CPC H04N 19/18 (2014.11) [H04N 19/124 (2014.11); H04N 19/126 (2014.11); H04N 19/136 (2014.11); H04N 19/137 (2014.11); H04N 19/17 (2014.11); H04N 19/176 (2014.11); H04N 19/184 (2014.11); H04N 19/186 (2014.11); H04N 19/44 (2014.11); H04N 19/46 (2014.11); H04N 19/61 (2014.11); H04N 19/625 (2014.11); H04N 19/70 (2014.11); H04N 19/91 (2014.11)] | 20 Claims |
1. In a computer system that implements a video decoder, a method comprising:
receiving encoded data in a bit stream for at least part of a video sequence, wherein the encoded data includes, for a given block of a picture of the video sequence:
a first code that indicates a value for a DC differential for a DC coefficient of the given block, wherein the DC differential represents a difference between the DC coefficient and a DC predictor; and
a second code that indicates a refinement of the value for the DC differential, wherein presence of the second code in the bit stream is conditioned on a quantization step size being 1 or 2; and
decoding the encoded data, including, for the given block:
decoding the first code to determine the value for the DC differential;
decoding the second code to determine the refinement;
determining a multiple of the value for the DC differential by multiplying the value for the DC differential by a factor that depends on the quantization step size; and
adding the refinement to the multiple of the value for the DC differential.
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