Rettuns FK[X], the result of applying a one-way function F to X based upon either key K, or key K2 Random[[ Retums R I FKi[R]=
Test[X, Y] Retums land advances R if FK2[R I X] = Y. Otherwise returns 0. The time taken to return 0 must be identical for all bad inputs.
Read[X, Yi Retums M I FK2[X I M] if FKI[Xj = Y. Otherwise returns 0. The time taken to return 0 must be identical for all bad inputs.
Write[Xl Writes X over those parts of M that can legitimately be written over.
To authenticate ChipA and read ChipA's memory M:
System calls ChipT's Random function;
ChipT produces R I FK[R] and returns these to System;
System calls ChipA's Read function, passing in R, FK[R];
ChipA returns M and FK[R I M];
System calls ChipT's Test function, passing in M and FK[R I M];
System checks response from ChipT. If the response is l, then ChipA is considered authentic. If 0, ChipA is considered invalid To authenticate a write of M~ to ChipA's memory M:
Systetn calls ChipA's Write function, passing in Mõ.;
The authentication procedure for a Read is carried out;
If ChipA is authentic and M. = M, the write sueceoded. Othawise it failed.
The data flow for read authentication is shown in Fig. 171. The first thing to note about Protocol 3 is that FK[X] cannot be called directly. Instead FK[X] is called indirectly by Random, Test and Read:
Random[] calls FK,[X] X is not chosen by the caller. It is chosen by the Random function. An attacker must perform a brute force search using multiple calls to Random, Read, and Test to obtain a desired X, FK,[X]
pair-Test[X,Y] calls FK2[R I X] Does not return result directly, but compares the result to Y and then returns I or 0. Any attempt to deduce K2 by calling Test multiple times trying different values of F"[R I X] for a given X
is reduced to a brute force search where R cannot even be chosen by the attacker.
Read[X, Y] calls FKt[X] X and FK,[X] must be supplied by caller, so the caller must already know the X, FKI[X] pair. Since the call retarns 0 if Y# FK,[X], a caller can use the Read function for a brute force attack on K.
Read[X, Y] calls FK2[X I Mj, X is supplied by caller, however X can only be those values already given out by the Random function (since X and Y are validated via K,). Thus a chosen text attack must first collect pairs from Random (effectively a brute force attack). In addition, only part of M
can be used in a chosen text attack smce some of M is constant (read-only) and the decrement-only part of M can only be used once per consumable. In the next consumable the read-only part of M will be different.
Having FK[X] being called indirectly prevents chosen text attacks on the Authentication Chip. Since an attacker can only obtain a chosen R. FK,[R] pair by calling Random, Read, and Test multiple times until the desired R appeats, a brute force attack on K, is required in order to perform a limited chosen text attack on K2. Any attempt at a chosen text attack on K2 would be limited since the text cannot be coittpletety chosen:
parts of M are read-only, yet different for each Authentication Chip. The second thing to note is that two keys are used Given the small size of M, two different keys K, and K2 are used in order to ensure there is no correiation between F[R] and F[P4M]. K, is therefore used to help protect K2 against diffetcntial attacks. It is not enough to use a single bnger key since M is only 256 bits, and only part of M changes during the lifetime of the consumable. Othmwise it is potentially possible that an attacker via some as-yet mtdisoovered teclmique, could determine the effect of the limited changes in M to particular bit combinations in R and thus calculate FKjX I M] based on FKl[X]. As an added precaution, the Random and Test functions in ChipA
should be disabled so that in order to genetate R, FK[R] pairs, an attacker must use instances of ChipT, each of which is more expensive than ChipA (since a system must be obtained for each ChipT).
Similarly, there should be a minunum delay between calls to Random, Read and Test so that an attacker cannot call these functions at high speed. Thus each d-ip can only give a specific number of X, FK[X] pairs away in a certain time period. The only specific timing requirement of Pcotoeol3 is thai the return value of 0(indicating a bad input) must be produced in the same amount of time regardless of where the error is in the input. Attackeas can therefore not leam anything about what was bad about the input vaiue. This is true for both RD and TST fimdions.
Another thing to note about Protocol 3 is that Reading data from ChipA also requires authentication of ChipA. The SYstem can be sure that the contents of inemory (M) is what ChipA claims it to be if FK2[R I MJ is retutned comectly. A
clone chip may paetettd that M is a cenain value (for example it may pretmd that the constmtable is full), but it cannot tetutn Fra[R I M] for any R passed in by System. Thus the effective signature FK2[R I M] assures System that not only did an authentic ChipA send M, but also that M was not ahered in between ChipA
and System. Finaliy, the Write function as defined does not authenticate the Write. To authenticate a write, the System must perform a Read after each Write_ There are some basic advantages with Protocol 3:
K, and K2 are not revealed during the authentication process Given X, a clone chip cannot generate FK2[X I M] without the key or access to a real Authentication Chip.
System is easy to design, especially in low cost systems such as ink-jet printers, as no encryption or decryption is requirod by System itsoif.
A wide range of key based one-way functions exists, including symmetric cryptography, random number sequences, and message authentication codes.
Keyed one-way functions require fewer gates and are easier to verify than asymmetric algorithms).
Secure key size for a keyed one-way function does not have to be as large as for an asymmetric (public key) algorithm. A minimum of 128 bits can provide appropriate security if F[X] is a symmetric cryptographic function.
Consequently, with Protocol 3, the only way to authenticate ChipA is to read the contents of ChipA's memory. The security of this protocol depends on the underlying FK[X] scheme and the domain of R over the set of all Systems.
Although FK[X] can be any keyed one-way function, there is no advantage to implement it as asymmetric encryption.
The keys need to be longer and the encryption algorithm is more expensive in silicon. This leads to a second protocol for use with asymmetric algorithms - Protocol 4. Protocol 3 must be implemented with 2 Authentication Chips in order to keep the keys secure. This means that each System requires an Authentication Chip and each consumable requires an Authentication Chip Protocol 4 In some cases, System may contain a large amount of processing power.
Altematively, for instances of systems that are manufactured in large quantities, integration of ChipT into System may be desirable. Use of an asymmetrical encryption algorithm can allow the ChipT portion of System to be insecure.
Protocol 4 therefore, uses asymmetric cryptography. For this protocol, each chip contains the following values:
K Key for EK[X] and DK[X]. Must be secret in ChipA. Does not have to be secret in ChipT.
R Current random number. Does not have to be secret, but must be seeded with a different initial value for each chip instance. Changes with each successful aut4tentication as defined by the Test function.
M Memory vector of Authentication chip 53. Part of this space should be different for each chip, (does not have to be a random number).
There is no point in verifying anything in the Read function, since anyone can encrypt using a public key.
Consequently the following functions are defined:
E[Xl lntemal function only. Retunu EK[X] where E is asymmetric encrypt function E.
D[X] Intemal function only. Returns DK[X] where D is asymmetric decrypt function D.
RandomQ ChipT only. Returns EK[R].
Test[X, Y] Retums 1 and advances R if DK[R I X] = Y. Otherwise retutns 0. The time taken to return 0 must be identical for all bad inputs.
Read[XJ Returns M I EK[R I M) where R = DK[X] (does not test input).
Write[XJ Writes X over those parts of M that can legitimately be written over.
The public key KT is in ChipT, while the secret key KA is in ChipA. Having KT
in ChipT has the advantage that ChipT
can be implemented in software or hardware (with the proviso that R is seeded with a different random number for each system). To authenticate ChipA and m,ad ChipA's memory M:
System cal(s ChipT's Random fnnction;
ChipT produces ad returns EKT[R] to System;
System calls ChipA's Read fnnction, passing in EKT[R];
ChipA retun:ts M I FKA[R I MI, first obtaining R by DKA[EKT(R]];
System calls ChipT's Test function, passittg in M and EKA[R I M];
ChipT calculates DKT{FcA[R I M]] and compares it to R I M.
System checks response from ChipT. If the response is 1, then ChipA is considered authentic. If 0, ChipA is considered invalid.
To authenticate a write of Mõ, to ChipA's memory M:
System calls ChipA's Write function, passing in Mõ,_;
The authentication procedure for a Read is carried out;
If ChipA is authentic and M. = M, the write succeeded. Otherwise it failed.
The data flow for read authentication is shown in Fig. 172. Only a valid ChipA
would know the value of R., since R is not passed into the Authenticate fnnction (it is passed in as an encrypted value). R must be obtained by decrypting E[R], which can only be done using the secret key Kk. Once obtained, R must be appended to M and then the result re-encoded. ChipT can then verify that the decoded form of EyA[R I M] = R j M and hence ChipA is valid. Since KT # KA
EKT[R] * EKA[R]. Protocol 4 has the following advantages:
KA (the secret key) is not revealed during the authentication process Given EKr[X], a clone chip cannot generate X without KA or access to a real ChipA.
Since KT # K, ChipT can be implemented completely in software or in insec.une hardware or as part of System.
Only ChipA is required to be a secure Authentication Chip.
Since ChipT and ChipA contain different keys, intense testing of ChipT will reveal nothing about KA.
If ChipT is a physical chip, System is easy to design.
There are a number of well-documented and cryptanalyzed asymmetric algorithms to chose from for implementation, including patent-free and license-free sohrtions.
Even if System could be rewired so that CitipA requests were drtvoted to ChipT, ChipT could never answer for ChipA since KT :$: KA. The attack would have to be directed at the System ROM
itself to bypass the Authentication protocol.
However, Protocol 4 has a number of disadvantages:
All Authentication Chips need to contain both asymmetric encrypt and decrypt functionatity. Consequently each chip is larger, more complex, and more expensive than the chip required for Protocol 3.
For satisfactory security, each key needs to be 2048 bits (compared to a minimum of 128 bits for symmetric cryptography in Protocol 1). The associated intennediate memory used by the encryption and decryption algorithms is con-espondingly larger.
Key generation is non-trivial. Random numbers are not good keys.
If ChipT is implemented as a core, there may be difficulties in linking it into a given System ASIC.
If ChipT is implemented as software, not only is the implementation of System open to progranuning error and non-rigorous testing, but the integrity of the compiler and mathematics primitives must be rigorously checked for each implementation of System. This is more complicated and costly than simply using a well-tested chip.
Although many symmetric algorithms are specifically strengthened to be resistant to differential cryptanalysis (which is based on chosen text attacks), the private key KA is susceptible to a chosen text attack Protocol 4 Authentication Chips could not be exported from the USA, since they would be considered strong encryption devices.
As with Protocol 3, the only specific timing requirement of Protocol 4 is that the return value of 0 (indicating a bad input) must be produced in the same amount of time regardless of where the error is in the input. Attackers can therefore not learn anything about what was bad about the input value. This is true for both RD and TST functions.
Variation on call to TST
If there are two Authentication Chips used, it is theoretically possible for a clone manufacturer to replace the System Authentication Chip with one that retums 1(success) for each call to TST. The System can test for this by calling TST
a number of times - N times with a wrong hash value, and expect the result to be 0. The fmal time that TST is called, the ttue retumed value from ChipA is passed, and the return value is trusted.
The question then arises of how many times to call TST. The number of calls must be random, so that a clone chip manufacturer cannot know the number ahead of time. If System has a clock, bits from the clock can be used to determine how many false calls to TST should be made. Otlterwise the returned value from ChipA can be used. In the latter case, an attacker could still rewire the System to pemlit a clone ChipT to view the returned value from ChipA, and thus know which hash value is the correct one. The worst case of course, is that the System can be completely replaced by a cione System that does not require authenticated consumables - this is the limit case of rewiring and changing the System. For this reason, the variation on calls to TST is optional, depending on the System, the Consumable, and how likely modifications are to be made.
Adding such logic to System (for example in the case of a small desktop printer) may be considered not worthwhile, as the System is made more complicated. By contrast, adding such logic to a camera may be considered worthwhile.
Clone Consumable using Real Authentication Chin It is important to decrement the amount of consumable remaining before use that consumable portion. If the consumable is used first, a clone consumable could fake a loss of contact during a write to the special known address and then appear as a fresh new consumable. It is imporlant to note that this attack still requires a real Authentication Chip in each consumable.
Longevity of Kev A general problem of these two protocois is that once the authentication keys are chosen, it cannot easily be changed.
In some instances a key-compromise is not a problem, while for others a key compromise is disastrous.
Choosin~ a yrotocol Even if the choice of keys for Protocols 2 and 4 was straightforward, both protocols are impracti.cal at the present time due to the high cost of silicon implementation (both due to key size and functional implementation). Therefore Protoools I and 3 are the two protocols of choice. However, Protocols I and 3 contain much of the same components:
both require read and write access;
both require implementation of a keyed one-way function; and both require random number generation functionality.
Protocol 3 requires an additional key (K2), as well as some minimal state machine changes:
a state machine alteration to enable FK,[X] to be called during Random;
a Test fimction which calls FroC]
a state machine alteration to the Read function to call FKI[X] and FK2[XJ
Protocol 3 only requires minimal changes over Protocol 1. It is more secure and can be used in all places where Presence Only Autfientication is reqttind (Protocol 1). It is therefore the protocol of dioice. Given that Protocols I and 3 both make use of keyed one-way functions, the choice of one-way function is examined in more detail here. The following table outlines the attributes of the applicabk choices. The attributes are worded so that the attribute is seen as an advantage.
u A
"' Q pW
a 4 4 .. 3 U W v E- ao x t? x ~ x Free of patents Random key generation Can be exported from the USA
Fast Preferred Key Size (bits) for use in this application Block size (bits) 64 64 64 64 256 512 512 512 Cryptanalysis Attack-Free (apart from weak keys) Output size given input size N ?N 2N ?N 2N 128 128 160 160 Low storage requirements Low silicon complexity NSA designed An examination of the table shows that the ehoice is effectively between the 3 HMAC conshuds and the Random Sequence. The problem of key size and key geneiation elitninates the Random Sequence. Given that a number of attacks have alrestdy been ea<ried out on MD5 and since the hash result is only 128 bits, HMAC-MD5 is also eliminated. The choice is themfore between HMAGSHA 1 and HMAC-RIPEMD 160.
RIPEMD-160 is relatively new, and has not been as extensively pyptattalyud as SHAI. However, SHA-1 was designed by the NSA, so tltis may be seen by some as a negative attribute.
Given that there is not much between the two, SHA- I will be used for the HMAC
conshuct..
Choosing A Random Number Generator Each of the protocols described (1-4) requires a random number generator. The generator must be "good" in the sense that the random numbers generated over the life of all Systems cannot be predicted. If the random numbers were the same for each System, an attacker could easily record the correct responses from a real Authentication Chip, and place the responses into a ROM lookup for a clone chip. Witlt such an attack there is no need to obtain K, or K2. Therefote the random numbers from each System must be different enough to be unpredictable, or non-detenninistic. As such, the initial value for R (the random seed) should be programmed with a physically generated random nwnber gathered from a physically random phenomenon, one where there is no information about whether a particular bit will be 1 or 0.
The seed for R must NOT be generated with a computer-run random number generator. Otherwise the generator algorithm and seed may be compromised enabling an attacker to generate and thenrfore know the set of all R values in all Systems.
Having a diPferent R seed in each Authentication Chip means that the fust R
will be both random and unpredictable across all chips. The question therefore arises of how to generate subsequent R values in each chip.
The base case is not to change R at all. Consequently R and FKI[RJ will be the same for each call to Random[]. If they are the same, then FKI(R] can be a constant rather than calculated. An attacker could then use a single valid Authentication Chip to generate a valid lookup table, and then use that lookup table in a clone chip programmed especially for that System. A constant R is not secure.
The simplest eonceptua.i method of changing R is to increment it by 1. Since R
is randan to begin with, the values across differing systems are still ltkely to be random. However given an initial R, all subsequent R values can be determined directly (there is no need to iterate 10,000 times - R will take on values from Ro to Ra+ 10000). An incrementing R is immune to the earlier attack on a constant R. Since R is always diffenent, there is no way to construct a lookup table for the particular System without wasting as many real Authentication Chips as the clone chip will replace.
Rather than increment using an adder, another way of changing R is to implement it as an LFSR (Linear Feedback Shift Register). This has the advantage of less silicon than an adder, but the advantage of an attacker not being able to directly detennine the range of R for a particular System, since an LFSR value-domain is determined by sequendal access. To determine which values an given initial R will generate, an attacker must iterate through the possibilities and enumetate them. The advantages of a changing R are also evident in the LFSR
solution. Since R is always diffenmt, there is no way to construct a lookup table for the particular System without using-up as many real Authentication Chips as the clone chip will replace (and only for that System). There is thenrfore no advantage in having a mons complex function to change R Regardless of the function, it will always be possible for an attaoker to iterate through the lifetime set of values in a simulation. 'ihe primary security lies in the initial randomness of R. Using an LFSR to change R(apart frotn using less silicon than an adder) simply has the advantage of not being restricted to a consecutive numeric range (i.e. knowing R, RN cannot be dinxtly calculated; an attacker must itemte through the LFSR N times).
The Random number generator within the Authentiea<ion Chip is aherefore an LFSR with 160 bits. Tap selection of the 160 bits for a maximal-period LFSR (i.e. the LFSR will cycle through all 2"0-1 states, 0 is not a valid state) yields bits 159, 4, 2, and 1, as shown in Fig. 173. The LFSR is sparse, in that not many bits are used for feedba.ck (only 4 out of 160 bits are used). This is a problem for cryptographic applications, but not for this application of non-sequential number generation. The 160-bit seed value for R can be any random number except 0, since an LFSR filled with Os will produce a never-ending stream of Os. Since the LFSR described is a maximal period LFSR, all 160 bits can be used directly as R There is no need to construct a number sequentially from output bits of ba. After each successfiil call to TST, the tandom number (R) must be advanced by XORing bits 1, 2, 4, and 159, and shifting the result into the high order bit. 'Ibe new R and corresponding FyjR] can be retrieved on the next call to Random.
Holding out Against Loeical Attadcs Protocol 3 is the authentication scheme used by the Authentication Chip. As such, it should be resistant to defeat by logical means. While the effect of various types of attacks on Protocol 3 have been mentioned in discussion, this section details each type of attack in turn with reference to Protocol 3.
Brate Force attack A Brute Force attack is guaranteed to break Protocol 3. However the length of the key means that the time for an attacker to perform a brute force attack is too long to be worth the effort.
An attacker only needs to break K2 to build a clone Authentication Chip. K, is merely present to strengthen K2 against other foctns of attack. A Brute Force Attack on K2 must therefore break a 160-bit key. An attack against K2 requires a maximum of 2160 attempts, with a 50%
chance of fuiding the key after only 2159 attempts. Assuming an an-ay of a trillion processors, each running one million tests per second, 2'5' (7.3 x 10 7) tests takes 23 x 1023 yeats, which is longer than the lifetime of the universe. There are only 100 million personal computers in the world. Even if these were all connected in an attack (e.g. via the Internet), this number is still 10,000 times smaller than the trillion-processor attack described. Further, if the manufacture of one trillion processors becomes a possibility in the age of nanocomputers, the time taken to obtain the key is longer than the lifetime of the universe. -Guessing the key attack It is theoretically possible that an atta:cker can simply "guess the key". In fact, given enough time, and trying every possible number, an attacker will obtain the key. This is identical to the Brute Force attack described above, where 2'5' attempts must be made before a 50% chance of success is obtained. The chances of someone simply guessing the key on the first try is 2160. For comparison, the chance of someone winning the top prize in a U.S. state lottery and being killed by lightning in the same day is only 1 in 261. The chance of someone guessing the Authentication Chip key on the first go is 1 in 2160, which is comparative to two people choosing exactly the same atoms frotn a choice of all the atoms in the Earth i.e. extremely unlikely.
Ouantum Comnuter attack To break KZ, a quantum computer containing 160 qubits embedded in an appropriate algorithm must be built. An attack against a 160-bit key is not feasible. An outside estimate of the possibility of quantum computers is that 50 qubits may be achievable within 50 years. Even using a 50 qubit quantum computer, 210 tests are required to crack a 160 bit key. Assuming an army of I billion 50 qubit quantum computers, each able to try 2S0 keys in I microsecond (beyond the current wildest estimates) fmding the key would take an average of 18 billion years.
CNahertext Only attack An attacker can latmch a Cyphertext Only attack on K, by calling monitoring calls to RND and RD, and on KZ by monitoring calls to RD and TST. However, given that all these calls also reveal the plaintext as well as the hashed form of the plaintext, the attack would be tiansformed into a strottger form of attack - a Known Plaintext attack.
Known Plaintext attack It is easy to connect a logic analyzer to the connection between the System and the Authentication Chip, and thereby monitor the flow of data. This flow of data results in known plaintext and the hashed form of the plaintext, which can therefore be used to launch a Known Plaintext attack against both K, and K2.
To launch an attack against K,, multiple calls to RND and TST must be made (with the call to TST being successful, and therefore requiring a call to RD on a valid chip). This is straightforward, requiring the attacker to have both a System Authentication Chip and a Consumable Authentication Chip. For each K, X, HK,[X] pair revealed, a K2 Y, HK2[Y] pair is also revealed. The attacker must collect these pairs for further analysis. The question arises of how many pairs must be collected for a meaningful attack to be launched with this data. An example of an attack that requires collection of data for statistical analysis is Differential Cryptanalysis. However, there are no known attacks against SHA-1 or HMAC-SHA1, so there is no use for the collected data at this time.
Chosen Plaintext attacks Given that the cryptanalyst has the ability to modify subsequent chosen plaintexts based upon the results of previous experiments, KZ is open to a partial focm of the Adaptive Chosen Plaintext attack, which is certainly a stronger form of attack than a simple Chosen Plaintext attack. A chosen plaintext attack is not possible against K,, since there is no way for a caller to modify R, which used as input to the RND function (the only function to provide the result of hashing with K,). Clearing R also has the effect of clearing the keys, so is not useful, and the SSI command calls CLR before storing the new R-value.
Adaptive Chosen alaintext attacks This kind of attack is not possible against K,, since K, is not susceptible to chosen plaintext attacks. However, a partial form of this attack is possible against KZ, especially since both System and consumables are typically available to the attacker (the System may not be available to the attacker in some instances, such as a specific car). The HMAC
conshnct provides security against all forms of chosen plaintext attacks. This is primarily because the HMAC construct has 2 secret input variables (the result of the original hash, and the secret key). Thus finding collisions in the hash function itself when the input variable is secret is even harder than fmding collisions in the plain hash function. This is because the fotmer requires direct access to SHA-I (not permitted in Protocol 3) in order to generate pairs of input/output fi+om SHA-1. The only values that can be collected by an attacker are HMAC[R] and HMAC[R I M].
These are not attacks against the SHA-1 hash function itseli; and reduce the attack to a Diffemtttial Cryptanalysis attacl4 examiaiug statistical differences between collected data. Given that there is no Differential Cryptanalysis attack known against SHA-1 or HMAC, Protocol 3 is resistant to the Adaptive Chosen Plaintext attacks.
Purnoseful F.rnor Attack An attacker can only launch a Purposeful &ror Attack on the TST and RD
functions, since these are the only functions that validate input against the keys. With both the TST and RD functions, a 0 value is produced if an error is found in the input - no further information is given. In addition, the time taken to produce the 0 result is independent of the input, giving the attacker no information about which bit(s) were wrong. A
Purposeful Error Attack is therefore finitless.
ChainmQ attack Any form of chaining attack assumes that the message to be hashed is over several blocks, or the input variables can somehow be set. The HMAC-SHA1 algorithm used by Protocol 3 only ever hashes a single 512-bit block at a time.
Consequently chaining attacks are not possible against Protocol 3.
Birthday attack The strongest attack known against HMAC is the birthday attack, based on the frequency of collisions for the hash function. However this is totally impractical for minimally reasonable hash functions such as SHA-1. And the.bfathday attack is only possible when the attacker has control over the message ihat is signed. Protocol 3 uses hashing as a fonm of digital signature. The System sends a number that must be incorporated into the response irnm a valid Audtientication Chip. Since the Authentieation Chip must respond with H[R I
M], but has no control over the input vahie R, the birthday attack is not possible. This is because the message has effectively aloeady been generated and signed. An attacker must instead search for a collision message that hashes to the same value (analogous to finding one person who shares your birthday). The clone chip must themfore attempt to find a new value R2 such tbat the bash of R2 and a chosen M2 yields the same hash value as H[R I M]. However the System Authentication Chip does not reveal the correct hash value (the TST function only retums I or 0 depending on whether the hash value is correct). Therefore the only way of finding out the correct hash value (in order to find a collision) is to interrogate a real Aathentieation Chip. But to find the correct value means to update M, and since the decaement-only parts of M are one-way, and the read-only parts of M cannot be changed, a clone consumable would have to update a real consumable before attempting to find a collision. The altemative is a Brute Force attack search on the TST fiutction to find a success (requiring each clone consumable to have access to a System consumable). A
Brute Force Search, as described above, takes longer than the lifetime of the universe, in this case, per authentication. Due to the fact that a timely gathering of a hash value implies a real consumable must be decremented, there is no point for a clone consumable to launch this kind of attack.
Substitution with a complete lookup table 'llte random number seed in each System is 160 bits. The worst case situation for an Authentication Chip is that no state data is changed. Consequently there is a constant value retumed as M.
However a clone chip must stlll retum FK2[R I Mj, which is a 160 bit value. Asstaning a 160-bit lookup of a 160-bit result, this requires 73 x l0u bytes, or 6.6 x IOM terabytes, certainly more space than is feasible for the near future.
This of course does not even take into account the method of collecting the values for the ROM. A complete lookup table is therefore completely impossible.
Substitutiott with a snacse lookuo table A sparse lookup table is only feasible if the messages sent to the Authentieation Chip are somehow predictable, rather thaa effectively random. The random number R is seeded with an unknown random number, gathered from a naturally random event There is no possibility for a clone manufacturer to lrnow what the possible range of R is for all Systertts, since each bit has a 500/a chance of being a 1 or a 0. Since the range of R in all systems is unknown, it is not possible to build a sparse lookup table that can be used in all systems. The general aparse lookup table is therefore not a possible attack. However, it is possible for a clone manufacduxr to irnow what the range of R is for a given System. This can be accomplished by loading a LFSR with the aunent resalt fiom a call to a specific System Authentication Chip's RND
funaion, and iterating somo itumber of tQUes into the futtue. If this is done, a special ROM can be buih which will only contain the responses for that particular range of R, i.e. a ROM specifically for the consumables of that particular System. But the attacker still needs to place emrect information in the ROM.
The attacker will therefore need to find a valid Authentication Chip and call it for each of the values in R.
Suppose the clone Authentication Chip reports a full consumable, and then allows a single use before simulating loss of connection and insertion of a new full consumable. "Ihe clone wnsumable would therefore need to contain responses for authentication of a full consumable and authentication of a partially used consumable. The worst case ROM contains entries for full and partially used consumables for R over the lifetime of System. However, a valid Auttkxttication Chip must be used to genetate the information, and be partially used in the process. If a given System only produces about n R-values, the sparse lookup-ROM required is lOn bytes multiplied by the number of different vahies for M. The time taken to build the ROM depends on the amount of time enforced between calis to RD.
After all this, the clone manufachwer must rely on the consumer retuming for a refiQ since the cost of building the ROM in the Srst place consumes a single consumable. The clone manufactuner's business in such a situation is consequently in the refills. The time and cost then, depends on the size of R
and the number of different values for M
that must be incorporated in the lookup. In addition, a custom clone consumable ROM must be built to match each and every System, and a different valid Authentication Chip must be used for each SysOem (in order to provide the full and partially used data). The use of an Authentication Chip in a System must therefore be examined to determine whether or not this kind of attack is worthwhile for a clone manufacturer. As an example, of a camera system that has about 10,000 prints in its lifetime. Assume it has a single Detaenent Only value (number of prints remaining), and a delay of I second between calls to RD. In such a system, the sparse table will take about 3 hours to build, and consumes lOOK.
Remember that the constcuction of the ROM requaw the consumption of a valid Authentication Chip, so any money charged must be worth more than a single consumable and the clone consunuible combined. 'lhus it is not cost effective to perform this function for a single consumable (unless the clone consumable somehow contained the equivalent of muldple authentic consumables). If a clone manufaciurer is going to go to the iroubk of build'mg a custom ROM for each owner of a System, an easier approach would be to update System to completely ignore the Authentication Chip.
Consaluatdy, tbis attack is possible as a per-System attack, and a decision must be made about the chance of this occutring for a given System/Consumable combination. The chance will depend on the cost of the consumable and Authentication (:hips, the kmgevity of the consumablo, the profit margin on the consumable, the time taken to generate the ROM, the size of the resultant ROM, and whether customers will come back to the clone manufacturer for refills that use the same clone chip etc.
Diffennttial ctvotanalvsis Existing differential attacks are heavily dependent on the struature of S
boxes, as used in DES and other similar afgorithms. Aldwugh other algorithms such as HMAC-SHA1 used in Protocol 3 have no S boxes, an attacker can undertake a differential-like attack by undptaking statistical analysis of:
Minimal-differettce inputs, and their corresponding outputs Minimal-difference outpuls, and their corresponding inputs To taimch an attack of this nature, sets of input/output pairs must be collected. The coUection from Protocol 3 can be via Known Plaintext, or from a Partially Adaptive Chusen Plaintext attack.
Obviously the lat0er, being chosen, will be more useful. Hashing algorithms in genetal are designed to be resistant to differential analysis. SHA-1 in particular has been specifically strengthened, especially by the 80 word expansion so that minimal differences in input produce will still produce outputs tltat vary in a larga number of bit positions (compared to 128 bit hash functions). In addition, the infonnation collected is not a direct SHA-1 input/output set, due to the nature of the HMAC algorithm. The HMAC
atgorithm hashes a known value with an unknown value (the key), and the resuit of this hash is then rehashed with a separate unknown value. Since the attacker does not Irnow the secret value, nor the result of the fust hash, the inputs and outputs from SHA-1 are not known, making any differential attack extremely difficult. The following is a more detailed discussion of minimally different inputs and outputs from the Authentication Chip.
Minimal Difference Inputs This is where an attacker takes a set of X, FK[X] values where the X values are minimally different, and examines the statistical differences between the outputs FK[X]. The attack relies on X
values that only differ by a minimal number of bits. The question then arises as to how to obtain minimally different X
values in order to compare the FK[X] values.
KI:With Ki, the attacker needs to statistically examine minimally different X, FKI[X] pairs. However the attacker cannot choose any X value and obtain a related FKI[X] value. Since X, FKAX]
pairs can only be generated by calling the RND function on a System Authentication Chip, the attacker must call RND
multiple times, recording each observed pair in a table. A search must then be made through the observed values for enough minimally different X
values to undertake a statistical analysis of the FKJX] values.
K1:With K2, the attacker needs to statisticalty examine minimally different X, FK2[X] pairs. The only way of generating X, FK2[X] pairs is via the RD function, which produces Fr2[X] for a given Y, FKI[Y] pair, where X = Y I M.
This means that Y and the changeable part of M can be chosen to a limited extent by an attacker. 'Ihe amount of choice must therefore be limited as much as possible.
The fust way of limiting an attacker's choice is to limit Y, since RD requires an input of the format Y, FKI[Y].
Although a valid pair can be readily obtained from the RND function, it is a pair of RND's choosing. An aitacker can only provide their own Y if they have obtained the appropriate pair from RND, or if they know Ki. Obtaining the appropriate pair from RND requires a Brute Force search. Knowing K, is only logically possible by performing cryptanalysis on pairs obtained from the RND function - effectively a known text attack. Although RND can only be called so many times per second, K, is common across System chips. Therefore known pairs can be generated in paralleL
The second way to limit an attacker's choice is to limit M, or at least the attacker's ability to choose M. The limiting of M is done by making some parts of M Read Only, yet different for each Authentication Chip, and other parts of M
Decrement Only. The Read Only parts of M should ideally be different for each Authentication Chip, so could be information such as serial numbers, batch numbers, or random numbers. The Decrement Only parts of M mean that for an attacker to try a different M, they can only decrement those parts of M so many times - after the Decrement Only parts of M have been reduced to 0 those parts cannot be changed again.
Obtaining a new Authentication chip 53 provides a new M, but the Read Only portions will be differbnt from the previous Authentication Chip's Read Only portions, thus reducing an attackes's ability to choose M even furtlter.
Consequently an attacker can only gain a limited number of chances at choosing values for Y and M.
Minimal Difference Outputs This is where an attacker takes a set of X, FK(X] vahies where the FK[X]
values are mmima(ly different, and examines the statistical differences between the X values. The attack relies on FK[X]
values that only differ by a minimal number of bits. For both K, and K2, there is no way for an attadcer to generate an X
value for a given FK[X]. To do so would violate the fact that F is a one-way function. Consequently the only way for an attacker to mount an attack of this nature is to record all observed X, FK[X] pairs in a table. A search must then be made through the observed values for enough minimally diiT'erent FK[X] values to undertake a statistical analysis of the X values. Given that this requires more work than a minimally different input attack (which is extremely limited due to the trstriction on M and the choice of R), this attack is not fruitful.
Message substitution attacks In order for this kind of attack to be carried out, a clone consumable must contain a real Authentication chip 53, but one that is effectively reusable since it never gets decremented. The clone Authentication Chip would interc.ept messages, and substitute its own. However this auack does not give success to the attacker. A clone Authentication Chip may choose not to pass on a WR command to the reat Authentication Chip.
However the subsequent RD
command must return the cotrect response (as if the WR had succeeded). To return the comect response, the hash value must be known for the specific R and M. As described in the Birthday Attack section, an attacker can only determine the hash value by actually updating M in a real Chip, which the atiaclcer does not want to do. Even changing the R sent by System does not help since the System Authentication Chip must match the R
during a subsequent TST. A
Message substitution attack would therefore be unsuccessful. This is only true if System updates the amount of consumable remaining before it is used.
Reverse eneineerine the key eenetator If a pseudo-random number generator is used to generate keys, there is the potential for a clone manufacture to olnain the generator program or to deduce the random seed used. This was the way in which the Netscape security program was initially broken.
Bypassinc authentication altoQether Protocol 3 requires the System to update the consumable state data before the consumable is used, and follow every write by a read (to authenticate the write). Thus each use of the consumable requires an authentication. If the System adheres to these two simple rules, a clone manufacturer will have to simulate authentication via a method above (such as sparse ROM lookup).
Reuse of Authentication Chius As described above, Protocol 3 requires the Systern to update the consumable state data before the consamable is used, and follow every write by a read (to authenticate the write). Thus each use of the consumable requires an authentication. If a consumable has been used up, then its Authentication Chip will have had the appropriate state-data values deaemented to 0. The chip can therefore not be used in another consumable. Note that this only holds true for Authett-tication Chips that hold Decrement-Only data items. If there is no state data decremented with each usage, there is nothing stopping the reuse of the chip. This is the basic diffecetce between Presence-Only Authentication and Consumable Lifetime Authentication. Pcotocol 3 allows both. The bottom line is that if a consumable has Deorement Only data items that are used by the System, the Audtentication Chip camot be reused without being coinpletely reptngrmnmed by a valid Programming Station that has knowledge of the secret key.
Management decision to omit authentication to save costs Aithough not stricxly an extemal attack, a decision to omit authentication in future Systems in order to save costs will have widely varying effects on different markets. In the case of high volume consumables, it is essential to remember that it is very d"df'icutt to introduce autLentication after the tnaticet has started, as systans ceqniriag authenticated consutnables will not work with older consumables still in circulation.
Likewise, it is impractical to discontinue audwAiaation at any stage, as otda Systems will not work with the new, uoauthenticated, consumables. In he second case, older Systems can be individually ahtred by replacing the System Authentication Chip by a simple chip that has the same programming interface, but whose TST function always succeeds. Of course the System may be programmed to test for an atways-succeeding TST function, and shut down. In the case of a specialized pairing, such as a car/car-keys, or door/door-key, or some other similar situation, the omission of authentication in fumre systems is trivial and non-repercussive. This is because the consumer is sold the entire set of System and Consumable Authentication Chips at the one time.
Garrote/bn'be attack This fam of attaclt is only suecessfal in one of two cictmstanoes:
Ki, K2, and R are already recorded by the chip-programmer, or the attacker can coerce future values of Ki, K2i and R to be recorded.
If humans or computer systems extemal to the Programmmg Station do not know the keys, there is no amount of force or bribery that can reveal them. The level of security against this kind of attack is ultimately a decision for the System/Consumable owner, to be made according to the desired level of service.
For example, a car c,anpany may wish to keep a record of all keys manufactured, so that a person can request a new key to be made for their car.
However this allows the potential compromise of the entite key database, allowing an attacker to ntake lceys for any of the manufacturer's existing cars. It does not allow an attacker to make keys for any new cars. Of course, the key database itself may also be encrypted with a further key that requires a certain number of people to combine their key portions together for access. If no record is kept of which key is used in a particular car, there is no way to make additional keys should one become lost Thus an owner wili have to replace his car's Authentication Chip and all his car-keys. This is not necessarily a bad situation. By contrast, in a consumable such as a printer ink cartridge, the one key combination is used for all Systems and all consumables. Certainly if no backup of the keys is kept, there is no human with knowledge of the key, and therefore no attack is posstble. However, a no-backup situation is not desirable for a consumable such as ink cartridges, since if the key is lost no more consumables can be made. The manufacturer should therefore keep a backup of the key information in several parts, where a~errain number of people must together combine their portions to reveal the full key information. This may be required if case the chip programming station needs to be reloaded In any case, none of these attacks are against Protoeol3 itselC since no humans are involved in the authentication process. Instead, it is an attack against the progranunuig stage of the chips.
IRWAC-SHAI
The mechanism for authenfication is the HMAC-SHAI algoridun, acting on one oF
HMAC-SHAI (R, Ki), or HMAC-SHAI (R I M, K2) We will now examine the HMAC-SHA1 algorithm in greater detail than covered so far, and descnbas an optimization of the algorithm that requines fewer memory resources than the original definition.
HMAC
The HMAC algorithm, proceeds, given the following definitions:
H = the hash function (e.g. MD5 or SHA-1) n = number ofbits output fimrn H(e.g.160 for SHA-1,128 bits for MDS) M= the data to which the MAC function is to be applied K= the secret key shared by the two parfies ipad= 0x36 repeated 64 times opad = Ox5C repeated 64 times The HMAC algorithm is as follows:
Extend K to 64 bytes by appending OxOO bytes to the end of K
XOR the 64 byte string created in (1) with ipad Append data sa~eam M to the 64 byte string created in (2) Apply H to the su+eam geimated in (3) XOR the 64 byte string created in (1) with opad Append the H result from (4) to the 64 byte string resulting from (5) Apply H to the output of (6) and output the result Thus:
HMAC[Ml ? H[(K opad) I H[(IC iPad)1Mll HMAC-SHAI algorithm is simply HMAC with H= SHA-1.
'Ilhe SHAI bashing algorithm is defined in the algorithm as sunnmarized here.
Nine 32-bit constants are defined. 'Ihene are 5 constants used to initialize the chaining variables, and there are 4 additive constants.
Initial Chaining Values Additive Constaats hi 0x67452301 ys Ox5A827999 h2 OxEFCDAB89 Y2 Ox6ED9EBA1 h3 Ox98BADCFE Y3 Ox8F1BBCDC
hi 0x10325476 y4 OxCA62C1D6 hs OxC3D2E1F0 Non-optimized SHA-1 requires a total of 2912 bits of data storage:
Five 32-bit chaining variables are defined: Hi, H2, H3, I'14 and H5.
Five 32-bit working variables are defined: A, B, C, D, and E.
One 32-bit tetnporary variable is defined: t Eighty 32-bit temporary registers ane defined: X.
The following functions are defined for SHA-1:
Symbolic Nomenclature Description + Addition modulo 2 32 X Y Result of rotating X left through Y bit positions f(X,Y,Z) (XAY)V(-XAZ) g(X.Y.Z) (XAY)V(XAZ)V(YAZ) h(X,1',Z) X Y Z
ne hashing algoritlun consists of firstly padding the input message to be a multiple of 512 bits and initializing the chaining variables Hi.s with h,_s. The padded message is then processed in 512-bit chunks, with the output hash value being the final 160-bit value given by the concatenation of the chaining variables: H, I HZ I H3 I H. I HS. The steps of the SHA-1 algorithm are now examined in greater detail.
Step I. Prearocessine The first step of SHA-1 is to pad the input message to be a multiple of 512 bits as follows and to initialize the chaining variables.
Steps to follow to preprocess the Input message Pad the input message Append a 1 bit to the message Append 0 bits such that the length of the padded message is 64-bits short of a multiple of 512 bits.
Append a 64-bit value containing the length in bits of the original input message. Store the length as most significant bit through to least significant bit.
Ittitialize the chaining variables H, E-- hl, HZ F- hZ, H3 E-- h3, H4 +- h4, H5 F- hs Step 2. Processing The padded input message can now be processed. We process the message in 512-bit blocks. Each 512-bit block is in the form of 16 x 32-bit words, refen ed to as InputWordo.1s.
Steps to follow for each 512 bit block (InputWord..,s) Copy the 512 input bits into Xo.1s For j-0 to 15 Xj = InputWortt.
Expand XQ_is into Xi&79 For j=16 to 79 Xi F- ((Xi-s Xi.s X}14 7Ci.is) 1) Initialize working variables A F- Hi, B<- H2, C+- H3, D E- Hi, E E- Hs Round I For j-0 to 19 tf- ((A 5)+f(B,C,D)+E+X;+y,) Et-D,D<--C,C<-(B 30),BF-A,AFt Round 2 Forj=20to39 t<-- ((A 5)+h(B, C, D)+E+Xj +y2) E~D,DFC,C<-(B 30),BF-A,AF-t Round 3 For j= 40 to 59 tE- ((A 5) + g(B, C, D) + E + Xi +y3) E<--D,D<--C,CF(B 30),BF-A,At-t Round4 Forj=60to79 tF ((A 5)+h(B,C, D)+E+Xj +y4) E+-D,D+-C,CE-(B 30),B.,--A,AF-t Update chaining variables H, E- H, + A, H2 <- H2 + B, H3 E--H3+C,I-I4<-H4 + D, Hst-Hs+E
Step 3. Completion ARa aIl the 512-bit blodcs of the padded input message have been processed, the output hash value is the fina1160-bit value given by: H, I H2 1 H31 H4 I Hs-Optimization for Hardware Imglementation The SHA-1 Step 2 procedure is not optimized for hardware. In particular, the 80 temporaty 32-bit registers use up valuable silicon on a hardware implemetttion. 'tltis section describes an optanization to the SHA-1 algorithm that only uses 16 temporary registers. The reduction in silicon is from 2560 bits down to 512 bits, a saving of over 2000 bits. It may not be important in some applications, but in the Authentication Chip storage space must be reduced where possible. Ihe optimization is based on the fact that ahhough the original 16-word mossage black is expanded into an 80-word message block, the 80 words are not updated during the algorithm. In addition, the words rely on the previous 16 words only, and hence the expanded words can be calculated on-the-fly during procxssing, as long as we keep 16 words fa the backward tofermces. We requi<e rotating oonntas to keep tcack of which register we are up 0o using, but the effect is to save a large amount of storage. Rather than index X by a single value j, we use a 5 bit counter to cotmt thcnugh the iterations.l7tis can be achieved by initializing a 5-bit register with either 16 or 20, and decrementing it until it reaches 0. In order to update the 16 temporary variables as if they were 80, we require 4 indexes, each a 4-bit register. Al14 indexes increment (with wraparound) during the course of the algorithm.
Steps to follow for each 512 bit block (InputWords-is) Initialize working variables A E- Hl, B t-- H2, C<- H3, D E-- H4, E<- Hs N, E- 13,N2E-8,N3<-2,N4F--0 Round 0 Do 16 times:
Copy the 512 input bits into Xa. X1,14 = InputWordN4 u t Nl, N2, N3).pda N4 Round IA Do 16 times:
tF- ((A 5)+t(B, C. D)+E+XN4+y1) [ 1'll, N2, Nalapdw N.
EF-D,DE-C,C+--(B 30),BFA,AE-t Round 1 B Do 4 times:
XN4 <-- \\XNI (D XNZ XN3 (D XN4) 1) t<--((A 5)+t(B,C,D)+E+XN4+y,) N 1, N2, N3. N4 E<--D,DE-C,C<---(B 30),BE-A,AE--t Round 2 Do 20 times:
XN4t- ((XNl Xm0XN3(DXN4) 1) t E- ((A 5) + h(B, C, D) + E+ XN4 + y2) N 1, N2, N3, N4 EE-D,DF--C,C*-(B 30),BE-A,AF-t Round 3 Do 20 times:
XN4E'((+'N14) XN2 XIi3(D XN4) 1) t t- ((A 5) +g(B, C, D)+E+XI.,4+y3) N l, N2, N3. N4 E<-D,D4-C,CF(B 30),BF-A,AF-t Round 4 Do 20 times:
XN4 + " ' (\~NI XN2 (D XN3 (D XN4) 1) t F- ((A 5) + h(B, C, D) + E+ XN4 + y4) N 1, N2, N3, N4 EFD,DE-C,CE-(B 30),BF-A,Af--t Update chaining variables Hl F- HI + A, H2 <-- H2 + B, H3<-- H3+C,H4F-H4+D, Hs<-Hs+E
The inerementing of NI, N2, and N3 during Rounds 0 and lA is optional_ A
software implementation would not increinent them, since it takes time, and at the end of the 16 times through the loop, all 4 counters will be their original values. Designers of hardware may wish to ineranent all 4 counters together to save on caitrol logic. Round 0 can be cocnplebely omitted if the caller loads the 512 bits of )Cai3.
HMAC-SHAI
In the Authentication Chip implementation, the HMAC-SHA1 unit only ever perfoims hashing on two types of inputs:
on R using Kl and on R I M using Kz. Since the inputs ane two constant lengths, rather than have HMAC and SHA-1 as separate entities on chip, they can be canbined and the hardware optimized.
The padding of inessages in SHA-1 Step 1(a 1 bit, a string of 0 bits, and the length of the message) is necessary to ensure that different messages will not look the same after padding. Since we only deal with 2 types of messages, our padding can be constant Os. In addition, the optimized version of the SHA-1 algorithm is used, where only 16 32-bit words are used for temporary storage. These 16 registers are loaded directly by the optitnized HMAC-SHAI hardware. The Nine 32-bit constants his and yi.4 are still required, although the fact that they are constants is an advantage for hardware implementation. Hardware optimized HMAC-SHA-1 requires a total of 1024 bits of data storage:
Five 32-bit chaining variables are defined: Hi, H2, H3i H4 and H5.
Five 32-bit working variables are defined: A, B, C, D, and E.
Five 32-bit variables for tempor;ry storage and final result: Buff1601_5 One 32 bit temporary variable is defined: t Sbtteen 32-bit temporary registers are defined: X.
The following two sections describe the steps for the two types of calls to HMAC-SHA 1.
HFP, Ka In the case of producing the keyed hash of R using Ki, the original input message R is a constant length of 160 bits.
We can therefore take advantage of this fact during processing. Rather than load Xa,s during the first part of the SHA-1 algoritfim, we load Xais directly, and thereby omit Round 0 of the optitnized Process Block (Step 2) of SHA-l. The pseudocode takes on the following steps:
Step Description Action 1 Process K ipad X04 +- K, 0x363636...
2 X, is +- Ox363636...
3 Hj_s F hi_s 4 Proocss Block Process R XO-4 E-- R
6 Xs-ts <-- 0 7 Process Block 8 Buff1601.s F- HI.s 9 Process K opad Xa <-- K, Ox5C5C5C...
Xs-is <-- Ox5C5C5C...
11 HI s <- hl-s 12 Process Block 13 Process previous H[x) Xo 4 t- Result 14 Xs.ts F 0 Process Block 16 Get results Buff1601.s E-- HI.s H(R1M.K71 In the case of producing the keyed hash of R I M using K2, the original input message is a constant length of 416 (256+160) bits. We can thenefoe take advantage of this fact during proce.ssing. Rather than load Xa.1s during the first part of the SHA-1 algorithm, we load Xau directly, and 1ha-eby omit Round 0 of the optimized Process Bloek (Step 2) of SHA-1. The pseudocode takes on the following steps:
Step Description Action 1 Process K ipad Xa +-- KZ Ox363636...
2 XS_lS +- 0x363636...
3 Hl_s E-- hi-s 4 Process Block Process R I M Xo.4 F- R
6 Xs.iZF-- M
7 Xu-15 FO
8 Process Block 9 Temp E- Hl_S
Process K opad Xa+- Kz Ox5C5C5C...
11 X, 15 F- Ox5C5C5C...
12 Hi_S E- hi-s 13 Process Block 14 Process previous H[x] Xa4 E--Temp Xs.15 E- 0 16 Process Block 17 Get results Result F- Hi_s Data Soaee Inteeritv Each Authentication Chip contains some non-volatile mernory in order to hold the variables required by Authentication Protocol 3. The following non-volatite variables are defined:
Variable Name Size (in bits) Description M[0..15] 256 16 words (each 16 bits) containing state data such as serial numbers, media remaining etc.
K, 160 Key used to transform R during authentication.
K2 160 Key used to transform M during authentication.
R 160 Cutrent random number AccessMode[0..15] 32 The 16 sets of 2-bit AccessMode values for M[nj.
MinTicks 32 The minimum number of clock ticks between calls to key-based functions Sl Written I If set, the secret key information (KF, K2, and R) has been written to the chip. If clear, the secret information has not been written yet.
IsTrusted I If set, the RND and TST functions can be called, but RD and WR functions cannot be called.
If clear, the RND and TST functions cannot be called, but RD and WR functions can be called.
Total bits 802 Note that if these variables are in Flash memory, it is not a simple matter to write a new value to replace the old. The memory must be erased first, and then the appropriate bits set. This has an effect on the algorithms used to change Flash memory based variables. For example, Flash memory cannot easily be used as shift registers. To update a Flash memory variable by a general opetation, it is necessary to follow these steps:
Read the entire N bit value into a general purpose register, Perform the operation on the general pucpose register;
Erase the Flash memory correspond'mg to the variable; and Set the bits of the Flash memory bcation based on the bits set in the general-putpose register.
A RESET of the Authentication Chip has no effect on these non-volatile variables.
M and AccessMode Variables M[0] through M[15] are used to hold consumable state data, such as serial numbers, batch numbers, and amount of consumable remaining. Each M[n] register is 16 bits, making the entire M vector 256 bits (32 bytes). Clients cannot read from or written to individual M[n] variables. Instead, the entire vector, referred to as M, is read or written in a single logical access. M can be read using the RD (tead) command, and written to via the WR (write) command.
The commands only succeed if K, and K2 are both defined' (SIWritten = 1) and the Authentication Chip is a consumable non-trusted chip (IsTtusted = 0). Although M may contain a number of different data types, they differ only in their write permissions. Each data type can always be read. Once in client memory, the 256 bits can be interpreted in any way chosen by the client The entire 256 bits of M are read at one time instead of in smalleer amounts for reasons of security, as described in the chapter entitled Authentication.
The different write permissions are outlined in the following table:
Data Type Access Note Read Only Can never be written to ReadWrite Can always be written to Decrement Only Can only be written to if the new value is less than the old value. Decrement Only values are typically 16-bit or 32-bit values, but can be any multiple of 16 bits.
To accomplish the protection required for writing, a 2-bit access mode value is defined for each M[n]. The following table defines the mtetprdation of the 2-bit access mode bit-pattem:
Bits Op Interpretation Action taken during Write command 00 RW ReadWrite The new 16-bit value is always written to M[n].
01 MSR Decrement Only The new 16-bit value is only written to M[n] if it is (Most Significant less than the value currently in M[n]. This is used for Region) access to the Most Significant 16 bits of a Decrattent Only number.
NMSR Decrement Only The new 16-bit value is only written to M[n] if (Not the Most M[n+l] can also be written. The NMSR access mode Significant Region) allows multiple precision values of 32 bits and more (multiples of 16 bits) to deerement 11 RO Read Only The new 16-bit value is ignored.
M[n] is left unchanged.
The 16 sets of access mode bits for the 16 M[n] registers are gathered togedter in a single 32-bit AccessMode regisw.
The 32 bits of the AccessMode tegister correspond to M[n] with n as follows:
MSB LSB
Each 2-bit value is stored in hi/lo fonnat Consequently, if M[0-5] were access mode MSR, with M[6-15] access mode RO, the 32-bit AccessMode register would be:
11-11-11-11-11-11-11-11-11-i i-01-01-O1-01-01-01 During execution of a WR (write) command, AccessMode[n) is examined for each M[n], and a decision made as to whether the new M[n] value will replace the old. The AccessMode register is set using the Authentication Chip's SAM (Set Access Mode) command. Note that the Decrement Only comparison is unsigned, so any Decrement Only values that require negative ranges must be shifted into a positive range. For example, a consumable with a Decrement Only data item range of -50 to 50 must have the range shifted to be 0 to 100.
The System must then interpnet the range 0 to 100 as being -50 to 50. Note that most instances of Decrement Only ranges are N to 0, so there is no range shift required. For Decrement Only data items, arrange the data in order from most significant to least significant 16-bit quantities from M[n] onward. The access mode for the most significant 16 bits (stored in M[n]) should be set to MSR.
The remaining registers (M[n+1], M[n+2] etc) should have the'v access modes set to NMSR. If erroneously set to NMSR, with no associated MSR region, each NMSR region will be considered independently instead of being a multi-precision comparison.
K, K, is the 160-bit secret key used to transform R during the authentication protocoL K, is progcammed along with KZ
and R with the SSI (Set Secret Information) command. Since K, must be kept secret, clients cannot directly read K,.
The commands that make use of K, are RND and RD. RND returns a pair R, FK,[R]
where R is a random number, while RD requires an X, FK,[X] pair as input. K, is used in the keyed one-way hash function HMAC-SHA1. As such it should be programmed with a physically generated raadom number, gathered from a physically random phenomenon. K, must NOT be generated with a computer-run random number generator. The security of the Authentication chips depends on K,. K2 and R being generated in a way that is not deterministic. For example, to set K,, a person can toss a fair coin 160 times, recording heads as 1, and tails as 0. K, is automatically cleared to 0 upon execution of a CLR command. It can only be programmed to a non-zero value by the SSI command.
K
K2 is the 160-bit secret key used to transform M I R during the authentication protocol. K2 is programmed along with K, and R with the SSI (Set Secret Infonnation) command Since K2 must be kept secret, clients cannot diroctly read K2.
The commands that make use of K2 are RD and TST. RD reduns a pair M, Fr2[M I
X] where X was passed in as one of the parameters to the RD function. TST requires an M, FK2[M I R] pair as input, where R was obtained from the Authentication Chip's RND function. K2 is used in the keyed one-way hash function HMAC-SHAI. As such it should be programmed with a physically generated random number, gathered &om a physically random phenomenon. K2 must NOT be generated with a computer-run random number generator. The security of the Authentication chips depends on Ki, K2 and R being generated in a way that is not deterministic.
For example, to set K2, a person can toss a fair coin 160 times, recording heads as 1, and tails as 0. K2 is automatically cleared to 0 upon execution of a CLR
commancl. It can only be progratnmed to a non-zero value by the SSI ootnmand.
R and IsTrusted R is a 160-bit random number seed that is programmed along with K, and K2 with the SSI (Set Secret Information) command. R does not have to be kept secret, since it is given freely to callers via the RND command. However R must be ehanged only by the Authentication Chip, and not set to any chosen value by a caller. R is used during the TST
command to ensuce that the R from the previous call to RND was used to generate the Fx2[M I R] value in the non-trusted Authentication Chip (ChipA). Both RND and TST are only used in tnisted Authentication Chips (ChipT).
IsTrusted is a 1-bit flag register that determines whether or not the Authentication Chip is a trusted chip (ChipT):
If the IsTntsted bit is set, the chip is considered to be a nusted chip, and hence clients can call RND and TST
functions (but not RD or WR).
If the IsTrusted bit is clear, the chip is not c.omidened to be trusted Therefore RND and TST functions cannot be called (but RD and WR fuactions can be called instead). System never needs to call RND or TST on the consumable (since a clone chip would simply return I to a function such as TST, and a constant value for RND).
The IsTrusted bit has the added advantage of reducing the number of availabk R, FK,(Rj pairs obtainable by an attacker, yet still maintain the integrity of the Authentication protocoL To obtain valid R, FK,IRj pairs, an attacker requires a System Authentication Chip, which is more expensive and less readily available than the consumables. Both R and the IsTrusted bit are cleared to 0 by the CLR command. They are both written to by the issuing of the SSI
command. The IsTrusted bit can only set by storing a non-zero seed value in R
via the SSI command (R must be non-zero to be a valid LFSR state, so this is quite teasatable). R is changed via a 160-bit maximal period LFSR with taps on bits 1, 2, 4, and 159, and is changed only by a successful call to TST
(where 1 is retumed).
Authentication Chips destined to be trusted Chips used in Systems (ChipT) should have their IsTrusted bit set during programming, and Authentication Chips used in Consumables (ChipA) should have their IsTrusted bit kept clear (by storing 0 in R via the SSI command during progranmiing). There is no command to read or write the IsTrusted bit directly. The security of the Aut4-enticahon Chip does not only rely upon the randomness of K, and K2 and the strength of the HMAC-SHA 1 algorithm. To prevent an attacker from building a sparse lookup table, the security of the Authentication Chip also depends on the range of R over the lifetime of all Systems. What this means is that an attacker must not be able to deduce what values of R there are in produced and future Systems. As such R should be ptogrammed with a physically generated n~ndom number. gathered from a physically random phenomenon. R must NOT be generated with a computer-run random number generator. The generation of R must not be deterministic. For example, to generate an R for use in a trusted System chip, a person can toss a fair coin 160 times, recording heads as 1, and tails as 0. 0 is the only.non-valid initial value for a trusted R is 0 (or the IsTrusted bit will not be set).
SlWrittett The SIWritten (Secret Infotination Written) 1-bit register holds the status of the secret infotmation stored within the Authentication Chip. The secret information is K,, KZ and R A client cannot directly access the SlWritten bit. Instead, it is cleared via the CLR cotttmand (which also clears K,, K2 and R). When the Authentication Chip is programmed with secret keys and random numba seed using the SSI command (regardless of the value wrttten), the SlWritt.en bit is set automatically. Although R is strictly not secret, it must be writben together with K, and K2 to ensure that an attacker cannot generate their own random number seed in order to obtaia ahosen R, FK,[R] pairs. The SlWritten status bit is used by all funetions that access K,, K2, or R If the SlWritten bit is clear, then ealls to RD, WR, RND, and TST are interpreted as calls to CLR
MinTicks There are two mechanisms for pmventing an attacker from generating multipie calls to TST and RD functions in a short period of time. The first is a clock limiting hardware compottettt that prevents the intemal clock from operating at a speed more than a particular maximum (e.g. 10 MHz). The second mechanisin is the 32-bit MinTicks register, which is used to specify the minimum number of clock ticks that must elapse between calls to key-based functions. The MinTicks variable is cleared to 0 via the CLR conunand. Bits can then be set via the SMT (Set MinTicks) command.
The input parameter to SMT contains the bit pattem that represents which bits of MinTicks are to be set. The practical effect is that an attacker can only increase the value in MinTicks (since the SMT function only sets bits). In addition, there is no fimction provided to allow a caller to read the current value of this register. The value of MinTicks depends on the operating clock speed and the notion of what constitutes a reasonable time between key-based function calls (application specific). The duration of a single tick depends on the operating dock speed. This is the maximum of the input clock speed and the Authentication Chip's clock-limiting hardware. For example, the Authentication Chip's clock-limiting hardware may be set at 10 MHz (it is not changeable), but the input clock is I MHz In this case, the value of I tick is based on 1 MHz, not 10 MHz If the input clock was 20 MHz instead of 1 MHz, the value of I tick is based on 10 MHz (since the clock speed is limited to 10 MHz).
Once the duration of a tick is known, the MinTicks value can to be set. The value for MinTicks is the minimum nwnber of ticks required to pass between calls to the key-based RD and TST
functions. The value is a real-time number, and divided by the length of an operating tick. Suppose the input clock speed matches the maximum clock speed of 10 MHz If we want a minimum of I second between calls to key based functions, the value for MinTtcks is set to 10,000,000. Consider an attacker attempting to collect X, FKi[X] pairs by calling RND, RD and TST multiple times. If the MinTicks value is set such that the amount of time between calls to TST is I second, then each pair requires I second to generate. To generate 2" pairs (only requiring 125 GB of storage), an attacker requires more than I year. An attack requiring 264 pairs would require 5.84 x I011 years using a single chip, or 584 years if I billion chips were used, making such an attack completely impractical in terms of time (not to mention the storage requirements!).
With regards to KI, it should be noted tltat the MinTicks variable only slows down an attacker and causes the attack to cost more since it does not stop an attacker using multiple System chips in parallel. However MinTicks does make an attack on K2 more difficult, since each consumable has a differatt M(part of M
is random read-only data). In order to launch a differential attack, minimally different inputs are required, and this can only be achieved with a single consumable (containing an effectively constant patt of M). Minimally different inputs require the attacker to use a single chip, and MinTicks causes the use of a single chip to be slowed down.
If it takes a year just to get the data to start searching for values to begin a differential attack this incteases the cost of attack and reduces the effective market time of a clone co swttable.
Authentication Chin Commands The System communicates with the Authentication Chips via a simple operation command set. This section details the actual commands and paramdms necessary for implementation of P+=otocol3. The Authentication Chip is defined here as conununicatmg to System via a serial interface as a minimum implementation.
It is a trivial matter to define an equivalent chip that openates over a wider interface (such as 8, 16 or 32 bits). Each eommand is defined by 3-bit opcode. The interpretation of the opcode can depend on the current value of the IsTrusted bit and the current value of the IsWritten bit. The following operations are defined:
Op T W Mn Input Output Description 000 - - CLR - - Clear 001 0 0 SSI [160, 160, 160] - Set Secret Information 010 0 1 RD [160,160] [256,160] Read M secureiy 010 1 l RND - [ 160, 160] Random 011 0 1 WR [256] - Write M
011 1 1 TST [256, 160] [11 Test 100 0 1 SAM [32) [32] Set Access Mode 101 - I GiT - [ 1] Get Is Tntsted 110 - I SMT [32] Set MinTicks Op = Opcode, T = IsTrusted value, W= IsWritten value, Mn = Mnemonic, [n] = number of bits required for parameter Any command not defined in this table is interpreted as NOP (No Operation).
Examples include opcodes 110 and I 1 I
(regardless of IsTmsted or IsWritten values), and any opcode other than SSI
when IsWritten = 0. Note that the opcodes for RD and RND are the same, as are the opcodes for WR and TST. The actual command nm upon receipt of the opcode will depend on the curnent value of the IsTrusted bit (as long as IsWritten is 1). Where the IsTrusted bit is clear, RD and WR functions will be called. Where the IsTrusted bit is set, RND
and TST functions will be called. The two sets of commands are mutually exclusive between tmsted and non-tusLad Authentication Chips, and the same opcodes enforces this relationship. Each of the commands is examined in detail in the subsequent sections. Note that some algorithms are specifically designed because Flash memory is assumed for the implementation of non-volatile variables.
CLR Clear Input None Output None Changes All The CLR (Clear) Command is designed to completely erase the contents of all Authentication Chip memory. This includes all keys and secret information, access mode bits, and state data.
After the execution of the CLR command, an Authentication Chip will be in a programmable state, just as if it had been freshly manufactured. It can be reprogrammed with a new key and reused. A CLR command consists of simply the CLR command opcode. Since the Authentication Chip is serial, this must be transfetred one bit at a time. The bit order is LSB to MSB for each conunand component. A CLR conunand is therefore sent as bits 0-2 of the CLR
opcode. A total of 3 bits are trinsfernd. The CLR command can be called directly at any time. The order of erasure is important. SlWritten must be cleared fust, to disable further calls to key access functions (such as RND, TST, RD and WR). If the AccessMode bits are cleared before SlWritten, an attacker could remove power at some point after they have been cleared, and manipulate M, thereby have a better chance of retrieving the secret infotmation with a partial chosen text attack. The CLR command is implemented with the following steps:
Step Action 1 Erase SlWriuen Erase IsTrusted Erase K, Erase K2 Erase R
Erase M
2 Erase AccessMode Erase MinTicks Once the chip has been cleared it is ready for reprogramming and reuse. A
blank chip is of no use to an attacker, since although they can create any value for M (M can be read from and written to), key-based futtctions will not provide any infotmation as Ki and K2 will be incortact. It is not necessary to consume any input parameter bits if CLR is called for any opcode other than CLR. An attacker will simply have to RESET
the chip. The reason for calling CLR is to ensure that all secret information has been destroyed, making the chip useless to an attacker.
SSI - Set Secret Information Input: Ki, K2, R = [160 bits, 160 bits, 160 bits]
Output: None Changes: Ki, K2, R, SlWriltea, IsTtus6ed The SSI (Set Secret Information) command is used to load the K,, K2 and R
variables, and to set SlWritten and IsTrusted flags for later calls to RND, TST, RD and WR commands. An SSI
command consists of the SSI command opcode followed by the secret information to be stored in the Ki, K2 and R
registers. Since the Authentication Chip is serial, this must be transfemod one bit at a time. The bit order is LSB to MSB
for each conunand component An SSI
conunand is therefore sent as: bits 0-2 of the SSI opcode, followed by bits 0-159 of the new value for Ki, bits 0-159 of the new value for K2, and finally bits 0-159 of the seed value for R. A total of 483 bits are ttansfeired. The Kt, K2, R, SlWritten, and IsTntsted reglsters are all cleared to 0 with a CLR eoaunand.
They can only be set using the SSI
command.
The SSI command uses the flag SlWritten to store the fact dtat data has been loaded into K,, K2, and R. If the SlWritten and IsTntsted flags are clear (this is the case a8er a CLR
instruction), then Ki, K2 and R are loaded with the new values_ If either flag is set, an attempted call to SSI results in a CLR
command being executed, since only an attacker or an erroneous client would attempt to change keys or the random seed without calling CLR fnst. The SSI
command also sets the IsTrusted flag depending on the value for R. If R = 0, then the chip is considered untrustworthy, and therefore IsTrust.ed remains at 0. If R?~ 0, then the chip is considered tivstworthy, and therefore IsTrusted is set to 1. Note that the setting of the IsTrusted bit only occurs during the SSI
command. If an Authentication Chip is to be reused, the CLR command must be called fust The keys can then be safely reprogrammed with an SSI command, and fresh state information loaded into M using the SAM and WR commands. The SSI
command is implemented with the following steps:
Step Action I CLR
2 K, <- Read 160 bits from client 3 K2 Read 160 bits from client 4 R<- Read 160 bits from client IF (R # 0) IsTrusted F- I
6 SI Written E- 1 RD - Read Input: X, FKI[X] _[160 bits, 160 bits]
Output: M, FK2[X M] = [256 bits, 160 bits]
Changes: R
The RD (Read) conunand is used to securely read the entire 256 bits of state data (M) from a non-trusted Authentication Chip. Only a valid Authentication Chip will respond correctly to the RD request. The output bits from the RD command can be fed as the input bits to the TST command on a trusted Authentication Chip for verification, with the fust 256 bits (M) stored for later use if (as we hope) TST retums 1.
Since the Authentication Chip is serial, the cotnmand and input parazttetas must be transferred one bit at a time. The bit order is LSB to MSB for each command component A RD command is therefore: bits 0-2 of the RD opcode, followed by bits 0-159 of X, and bits 0-159 of FKAX]. 323 bits are transfetred in total. X and FKj[X] are obtained by calling the trusted Authentication Chip's RND
command. The 320 bits output by the trusted chip's RND command can therefore be fed directly into the non-tnuted chip's RD command, with no need for these bits to be stored by System. The RD
cornmand can only be used when the following conditions have been met:
SlWritten = 1 indicating that Ki, K2 and R have been set up via the SSI
command; and IsTrusted = 0 indicating the chip is not uusted since it is not permitted to generate random ntnnber sequences;
In addition, calls to RD must wait for the MinTicksRemaining register to reach 0. Once it has done so, the register is reloaded with MinTicks to ensure ihat a minimum time will elapse betweeit calls to RD. Once MinTicksRemaining has been reloaded with MinTicks, the RD command va-ifies that the input parameters are valid This is accomplished by intemally generating FK1[X] for the input X, and then comparing the result against the input FKI[X]. This generation and comparison must take the same amount of time regardless of whether the input parameters are correct or not. If the times are not the same, an attacker can gain infonnation about which bits of FKI[X] are incorrect. The only way for the input parameters to be invalid is an enroneous System (passing the wrong bits), a case of the wrong consumable in the wrong System, a bad trusted chip (generating bad pairs), or an attack on the Authentication Chip. A constant value of 0 is retumed when the input parameters are wrong. The time taken for 0 to be returned must be the same for all bad inputs so that attackers can leam nothing about what was invalid. Once the input parameters have been verified the output values are calculated. The 256 bit content of M are transferred in the following order: bits 0-15 of M[0], bits 0-15 of M[1], through to bits 0-15 of M[15]. Fr2[X I M) is calculated and output as bits 0-159. The R register is used to store the X value during the validation of the X, FKI[X] pair. This is because RND and RD are mutually exclusive.
The RD command is implemented with the following steps:
Step Action I IF (MinTicksRemaining * 0 2 MinTicksRemaining F- MinTicks 3 R E- Read 160 bits from client 4 Hash f- Calculate FKi[R]
OK <- (Hash = next 160 bits from client) Note that this operation must take constant time so an attacker cannot determine how much of their guess is correct.
6 IF (OK) Output 256 bits of M to client ELSE
Output 256 bits of 0 to client 7 Hash <-- Calculate Fr2[R I MJ
8 IF (OK) Output 160 bits of Hash to client ELSE
Output 160 bits of 0 to client RND - Rffitdom Input: None Output: R, FKI[R] _[160 bits, 160 bits]
Changes: None The RND (Random) command is used by a client to obtain a valid R, FK,[R] pair for use in a subsequent authentication via the RD and TST commands. Since there are no input parameters, an RND command is therefore simply bits 0-2 of the RND opcode. The RND command can only be used when the following conditions have been met:
SlWritten = I indicating K, and R have been set up via the SSI command;
IsTrusted = I indicating the chip is permitted to generate random number sequences;
RND returns both R and FK,[Rj to the caller. The 288-bit output of the RND
command can be fed straight into the non-trusted chip's RD command as the input parameters. Tlwre is no need for the client to store them at all, since they are not required again. However the TST command will only succeed if the random number passed into the RD
command was obtained fust from the RND command. If a caller only calls RND
multiple times, the same R, F,r,[R]
pair will be returned each time. R will only advance to the next random number in the sequence after a successful call to TST. See TST for more information. The RND command is implemented with the following steps:
Step Action I Output 160 bits of R to client 2 Hash <-- Calculate FK,[R]
3 Output 160 bits of Hash to client TST - Test Input: X, FK2[R I X] [256 bits, 160 bits]
Output: I or 0=[l bit]
Changes: M, R and MinTicksRemaining (or all registers if attack detected) The TST (Test) command is used to authenticate a read of M from a non-trusted Authentication Chip. The TST (Test) comm.aad consists of the TST command opcode followed by input parameters: X
and Fr2[R ~ Xj. Since the Authentication Chip is sexia(, this must be transfen'ed one bit at a time. The bit order is LSB to MSB for each command component. A TST command is therefore: bits 0-2 of the TST opcode, followed by bits 0-255 of M, bits 0-159 of Fn[R I M). 419 bits are transferned in total. Since the last 416 input bits are obtained as the output bits from a RD command to a non-trusted Authenlication Chip, the entire data does not even have to be stored by the client.
Instead, the bits can be passed directly to the trusted Authentication Chip's TST command. Only the 256 bits of M
should be kept from a RD command. The TST command can only be used when the following conditions have been met:
SlWritten = I indicating K2 and R have been set up via the SSI command;
IsTnisted =1 indicating the chip is pemtitted to generate random number sequences;
In addition, calls to TST must wait for the MinTicksRemaining register to reach 0. Once it has done so, the register is reloaded with MinTicks to ensure that a minimum time will elapse between calls to TST. TST causes the internal M
value to be replaced by the input M value. FrAlVl I K] is then calculated, and compared against the 160 bit input hash value. A single output bit is produced: I if they are the same, and 0 if they are diffenent. The use of the intemal M value is to save space on chip, and is the reason why RD and TST are mutuaily exclusive commands. If the output bit is 1, R
is updated to be the next random number in the sequence. This forces the caller to use a new random number each time RD and TST are called. The resultant output bit is not output until the entire input string has been compared, so that the time to evaluate the comparison in the TST fimction is always the same.
Thus no attacker can compare execution times or number of bits processed before an output is given.
The next random number is generated from R using a 160-bit maximal period LFSR
(tap selections on bits 159, 4, 2, and 1). The initial 160-bit value for R is set up via the SSI command, and can be any random number except 0 (an LFSR filled with Os will produce a never-ending stream of Os). R is transfomled by XORing bits 1, 2, 4, and 159 together, and shifting all 160 bits right I bit using the XOR result as the input bit to blsy. The new R will be retumed on the next call to RND. Note that the time taken for 0 to be returned from TST
must be the same for all bad inputs so that attackers can leam nothing about what was invalid about the input.
The TST command is implemented with the following steps:
Step Action 1 IF (MinTicksRemaining * 0 2 MinTicksRemaining t- MinTicks 3 M<-- Read 256 bits from client 4 IF(R=0) GOTO CLR
Hash <- Calculate FK2[R I M]
6 OK E-- (Hash = next 160 bits from client) Note that this operation must take constant time so an attacker cannot determine how much of their guess is correct.
7 IF (OK) Temp<- R
Erase R
Advance TEMP via LFSR
R <-- TEMP
8 Output 1 bit of OK to client Note that we can't simply advance R directly in Step 7 since R is Flash memory, and must be erased in order for any set bit to become 0. If power is removed from the Authentication Chip during Step 7 after erasing the old value of R, but before the new value for R has been written, then R will be erased but not telxogrammed. We therefore have the situation of IsTtusted=1, yet R=O, a situation only possible due to an atiacker. Step 4 detects this event, and takes action if the attack is detected. This problem can be avoided by having a second 160-bit Flash register for R and a Validity Bit, toggled after the new value has been loaded. It has not been included in this implementation for reasons of space, but if chip space allows it, an extra 160-bit Flash register would be useful for this purpose.
WR - Writc Input: M~ = (256 bits]
Output: None Changes: M
A WR (Write) command is used to update the writeable parts of M containing Authentication Chip state data. The WR
command by itself is not secure. It must be followed by an authenticated read of M (via a RD command) to ensure that the change was made as specified. The WR command is called by passing the WR
command opcode followed by the new 256 bits of data to be written to- M. Since the Authentication Chip is serial, the new value for M must be transferned one bit at a time. The bit order is LSB to MSB for each command component. A WR txrmmand is therefore: bits 0-2 of the WR opcode, followed by bits 0-15 of M[O], bits 0-15 of M[l], through to bits 0-15 of M[15].
259 bits are transferred in total. The WR command can only be used when SIWritten = 1, indicating that KI, KZ and R
have been set up via the SSI command (if SlWritten is 0, then Ki, K2 and R
have not been setup yet, and the CLR
command is calkd instead). The ability to write to a specific M[n] is govemed by the corresponding Access Mode bits as stored in the AccessMode register. The AccessMode bits can be set using the SAM command. When writing the new value to M[n] the fact that M[n] is Flash memory must be taken into account. All the bits of M[n] must be erased, and then the appropriate bits set. Since these two steps occur on different cycles, it leaves the possibility of attack open.
An attacker can remove power after erasure, but before }rogramming with the new value. However, there is no advantage to an attacker in doing this:
A Read/Write M[n] changed to 0 by this means is of no advantage since the attacker could have written any value using the WR command anyway.
A Read Only M[n] changed to 0 by this means allows an additional known text pair (where the M(n] is 0 instead of the original value). For futurc use M[n] values, they are already 0, so no information is given.
A Decrement Only M[n] changed to 0 simply speeds up dte time in which the consumable is used up. It does not give any new infonnation to an attacker that using the consumable would give.
The WR command is implemented with the following steps:
Step Action I DecEncountered *- 0 EqEncountered E-- 0 nE-15 2 Temp E- Read 16 bits from client 3 AM = AccessMode[--n]
Compare to the previous value LT F- (Temp < M[--n]) [comparison is unsignedj EQ (Temp = M[--n]) 6 WE<--(AM=RW)v ((AM = MSR) A LT) v ((AM = NMSR) A (DecEncountered v LT)) 7 DecEncountered t- ((AM = MSR) A LT) v ((AM = NMSR) A DecEncountered) v ((AM = NMSR) A EqEncountered A LT) EqEncountered F- ((AM = MSR) A EQ) v ((AM = NMSR) A EqEncountered A EQ) Advance to the next Access Mode set and write the new M[-n] if applicable 8 IF (WE) Erase M[--n]
M[--n] 4- Temp n 11 IF (n at 0) SAM - Set AccessMode Input: AccessMode_ = [32 bits]
Output: AccessMode = [32 bits]
Changes: AccessMode The SAM (Set Access Mode) command is used to set the 32 bits of the AccessMode register, and is only available for use in consumable Authentication Chips (where the IsTrusted flag = 0). The SAM
command is called by passing the SAM command opcode followed by a 32-bit value that is used to set bits in the AccessMode register. Since the Authentication Chip is serial, the data must be transfen-ed one bit at a time.
The bit order is LSB to MSB for each command component A SAM command is therefone: bits 0-2 of the SAM opcode, followed by bits 0-31 of bits to be set in AccessMode. 35 bits are transferred in total. The AccessMode register is only cleared to 0 upon execution of a CLR command. Since an access mode of 00 indicates an access mode of RW
(read/write), not setting any AccessMode bits after a CLR means that all of M can be read from and written to. The SAM
command only sets bits in the AccessMode register. Consequently a client can change the access mode bits for M[n] from RW to RO (read only) by setting the appropriate bits in a 32-bit word, and calling SAM with that 32-bit value as the input parameter. This allows the programming of the access mode bits at different times, perhaps at different stages of the manufacturing process.
For example, the read only random data can be written to during the initial key programming stage, while allowing a second programming stage for items such as consumable serial numbers.
Since the SAM command only sets bits, the effect is to allow the access mode bits corresponding to M[n] to progress from RW to either MSR, NMSR, or RO. It should be noted that an access mode of MSR can be changed to RO, but this would not help an attacker, since the authentication of M after a write to a doctored Authentication Chip would detect that the write was not successful and hence abort the operation. The setting of bits corresponds to the way that Flash memory works best. The only way to clear bits in the AccessMode register, for example to change a Decrement Only M[n] to be Read/Write, is to use the CLR conunand. The CLR command not only erases (clears) the AccessMode register, but also clears the keys and all of M. Thus the AccessMode[n] bits corresponding to M[n] can only usefully be changed once between CLR c,anmands. The SAM command retums the new value of the AccessMode register (after the appropriate bits have been set due to the input parameter). By calling SAM with an input parameter of 0, AccessMode will not be changed, and therefore the current value of AccessMode will be retumed to the caller.
The SAM command is implemented with the following steps:
Step Action I Temp <- Read 32 bits from client 2 SetBits(AccessMode, Temp) 3 Output 32 bits of AccessMode to client GIT- Get Is Trusted Input: None Output: IsTrustad = [I bit]
Changes: None The GIT (Get Is Trusted) command is used to read the current value of the IsTrusted bit on the Authentication Chip. If the bit retutned is 1, the Authentication Chip is a tnLsted System Authetttication (.:hip. If the bit reumed is 0, the Authentioation Chip is a consumable Authentication Chip. A GIT command consists of simply the GIT command opcode. Since the Authentication Chip is sorial, this must be transfen-ed one bit at a time. The bit order is LSB to MSB
for each command component. A GIT command is therefore sent as bits 0-2 of the GIT opcode. A total of 3 bits are transferred. The GIT command is implemented with the following steps:
Step Action 1 Output IsTrusted bit to client SMT - Set MinTicks Input: MinTicks. = [32 bits]
Output: None Changes: MinTicks The SMT (Set MinTicks) command is used to set bits in the MinTicks register and hence defme the minimum number of ticks that must pass in between calls to TST and RD. The SMT comntand is called by passing the SMT command opcode followed by a 32-bit value that is used to set bits in the MinTicks register. Since the Authentication Chip is serial, the data must be transfetred one bit at a time. The bit order is LSB
to MSB for each command component An SMT command is therefore: bits 0-2 of the SMT opcode, followed by bits 0-31 of bits to be set in MinTicks. 35 bits are transferred in total. The MinTicks register is only cleared to 0 upon execution of a CLR command. A value of 0 indicates that no ticks need to pass between calls to key-based functions. The functions may therefore be called as &equently as the clock speed Iimiting hardware allows the chip to tun.
Since the SMT command only sets bits, the effect is to allow a client to set a value, and only increase the time delay if fnrdter calls are made. Setting a bit that is already set has no effect, and setting a bit that is ciear only serves to slow the chip down further. The setting of bits cotresponds to the way that Flash memory works best The only way to clear bits in the MinTicks register, for example to change a value of 10 ticks to a value of 4 ticks, is to use the CLR
command. However the CLR command clears the MinTicks register to 0 as well as clearing all keys and M. It is thet+efone useless for an attacker. Thus the MinTicks negister can only usefully be changed once between CLR
commands.
The SMT command is implemented with the following steps:
Step Action 1 Temp <- Read 32 bits from client 2 SetBits(MinTicks, Temp) Proeramminst Authentication Chins Authentication Chips must be programmed with logically secure infonmation in a physically secure environment Consequently the programming procedures cover both logical and physical security. Logical security is the process of ensurmg that Ki, K2, R, and the random M[n] values are generated by a physically random process, and not by a computer. It is also the process of ensuring that the order in which parts of the chip are progtammed is the most logically secure. Physical security is the process of ensuring that the programming station is physically secure, so that K, and K2 remain secret, both during the key generation stage and during the lifetime of the storage of the keys. In addition, the progamming station must be resistant to physical attempts to obtain or destroy the keys. The Authentication Chip has its own security mechanisnis for ensuring that K, and K2 are kept secret, but the Programming Station must also keep K, and K2 safe.
Overview After manufacture, an Authentication Chip must be progiammed before it can be used. In all chips values for K, and K2 must be established. If the chip is destined to be a System Authentication Chip, the initial value for R must be determined. If the chip is destined to be a consumable Authentication Chip, R
must be set to 0, and initial values for M
and AccessMode must be set up. The following stages are therefore identified:
Determine Interaction between Systems and Consumables Determine Keys for Systems and Consumables Determine MinTicks for Systems and Consumables Program Keys, Random Seed, MinTicks and Unused M
Program State Data and Access Modes Once the consumable or system is no longer required, the attached Authentication Chip can be reused. This is easily accomplished by reprogrammed the chip starting at Stage 4 again. Each of the stages is examined in tlte subsequent sections.
Stage 0: Manufacture Tlie manufacture of Authentication Chips does not require any special security. There is no secret information programmed into the chips at manufacturing stage. The algorithms and chip ptncess is not special. Standard Flash processes are used. A theft of Authentication Chips between the chip manufacdrrer and programming station would only provide the clone manufacburer with blank chips. 'Ihis merely compromises the sale of Authentication chips, not anything authenticated by Authentication C.hips. Since the programming station is the only mechanism with consumable and system product keys, a clone manufacturer would not be able to program the chips with the correct key. Clone manufacturets would be able to program the blank chips for their own systems and consumables, but it would be difficult to place these items on the market without detection. I:n addition, a single theft would be difficult to base a business around.
S
&Me 1: Detennine Interaction between Systems and Consumables The decision of what is a System and what is a Consumable needs to be determined before any Authentication Chips can be programmed. A decision needs to be made about which Consumables can be used in which Systems, since all connected Systems and Consumables must share the same key infornurtion. They also need to share state-data usage mechanisms even if some of the interpretations of that data have not yet been determined. A simple example is that of a car and car-keys. The car itself is the System, and the car-keys are the consumables. There are several car-keys for each car, each containing the same key information as the specific car.
However each car (System) would contain a different key (sharod by its car-keys), since we don't want car-keys from one car working in another. Another example is that of a photocopier that requires a particular toner cartridge. In simple betms the photocopier is the System, and the toner cartridge is the consumable. However the decision must be made as to what compatibility there is to be between cartridges and photocopies. The decision has historically been made in terms of the physical packaging of the toner cartridge: certain cartridges will or won't fit in a new model photooopier based on the design decisions for that copier_ When Authentication Chips are used, the components that must work together must share the same key infotmation.
[n addition, each type of consumable requires a diffenant way of dividittg M
(the state data). Although the way in which M is used will vary from application to application, the method of allocating M[n] and AccessMode[n] will be the same:
Define the consumable state data for specific use Set some M[n] registers aside for future use (if required). Set these to be 0 and Read Only. The value can be tested for in Systems to maintain compatibility.
Set the remaining M[n] registers (at least one, but it does not have to be M[15]) to be Read Only, with the contents of each M[n] completely random. This is to make it more difficult for a clone manufacturer to attack the authentication keys.
The following examples show ways in which the state data may be organized.
Example 1 Suppose we have a car with associated car-keys. A 16-bit key number is more than enough to uniquely identify each car-key for a given car. The 256 bits of M could be divided up as follows:
M(n) Access Description 0 RO Key number (16 bits) 1-0 RO Car engine number (64 bits) 5-8 RO For future expansion = 0(64 bits) 8-15 RO Random bit data (128 bits) 71 If the car manufacturer keeps all logica! keys for all cars, it is a trivial matter to manufadure a new physical car-key for a given car should one be lost. The new car-key would contain a new Key Number in M[0], but have the same K, and K2 as the car's Authentication Chip. Car Systems could allow specific key numbers to be invalidated (for example if a key is lost). Such a system might require Key 0 (the master key) to be inserted first, then all valid keys, then Key 0 again. Only those valid keys would now work with the car. In the worst case, for example if all car-keys are lost, then a new set of logical keys could be generated for the car and its associated physical car-keys if desired. "Ihe Car engine number would be used to tie the key to the particular car. Future use data may include such things as rental inforination, such as driver/renter details.
Examnle 2 Suppose we have a photocopier image unit which should be replaced every 100,000 copies. 32 bits are required to stota the number of pages remaining. The 256 bits of M could be divided up as follows:
Mini Access Description 0 RO Serial number (16 bits) 1 RO Batch number (16 bits) 2 MSR Page Count Remaining (32 bits, hi/lo) 4-7 RO For futtu+e expansion = 0(64 bits) 8-15 RO Random bit data (128 bits) If a lower quality image unit is made that must be replaced after only 10,000 copies, the 32-bit page count can still be used for compaftility with existing photocopiers. This allows several consumable types to be used with the same system.
Examole 3 Consider a Polaroid camera consumable containing 25 photos. A 16-bit countdown is all that is required to store the number of photos remaining. The 256 bits of M could be divided up as follows:
M[n] Access Description 0 RO Serial number (16 bits) 1 RO Batch number (16 bits) 2 MSR Photos Remaining (16 bits) 3-6 RO For future expansion = 0(64 bits) 7-15 RO Random bit data (144 bits) The Photos Remaining value at M[2] allows a number of consumable types to be built for use with the same camera System. For example, a new consumable with 36 photos is trivial to program.
Suppose 2 years after the introduction of the camera, a new type of camera was intr-oduced. It is able to use the old consumable, but also can process a new film type. M[3] can be used to define Film Type. Old film types would be 0, and the new film types would be some new value. New Systems can take advantage of this. Original systems would detect a non-zero value at M[3] and realize incompatibility with new film types. New Systems would understand the value of M[3] and so react appropriately. To maintain compatibility with the old consumable, the new consumable and System needs to have the same key information as the old one. To make a cleart break with a new System and its own special eon.sumables, a new key set would be required.
Examnle 4 Consider a printer consumable containing 3 inks: cyan, magenta, and yellow.
Each ink amount can be decremented separately. The 256 bits of M could be divided up as follows:
M[n] Access Description 0 RO Serial number (16 bits) I RO Batch number (16 bits) 2 MSR Cyan Remaining (32 bits, hi/lo) 4 MSR Magenta Remaining (32 bits, hi/lo) NMSR
6 MSR Yellow Remaining (32 bits, hi/lo) 8-11 RO For future expansion = 0 (64 bits) 12-15 RO Random bit data (64 bits) Stage 2: Determine Keys for Systems and Consumables Once the decision has been made as to which Systems and consumables are to share the same keys, those keys must be defined. The values for K, and K2 must therefore be determined. In most cases, K, and KZ will be generated once for all time. All Systems and consumables that have to work together (both now and in the future) need to have the same K, and K2 values. K, and K2 must therefore be kept secret since the entire security mechanism for the System/Consumable combination is made void if the keys are compromised. If the keys are compromised, the damage depends on the number of systems and consumables, and the ease to which they can be reprogrammed with new non-compromised keys: In the case of a photocopier with toner cartridges, the worst case is that a clone manufacturer could then manufacture their own Authentication Chips (or worse, buy them), program the chips with the known keys, and then in.sert them into their own consumables. In the case of a car with car-keys, each car has a different set of keys.
This leads to two possible general scenarios. The fust is that after the car and car-keys are progtammed with the keys, K, and KZ are deleted so no record of their values are kept, meaning that there is no way to compromise K, and K2.
However no more car-keys can be made for that car without reprogramming the car's Authentication Chip. The second scettario is that the car manufacturer keeps K, and K2, and new keys can be made for the car. A compromise of K, and K2 means that someone could make a car-key specifically for a particular car. -"ihe keys and rendom data used in the Authentication Chips must therefore be generated by a means that is non-deterministic (a completely computer generated pseudo-random number cannot be used because it is deterministic -knowledge of the generator's seed gives all future numbers). K, and K2 should be generated by a physically random process, and not by a computer. However, random bit generators based on natural sources of randotnness are subject to influence by external factors and also to malfunction. It is imperative that such devices be tested periodically for statistical randomness.
A simpie yet useful source of random numbers is the Lavarand system from SGi. This generator uses a digital camera to photograph six lava lamps every few minutes. Lava lamps contain chaotic turbnlent systems. The resukattt digital images are fed into an SHA-1 implementation that produces a 7-way hash, resulting in a 160-bit value from every 7th bye from the digitized image. These 7 sets of 160 bits total 140 bytes. The 140 byte value is fed into a BBS
generator to position the start of the output bitstream_ The output 160 bits from the BBS would be the key or the Authentication chip 53_ An extreme example of a non-deterministic random process is someone flipping a coin 160 times for K, and 160 times for K2 in a clean room. With each head or tail, a I or 0 is entered on a panel of a Key Programmer Device. The process must be undertaken with several observers (for verification) in silence (someone may have a hidden microphone). The point to be made is that secure data entry and storage is not as simple as it sounds. The physical security of the Key Prograrnmer Device and accompanying Prog'amrning Station requires an entire document of its own. Once keys K, and KZ have been determined, they must be kept for as long as Authentication Chips need to be made that use the key.
In the first car/car-key scenario K, and K2 are destroyed after a single System chip and a few consumable chips have been programmed. In the case of the photocopier / toner cartridge, K, and K2 must be retained for as long as the toner-cartridges are being made for the photocopiers. The keys must be kept securely.
Sta~e 3: Determine MinTicks for Systems and Consumables The value of MinTicks depends on the operating clock speed of the Authentication Chip (System specific) and the notion of what constitutes a reasonable time between RD or TST function calls (application specific). The duration of a single tick depends on the operating clock speed. This is the maximum of the input clock speed and the Authentication Chip's clock-limiting hardware. For example, the Authentication Chip's clock-limiting hardware may be set at 10 MHz (it is not changeable), but the input clock is I MHz In this case, the value of 1 tick is based on I
MHz, not 10 MHz. If the input clock was 20 MHz instead of 1 MHz, the value of I tick is based on 10 MHz (since the clock speed is limited to 10 MHz). Once the duration of a tick is known, the MinTicks value can be seL The value for MinTicks is the minimum number of ticks required to pass between calls to RD
or RND key-based functions.
Suppose the input clock speed matches the maximum clock speed of 10 MHz. If we want a minimum of I second between calls to TST, the value for MinTicks is set to 10,000,000. Even a value such as 2 seconds might be a completely reasonable value for a System such as a printer (one authentication per page, and one page produced every 2 or 3 seconds).
Stage 4; Prooram Kevs. Random Seed, MinTicks and Unused M
Authentication Chips are in an unknown state after manufacture. Alternatively, they have already been used in one consumable, and must be reprogrammed for use in another. Each Authentication Chip must be cleared and programmed with new keys and new state data. Clearing and subsequent programming of Authentication Chips must take place in a secure Programming Station environment.
Proerammine a Trusted System Authentication Chin If the chip is to be a trusted System chip, a seed value for R must be generated. It must be a random number derived from a physica8y random process, and must not be 0. The following tasks must be undertaken, in the following order, and in a secure progranuning environment:
RESET the chip CLR[]
Load R (160 bit register) with physically random data SSI[K1, KZ, R]
SMT[MinTickss,..]
The Authentication Chip is now ready for insertion into a System. It has been completely programmed. If the System Authentication Chips are stolen at this point, a clone manufacturer could use them to generate R, FK,[R] pairs in order to launch a known text attack on K,, or to use for launching a partially chosen-text attack on Kz. This is no different to the purchase of a number of Systems, each containing a tnisted Authentication Chip. The security relies on the strength of the Authentication protocols and the randomness of K, and KZ.
Proaramminy, a Non-Tnuted Consumable Authentication Chin If the chip is to be a non-trusbed Consumable Authentication Chip, the progtatnmutg is slightly different to that of the trusted System Authentication Chip. Firstly, the seed value for R must be 0.
It must have additional programming for M and the AccessMode values. The future use M[n] must be programmed with 0, and the random M[n] must be programmed with random data. The following tasks must be undertaken, in the following order, and in a secure programming environment:
RESET the chip CLR[]
Load R(160 bit register) with 0 SSI[K,, KZ, R]
Load X (256 bit register) with 0 Set bits in X corresponding to appropriate M[n] with physically random data WRP]
Load Y (32 bit register) with 0 Set bits in Y corresponding to appropriate M[n] with Read Only Access Modes SAM[Y]
SMT[MinTicksc.,,,.,j The non-trusted consumable chip is now ready to be programmed with the generel state data. If the Authentication Chips are stolen at this point, an attacker could perform a timited chosen text attacic. In the best situation, parts of M are Read Only (0 and random data), with the remainder of M completely chosen by an attacker (via the WR command). A
number of RD calls by an attacker obtains FK2[MIR] for a iimited M. In the worst situation, M can be completely chosen by-an attacker (since all 256 bits are used fa state data). In both ta.tes however, the attacker cannot choose any value for R since it is supplied by calls to RND from a System Authentic,ation Chip. The only way to obtain a chosen R
is by a Btute Force attack. It should be noted that if Stages 4 and 5 are catried out on the same Programming Station (the preferred and ideal situation), Authentication Chips cannot be removed in between the stages. Hence there is no possibility of the Authentication Chips being stolen at this point The decision to program the Authentication Chips at one or two times depends on the nequit+anents of the Sysoem/Co sumable manufactturr.
Stap-e 5: Proeram State Data and Access Modes This stage is only required for consumable Authentication Chips, since M and AccessMode registers cannot be altered on System Authentication Chips. The fuhme use and random values of M[n] have already been ptvgratnmed in Stage 4. The remaining state data values need to be programmed and the associated Access Mode values need to be set Bear in mind that the speed of this stage will be limited by the value stored in the MinTicks n:gister. This stage is separated from Stage 4 on account of the differences either in physical location or in time between where/when Stage 4 is performed, and wherelwhen Stage 5 is performed. Ideally, Stages 4 and 5 are performed at the same time in the same Programming Station. Stage 4 produces valid Authentication Chips, but does not load them with initial state values (other than 0). This is to allow the programtning of the chips to coincide with production line runs of consumables.
Although Stage 5 can be run multiple times, each time setting a different state data value and Access Mode value, it is more likely to be run a single time, setting all the remaining state data values and setting all the remaining Access Mode values. For example, a production line can be set up where the batch number and serial number of the Authentication Chip is produced according to the physical consumable being produced. This is much harder to match if the state data is loaded at a physically different factory.
'il-e Stage 5 process involves first checking to ensure the chip is a valid consumable chip, which includes a RD to gather the data from the Authentication Chip, followed by a WR of the initial data values, and then a SAM to pertnanently set the new data values. 'Ilte steps are outlined here:
IsTrusted = GIT[]
If (IsTtnsted), exit with error (wrong kind of chip!) Call RND on a valid System chip to get a valid input pair Call RD on chip to be programmed, passing in valid input pair Load X(256 bit register) with results from a RD of Authentication Chip Call TST on valid System chip to ensure X and consumable chip are valid If (TST retums 0), exit with error (wrong consumable chip for system) Set bits of X to initial state values WR[XI
Load Y(32 bit register) with 0 Set bits of Y corresponding to Access Modes for new state values SAM[Y]
Of course the validation (Steps I to 7) does not have to occur if Stage 4 and 5 follow on from one another on the same Programming Station. But it should occur in all other situations where Stage 5 is run as a separate programming process from Stage 4. If these Authentication Chips are now stolen, they are already programmed for use in a particular consumable. An attacker could place the stolen chips into a clone consumable. Such a theft would limit the number of cloned products to the number of chips stolen. A single theft should not create a supply constant enough to provide clone manufacnu+ers with a cost-effective business_ The altemative use for the chips is to save the attacker from purchasing tite same number of consumables, each with an Authentication Chip, in order to launch a partially chosen text attack or brute force attack. There is no special security breach of the keys if such an attack were to occur.
Manufacture 'Ihe circuitry of the Authentication Chip must be resistant to physical attack. A sumtnary of manufacturing implementation guidelines is presented, followed by specification of the chip's physical defenses (ordered by attack).
Guidelines for Manufacduitte The following are general guidelines for implementation of an Authentication Chip in terms of manufacture:
Standard process Minimum size (if possible) Clock Filter Noise Generator Tamper Prevention and Detection circ.uitry Protected memory with tamper detection Boot circuitry for loading program code Special implementation of FETs for key data paths Data connections in polysilicon layers where possible OverUnderPower Detection Unit No test circuitry Standard Process The Authentication Chip should be implemented with a standard manufacturing process (such as Flash). This is necessary to:
Allow a great range of manufacturing k"tion options Take advantage of well-defined and well-known technology Reduce cost Note that the standard process still allows physical protection mechanisms.
Minimum si~c The Authentication chip 53 must have a low manufaeturing cost in order to be included as the authentication mechanism for low cost consumables. It is therefore desirable to keep the chip size as low as reasonably possible.
Each Authentication Chip requires 802 bits of non-volatile memory. In addition, the storage ttquired for optimized HMAC-SHAI is 1024 bits. The remainder of the chip (state machine, processor, CPU or whatever is chosen to implement Protocol3) must be kept to a minimum in order that the number of transistors is minimized and thus the cost per chip is minimized. The circuit areas that process the secret key infonnation or could reveal information about the key should also be minimized (see Non-Flashing CMOS below for special data paths).
Clock Filtcs The Authentication Chip circuitry is designed to operate within a specific clock speed range. Since the user directly supplies the clock signai, it is possible for an attacker to attempt to introduce race-conditions in the circuitry at specific times during processing. An example of this is whene a high clock speed (higher than the cincuitry is designed for) may prevent an XOR from working properly, and of the two inputs, the fnst may always be returned. These styles of transient fault attacks can be very efficient at recovering sect+et key information. The lesson to be leamed from this is that the input clock signal cannot be trusted. Since the input clock signal cannot be trusted, it must be limited to operate up to a maximum frequency. 'Ibis can be achieved a number of ways. One way to filter the clock signal is to use an edge detea unit passing the edge on to a delay, which in turtt enables the input clock signal to pass through.
Fig. 174 shows clock signal flow within the Clock Filter. The delay should be set so that the maximum clock speed is a particular fieptency (e.g. about 4 MHz). Note that this delay is not progn;mmable - it is fixed. The filtered clock signal would be further divided intemally as required.
Noise Generator Each Authentication Chip should contain a noise generator that generates continuous circuit noise. The noise will interfere with other electromagnetic emissions from the chip's regular activities and add noise to the l,M signal.
Placement of the noise generator is not an issue on an Authentication Chip due to the length of the emission wavelengths. The noise generator is used to generate electronic noise, multiple state changes each clock cycie, and as a source of pseudo-random bits for the Tamper Prevention and Detection circuitry. A simple implementation of a noise generator is a 64-bit LFSR seeded with a non-zero number. The clock used for the noise generator should be nuuting at the maximum clock rate for the chip in order to generate as much noise as possible.
Tamper Prevention and Detection cQCOitrv A set of circuits is required to test for and prevent physical attacks on the Authentication Chip. However what is actually detected as an attack may not be an intentional physical attadc. It is therefore important to distinguish between these two types of attacks in an Authentication Chip:
where you can be certain that a physical attack has occutred.
whene you cannot be certain that a physical attack has occutred.
The two types of detection differ in what is perfotmed as a result of the deteotion. In the first case, where the circuitry can be certain that a true physical attack has occutred, erasure of Flash memory key information is a sensible action. In the second case, where the circuitry cannot be sure if an attack has occutred, there is still certainly something wrong.
Action must be taken, but the action should not be the erasure of secret key infocmation. A suitable action to take in the second case is a chip RESET. If what was detected was an attack that has permanently damaged the chip, the same conditions will occur next time and the chip will RESET again. If, on the other hand, what was detected was part of the nonnal operating environment of the chip, a RESET will not hann the key.
A good example of an event that circuitry cannot have knowledge about, is a power glitch. The glitch may be an intentional attack, attempting to reveal information about the key. It may, however, be the result of a faulty connection, or simply the start of a power-down sequence. It is therefore best to only RESET the chip, and not erase the key. If the chip was powering down, nothing is lost. If the System is faulty, repeated RESETs will cause the consumer to get the System repaired. In both cases the consumable is still intact.A good example of an event that circuitry can have knowledge about, is the cutting of a data line within the chip. If this attack is somehow detected, it could only be a result of a faulty chip (manufaciuring defect) or an attack In either case, the erasure of the secret information is a sensible step to take.
Consequently each Authentication Chip should have 2 Tamper Detection Lines as illustrated in Fig - one for deftnite attacks, and one for posstble attacks. Connected to these Tamper Deteetion Lines would be a number of Tamper Detection test units, eaoh testing for different fonns of tampering. In addition, we want to ensure tfiat the Tamper Detection Lines and Circuits themselves cannot also be tampered with.
At one end of the Tamper Detection Line is a source of pseudo-rattdom bits (clocking at high speed compared to the general opecating circuitry). The Noise Generator circuit described above is an adequate source. The generated bits pass through two different paths - one catries the originai data, and the other carries the inverse of the data. The wires canying these bits are in the layer above the general chip ciratitry (for example, the memory, the key manipulation circuitry ete). The wires must also cover the random bit genetator. The bits are recombined at a number of places via an XOR gate. If the bits are different (they should be), a I is output, and used by the particular unit (for example, each output bit from a memory read should be ANDed with this bit value). The lines fmally come togefher at the Flash memory Erase circuit, where a complete erasure is triggered by a 0 from the XOR Attached to the line is a number of triggers, each detecting a physical attack on the chip. Each trigger has an oversize nMOS transistor attached to GND.
"I'he Tamper Detection Line physically goes through this nMOS transistor. If the test fails, the trigger causes the Tamper Detect Line to become 0. The XOR test will therefore fail on either this clock cycle or the next one (on average), thus RESETing or erasing the chip. Fig. 175 illustrates the basic principle of a Tamper Detection Line in terms of tests and the XOR connected to either the Erase or RESET circuitry.
The Tamper Detection Line must go through the drain of an output transistor for each test, as illustrated by the oversize nMOS transistor layout of Fig. 176. :It is not possible to break the Tamper Detect Line since this would stop the flow of ls and Os from the random source. The XOR tests would therefore fail. As the Tamper Detect Line physically passes ttu+ough each test, it is not possible to eliminate any particular test without breaking the Tamper Detect Line. It is important that the XORs take values from a variety of places along the Tamper Detect Lines in order to reduce the chances of an attack. Fig. 177 illustrates the taking of multiple XORs from the Tamper Detect Line to be used in the different parts of the chip. Each of these XORs can be considered to be generating a ChipOK bit that can be used within each unit or sub-unit.
A sample usage would be to have an OK bit in each unit that is ANDed with a given ChipOK bit each cycle. The OK
bit is loaded with 1 on a RESET. If OK is 0, that unit will fail until the next RESET. If the Tamper Detect Line is functioning correctly, the chip will either RESET or erase all key information. If the RESET or erase circuitry has been destroyed, then this unit will not function, thus thwarting an attacker. The destination of the RESET and Erase line and associated circuitry is very context sensitive. It needs to be protected in much the same way as the individual tamper tests. There is no point generating a RESET pulse if the attacker can simply cut the wire leading to the RESET
circuitry. The actual implementation will depend very much on what is to be cleared at RESET, and how those items are cleared. Finally, Fig. 178 shows how the Tamper Lines cover the noise generator circuitry of the chip. The generator and NOT gate are on one level, while the Tamper Detect Lines nu- on a level above the generator.
Protected memory with tamner detection It is not enough to simply store secret information or program code in Flash memory. The Flash memory and RAM
must be protected from an attacker who would attempt to modify (or set) a particular bit of program code or key infonnation. The mechanism used must conform to being used in the Tamper Detection Circuitry (described above).
The first part of the solation is to ensure that the Tamper Detection Line passes directly above each Flash or RAM bit.
This ensures that an attacker cannot probe the contents of Flash or RAM. A
breach of the covering wire is a break in the Tamper Detection Line. The breach causes the Erase signal to be set, thus deleting any contents of the memory.
The high frequency noise on the Tamper Detection Line also obscures passive observation.
The second part of the solution for Flash is to use multi-level data storage, but only to use a subset of those muttiple levels for valid bit representations. Normally, when multi-level Flash storage is used, a single floating gate holds more than one bit. For example, a 4-voltage-state tcansistor can represent two bits. Assuming a minimum and maximum voltage representing 00 and I 1 respectively, the two middle voltages represent 01 and 10. In the Authentication Chip, we can use the two middle voltages to represent a single bit, and consider the two extremes to be invalid states. If an attacker attempts to force the state of a bit one way or the other by closing or cutting the gate's circuit, an invalid voltage (and hence invalid state) results.
The second part of the solution for RAM is to use a parity bit. The data part of the register can be checked against the parity bit (which will not match after an attack). The bits coming from Flash and RAM can therefore be validated by a number of test units (one per bit) connected to the common Tamper Detection Line. The Tamper Detection circuitry would be the first circuitry the data passes through (thus stopping an attacker from cutting the data lines).
Boot circuitry for loading proaram code Program code should be kept in multi-level Flash instead of ROM, since ROM is subject to being altered in a non-testable way. A boot mechanism is therefore required to load the program code into Flash memory (Flash memory is in an indetera-inate state after manufacture). The boot circuitry must not be in ROM - a small state-machine would suffice. Otherwise the boot code could be modified in an undetectable way. The boot circuitry must erase all Flash memory, check to ensure the erasure worked, and then load the program code.
Flash memory must be erased before loading the program code. Otherwise an attacker could put the chip into the boot state, and then load program code that simply extracted the existing keys. The state machine must also check to ensure that all Flash memory has been cleared (to ensure that an attacker has not cut the Erase line) before loading the new program code. The loading of program code must be undertaken by the secure Programming Station before secret information (such as keys) can be loaded.
Special implementation of FETs for key data aaths The normal situation for FET implementation for the case of a CMOS Inverter (which involves a pMOS transistor combined with an nMOS transistor) is shown in Fig. 179. During the transition, there is a small period of time where both the nMOS transistor and the pMOS transistor have an intermediate resistance. The resultant power-ground short circuit causes a temporary increase in the current, and in fact accounts for the majority of current consumed by a CMOS device. A small amount of infiared light is emitted during the short circuit, and can be viewed through the silicon substrate (silicon is transparent to infrared light). A small amount of light is also emitted during the charging and discharging of the transistor gate capacitance and transmission line capacitance.
For circuitry that manipulates secret key information, such information must be kept hidden. An alternative non-flashing CMOS implementation should therefore be used for all data paths that manipulate the key or a partially calculated value that is based on the key. The use of two non-overlapping clocks ~1 and ~2 can provide a non-flashing mechanism. ~l is connected to a second gate of all nMOS transistors, and 02 is connected to a second gate of all pMOS transistors. The transition can only take place in combination with the clock. Since 01 and 02 are non-overlapping, the pMOS and nMOS trsnsistors will not have a simultaneous intermediate resistance. The setup is shown in Fig. 180.
Finally, regular CMOS inverters can be positioned near critical non-Flashing CMOS components. These inverters should take their input signal from the Tamper Detection Line above. Since the Tamper Detection Line operates multiple times faster than the regular operating circuitry, the net effect will be a high rate of light-bursts next to each non-Flashing CMOS component. Since a brigbt light overwhehns observation of a nearby faint light, an observer will not be able to detect what switching operations are occun-ing in the chip proper. These regular CMOS inverters will also effectively increase the amount of circuit noise, reducing the SNR and obscuring useful EMI.
There are a number of side effects due to the use of non-Flashing CMOS:
The effective speed of the chip is reduced by twice the rise time of the clock per clock cycle. This is not a problem for an Authentication Chip.
The amount of cuirent drawn by the non-Flashing CMOS is reduced (since tlte short circuits do not occur).
However, this is offset by the use of regular CMOS inverters.
Routing of the clocks increases chip area, especially since multiple versions of 01 and 02 are required to cater for different levels of propagation. The estimation of chip area is double that of a regular implementation.
Design of the non-Flashing areas of the Authentication Chip are slightly more complex than to do the same with a with a regular CMOS design. In particular, standard cell components cannot be used, making these areas full custom. This is not a problem for something as small as an Authentication Chip, particularly when the entire chip does not have to be protected in this manner.
Connections in polysilicon layers where possible Wherever possible, the connections along which the key or secret data flows, should be made in the polysilicon layers.
Where necessary, they can be in metal 1, but must never be in the top metal layer (containing the Tamper Detection Lines).
OverUnderPower Detection Unit Each Authentication Chip requires an OverUnderPower Detection Unit to prevent Power Supply Attacks. An OverUnderPower Detection Unit detects power glitches and tests the power level against a Voltage Reference to ensure it is within a certain tolerance. The Unit contains a single Voltage Reference and two comparators. The OverUnderPower Detection Unit would be connected into the RESET Tamper Detection Line, thus causing a RESET
when triggered_ A side effect of the OverUnderPower Detection Unit is that as the voltage drops during a power-down, a RESET is triggered, thus erasing any work registers.
No Test Circuitrv Test hardware on an Authentication Chip could very easily introduce vulnerabilities. As a result, the Authentication Chip should not contain any BIST or scan paths. The Authentication Chip must therefore be testable with external test vectors. This should be possible since the Authentication Chip is not complex.
Readine ROM
This attack depends on the key being stored in an addressable ROM. Since each Authentication Chip stores its authentication keys in intemal Flash memory and not in an addressable ROM, this attack is irrelevant.
Reverse Engineering the Chio Reverse engineering a chip is only useful when the security of authentication lies in the algorithm alone. However our Authentication Chips rely on a secret key, and not in the secrecy of the algorithm. Our authentication algorithm is, by contrast, public, and in any case, an attacker of a high volume consumable is assumed to have been able to obtain detailed plans of the intemals of the chip. In light of these factors, reverse engineering the chip itself, as opposed to the stored data, poses no threat.
UsuroinQ the Authentication Process There are several forms this attack can take, each with varying degrees of success. In all cases, it is assumed that a clone manufacturer will have access to both the System and the consumable designs. An attacker may attempt to build a chip that tricks the System into retuming a valid code instead of generating an authentication code. This attack is not possible for two reasons. The first reason is that System Authentication chips and Consumable Authentication Chips, although physically identical, are programmed differently. In particular, the RD opcode and the RND opcode are the same, as are the WR and TST opcodes. A System authentication Chip cannot perform a RD command since every call is interpreted as a call to RND instead. The second reason this attack would fail is that separate serial data lines are provided from the System to the System and Consumable Authentication Chips.
Consequently neither chip can see what is being transmitted to or received from the other. If the attacker builds a clone chip that ignores WR commands (which decrement the consumable remaining), Protocol 3 ensures that the subsequent RD will detect that the WR did not occur. The System will therefore not go ahead with the use of the consumable, thus thwarting the attacker. The same is true if an attacker simulates loss of contact before authentication -since the authentication does not take place, the use of the consumable doesn't occur. An attacker is therefore limited to modifying each System in order for clone consumables to be accepted Modification of System The simplest method of modification is to replace the System's Authentication Chip with one that simply reports success for each call to TST. This can be thwarted by System calling TST
several times for each authentication, with the first few times providing false values, and expecting a fail from TST. The final call to TST would be expected to succeed. The number of false calls to TST could be determined by some part of the retumed result from RD or from the system clock. Unfortunately an attacker could simply rewire System so that the new System clone authentication chip 53 can monitor the retumed result from the consumable chip or clock. The clone System Authentication Chip would only return success when that monitored value is presented to its TST
function. Clone consumables could then return any value as the hash result for RD, as the clone System chip would declare that value valid. There is therefore no point for the System to call the System Authentication Chip multiple times, since a rewiring attack will only work for the System that has been rewired, and not for all Systems. A similar form of attack on a System is a replacement of the System ROM. The ROM program code can be altered so that the Authentication never occurs. There is nothing that can be done about this, since the System remains in the hands of a consumer. Of course this would void any watranty, but the consumer may consider the alteration worthwhile if the clone consumable were extremely cheap and more readily available than the original item.
The System/consumable manufacturer must therefore determine how ldcely an attack of this nature is. Such a study must include given the pricing structure of Systems and Consumables, frequency of System service, advantage to the consumer of having a physical modification perfortned, and where consumers would go to get the modification performed. The limit case of modifying a system is for a clone manufacturer to provide a completely clone System which takes clone consumables. This may be simple competition or violation of patents. Either way, it is beyond the scope of the Authentication Chip and depends on the technology or service being cloned.
Direct viewing of chip operation by conventional probing In order to view the chip operation, the chip must be operatittg. However, the Tatnper Prevention and Detection circuitry covers those sections of the chip that process or hold the key. It is not possible to view those sections through the Tamper Prevention lines. An attacker cannot simply slice the chip past the Tamper Prevention layer, for this will break the Tamper Detection Lines and cause an erasure of all keys at power-up.
Simply destroying the erasure circuitry is not sufficient, since the multiple ChipOK bits (now all 0) feeding into multiple units within the Authentication Chip will cause the chip's regular operating circuitry to stop functioning. To set up the chip for an attack, then, requires the attacker to delete the Tamper Detection lines, stop the Etasure of Flash memory, and somehow rewire the components that relied on the ChipOK lines. Even if all this could be done, the act of slicing the chip to this level will most likely destroy the charge pattems in the non-volatile memory that holds the keys, making the process fiuidess.
Direct viewine of the non-volatile memorv If the Authentication Chip were sliced so that the floating gates of the Flash memory were exposed, without discharging them, then the keys could probably be viewed directly using an STM
or SKM. However, slicing the chip to this level without discharging the gates is probably impossible_ Using wet etching, plasma etching, ion milling, or chemical mechanical polishing will almost certainly discharge the small charges present on the floating gates. This is true of regular Flash memory, but even more so of multi-level Flash memory.
Viewing the li t bursts caused by state chanees All sections of circuitry that manipulate secret key information are implemented in the non-Flashing CMOS described above. This prevents the emission of the majority of light bursts. Regular CMOS inverters placed in close proximity to the non-Flashing CMOS will hide any faint emissions caused by capacitDr charge and discharge. The inverters are connected to the Tamper Detection circuitry, so they change state many times (at the high clock rate) for each non-Flashing CMOS state change.
Monitorina EMI
The Noise Generator described above will cause circuit noise. The noise will interfere with other electromagnetic emissions from the chip's regular activities and thus obscure any meaningful reading of intemal data transfers.
Viewine L. fluctuations The solution against this kind of attack is to decrease the SNR in the Idd signal. This is accomplished by increasing the amount of circuit noise and decreasing the amount of signal. The Noise Generator circuit (which also acts as a defense against EMI attacks) will also cause enough state changes each cycle to obscure any meaningfiul information in the I&
signal. tn addition, the special Non-Flashing CMOS implementation of the key-carrying data paths of the chip prevents cun-ent from flowing when state changes occur. This has the benefit of reducing the amount of signal.
Differential Fault Anaiysis Differential fault bit errors are introduced in a non-targeted fashion by ionization, microwave radiation, and environmental stress. The most likely effect of an attack of this nature is a change in Flash memory (causing an invalid state) or RAM (bad parity). Invalid states and bad parity are detected by the Tamper Detection Circuitry, and cause an erasure of the key. Since the Tamper Detection Lines cover the key manipulation circuitry, any error introduced in the key manipulation circuitry will be mitrored by an error in a Tamper Detection Line. If the Tamper Detection Line is affected, the chip will either continually RESET or simply erase the key upon a power-up, rendering the attack fruitless. Rather than relying on a non-targeted attack and hoping that "just the right part of the chip is affected in just the right way", an attacker is better off trying to inaroduce a targeted fault (such as overwrite attacks, gate destruction etc). For information on these targeted fault attacks, see the relevant sections below.
Clock Glitch Attacks . q The Clock Filter (described above) eliminates the possibility of clock glitch attacks.
Power Supply Attadcs The OverUnderPower Detection Unit (described above) eliminates the possibility of power supply attacks.
Overwriting ROM
Authentication Chips store Program code, keys and secret information in Flash memory, and not in ROM. This attack is therefore not possible.
Modifying EEPROM/Flash Authentication Chips store Program code, keys and secret infotmation in Flash memory. However, Flash memory is covered by two Tamper Prevention and Detection L'ntes. If either of these lines is broken (in the process of destroying a gate) the attack will be detected on power-up, and the chip will either RESET (continually) or erase the keys from Flash memory. However, even if the attacker is able to somehow access the bits of Flash and destroy or short out the gate holding a particular bit, this will force the bit to have no charge or a full charge. These are both invalid states for the Authentication Chip's usage of the multi-level Flash memory (only the two middle states are valid). When that data value is transferred from Flash, detection circuitry will cause the Erasure Tamper Detection Line to be triggered -thereby erasing the remainder of Flash memory and RESETing the chip. A Modify EEPROM/Flash Attack is therefore fivitless.
Gate Destruction Attacks Gate Destruction Attacks rely on the ability of an attacker to modify a single gate to cause the chip to reveal information during operation. However any circuitry that manipulates secret information is covered by one of the two Tamper Prevention and Detection lines. If either of these lines is broken (in the process of destroying a gate) the attack will be detected on power-up, and the chip will either RESET (continually) or erase the keys from Flash memory. To launch this kind of attack, an attacker must fust reverse-engineer the chip to determine which gate(s) should be targeted. Once the location of the target gates has been determined, the attacker must break the covering Tamper Detection line, stop the Erasure of Flash memory, and somehow rewire the components that rely on the ChipOK lines.
Rewiring the circuitry cannot be done without slicing the chip, and even if it could be done, the act of slicing the chip to this level will most likely destroy the charge pattems in the non-volatile memory that holds the keys, making the process fruitless.
Overwrite Attacks An Overwrite Attack relies on being able to set individual bits of the key without knowing the previous value. It relies on probing the chip, as in the Conventional Probing Attack and destroying gates as in the Gate Destruction Attack.
Both of these attacks (as explained in their respective sections), will not succeed due to the use of the Tamper Prevention and Detection Circuitry and ChipOK lines. However, even if the attacker is able to somehow access the bits of Flash and destroy or short out the gate holding a particular bit, this will force the bit to have no charge or a full charge. These are both invalid states for the Authentication Chip's usage of the multi-level Flash memory (only the two middle states are valid). When that data value is transferred from Flash detection circuitry will cause the Erasure Tamper Detection Line to be triggered - thereby erasing the remainder of Flash memory and RESETing the chip. In the same way, a parity check on tampered values read from RAM will cause the Erasure Tamper Detection Line to be triggered. An Overwrite Attack is therefore fiuitless.
Memory Remanence Attack Any working registers or RAM within the Authentication Chip may be holding part of the authentication keys when power is removed. The working registers and RAM would continue to hold the infotmation for some time after the removal of power. If the chip were sliced so that the gates of the registers/RAM were exposed, without discharging them, then the data could probably be viewed directly using an sTM. The first defense can be found above, in the description of defense against Power Glitch Attacks. When power is removed, all registers and RAM are cleared, just as the RESET condition causes a clearing of memory. The chances then, are less for this attack to succeed than for a reading of the Flash memory. RAM charges (by nature) are more easily lost than Flash memory. The slicing of the chip to reveal the RAM will certainly cause the charges to be lost (if they haven't been lost simply due to the memory not being refreshed and the time taken to perform the slicing). This attack is therefore fruitless.
Chip Theft Attack There are distinct phases in the lifetime of an Authentication Chip. Chips can be stolen when at any of these stages:
After manufacture, but before programming of key After programming of key, but before programming of state data After progranuning of state data, but before insertion into the consumable or system After insertion into the system or consumable A theft in between the chip manufacturer and programming station would only provide the clone manufacturer with blank chips. This merely compromises the sale of Authentication chips, not anything authenticated by the Authentication chips. Since the programming station is the only mechanism with consumable and system product keys, a clone manufacturer would not be able to program the chips with the correct key. Clone manufacturers would be able to program the blank chips for their own Systems and Consumables, but it would be difficult to place these items on the market without detection. The second forrn of theft can only happen in a situation where an Authentication Chip passes through two or more distinct programming phases. This is possible, but unlikely. In any case, the worst situation is where no state data has been progratnmed, so all of M is read/write. If this were the case, an attacker could attempt to launch an Adaptive Chosen Text Attack on the chip. The I-IMAC-SHAI algorithm is resistant to such attacks. The third fortn of theft would have to take place in between the programming station and the installation factory. The Authentication chips would already be programmed for use in a particular system or for use in a particular consumable.
The only use these chips have to a thief is to place them into a clone System or clone Consumable. Clone systems are irrelevant - a cloned System would not even require an authentication chip 53.
For clone Consumables, such a theft would limit the number of cloned products to the number of chips stolen. A
single theft should not create a supply constant enough to provide clone manufacturers with a cost-effective business.The fmal form of theft is where the System or Consumable itself is stolen. When the theft occurs at the manufacturer, physical security protocols must be enhanced. If the theft occurs anywhere else, it is a matter of concem only for the owner of the item and the police or insurance company. The security mechanisms that the Authentication Chip uses assume that the consumables and systems are in the hands of the public. Consequently, having them stolen makes no difference to the security of the keys.
Authentication Chip Desi~tt The Authentication Chip has a physical and a logical external interface. The physical interface defines how the Authentication Chip can be connected to a physical System, and the logical interface determines how that System can communicate with the Authentication Chip.
Physical Interface The Authentication Chip is a small 4-pin CMOS package (actual intemal size is approximately 0.30 mm' using 0.25 m Flash process). The 4 pins are GND, CLK, Power, and Data. Power is a nominal voltage. If the voltage deviates from this by more than a fixed amount, the chip will RESET. The recommended clock speed is 4-10 MHz Intemal circuitry filters the clock signal to ensure that a safe maximum clock speed is not exceeded. Data is transmitted and received one bit at a time along the serial data line. The chip performs a RESET upon power-up, power-down. In addition, tamper detection and prevention circuitry in the chip will cause the chip to either RESET or erase Flash memory (depending on the attack detected) if an attack is detected. A special Programming Mode is enabled by holding the CLK voltage at a particular level. This is defuied further in the next section.
Logical Interface The Authentication Chip has two operating modes - a Normal Mode and a Programming Mode. The two modes are required because the operating program code is stored in Flash memory instead of ROM (for security reasons). The Programming mode is used for testing purposes after manufacture and to load up the operating program code, while the normal mode is used for all subsequent usage of the chip.
Prouamming Mode The Programming Mode is enabled by holding a specific voltage on the CLK line for a given amount of time. When the chip enters Programming Mode, all Flash memory is erased (including all secret key infonnation and any program code). The Authentication Chip then validates the erasure. If the erasure was successful, the Authentication Chip receives 384 bytes of data corresponding to the new program code. The bytes are transfecred in order byteo to byte383.
The bits are transferred from bita to bit7. Once all 384 bytes of program code have been loaded, the Authentication Chip hangs. If the erasure was not successful, the Authentication Chip will hang without loading any data into the Flash memory. After the chip has been programmed, it can be restarted. When the chip is RESET with a normal voltage on the CLK line, Normal Mode is entered.
Notmal Mode Whenever the Authentication Chip is not in Programming Mode, it is in Normal Mode. When the Authentication Chip starts up in Normal Mode (for example a power-up RESET), it executes the program currently stored in the program code region of Flash memory. The program code implements a communication mechanism between the System and Authentication Chip, accepting commands and data from the System and producing output values. Since the Authentication Chip communicates serially, bits are transfen-ed one at a time.The System communicates with the Authentication Chips via a simple operation command set. Each command is defined by 3-bit opcode. The interpretation of the opcode depends on the current value of the IsTntsted bit and the Is Written bit.
The following operations are defmed:
Op T W Mn Input Output Description 000 - - CLR - Clear 001 0 0 SSI [160, 160, 160] Set Secret Information 010 0 1 RD [160, 160] [256, 160] Read M securely 010 1 1 RND - [ 160, 160] Random 011 0 1 WR [256] - Write M
01 l 1 1 TST [256, 160] [1] Test 100 0 1 SAM [32] [32] Set Access Mode 101 - 1 G IT - [ 1] Get Is Trusted 110 - 1 SMT [32] - Set MinTicks Op = Opcode, T = IsTrusted value, W= IsWritten value, Mn = Mnemonic, [n] = number of bits required for parameter Any command not defined in this table is interpreted as NOP (No operation).
Examples include opcodes 110 and 1 I 1 (regardless of IsTrusted or IsWritten values), and any opcode other than SSI
when IsWritten = 0. Note that the opcodes for RD and RND are the same, as are the opcodes for WR and TST. The actual command run upon receipt of the opcode will depend on the current value of the IsTrusted bit (as long as IsWritten is 1). Where the IsTrusted bit is clear, RD and WR functions will be called. Where the IsTrusted bit is set, RND
and TST functions will be called. The two sets of commands are mutually exclusive between trusted and non-trusted Authentication Chips. In order to execute a command on an Authentication Chip, a client (such as System) sends the command opcode followed by the required input parameters for that opcode. The opcode is sent least significant bit through to most significant bit. For example, to send the SSI command, the bits 1, 0, and 0 would be sent in that order. Each input parameter is sent in the same way, least significant bit first through to most significant bit last.
Retum values are read in the same way - least significant bit first and most significant bit last. The client must know how many bits to retrieve.
In some cases, the output bits from one chip's command can be fed directly as the input bits to another chip's command. An example of this is the RND and RD commands. The output bits from a call to RND on a trusted Authentication Chip do not have to be kept by System. Instead, System can transfer the output bits directly to the input of the non-trusted Authentication Chip's RD command. The description of each command points out where this is so_ Each of the commands is examined in detail in the subsequent sections. Note that some algorithms are specifically designed because the permanent registers are kept in Flash memory.
Registers The memory within the Authentication Chip contains some non-volatile memory to store the variables required by the Authentication Protocol. The following non-volatile (Flash) variables are defined:
Size Variable Name (in bits) Description M[0..15] 256 16 words (each 16 bits) containing state data such as serial numbers, media remaining etc_ K, 160 Key used to transform R during authentication.
K2 160 Key used to transform M during authentication.
R 160 Current random number AccessMode[0..15] 32 The 16 sets of 2-bit AccessMode values for M[n].
MinTicks 32 The minimum number of clock ticks between calls to key-based functions SlWritten I If set, the secret key information (KI, K2, and R) has been written to the chip. If clear, the secret information has not been written yet.
IsTrusted 1 If set, the RND and TST functions can be called, but RD
and WR functions cannot be called.
If clear, the RND and TST functions cannot be called, but RD and WR functions can be called.
Total bits 802 Architecture Overview This section chapter provides the high-level defmition of a purpose-built CPU
capable of implementing the functionality required of an Authentication Chip. Note that this CPU is not a general purpose CPU. It is tailor-made for implementing the Authentication logic. The authentication commands that a user of an Authentication Chip sees, such as WRITE, TST, RND etc are all implemented as small programs written in the CPU instruction set. The CPU
contains a 32-bit Accumulator (which is used in most operations), and a number of registers. The CPU operates on 8-bit instructions specifically tailored to implementing authentication logic.
Each 8-bit instruction typically consists of a 4-bit opcode, and a 4-bit operand.
Operatine Speed An internal Clock Frequency Limiter Unit prevents the chip from operating at speeds any faster than a predetermined frequency. The frequency is built into the chip during manufacture, and cannot be changed. The frequency is recommended to be about 4-10 MHz.
Composition and Block Diagram The Authentication Chip contains the following components:
DEMANDES OU BREVETS VOLUMINEUX
LA PRESENTE PARTIE DE CETTE DEMANDE OU CE BREVETS
COMPREND PLUS D'UN TOME.
CECI EST LE TOME rl DE _2 NOTE: Pour les tomes additionels, veillez contacter le Bureau Canadien des Brevets.
JUMBO APPLICATIONS / PATENTS
THIS SECTION OF THE APPLICATION / PATENT CONTAINS MORE
THAN ONE VOLUME.
THIS IS VOLUME OF
NOTE: For additional volumes please contact the Canadian Patent Office.
Claims (5)
1. A user interface for operating a device, said user interface comprising a card which is inserted in a machine and on the face of the card is contained a visual representation of the effect the card will have on the output of the machine.
2. A user interface as claimed in claim 1 wherein said machine comprises a camera device capable of transforming a sensed image substantially in accordance with the transformation of a standard image comprising said visual representation.
3. A user interface as claimed in claim 2 wherein said camera includes and integral printer and said transformation of said sensed image is printed out on said printer.
4. A user interface as claimed in claim 1 wherein said machine comprises a book reader and said card includes a books contents for display by said book reader as indicated by the visual representation on the front of said card.
5. A user interface as claimed in claim 1 wherein said card comprises, on one surface, the visual representation of said effect, and on a second surface, a visually encoded representation of said effect able to be read by a sensing device of said machine and decoded so as to produce said effect.
Applications Claiming Priority (143)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPO7938 | 1997-07-15 | ||
| AUPO8017A AUPO801797A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART06) |
| AUPO7977A AUPO797797A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART44) |
| AUPO7939A AUPO793997A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART29) |
| AUPO7981A AUPO798197A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART50) |
| AUPO8023 | 1997-07-15 | ||
| AUPO7983A AUPO798397A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART52) |
| AUPO7934 | 1997-07-15 | ||
| AUPO8019 | 1997-07-15 | ||
| AUPO7998A AUPO799897A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART11) |
| AUPO7981 | 1997-07-15 | ||
| AUPO7986A AUPO798697A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART51) |
| AUPO007997 | 1997-07-15 | ||
| AUPO7934A AUPO793497A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART45) |
| AUPO8016 | 1997-07-15 | ||
| AUPO7991 | 1997-07-15 | ||
| AUPO8005A AUPO800597A0 (en) | 1997-07-15 | 1997-07-15 | Supply method and apparatus (F2) |
| AUPO8028 | 1997-07-15 | ||
| AUPO8014A AUPO801497A0 (en) | 1997-07-15 | 1997-07-15 | Media device (ART07) |
| AUPO8021A AUPO802197A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART40) |
| AUPO7985A AUPO798597A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART37) |
| AUPO8000A AUPO800097A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART43) |
| AUPO8020A AUPO802097A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART38) |
| AUPO8016A AUPO801697A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART26) |
| AUPO8022A AUPO802297A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART33) |
| AUPO8024 | 1997-07-15 | ||
| AUPO8003 | 1997-07-15 | ||
| AUPO7990 | 1997-07-15 | ||
| AUPO7999A AUPO799997A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART10) |
| AUPO7988A AUPO798897A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART02) |
| AUPO8027 | 1997-07-15 | ||
| AUPO7942 | 1997-07-15 | ||
| AUPO8005 | 1997-07-15 | ||
| AUPO7978 | 1997-07-15 | ||
| AUPO7982A AUPO798297A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART19) |
| AUPO7938A AUPO793897A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART25) |
| AUPO7987 | 1997-07-15 | ||
| AUPO8021 | 1997-07-15 | ||
| AUPO8019A AUPO801997A0 (en) | 1997-07-15 | 1997-07-15 | Media processing method and apparatus (ART21) |
| AUPO8031 | 1997-07-15 | ||
| AUPO7999 | 1997-07-15 | ||
| AUPO8020 | 1997-07-15 | ||
| AUPO8023A AUPO802397A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART39) |
| AUPO7940 | 1997-07-15 | ||
| AUPO8025A AUPO802597A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART08) |
| AUPO8029A AUPO802997A0 (en) | 1997-07-15 | 1997-07-15 | Sensor creation method and apparatus (ART36) |
| AUPO7991A AUPO799197A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART01) |
| AUPO7989 | 1997-07-15 | ||
| AUPO7985 | 1997-07-15 | ||
| AUPO7939 | 1997-07-15 | ||
| AUPO7942A AUPO794297A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART23) |
| AUPO8030 | 1997-07-15 | ||
| AUPO7988 | 1997-07-15 | ||
| AUPO8003A AUPO800397A0 (en) | 1997-07-15 | 1997-07-15 | Supply method and apparatus (F1) |
| AUPO7993A AUPO799397A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART03) |
| AUPO8026 | 1997-07-15 | ||
| AUPO8014 | 1997-07-15 | ||
| AUPO7979A AUPO797997A0 (en) | 1997-07-15 | 1997-07-15 | Media device (ART16) |
| AUPO7986 | 1997-07-15 | ||
| AUPO7979 | 1997-07-15 | ||
| AUPO8012A AUPO801297A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART05) |
| AUPO7940A AUPO794097A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART28) |
| AUPO8029 | 1997-07-15 | ||
| AUPO7977 | 1997-07-15 | ||
| AUPO8032A AUPO803297A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART09) |
| AUPO8018 | 1997-07-15 | ||
| AUPO8017 | 1997-07-15 | ||
| AUPO8031A AUPO803197A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART12) |
| AUPO7998 | 1997-07-15 | ||
| AUPO8025 | 1997-07-15 | ||
| AUPO7997 | 1997-07-15 | ||
| AUPO7980A AUPO798097A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART22) |
| AUPO7982 | 1997-07-15 | ||
| AUPO8027A AUPO802797A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART54) |
| AUPO8012 | 1997-07-15 | ||
| AUPO8022 | 1997-07-15 | ||
| AUPO7993 | 1997-07-15 | ||
| AUPO8028A AUPO802897A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART56) |
| AUPO8030A AUPO803097A0 (en) | 1997-07-15 | 1997-07-15 | Media device (ART13) |
| AUPO7980 | 1997-07-15 | ||
| AUPO8024A AUPO802497A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART27) |
| AUPO7983 | 1997-07-15 | ||
| AUPO7978A AUPO797897A0 (en) | 1997-07-15 | 1997-07-15 | Media device (ART18) |
| AUPO7989A AUPO798997A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART20) |
| AUPO7990A AUPO799097A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART46) |
| AUPO8015A AUPO801597A0 (en) | 1997-07-15 | 1997-07-15 | Media device (ART17) |
| AUPO8000 | 1997-07-15 | ||
| AUPO8032 | 1997-07-15 | ||
| AUPO8015 | 1997-07-15 | ||
| AUPO8018A AUPO801897A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART24) |
| AUPO8026A AUPO802697A0 (en) | 1997-07-15 | 1997-07-15 | Image processing method and apparatus (ART53) |
| AUPO7987A AUPO798797A0 (en) | 1997-07-15 | 1997-07-15 | Data processing method and apparatus (ART32) |
| AUPO8504 | 1997-08-11 | ||
| AUPO8502A AUPO850297A0 (en) | 1997-08-11 | 1997-08-11 | Image processing method and apparatus (art48) |
| AUPO8504A AUPO850497A0 (en) | 1997-08-11 | 1997-08-11 | Image processing method and apparatus (art42) |
| AUPO8499 | 1997-08-11 | ||
| AUPO8502 | 1997-08-11 | ||
| AUPO8498 | 1997-08-11 | ||
| AUPO8505A AUPO850597A0 (en) | 1997-08-11 | 1997-08-11 | Image processing method and apparatus (art01a) |
| AUPO8500A AUPO850097A0 (en) | 1997-08-11 | 1997-08-11 | Image processing method and apparatus (art31) |
| AUPO8499A AUPO849997A0 (en) | 1997-08-11 | 1997-08-11 | Image processing method and apparatus (art47) |
| AUPO008497 | 1997-08-11 | ||
| AUPO8505 | 1997-08-11 | ||
| AUPO8501A AUPO850197A0 (en) | 1997-08-11 | 1997-08-11 | Image processing method and apparatus (art30) |
| AUPO8497 | 1997-08-11 | ||
| AUPO8498A AUPO849897A0 (en) | 1997-08-11 | 1997-08-11 | Image processing method and apparatus (ART14) |
| AUPO8500 | 1997-08-11 | ||
| AUPO8501 | 1997-08-11 | ||
| AUPO9403A AUPO940397A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART65) |
| AUPO9404A AUPO940497A0 (en) | 1997-09-23 | 1997-09-23 | A device and method (F3) |
| AUPO9398A AUPO939897A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART60) |
| AUPO9400A AUPO940097A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART62) |
| AUPO9395 | 1997-09-23 | ||
| AUPO9396A AUPO939697A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART58) |
| AUPO9401A AUPO940197A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART63) |
| AUPO9394 | 1997-09-23 | ||
| AUPO9403 | 1997-09-23 | ||
| AUPO9394A AUPO939497A0 (en) | 1997-09-23 | 1997-09-23 | Image processing method and apparatus (ART57) |
| AUPO9396 | 1997-09-23 | ||
| AUPO9402A AUPO940297A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART64) |
| AUPO9402 | 1997-09-23 | ||
| AUPO9399 | 1997-09-23 | ||
| USPO9405 | 1997-09-23 | ||
| AUPO009397 | 1997-09-23 | ||
| AUPO9401 | 1997-09-23 | ||
| AUPO9400 | 1997-09-23 | ||
| AUPO9398 | 1997-09-23 | ||
| AUPO9405A AUPO940597A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART66) |
| AUPO9397 | 1997-09-23 | ||
| AUPO9395A AUPO939597A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART4) |
| AUPO9399A AUPO939997A0 (en) | 1997-09-23 | 1997-09-23 | Data processing method and apparatus (ART61) |
| AUPO9404 | 1997-09-23 | ||
| AUPP0959A AUPP095997A0 (en) | 1997-12-16 | 1997-12-16 | A data processing method and apparatus (art 68) |
| AUPP0959 | 1997-12-16 | ||
| AUPP1397 | 1998-01-19 | ||
| AUPP1397A AUPP139798A0 (en) | 1998-01-19 | 1998-01-19 | A media device (art 69) |
| AUPP2370 | 1998-03-16 | ||
| AUPP2371 | 1998-03-16 | ||
| AUPP2370A AUPP237098A0 (en) | 1998-03-16 | 1998-03-16 | Data processing method and apparatus (dot 01) |
| AUPP2371A AUPP237198A0 (en) | 1998-03-16 | 1998-03-16 | Data processing method and apparatus (dot02) |
| AUPP4094A AUPP409498A0 (en) | 1998-06-12 | 1998-06-12 | An authentication system (AUTH01) |
| AUPP4094 | 1998-06-12 | ||
| CA002296439A CA2296439C (en) | 1997-07-15 | 1998-07-15 | A camera with internal printing system |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002296439A Division CA2296439C (en) | 1997-07-15 | 1998-07-15 | A camera with internal printing system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2595719A1 true CA2595719A1 (en) | 1999-01-28 |
Family
ID=38663530
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002595719A Abandoned CA2595719A1 (en) | 1997-07-15 | 1998-07-15 | Image transformation means including user interface |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2595719A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108737751A (en) * | 2017-04-24 | 2018-11-02 | 三星电子株式会社 | Crosstalk processing module, the method and image processing system for handling crosstalk |
| CN110036279A (en) * | 2016-12-06 | 2019-07-19 | 三菱电机株式会社 | Check device and inspection method |
| CN112561792A (en) * | 2020-12-25 | 2021-03-26 | 北京百度网讯科技有限公司 | Image style migration method and device, electronic equipment and storage medium |
| CN113554482A (en) * | 2021-07-16 | 2021-10-26 | 深圳市莱定智能科技有限公司 | Clothing intelligence customization system based on size big data |
-
1998
- 1998-07-15 CA CA002595719A patent/CA2595719A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110036279A (en) * | 2016-12-06 | 2019-07-19 | 三菱电机株式会社 | Check device and inspection method |
| CN108737751A (en) * | 2017-04-24 | 2018-11-02 | 三星电子株式会社 | Crosstalk processing module, the method and image processing system for handling crosstalk |
| CN108737751B (en) * | 2017-04-24 | 2021-11-05 | 三星电子株式会社 | Crosstalk processing module, method for processing crosstalk and image processing system |
| CN112561792A (en) * | 2020-12-25 | 2021-03-26 | 北京百度网讯科技有限公司 | Image style migration method and device, electronic equipment and storage medium |
| CN112561792B (en) * | 2020-12-25 | 2023-10-03 | 北京百度网讯科技有限公司 | Image style migration method and device, electronic equipment and storage medium |
| CN113554482A (en) * | 2021-07-16 | 2021-10-26 | 深圳市莱定智能科技有限公司 | Clothing intelligence customization system based on size big data |
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Legal Events
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| EEER | Examination request | ||
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