Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
121 words
A hybrid predictive coder for digital video signals, characterised in that the difference between the digital video, signals and a prediction signal is subjected to a transform before effecting quantization, namely a transform applied to the values of a block of pixels to produce sets of coefficients in the spatial frequency domain, a quantizer (14) operative on the coefficients to produce a coded output, a local decoder (18) operative on the coded output, means (20) for adding the prediction signal to the output of the local decoder (18), a framestore (22) receiving the output of the adding means and a multiplier (26) for multiplying the output of the framestore by a factor slightly less than unity to form the prediction signal.
Claim 2
Dependent Claim
121 words
A hybrid predictive coder for digital video signals, characterised in that the difference between the digital video, signals and a prediction signal is subjected to a transform before effecting quantization, namely a transform applied to the values of a block of pixels to produce sets of coefficients in the spatial frequency domain, a quantizer (14) operative on the coefficients to produce a coded output, a local decoder (18) operative on the coded output, means (20) for adding the prediction signal to the output of the local decoder (18), a framestore (22) receiving the output of the adding means and a multiplier (26) for multiplying the output of the framestore by a factor slightly less than unity to form the prediction signal.
Claim 3
Dependent Claim
16 words
A hybrid predictive coder according to claim 1, wherein the said factor is greater than 0.9.
Claim 4
Dependent Claim
14 words
A hybrid predictive coder according to claim 2, wherein the said factor is 31/32.
Claim 5
Dependent Claim
25 words
A hybrid predictive coder according to claim 1, 2 or 3, comprising a motion compensator (24) between the framestore (22) and the multiplying means (26).
Claim 6
Dependent Claim
44 words
A hybrid predictive coder according to any of claims 1 to 4, wherein the output of the multiplier (26) is truncated to form the prediction signal and the bits discarded by the truncation are fed back to the input to the multiplying means (26).
Claim 7
Dependent Claim
16 words
A hybrid predictive coder according to claim 5, wherein the feedback is on a pixel-by-pixel basis.
Claim 8
Dependent Claim
21 words
A hybrid predictive coder according to any of claim 1 to 6, wherein the said transform is a discrete cosine transform.