Method of coding a video signal for transmission in a restricted bandwidth
First Claim
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1. A method of coding a video signal for transmission in a restricted bandwidth, the method comprising the steps of:
- sub-dividing a frame of picture information of the video signal into a set of constituent blocks;
pre-filtering the video signal with a digital anti-aliasing filter;
measuring the amount of picture activity in each block;
coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block;
adding to each thus coded block a supplementary signal which is related to the sampling rate used in that block; and
transmitting the coded video signal in analogue form.
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Abstract
A video signal is coded for transmission in a restricted bandwidth by sub-dividing a frame of picture information into a set of constituent blocks, measuring the amount of picture activity in each block, sampling the information in each block at a rate related to the amount of picture activity in that block, and adding to the coded block a supplementary signal indicating the sampling rate used for the block. Thus a decision is made on a block-by-block basis as to whether the block is transmitted with full accuracy or whether it can be adequately reconstructed from the previous frames.
102 Citations
35 Claims
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1. A method of coding a video signal for transmission in a restricted bandwidth, the method comprising the steps of:
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sub-dividing a frame of picture information of the video signal into a set of constituent blocks; pre-filtering the video signal with a digital anti-aliasing filter; measuring the amount of picture activity in each block; coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; adding to each thus coded block a supplementary signal which is related to the sampling rate used in that block; and transmitting the coded video signal in analogue form. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
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digital anti-aliasing filter means for pre-filtering the video signal; means for sub-dividing a frame of picture information of the video signal into a set of constituent blocks; means for measuring the amount of picture activity in each block; means for coding a block by sampling the picture information in a block at a rate related to the amount of measured activity in that block; means for adding to each thus-coded block a supplementary signal which is related to the sampling rate used in that block; and means for transmitting the coded video signal in analogue form. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method of coding a video signal for transmission in a restricted bandwidth, the method comprising the steps of:
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sub-dividing a frame of picture information of the video signal into a set of constituent blocks; measuring the amount of picture activity in each block; coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; adding to each thus coded block a supplementary signal which is related to the sampling rate used in that block; transmitting the coded video signal; wherein in blocks where a low sampling rate is used a sample is transmitted representing the mean sample value for that block. - View Dependent Claims (27)
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28. A method of coding a video signal for transmission in a restricted bandwidth, the method comprising the steps of:
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sub-dividing a frame of picture information of the video signal into a set of constituent blocks; measuring the amount of picture activity in each block on a cumulative basis frame by frame taken from the last frame transmitted at a high sampling rates; coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; and adding to each thus coded block a supplementary signal which is related to the sampling rate used in that block.
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29. A method of coding a video signal for transmission in a restricted bandwidth, the method comprising the steps of:
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sub-dividing a frame of picture information of the video signal into a set of constituent blocks; measuring the amount of picture activity in each block by summing a function of the difference between successive frames of the samples in a block, the function being a power of greater than 2; coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; and adding to each thus coded block a supplementary signal which is related to the sampling rate used in that block.
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30. A method of coding a video signal for transmission in a restricted bandwidth, the method comprising the steps of:
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sub-dividing a frame of picture information of the video signal into a set of constituent blocks; coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; and adding to each thus coded block a supplementary signal which is related to the sampling rate used in that block; determining for each frame, a set of main vectors; and transmitting, for each block measured as inactive, one of the set of motion vectors. - View Dependent Claims (31)
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32. Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
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means for sub-dividing a frame of picture information of the video signal into a set of constituent blocks; means for measuring the amount of picture activity in each block; means for coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; means for adding to each thus-coded block a supplementary signal which is related to the sampling rate used in that block; and means for transmitting the coded video signal;
wherein the coding means further comprises means for deriving a mean sample value for a block of transmission if that block is sampled at a low sampling rate.
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33. Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
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means for sub-dividing a frame of picture information of the video signal into a set of constituent blocks; means for measuring the amount of picture activity in each block on a cumulative basis frame by frame taken from the best frame transmitted at a high sampling rate; means for coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; and means for adding to each thus-coded block a supplementary signal which is related to the sampling rate used in that block.
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34. Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
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means for measuring the amount of picture activity in each block by summing a function of the difference between successive frames of the samples in a block, the function being a power of greater than 2; means for coding a block by sampling the picture information in the block at a rate related to the amount of measured activity in that block; and means for adding to each thus-coded block a supplementary signal which is related to the sampling rate used in that block.
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35. Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
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means for sub-dividing a frame of picture information of the video signal into a set of constituent blocks; means for measuring the amount of picture activity in each block; means for coding a block by sampling the picture information in the block at a rate related to the sampling rate used in that block; means for determining, for each frame, a set of motion vectors; and transmission means for transmitting the coded video signal and, for each block measured as inactive, one of the set of motion vectors.
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Specification