CPC H04N 19/12 (2014.11) [H04N 19/129 (2014.11); H04N 19/132 (2014.11); H04N 19/176 (2014.11); H04N 19/46 (2014.11)] | 16 Claims |
1. An apparatus for decoding a picture using predictive coding and block-based transform residual coding, comprising:
a processor; and
a memory having instructions which, when executed by the processor, cause the apparatus to:
select, for a predetermined transform block, a transformation out of a predetermined list of transformations, the selected transformation comprising an identity transformation and at least one non-identity transformation,
decode, for the predetermined transform block, a block of coefficients from a data stream by decoding for a current coefficient a significance flag indicative of whether the current coefficient is zero or not using a context, wherein:
when the selected transformation is the identity transformation, the context depends on a number of coefficients being non-zero among a first set of coefficients immediately neighboring the current coefficient, and
when the selected transformation is one of the at least one non-identity transformation, the context depends on values of a second set of coefficients and a position of the current coefficient, the second set of coefficients including at least one coefficient immediately neighboring the current coefficient and at least one coefficient positioned farther away from the current coefficient than any of the coefficients immediately neighboring the current coefficient,
derive from the block of coefficients a residual sample array for the predetermined transform block so that the block of coefficients is related to the residual sample array according to the selected transformation, and
correct a prediction for the predetermined transform block using the residual sample array to reconstruct the predetermined transform block.
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