| CPC H04N 19/132 (2014.11) [H04N 19/105 (2014.11); H04N 19/176 (2014.11); H04N 19/18 (2014.11)] | 3 Claims |
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1. An image decoding method performed by a decoding apparatus, the method comprising:
deriving dequantized transform coefficients of a target block from a bitstream;
deriving primary transform coefficients for the target block based on a non-separable transform for the dequantized transform coefficients;
deriving residual samples for the target block based on a separable transform for the primary transform coefficients; and
generating a reconstructed picture based on the residual samples for the target block and prediction samples for the target block,
wherein the non-separable transform is performed based on a transform matrix,
wherein the transform matrix includes modified basis vectors,
wherein each of the modified basis vectors includes fewer than N elements,
wherein the N is equal to a number of dequantized transform coefficients located in a region in which the non-separable transform is applied in the target block,
wherein the region in which the non-separable transform is applied is a 8×8 top-left region in the target block and the N is equal to 64, and
wherein a number of the modified basis vectors is less than N.
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