| CPC H04N 19/159 (2014.11) [H04N 19/12 (2014.11); H04N 19/176 (2014.11); H04N 19/61 (2014.11); H04N 19/625 (2014.11)] | 5 Claims |
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3. An encoder comprising:
memory; and
a processor coupled to the memory, the processor being configured to:
when intra prediction is to be used for a current block included in a picture, determine whether a basis selection mode in which a first inverse transform basis is selectable from among a plurality of first inverse transform basis candidates is used, and determine whether a size of the current block satisfies with a predetermined condition; and
when the basis selection mode is used for the current block and the size of the current block satisfies with the predetermined conditions,
(i) perform a first transform with a first transform basis on residual signals of the current block to generate first transform coefficients,
(ii-1) perform a second transform on the first transform coefficients with a second transform basis to generate second transform coefficients and quantize the second transform coefficients when the intra prediction mode is not a predetermined mode, and
(ii-2) quantize the first transform coefficients when the intra prediction mode is the predetermined mode,
wherein the first transform is a separable transform, and the second transform is a non-separable transform.
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