| CPC H04N 19/625 (2014.11) [H04N 19/129 (2014.11); H04N 19/176 (2014.11); H04N 19/18 (2014.11)] | 4 Claims |
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1. A decoder for a video decoding, the decoder comprising:
a memory; and
at least one processor connected to the memory, the at least one processor configured to:
obtain, based on zero transform coefficients being at specific transform coefficient locations, a secondary transform index from a bitstream;
derive an inverse secondary transform matrix corresponding to the secondary transform index, wherein the inverse secondary transform matrix is used for an inverse secondary transform outputting N coefficients (N×1 vector) based on inputted L (L<N) coefficients (L×1 vector);
derive quantized transform coefficients for a current block from the bitstream;
obtain non-zero transform coefficients by performing a dequantization for the quantized transform coefficients;
perform the inverse secondary transform for the non-zero transform coefficients based on the inverse secondary transform matrix;
perform an inverse primary transform for a block to which the inverse secondary transform is applied; and
reconstruct the current block based on a block to which the inverse primary transform is applied,
wherein the specific transform coefficient locations are arranged in a diagonal scan order from a (L+1)th location to a 16th location in the transform coefficients of the block to which the inverse secondary transform is applied, the block being a 4×4 block, N being 16, and L being 8.
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