FR2805117A1 - Image compression digital word coding having sub assembly coding parameters selected and coded/decoded words evaluation made whilst value less than coding parameters and displaying characteristics. - Google Patents

Abstract

The digital signal coding value determination has an assembly of digital words representing the image size. A sub assembly of the coding parameters are selected (E10). The coding icons are selected and an evaluation made of the coded and decoded words made (E18) whilst the value is less than a parameter of coding selected. The characteristics representative of the modifications are then displayed (E19).

Description

The present invention generally relates to digital signal coding.

The purpose of the coding is to compress the signal, which makes it possible to transmit or memorize, respectively, the digital signal by reducing the transmission time, or the transmission rate, respectively by reducing the memory space used.

The invention lies in the field of lossy compression of digital signals.

In the particular case of a still image signal, the encoding technique commonly called JPEG (according to the English Joint Photographic Expert Group) is very easy to use. Indeed, this technique having been designed to encode natural images in color, it proposes a unique parameter to be adjusted by the user, namely the report compression on quality.

New compression techniques are now being developed, such as the so-called JPEG2000, to meet specific needs existing in a wide range of applications, such as medical imaging, computer-generated images, digital photography, imaging satellite, for example. To process very different types of image, a large number of adjustment parameters available, to adapt the treatment to each particular type of application.

However, the large number of parameters to be adjusted makes the use of such a compression technique difficult. The present invention seeks to overcome the disadvantages of the prior art by providing a method and apparatus for a user to determine the value of encoding parameters in a simple manner.

To this end, the invention proposes a method for determining the value of coding parameters for coding a set of data representative of physical quantities, characterized in that it comprises the steps of selecting a subset of coding parameters. - Evaluating the changes made to the coded and decoded data set when the value of at least one of the selected coding parameters is changed, - Displaying characteristics representative of said modifications. Correlatively, the invention relates to a device for determining the value of coding parameters for coding a set of data representative of physical quantities, characterized in that it comprises - means for selecting a subset of coding parameters means for evaluating the modifications made to the coded and decoded data set when the value of at least one of the selected coding parameters is modified, means for displaying characteristics representative of said modifications.

The invention allows a user to easily modify one or more coding parameters, and to visualize the effect of this modification. The user thus knowingly chooses the coding parameters that best suit, according to his own choice criteria, the data he wishes to code.

According to a preferred characteristic, the selected coding parameters are set to a respective predetermined initial value. The user then chooses to modify one or more coding parameters. According to another preferred feature, the method comprises the step of displaying an icon representing each of the selected parameters. Thus, the selection of coding parameters is simple for the user.

According to a preferred characteristic, the evaluation step comprises the sub-steps of - acquisition of an initial value for each of the selected coding parameters, then, for the said at least one of the selected coding parameters - acquisition of a predetermined number of values of the parameter considered, - acquisition of environmental characteristics affected by the modification of the parameter, - simulation of coding and decoding of the data set, with each of the values of the parameter considered.

According to preferred features - the coding parameters and their respective default values are contained in a first predetermined table, - the coding parameters and the respective representative values are contained in a second predetermined table, - the coding parameters and the characteristics of the coding. environment respectively affected by the modification of each parameter are contained in a third predetermined array.

These tables allow you to quickly and easily assign values to the encoding parameters, to guide the user's choice to modify these values, and to determine the changed characteristics when encoding parameters are changed.

According to a preferred characteristic, unselected coding parameters are set to a respective predetermined value.

The determination device comprises means for implementing the preceding characteristics. The invention also relates to a method of encoding a set of data representative of physical quantities, which characterizes what it comprises the determination method previously presented, which comprises a coding step which uses the previously determined coding parameters.

The invention also relates to a coding device which comprises means for covering the preceding characteristics.

The determination device, the method and the coding device have advantages similar to those previously presented. The invention also relates to a digital apparatus including the determination or coding device, or means for implementing the determination or coding method. This digital camera is for example a digital camera, a digital camcorder, a scanner, a printer, a photocopier, a fax machine. The advantages of the device and the digital device are identical to those previously exposed.

An information storage means, readable by a computer or by a microprocessor, whether or not integrated into the device, possibly removable, stores a program implementing the determination or coding method.

The features and advantages of the present invention will appear more clearly on reading a preferred embodiment illustrated by the accompanying drawings, in which - Figure 1 is an embodiment of a device embodying the invention - FIG. 2 represents a coding device according to the invention and a corresponding decoding device, FIG. 3 is a coding method embodiment of the invention, FIG. 4 is a table containing coding parameters and FIG. their respective default values; - FIG. 5 represents a display of coding parameters according to the present invention; - FIG. 6 represents a table containing the coding parameters and their respective representative values; FIG. 7 represents a table containing the parameters of coding and associated environmental characteristics, - Figure 8 represents a display encoding parameters and parameter selection according to the present invention.

According to the embodiment chosen and represented in FIG. 1, a device embodying the invention is for example a microcomputer 10 connected to different peripherals, for example a digital camera 107 (or a scanner, or any means of acquisition or image storage) connected to a graphics card and providing information to be processed according to the invention.

Device 10 comprises a communication interface 112 connected to a network 113 capable of transmitting digital data to be processed or conversely transmitting data processed by the device. The device 10 also comprises a storage means 108 such as for example a hard disk. It also includes a disk drive 110 110. This disk 110 may be a diskette, a CD-ROM, or a DVD-ROM, for example. The disk 110 as the disk 108 may contain processed data according to the invention as well as the program or programs implementing the invention once read by the device 10, will be stored in the hard disk 108. Alternatively, the program allowing the device to implement the invention, can be stored in read-only memory 102 (called ROM in the drawing). In the second variant, the program can be received to be stored in a manner identical to that previously described via the communication network 113.

The device 10 is connected to a microphone 111. The data to be processed according to the invention will in this case be an audio signal.

This same device has a screen 104 for viewing the data to be processed or to interface with the user can thus set certain processing modes, using the keyboard 114 or any other means (eg mouse).

The CPU 100 (called the CPU in the drawing) executes the instructions relating to the implementation of the invention, instructions stored in the read-only memory 102 or in the other storage elements. During power-up, the processing programs stored in a non-volatile memory, for example the ROM 102, are transferred into RAM RAM 103 will then contain the executable code of the invention and registers to store the variables necessary for the implementation of the invention.

More generally, an information storage means, readable by a computer or by a microprocessor, whether or not integrated into the device, possibly removable, stores a program implementing the coding, transmission and respectively decoding method.

The communication bus 101 allows communication between different elements included in the microcomputer 10 or connected to it. representation of the bus 101 is not limiting and in particular the central unit 1 is able to communicate instructions to any element of the microcomputer directly or via another element of the microcomputer With reference to FIG. Embodiment of encoding device 3 according to the invention is intended to encode a digital signal in the compress. The coding device is integrated in a device, which for example digital camera, a digital video camera, a scanner, printer, a photocopier, a fax machine, a database management system, or a computer.

The device according to the invention comprises a signal source 30, image signal IM, whether it is a still image or an image sequence. In general, the signal source either contains the digital signal, for example a memory, a hard disk or a CD-ROM, or converts an analog signal into a digital signal, and is for example an analog video camera associated with an analog-digital converter. The image source 30 generates a series of digital samples representing an IM image. The image signal IM is a series of digital words, for example bytes. Each byte value represents a pixel of the IM image, here at 256 gray levels or in color.

An output signal source 30 is connected to a circuit 31 for determining and controlling coding parameters.

The circuit is connected to a display circuit 310 which makes it possible to display coding parameters, the image to be coded, and coding and decoding simulation results.

The present invention more particularly relates to the circuits 31 and 310 and their operation, which will be detailed hereinafter.

The circuit is connected to a coding circuit 33, which performs a coding known in itself the image. For example, the coding used is in accordance with the JPEG2000 standard (in English Joint Photographic Expert Group), in the course of standardization and whose description is available via the Internet at the following address: http: //www.jpeg.orglcd 5444-1.pdf. The coding includes quantization and entropy coding as an arithmetic coding or Huffman coding.

The coding circuit 33 is connected to a coded data processing circuit 34 for transmitting the compressed FC file containing the coded picture. The circuit 34 stores and / or transmits the compressed file FC to a decoding device The decoding device 4 receives the coded data and then performs operations opposite to those of the coding circuit 33. The decoding circuit 4 is connected to the circuit 40 of FIG. use of the decoded data, for example to view decoded picture IM '.

FIG. 3 represents an embodiment of an image coding method, according to the invention. This method is implemented in the coding device and comprises steps E10 to E20.

The method implemented in the form of an algorithm that can be stored in full in part in any information storage means capable of cooperating with the microprocessor. This storage means is readable by a computer or a microprocessor. This storage means is integrated or device, and can be removable. For example, it may comprise magnetic tape, a floppy disk or a CD-ROM (compact disk with frozen memory).

Step E10 is the acquisition of a subset of coding parameters that will be adjusted according to the invention. According to a first embodiment, all the coding parameters are regulated by the invention. According to a second coding mode, certain parameters are automatically set are set to a respective predetermined value, and the others are set according to the invention.

The main coding parameters used in JPEG2000 are shown in Figure 4. This shows a table of coding parameters and their respective default values. This table is stored in a memory of the device implementing the invention.

The filter <I> Filter </ I> parameter represents the filter used in the wavelet transform. This filter is by default the 9l7 filter.

Parallelism <I> Parallelism </ I> represents the use of parallel processing capabilities in coding and decoding. According to the JPEG2000 standard, the bitstream can be organized to facilitate parallel processing. The default value of this parameter is no which means that does not take into account the parallelism.

Flow rate <I> parameter </ I> represents the desired coding rate. is at no value, it means compression is driven by quality. The default value for this parameter is 1.0 bit per pixel.

The <I> Quality </ I> parameter represents the coding quality. Its default is none, which means compression is rate-driven, by default.

The <I> decomposition </ I> parameter represents the type of decomposition into frequency sub-bands. Its default value is a dyadic decomposition according to which each low frequency subband is divided into four subbands. The decomposition may also be of the wavelet packet type, wherein the high frequency sub-bands are also decomposed into four sub-bands. The <I> Reversibility </ I> reversibility parameter is a logical value that holds true if the wavelet transform is implemented using the integer arithmetic, and false if the wavelet transform is implemented using number arithmetic. floating point.

The <I> </ I> Levels <I> </ I> parameter of resolution levels is an integer equal to the number of resolution levels in the discrete wavelet transformation. Its default value is five.

The <I> Tile </ I> parameter represents the size of the tiles that can be used to divide the image into sub-frames as it decompresses. This two-dimensional parameter determines the height and width of the tiles. Its default is no tile meaning the image is not divided, or it is considered to be the only tile.

The Cell <I> Cell </ I> parameter represents the size of cells that can be formed in the tiles. The cells are sub-images overlapping two by two on a row and a column, to avoid discontinuities along the edges of the cells during image reconstruction. This parameter is two-dimensional and determines the height and width of the cells. The default value is 512, which means that each cell has a height of 512 pixels.

The Block <I> Block </ I> parameter represents a block size. After wavelet transform, the wavelet coefficients are quantized and entropically encoded. For this, they are considered block by block. This parameter is two-dimensional and represents the height and width of the blocks. The default value of this parameter is (64, 64).

The weighting <I> Weighting </ I> parameter represents a visual weighting that combines different magnitudes with different sub-bands to match the human eye. For example, lower weights are associated with higher frequency sub-bands, because the human eye is less able to identify errors in high frequencies. The default is no weighting, which means that the same weight is assigned to all subbands. The Masking <I> Masking </ I> parameter represents the use or otherwise of a visual masking, whose function is to reduce a visual error, while increasing a numerical error. Visual masking gives good results for high compression rates. The default value of this parameter is no.

Parameter <I> Protection </ I> represents the error protection that can be used when the compressed image is to be transmitted over a noisy channel. The default value of this parameter is no protection.

The next step E11 is the acquisition of an initial value for each coding parameter included in the previously determined subset. This step consists in reading in memory a predetermined default value for each coding parameter.

The next step E12 is the display of an icon representative of each of the parameters included in the previously determined subset, the screen intended for the user.

An icon is a graphical or textual representation of a parameter, function, or object.

In Figure 5, each icon is in the form of a button with the name of the parameter and the current value thereof.

in addition, is displayed a representation of the image to be encoded, and an icon for starting the coding of the image when the user selects this icon.

The next step E13 is a test to determine if the coding icon has been selected by the user. The selection is conventionally carried out thanks to a mouse.

When the response is positive, step E13 is followed by step E14 coding the image with the current values of the coding parameters. When the answer is negative to the test of the step, then this step is followed by the step E15 which is a test to determine if a parameter icon has been selected. Here again, the selection is conventionally carried out thanks to a mouse. If the result of the test is negative, then this step is followed by step E13 previously described.

If the answer is positive in step E15, then this step is followed by the step which is the acquisition of a set of predetermined values for the parameter in question.

Fig. 6 shows an array containing predetermined values for each coding parameter. The predetermined values are representative of the parameters, i.e., they are distributed within the range of typical values of each parameter. They are limited in number, here in number of two or three. This table stored in a memory of the device implementing the invention.

The next step E17 is the acquisition of the environment characteristics that are affected by the modification of the current selected encoding parameter.

By environment characteristic is meant here - the decoded image, - characteristics extracted from the decoded image: quality, height width, energy, for example, - characteristics extracted from the software and hardware environment, such as the memory used during the coding, during the decoding, coding time, decoding, for example.

For each coding parameter, a predetermined relationship exists between the parameter and one or more environment characteristics. FIG. 7 represents a table containing the coding parameters with which environment characteristics are respectively associated. This table is stored in a memory of the device implementing the invention and serves to know the environment characteristics that are affected by the modification of each of the coding parameters.

The next step E18 is the coding and decoding simulation of the image, for each of the values representative of the selected parameter. For example, in Figure 8, flow rate, which has three representative values, has been selected. Three simulations are thus performed. During each of them, the six environmental characteristics affected by the rate parameter change are measured.

In the next step E19, the values of the environment characteristics are displayed for each simulation, as well as the value of the flow rate. Thus, in FIG. 8, the decoded image, quality, size of the memory used for the coding, coding time, size of the memory used for the decoding, decoding time, bit rate, are displayed for the three simulations. additional icon allows the user to select one of the current parameter values.

 Step E20 is the selection of one of the values of the current parameter. This value becomes the current value of the processed parameter. This step is followed by step E13 previously described.

The user can thus set step by step each coding parameter, while viewing the result of his choices.

Of course, the present invention is not limited to the embodiments described and shown, but encompasses, on the contrary, any variant within the scope of the skilled person.

Claims (5)

<B> <U> CLAIMS </ U> </ B> A method for determining the encoding parameter value for encoding a set of data representative physical quantities, characterized in that it comprises the steps - selecting (E10) a subset of coding parameters, - evaluation (E18 ) changes made to the coded and decoded data set when the value of at least one of the selected coding parameters is changed, -display (E19) of characteristics representative of said changes. 2. Method according to claim 1, characterized in that the selected coding parameters are set to a respective predetermined initial value. 3. Method according to claim 1 or characterized in that it comprises the step (E12) of displaying an icon representing each of the selected parameters. 4. Method according to any one of claims 1 to 3, characterized in that the evaluation step comprises the substeps - acquisition (E11) of an initial value for each of the selected coding parameters, then, for said at least one of the selected coding parameters - acquisition (E16) of a predetermined number of values of the considered parameter, - acquisition (E17) of environment characteristics affected by the modification of the parameter, - simulation (E18) of encoding and decoding of the data set, with each of the values of the parameter under consideration. 5. Method according to any one of claims 1 to 4, characterized in that the coding parameters and their respective default values are contained in a first predetermined table. Method according to one of Claims 1 to 5, characterized in that the coding parameters and the respective representative values are contained in a second predetermined table. Method according to one of Claims 1 to 6, characterized in that the coding parameters and the environmental characteristics respectively affected by the modification of each parameter are contained in a third predetermined table. Method according to one of Claims 1 to 7, characterized in that unselected coding parameters are set to a respective predetermined value. A method of encoding a set of data representative physical quantities, characterized in that it comprises the determination method according to any one of claims 1 to 8, and in that comprises coding step (E14) which uses the coding parameters previously determined. 10. A device for determining the value of coding parameters for coding a set of data representative of physical quantities, characterized in that it comprises - means (31) for selecting a subset of coding parameters; means (31) for evaluating the modifications made to the coded and decoded data set when the value of at least one of the selected coding parameters is modified, - means (310) for displaying characteristics representative of said modifications. 11. Device according to claim 10, characterized in that is adapted to put the selected coding parameters to a respective predetermined initial value. Device according to claim 10 or 11, characterized in that it comprises means (310) for displaying an icon representative of each of the selected parameters. 13. Device according to any one of claims 10 to 12, characterized in that the evaluation means (31) are adapted to - acquire an initial value for each of the selected coding parameters, then for said at least one selected coding parameters - acquiring a predetermined number of values of the considered parameter, - acquiring environment characteristics affected by the parameter modification, - simulating the coding and decoding of the data set, with each of the values of the parameter considered. . 14. Device according to any one of claims 10 to 13, characterized in that it comprises memory means (103) for storing a first predetermined table containing the encoding parameters and their default value. 15. Device according to any one of claims 10 to 14, characterized in that it comprises memory means (103) for storing a second predetermined table containing the coding parameters and respective representative values. 16. Device according to any one of claims 10 to 15, characterized in that it comprises memory means (103) for storing a third predetermined table containing the coding parameters and environmental characteristics respectively affected by the modification. of each parameter. 17. Device according to any one of claims 10 to 16, characterized in that it is adapted to put unselected coding parameters to a respective predetermined value. 18. Encoding device data set representative of physical quantities, characterized in that it comprises the determination device according to any one of claims 10 to 17, and in that it comprises coding means (33) using the encoding parameters previously determined. 19. Determination device according to any one of claims 10 to 17, characterized in that the selection and evaluation means are incorporated in a microprocessor (100), a read-only memory (1 comprising a program for processing the data, and a random access memory comprising registers adapted to record modified variables during the execution of said program 20. Coding device according to claim 18, characterized in that the selection, evaluation and coding means are incorporated in the microprocessor ( 100), - read-only memory (102) comprising a program for processing the data, and - a random access memory (103) comprising registers adapted to record modified variables during the execution of said program. ) of a digital image, characterized in that it comprises means adapted to implement the method according to any of the claims 1 to 9. 22. Apparatus for processing (10) a digital image, characterized in that it comprises the device according to any one of claims 10 to 20. Digital photographic apparatus, characterized in that it comprises Means adapted to implement the method according to any one of claims 1 to 9. Digital camera, characterized in that it comprises device according to any one of claims 10 to 20. 25. Digital camcorder, characterized in that it comprises means adapted to implement the method according to any one of claims 1 to 9. 26. Digital camcorder, characterized in that it comprises the device according to any one of claims 10 to 20. 27. Scanner, characterized in that it comprises means adapted to implement the method according to any one of claims 1 to 9. Scanner, characterized in that it comprises the device according to one that any digital printing machine, characterized in that it comprises means adapted to implement the method according to any one of claims 1 to 9. 30. Digital printer, characterized in that it comprises the device according to any one of claims 10 to 20. 31. A digital photocopier, characterized in that it comprises means adapted to implement the method according to any one of claims 1 to 9. 32. A digital photocopier, characterized in that it comprises the device according to any one of claims 10 to 20. 33. Digital fax machine, characterized in that it comprises means adapted to implement the method according to any one of claims 1 to 9. 34. Digital fax machine , characterized in that it comprises the device according to any one of claims 10 to 20.