| CPC H04N 19/176 (2014.11) [H04N 19/127 (2014.11); H04N 19/156 (2014.11); H04N 19/625 (2014.11)] | 20 Claims |
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1. A method comprising:
receiving, by a decoder, a bit stream including:
a transform block including transform coefficients; and
a group significance map including one or more significant coefficient group flags associated with the transform block, the group significance map including N rows and M columns;
determining, by the decoder, a set of flags of the one or more significant coefficient group flags that indicate non-zero coefficients in the transform block;
selecting, by the decoder, a distribution pattern for the transform block from a plurality of predetermined distribution patterns based on the group significance map, wherein selecting the distribution pattern is based on the set of flags, the selection of the distribution pattern including:
beginning with column M of the group significance map and moving in descending column order until a first column of the group significance map is detected in which the one or more significant coefficient group flags has a first non-zero value;
beginning with row N of the group significance map and moving in descending row order until a first row of the group significance map is detected in which the one or more significant coefficient group flags has a second non-zero value;
determining a boundary based on the first column of the group significance map and the first row of the group significance map; and
selecting the distribution pattern from the plurality of predetermined distribution patterns based on the boundary; and
determining, by the decoder, an output block based on an inverse discrete cosine transformation (IDCT) of the distribution pattern of the transform block.
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