Method of coding a video signal for transmission in a restricted bandwidth
AssigneeBritish Broadcasting Corporation
InventorsNicholas D. Wells, Michael J. Knee, Charles P. Sandbank
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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.
Claims35
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.
Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
- 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.
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;
- 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.
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;
- 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.
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;
- 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.
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;
- 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.
Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
- 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.
Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
- 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.
Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
- 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.
Video signal coding apparatus for coding a video signal for transmission in a restricted bandwidth, comprising:
- 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.
Dependencies are inferred from the claim text.