GB2291553A - Digital image compression system - Google Patents
Digital image compression system Download PDFInfo
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- GB2291553A GB2291553A GB9414166A GB9414166A GB2291553A GB 2291553 A GB2291553 A GB 2291553A GB 9414166 A GB9414166 A GB 9414166A GB 9414166 A GB9414166 A GB 9414166A GB 2291553 A GB2291553 A GB 2291553A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
- H04N19/93—Run-length coding
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- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Compression Or Coding Systems Of Tv Signals (AREA)
- Compression Of Band Width Or Redundancy In Fax (AREA)
Abstract
The digital image compression system compares current and preceding digital images on a pixel-by-pixel basis using an exclusive-or operation to identify the differences therebetween. The result of the exclusive-or operation between the two images is then compressed using a loss-less compression algorithm (e.g. run length encoding) for subsequent processing or storage. Compression of selected portions of the current and preceding image is also disclosed. <IMAGE>
Description
DIGITAL IMAGE PROCESSING SYSTEM AND METHOD
The present invention relates to a system and method of compressing and decompressing a sequence of digital images.
In order to be able to efficiently store or transmit a sequence of digital images it is desirable to compress the sequence such that the amount of data constituting the compressed sequence is less than that constituting the original sequence and to still be able to recover the original sequence from the compressed sequence.
Such compression can be utilised in, for example, video conferencing systems, video telephones or collaborative working systems.
The users of such systems communicate both aurally and visually. The ability to see the other party gives a more natural and interactive quality to the communication and allows the parties to more confidently evaluate their counter-part. In such systems there is a need to exchange large amounts of data to keep the displayed images of the parties updated. Further, a sequence of compressed digital images requires less bandwidth to transmit as compared to a sequence of complete digital images.
Digital image compression also finds application in storing image data on mass storage media, such CD-ROMS or magnetic storage media, to reduce the amount of storage space required to record a sequence of digital images.
Contiguous images generated, by image capture apparatus, such as a video camera, during a video conference or derived from a mass storage media are often substantially similar and vary only by small amounts.
Accordingly, attempts have been made use this property in order to reduce the amount of data which needs to be exchanged to support a video conference or to record a sequence of digital images. The reduction is achieved by exchanging or storing, for example, only selective areas of the digital images or eliminating the areae which are, as between contiguous images, constant.
EP 0 221 743 discloses a method and system for compressing television video signals for digital transmission while still allowing full motion video to be supported. Successive digital video images are compared, on a pixel-by-pixel basis, using a value derived from the colour components of each pixel. If the comparison indicates that the difference between compared pixels is greater than a predetermined value, then that particular pixel is transmitted by a control computer to appropriate receiving apparatus.
US 4,996,594 discloses a dynamic image transmission system which stores in memory image data relating to successive digital images. A dynamic portion of an input digital image containing movement is extracted by comparing the current image with image data of successive images. A transmission means transmits the extracted part of the input digital image to appropriate receiving apparatus.
Both of the above prior art systems require complex calculations to be performed in order to determine which region of an input image should be retained and transmitted and which portion should be discarded.
Accordingly the present invention provides a method for compressing a sequence of digital images comprising, for a current digital image and the preceding digital image, the steps of performing an exclusive-or operation between the current digital image and the preceding digital image to produce an intermediate digital image, and encoding the intermediate digital image, using a compression algorithm, to produce an encoded digital image.
By using an exclusive-or operation the present invention provides a very simple and fast method for compressing or decompressing a sequence of digital images. In contrast to the prior art the present invention obviates the need to perform complex arithmetic operations in order to compress a sequence of digital images. The exclusive-or operation is very fast as compared to the arithmetic operations of the prior art systems.
Further, an exclusive-or operation between two digital images which are substantially similar but for minor variations results in data having a large number of consecutive zeros and a small number of ones. The ones represent the differences between the two digital images.
Encoding techniques exist which are suitable for use with data having such large runs of zeros. Such encoding techniques can be found in, for example, "Data Compression Techniques and Applications, Hardware and Software Considerations", by Gilbert Held, published by John Wiley & BR<
Son, second edition. As it is desirable to decode an encoded digital image to reproduce the original digital image the present invention uses a loss-less encoding technique such as run length encoding to encode a digital image thereby allowing the complete original digital image to be recovered.
The data representing the digital images can take many forms. For example, the digital image may comprise many independently addressable bits having one of two possible states. Accordingly, the exclusive-or operation can be performed on a bit-by-bit basis to identify the differences between the current digital image and the preceding digital image. Alternatively, the digital image may be colour and comprise pixels each having three bytes representing the RGB or YUV components thereof. The exclusive-or operation may accordingly be conducted using corresponding data derived from the three colour components of the pixels of the images. Therefore, the present invention can be utilised regardless of the number of bits used to represent the elements of a digital image.By using the method of the present invention in a screen sharing or collaborative working environment, a significant reduction in the amount screen data or bandwidth required to update the screens thereof can be realised. This advantage comes about as a consequence of only a small portion of the screen or a window in such an environment changing at any one time. The remainder of the screen or the area outside the window currently of interest generally remains unchanged.
Accordingly, when successive screens are subjected to an exclusive-or operation a significant number of zeros will result.
However, even more advantageously the present invention also provides a method for compressing a sequence of digital images wherein the exclusive-or operation is performed between selected portions of the current digital image and the preceding digital image, the portions being selected from the same respective locations in the current digital image and the preceding digital image. The selected portions cf the current and preceding digital images can correspond to a window which has been updated in a screen sharing or collaborative working environment as opposed to the whole screen.
Having compressed a sequence of digital images it is desirable to be able to reconstruct the original sequence from the compressed sequence.
Accordingly the present invention provides a method for decompressing a sequence of encoded digital images comprising, for each encoded digital image, the steps of decoding the encoded digital image to produce an intermediate digital image, producing a decompressed digital image by performing an exclusive-or operation between the intermediate digital image and the preceding decompressed digital image.
The present information also provides a system for compressing a sequence of digital images comprising, for a current digital image and the preceding digital image, means for performing an exclusive-or operation between the current digital image and the preceding digital image to produce an intermediate digital image, and means for encoding the intermediate digital image, using a compression algorithm, to produce an encoded digital image.
The present invention further provides a system for decompressing a sequence of encoded digital images comprising, for an encoded digital image, the steps of decoding the encoded digital image to produce an intermediate digital image, producing a decompressed digital image by performing an exclusive-or operation between the intermediate digital image and the preceding decompressed digital image.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
figure 1 shows schematically a digital image processing system according to the present invention,
figure 2 schematically illustrates image compression according to the present invention,
figure 3 schematically illustrates image decompression according to the present invention,
figure 4 shows a flow diagram illustrating image compression according to the present invention,
figure 5 shows a flow diagram illustrating image decompression according to the present invention.
Figure 1 illustrates schematically a digital image processing system DIPS for processing a sequence of digital images II to Ix. The system comprises a memory M for storing current In and preceding In-l digital images, a processor P capable of accessing, via a bus B, the contents of the memory M and performing an exclusive-or operation between two given operands, and input (I/P) and output (O/P) interfaces for respectively receiving the sequence of digital images and outputting the compressed sequence of digital images. The processor comprises five registers Rl to Rg. Registers R1 to R4 contain respective pointers P1, P2,
P3 and P4.The pointers P1, P2, P3 and P4 are respectively used to determine where in the memory M the following are stored: the first data unit of the preceding digital image In-i, the first data unit of tulle current digital image In, the first data unit of the result of the exclusive-or operation between the current In and preceding Inl digital images or the result of decoding an encoded digital image (the intermediate digital image IDI), and the first data unit of the result of the encoded or decoded digital image EDI. Register R5 is used as a temporary register to exchange the contents of the other registers R1 to
R4. The system DIPS can operated in either image compression or image decompression modes.
Image compression is effected as follows. At initialisation of the system DIPS, the memory contents are reset and the pointers P1 and P4 loaded with predetermined memory addresses. The first digital image I] is received via the input interface I/P and is stored in memory M at an address determined by pointer P1. The first digital image II is also output via the output interface O/P for further processing. The second digital image I2, is received via the input interface I/r and is stored in memory M starting at an address determined by pointer P2.The processor P performs an exclusive-or operation between the second I2 or current digital image In and the first I1 or preceding digital image In to produce an intermediate digital image IDI. The intermediate digital image IDI is stored in memory M starting at an address pointed to by pointer P3. The exclusive-or operation between the first II and second I2 digital images is effected on a pixel-by-pixel basis. As between the first digital image Ii and the second digital image I2 the operands of the exclusive-or operation are taken from corresponding locations in the images.
As a consequence of the exclusive-or operation the intermediate digital image IDI contains data which are, in the case where compared pixels are identical, zero or, in the case where the compared pixels are different, some other value. The data of the intermediate digital image
IDI which are non-zero represent the differences between the first 11 and second I2 digital images.
The processor P encodes the intermediate digital image IDI using a loss-less algorithm, such as run length encoding, Huffman encoding or
LZW, to produce an encoded digital image EDI. The encoded digital image
EDI is stored in memory starting at an address determined by pointer P4.
The encoded digital image EDI can then be output via output interface O/P for further processing. The output operation can be effected using either the processor P or direct memory access techniques as are well known in the art.
Having produced an encoded digital image EDI the contents P] and P2 of registers R1 and R2 are exchanged such that the first digital image I is discarded and the third digital image 13 is loaded into memory M.
Pointer P1 is saved in register R5. Pointer P1 is set to equal pointer P2 thereby discarding the first digital image Il and retaining the second digital image I2. The second digital image 12 thereby becomes the preceding digital image Inl relative to the third digital image 13. The pointer P2 is set to equal the contents of register R; and the third digital image I3 is stored in memory M starting at the location determined by pointer P2.Therefore, the first digital image II is discarded or over-written by the third digital image 13, the second digital image is pointed to by pointer P] and the third digital image is pointed to by pointer P. The system DIPS processes the second 12 and third I3 digital images as per images II and I2. The encoded digital image EDI is then output via output interface 0/P for further processing.
Therefore, generally, the system processes successive digital images as follows. A current digital image In and a preceding digital image In1 are stored in the memory M starting at predetermined locations determined by pointers P2 and P1 respectively. The processor P performs an exclusive-or operation between the current digital image In and the preceding digital image 1n-1 to produce an intermediate digital image IDI.
The images In and Inl are subjected to the exclusive-or operation on, for example, a pixel-by-pixel basis. As between the current digital image In and the preceding digital image Inl the operands of the exclusive-or operation are taken from corresponding locations. The intermediate digital image IDI is stored in memory M starting at a location determined by the contents of register R3.
The processor P encodes the intermediate digital image IDI using a loss-less algorithm such as run length, Huffman, LZW or other suitable encoding to produce an encoded digital image EDI. The encoded digital image EDI is stored in memory M starting at a location determined by pointer P4. The encoded digital image EDI is then output via the output interface O/P for further processing. It can be seen from figures 2 and 3 that a very simple compression algorithm has been used for illustrative purposes. The encoding technique operates by identifying runs of, for example, contiguous ones or zeros and transmitting in their place an indication of the number of contiguous ones or zeros in a contiguous run together with an indication of the data constituting the run. The first number indicates the number of contiguous occurrences of the second number in the intermediate digital image IDI. Therefore, the first thirteen bits of the intermediate digital image IDI are zero. The next three bits are all one etc. The encoding technique used is a sample form of run length encoding. Such encoding techniques are well known within the art and can be found in the above mentioned book entitled "Data
Compression". Further, such encoding techniques can be implemented using either software or dedicated hardware. Although the illustrative encoding technique transmits the type of data constituting the run as well as the number of units of that type of data, it can usually be assumed that the first data units of the current In and preceding 1n-1 digital images are identical.Accordingly, the efficiency of the encoding can be increased by transmitting only the numbers representing the length of each run and assuming that the first data units of the current In and preceding Inl digital images are always identical and would always result in the first data unit of the encoded digital image
EDI being zero. Therefore, the second number of the encoded digital image EDI will represent the beginning of a run of ones and so on alternating between zero and one for each new number of the encoded digital image EDI.
Still referring to figure 1, image decompression is effected as follows. At initialisation of the system DIPS, the memory contents are reset and the registers R! and R4 loaded with predetermined memory addresses. The first digital image Ii is received via the input interface I/F and is stored in memory M starting at an address determined by pointer P1. As the first digital image Ii is complete it is also output via the output interface O/P for further processing. An encoded digital image EDI, representing the encoded result of the exclusive-or operation between the first II and second I2 digital images, is received via the input interface I/P and is stored in memory M starting at an address determined by pointer P4.The encoded digital image EDI is decoded to produce an intermediate digital image IDI. The decoding technique used is the inverse of the encoding technique. The first number of the encoded digital image EDI indicates ho many contiguous occurrences there are of the second number. In the example shown it can be seen that the first thirteen data units of the intermediate digital image are zero and the next three data units are one etc. The intermediate digital image IDI is stored in memory M starting at the address indicated by pointer P3. The processor P performs an exclusiveor operation between the intermediate digital image IDI and the first digital image I1 to produce the second digital image 12 or a decompressed digital image.The second digital image I2 is stored in memory M starting at an address pointed to by pointer P2. The second digital image I2 is also output via output interface O/P for further processing.
Having produced the second digital image I2 the contents P1 and P2 of respective registers P1 and F2 are exchanged such that the first digital image Il is discarded. Pointer P] is saved in register Rg.
Pointer P1 is set to equal pointer P2 thereby discarding the first digital image Il and retaining the second digital image 12. The second digital image 12 thereby becomes the preceding decompressed digital image In-] relative to the third digital image I7. The pointer P2 is set to equal the contents of register Rg. A further encoded digital image EDI is received via input interface I/P and stored in memory M starting at an address determined by pointer P4. The encoded digital image EDI is decoded to produce an intermediate digital image IDI. The intermediate digital image IDI is stored in memory M starting at an address determined by pointer P3.The processor performs an exclusive-or operation between the intermediate digital image IDI and the preceding decompressed digital image In-1 to produce the current In or third I3 digital image. The current In or third I3 digital image is stored in memory M starting at an address indicated by pointer P2. Therefore, the first digital image Ii is discarded or over-written by the third digital image I3, the second digital image is pointed to by pointer P] and the third digital image is pointed to by pointer P2. The current In1 or third I3 digital image is output via output interface O/P for further processing.
Therefore, generally, the system processes successive encoded digital images as follows. A received encoded digital image EDI is stored in memory M starting at a location determined by pointer P4. The processor P decodes the received encoded digital image EDI to produce the intermediate digital image IDI. The intermediate digital image IDI is stored in memory M starting at the address indicated by pointer P3. The processor P performs an exclusive-or operation between the intermediate digital image IDI and the preceding decompressed digital image 1n-i to produce a current digital image In. The current digital image is stored in memory M starting at a location determined by pointer P2. The current digital image In is also output via output interface O/P for further processing.
Referring to figure 2, there is shown schematically the operation of a digital image processing system according the present invention.
The current digital image In and the preceding digital image 1n-1 are compared using an exclusive-or XOR operation to produce an intermediate digital image IDI. It can be seen that the preceding digital image 1n-i depicts a person without a hat and the current digital image In depicts a person with a hat and having one arm raised. The intermediate digital image IDI depicts only a hat and a raised arm. The intermediate digital image IDI is encoded using a loss-less encoding algorithm to form the encoded digital image EDI. The amount of data constituting the encoded digital image EDI is significantly reduced as a consequence of the exclusive-or operation together with the encoding.
In figure 3 there is shown schematically digital image decompression according to the present invention. An encoded digital image EDI is decoded to form an intermediate digital image IDI depicting only a hat and an arm. An exclusive-or operation is performed between the intermediate digital image IDI and the preceding digital image In1 comprising a figure with neither a hat nor a raised arm, to produce the current digital image In. The current digital image In comprises a figure with both a hat and a raised arm.
Referring to figure 4 there is shown a flow diagram representing the stages of image compression according to the present invention. At step 400 the current digital image is loaded into memory. Step 410 checks to determine whether or not the loaded current digital image is the first or initial digital image. If so, step 420 outputs the complete current digital image without any compression or encoding and control jumps to step 460. If not, an exclusive-or operation is performed between the current digital image and the preceding digital image at step 430 to produce an intermediate digital image. The intermediate digital image is encoded using a loss-less encoding technique at step 440 to produce an encoded digital image. The encoded digital image is output for further processing at step 450.The contents of registers Rl and R2 are exchanged using register R5 at step 460 thereby discarding the preceding digital image and making the current digital image the preceding digital image. Step 470 checks to determine whether or not there are any more digital images in the sequence to be processed. If so, the processing of the digital images continues at step 400. If not, the processing of digital images terminates.
Referring to figure 5 there is shown a flow diagram representing the stages of image decompression according to the present invention. At step 500, because the initial digital image received has not been encoded and is complete it is output for further processing. At step 510 an encoded digital image is loaded into memory. The encoded digital image is decoded at step 520 to produce an intermediate digital image. An exclusive-or operation is performed between the intermediate digital image and the preceding decompressed digital image at step 530 to produce the current digital image. The current digital image- is output for further processing at step 540. The pointers P] and P2 are exchanged at step 550 thereby making the current digital image the preceding decompressed digital image.At step 560 a check is made to determine whether or not there are further encoded digital images to be processed.
If so, processing of encoded digital images continues at step 500. If not, processing of encoded digital images terminates.
The encoded digital image EDI can be used in many different ways.
For example, it could be transmitted, via a communication interface, over a communication network to a plurality of video conferencing systems or video telephones. The bandwidth required to transmit such an encoded digital image is significantly less than that required to transmit a complete digital image which has not been so compressed. The sequence of digital images in a video conferencing terminal or video telephone are generated by suitable image capture apparatus such as a digital video camera or an analogue video camera together with an analogue-to-digital converter. The current digital image above can be loaded into memory on a video adapter card or other suitable video RAM for subsequent output on a video display terminal.
If an embodiment were used in a video conferencing system or video telephone to allow a reduced bandwidth to be utilised for communication it is preferable that periodically a complete digital image is transmitted to the other parties to the conference. Periodically transmitting such a complete digital image obviates the effects of propagation errors. Propagation errors arise when an encoded digital image becomes corrupted during, for example, transmission to another video telephone or video conferencing system. The corruption, as a consequence of the exclusive-or operation, is continually maintained.
Accordingly, replacing the current digital image with a complete digital image, without using an exclusive-or operation, eradicates any corruptions which may be present.
Alternatively, the embodiment can be utilised to store on, for example, a CD-ROM a sequence of digital images which may represent a film or part of a multi-media presentation. The first digital image of such a sequence is stored in its entirety and successive digital images are stored in a compressed form described above.
The digital image processing system can be realised using either dedicated hardware such as a memory in conjunction with a digital signal processor together with appropriate software for the digital signal processor or using a general purpose computer such as an IBM PS/2 with, for example, a graphics accelerator card such as an XGA adapter or an
Image Adapter card. The "IBM OS/2 Presentation Manager Programming
Reference", vol.1, page 4-19 et seq, describes a GpiBitBlt function which, in conjunction with the general purpose computer and graphics accelerator card, can be used to realise an embodiment of the present invention. The parameters of the GpiBitBlt function, Target, Source,
Count, Points and Rop are used to perform the exclusive-or operation between two digital images.Target represents the presentation space handle of one image or the preceding digital image InI. Source represents the presentation space handle of a second image or the current digital image In. Count is set to 3 thereby indicating that the Source and Target rectangles containing the current In and preceding Inl digital images respectively are the same size. Points specifies the bottom-left and top-right corners of the preceding In] and current In digital images in terms of Target and Source device co-ordinates respectively. Rop determines the final value of each pel in the Target rectangle. Rop in the present invention is set to perform the exclusive-or operation between the preceding digital image 1n-i' pointed to by Target, and current digital image 1n pointed to by Source.Accordingly, when successive digital images are loaded into the memory of the computer the
GpiBitBlt command is used to perform the exclusive-or operation required by the present invention. The Target rectangle, after using the
GpiBitBlt function, contains the intermediate digital image IDJ. The intermediate digital image IDI can then compressed using a loss-less compression algorithm to produce the encoded digital image.
The teaching of the present invention can be further utilised in a collaborative working environment. Within such an enTironment multiple applications may be simultaneously executing in respective windows. A plurality of such windows can be simultaneously displayed on a screen of a collaborative worlring system. During a collaborative working session the parties thereto may exchange information or alter the data contained in a single one of the plurality of displayed windows thereby leaving the remainder of the screen unchanged. The present invention can therefore be utilised to reduce the amount of information Which has to be exchanged between collaborative working terminals in order to update the screens or windows of such terminals. An exclusive-or operation between a current screen, containing the updates thereto, and a previous screen, without the updates, would result in data identifying only the differences between the two screens together with a significant number of zeros. The resultant data is then compressed using a loss-less compression algorithm and transmitted to another collaborative working terminal in the conventional manner. At the receiving collaborative working terminal, the compressed data is decompressed as per the present invention and an exclusive-or operation is performed between the decompressed data and the current screen display said terminal or appropriate portion thereof thereby updating the information on the screen of said terminal.
Claims (8)
1. A method for compressing a sequence of digital images (I1 to Ix) comprising, for a current digital image (In) and the preceding digital image (Inl) the steps of performing an exclusive-or operation between the current digital image (In) and the preceding digital image (inn) to produce an intermediate digital image, and encoding the intermediate digital image, using a compression algorithm, to produce an encoded digital image.
2. A method as claimed in claim 1, further comprising the step of selecting portions of the current digital image (In) and the preceding digital image (Inl) the portions being selected from the same respective locations in the current digital image (In) and the preceding digital image (Inl) and wherein the exclusive-or operation is performed between said selected portions.
3. A method for decompressing a sequence of encoded digital images (II to Ix) comprising, for each encoded digital image, the steps of decoding the encoded digital image to produce an intermediate digital image, producing a decompressed digital image (In) by performing an exclusive-or operation between the intermediate digital image and the preceding decompressed digital image (inn).
4. A method as claimed in any preceding claim, further comprising the step of obtaining the sequence of digital images (Il to Ix) from a mass storage medium.
5. A method as claimed in any of claims 1 to 3, further comprising the step of obtaining the sequence of digital images (J1 to Ix) from image capture apparatus.
6. A system for compressing a sequence of digital images (I1 to Ix) comprising, for a current digital image (In) and the preceding digital image (Ini), means for performing an exclusive-or operation between the current digital image (In) and the preceding digital image (In-l) to produce an intermediate digital image, and means for encoding the intermediate digital image, using a compression algorithm, to produce an encoded digital image.
7. A system as claimed in claim 6, further comprising means for selecting portions of the current digital image (In) and the preceding digital image (Inl), the portions being selected from the same respective locations in the current digital image (In) and the preceding digital image (inn) and wherein the exclusive-or operation is performed between said selected portions.
8. A system for decompressing a sequence of encoded digital images (I] to Ix) comprising, for an encoded digital image, the steps of decoding the encoded digital image to produce an intermediate digital image, producing a decompressed digital image (In) by performing an exclusive-or operation between the intermediate digital image and the preceding decompressed digital image (ins).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9414166A GB2291553A (en) | 1994-07-13 | 1994-07-13 | Digital image compression system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9414166A GB2291553A (en) | 1994-07-13 | 1994-07-13 | Digital image compression system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9414166D0 GB9414166D0 (en) | 1994-08-31 |
| GB2291553A true GB2291553A (en) | 1996-01-24 |
Family
ID=10758288
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9414166A Withdrawn GB2291553A (en) | 1994-07-13 | 1994-07-13 | Digital image compression system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2291553A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2332321A (en) * | 1997-12-05 | 1999-06-16 | Motorola Israel Ltd | Surveillance image transmission system |
| GB2336736A (en) * | 1998-04-24 | 1999-10-27 | Daewoo Electronics Co Ltd | Binary arithmetic image coding |
| GB2318956B (en) * | 1996-10-31 | 2001-07-04 | Fujitsu Ltd | Display screen duplication system and method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5298992A (en) * | 1992-10-08 | 1994-03-29 | International Business Machines Corporation | System and method for frame-differencing based video compression/decompression with forward and reverse playback capability |
-
1994
- 1994-07-13 GB GB9414166A patent/GB2291553A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5298992A (en) * | 1992-10-08 | 1994-03-29 | International Business Machines Corporation | System and method for frame-differencing based video compression/decompression with forward and reverse playback capability |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2318956B (en) * | 1996-10-31 | 2001-07-04 | Fujitsu Ltd | Display screen duplication system and method |
| GB2332321A (en) * | 1997-12-05 | 1999-06-16 | Motorola Israel Ltd | Surveillance image transmission system |
| GB2332321B (en) * | 1997-12-05 | 2000-05-10 | Motorola Israel Ltd | Image transmission apparatus and a method of transmitting images |
| GB2336736A (en) * | 1998-04-24 | 1999-10-27 | Daewoo Electronics Co Ltd | Binary arithmetic image coding |
| US6285795B1 (en) | 1998-04-24 | 2001-09-04 | Daewoo Electronics Co., Ltd. | Method and apparatus for encoding/decoding a binary shape signal |
| GB2336736B (en) * | 1998-04-24 | 2002-07-31 | Daewoo Electronics Co Ltd | Apparatus for encoding/decoding a binary shape signal |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9414166D0 (en) | 1994-08-31 |
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