EP0313301A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Signal coding
Assignee: British Telecommunications PLC
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Filing: 1988-10-17
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Granted: —
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Expires: 2008-10-17
Abstract
Abstract The current frame of the picture is compared (2) block-by-block with the previous frame to identify changed picture elements (pixels). The resulting matrix is matched ('vector quantised') (4) to one of a set of standard matrices ('VQ shapes'). Only those pixels flagged by the selected VQ shape are transmitted plus a "VQ shape code". This technique is modified in that the current frame is also compared (30) with a "background" frame stored (31) at the transmitter and at the receiver. Where, for any block, all the pixels flagged by the VQ shape are indicated by the second comparison as being the same as the background, the pixels are not sent - instead a shape code plus a "copy background" instruction is transmitted.
Inventors
- 👤 Michael Douglas Carr
- 👤 Anthony Richard Leaning
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 13:42
CPC Classifications
G; G06; G06T; G06T9/00; G06T9/008; H; H04; H04N; H04N19/00; H04N19/50; H04N19/503; H04N19/90; H04N19/94
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
185 words
A method of coding an image comprising, for each of a plurality of blocks of an image: (i) comparing picture elements of the block with those of the corresponding block of a previously coded image to produce a matrix of values each indicating whether the corresponding element is, in accordance with a predetermined criterion, deemed to have changed between the two images; (ii) matching the matrix to one of a predetermined set of such matrices each of which identifies a region of the block as being deemed to have changed, and generating a codeword identifying that one matrix of the set; (iii) comparing picture elements of the block with those of the corresponding block of a reference image composed of blocks from at least one earlier frame to determine whether the block is, in accordance with a predetermined criterion, deemed to have changed between the two images; (iv) coding for output those elements within the identified region, unless all the elements within the region are identified by comparison step (iii) as being unchanged relative to the reference image, whereupon a codeword indicating this is generated.
Claim 2
Independent Claim
185 words
A method of coding an image comprising, for each of a plurality of blocks of an image: (i) comparing picture elements of the block with those of the corresponding block of a previously coded image to produce a matrix of values each indicating whether the corresponding element is, in accordance with a predetermined criterion, deemed to have changed between the two images; (ii) matching the matrix to one of a predetermined set of such matrices each of which identifies a region of the block as being deemed to have changed, and generating a codeword identifying that one matrix of the set; (iii) comparing picture elements of the block with those of the corresponding block of a reference image composed of blocks from at least one earlier frame to determine whether the block is, in accordance with a predetermined criterion, deemed to have changed between the two images; (iv) coding for output those elements within the identified region, unless all the elements within the region are identified by comparison step (iii) as being unchanged relative to the reference image, whereupon a codeword indicating this is generated.
Claim 3
Dependent Claim
66 words
A method according to claim 1 in which, in the coding of the elements within the identified region, at least some of the elements are coded as the difference between that element and a predicted value for that element derived from one or more previously coded elements of the block, the sequence of coding of the elements being dependent on the orientation of the identified region.
Claim 4
Independent Claim
202 words
An apparatus for coding an image comprising, (i) means for comparing, for each of a plurality of blocks of an image, picture elements of the block with those of the corresponding block of a previously coded image to produce a matrix of values each indicating whether the corresponding element is, in accordance with a predetermined criterion, deemed to have changed between the two images; (ii) means for matching the matrix to one of a predetermined set of such matrices each of which identifies a region of the block as being deemed to have changed, and generate a codeword identifying that one matrix of the set; (iii) a store arranged to store a reference image composed of blocks from at least one earlier frame and means for comparing picture elements of the block with those of the corresponding block of the reference image to determine whether the block is, in accordance with a predetermined criterion, deemed to have changed between the two images; (iv) means for coding for output those elements within the identified region, unless all the elements within the region are identified by comparison step (iii) as being unchanged relative to the reference image, whereupon a codeword indicating this is generated.
Claim 5
Independent Claim
202 words
An apparatus for coding an image comprising, (i) means for comparing, for each of a plurality of blocks of an image, picture elements of the block with those of the corresponding block of a previously coded image to produce a matrix of values each indicating whether the corresponding element is, in accordance with a predetermined criterion, deemed to have changed between the two images; (ii) means for matching the matrix to one of a predetermined set of such matrices each of which identifies a region of the block as being deemed to have changed, and generate a codeword identifying that one matrix of the set; (iii) a store arranged to store a reference image composed of blocks from at least one earlier frame and means for comparing picture elements of the block with those of the corresponding block of the reference image to determine whether the block is, in accordance with a predetermined criterion, deemed to have changed between the two images; (iv) means for coding for output those elements within the identified region, unless all the elements within the region are identified by comparison step (iii) as being unchanged relative to the reference image, whereupon a codeword indicating this is generated.
Claim 6
Dependent Claim
61 words
An apparatus according to claim 3, including means for comparing successive images to identify parts of the image which have remained unchanged for a predetermined period of time, and in the event of such parts being identified, to: (a) update the stored reference image; and (b) code for output data indicating which parts of the reference image have been thus updated.
Claim 7
Dependent Claim
68 words
An apparatus according to claim 3, including means arranged in operation to effect periodic replacement of a minority of the blocks of the reference image stored in the store by the corresponding blocks of a recent image, the blocks being differently selected for successive replacements such that the store always contains a composite image made up of blocks from a plurality of frames of the image being coded.
Claim 8
Dependent Claim
84 words
A decoder for use with the coder of claim 3 or 5, comprising: (a) a frame store for storing a received image; (b) a second frame store; (c) control means responsive to received data to update the contents of the second frame store using the received data and responsive to a received codeword to update the second frame store with information from the first frame store; (d) means for repetitively reading the contents of the second frame store to produce a video output signal.
References Cited (Backward Citations)
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