| CPC H04N 19/132 (2014.11) [H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/18 (2014.11)] | 12 Claims |
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1. An image decoding apparatus, comprising:
a memory; and
at least one processor connected to the memory, the at least one processor configured to:
obtain intra prediction mode information and low-frequency non-separable transform (LFNST) index information for a current block from a bitstream,
wherein the current block is divided into a plurality of sub-partition transform blocks based on an intra sub-partition mode in which intra prediction is performed on each of the sub-partition transform blocks in the current block, and
wherein the LFNST index information for the current block is obtained, from the bitstream, based on a width and a height of a sub-partition transform block resulting from dividing the current block being greater than or equal to 4,
derive prediction samples of the sub-partition transform block based on an intra prediction mode derived from the intra prediction mode information for the current block,
determine an LFNST set including LFNST matrices based on the intra prediction mode,
select one of the LFNST matrices based on the LFNST set and the LFNST index information,
derive transform coefficients for the sub-partition transform block based on the one of the LFNST matrices,
derive residual samples for the sub-partition transform block based on the transform coefficients, and
generate reconstructed samples for the sub-partition transform block based on the prediction samples and the residual samples.
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