CPC H04N 19/12 (2014.11) [H04N 19/154 (2014.11); H04N 19/157 (2014.11); H04N 19/61 (2014.11)] | 2 Claims |
1. An encoder comprising:
a processor; and
memory,
wherein, using the memory, the processor:
derives a residual signal of a current block by subtracting a prediction signal from an input signal;
determines an intra prediction mode used for the current block;
performs a primary transform on the residual signal, using a primary transform basis, to generate first transform coefficients;
when the primary transform basis is different from predetermined transform bases, performs a quantization on the first transform coefficients without performing a secondary transform; and
when the primary transform basis is included in the predetermined transform bases, (i) performs a secondary transform on the first transform coefficients, using a secondary transform basis selected from among one or more candidate secondary transform bases associated with the intra prediction mode, to generate second transform coefficients, and (ii) performs a quantization on the second transform coefficients, and
wherein the secondary transform is performed on a part of the first transform coefficients generated by the primary transform.
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