| CPC H04N 19/132 (2014.11) [H04N 19/176 (2014.11); H04N 19/18 (2014.11); H04N 19/60 (2014.11)] | 4 Claims |
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1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining image information including a flag related to whether an Intra sub-partitions (ISP) mode is applied and information on transform coefficients from a bitstream;
deriving quantized transform coefficients for a current block based on the information on the transform coefficients;
deriving transform coefficients for the current block by performing a dequantization on the quantized transform coefficients;
deriving modified transform coefficients for the current block by applying a low-frequency non-separable transform (LFNST) to the transform coefficients based on an LFNST matrix;
deriving residual samples for the current block by applying an inverse primary transform on the modified transform coefficients; and
generating a reconstructed picture based on the residual samples and prediction samples for the current block,
wherein in case the flag represents that the ISP mode is not applied to the current block, based on a non-zero transform coefficient being present in a region other than a DC position of the current block, the image information includes an LFNST index related to the LFNST matrix,
wherein based on the flag representing that the ISP mode is applied to the current block, the image information includes the LFNST index related to the LFNST matrix without considering of whether the non-zero transform coefficient is present in the region other than the DC position of the current block, and
wherein based on a sub-partition block divided from the current block being a 4×4 block or a 8×8 block, the LFNST is applied from a top-left position of the sub-partition block up to 8th transform coefficients in a scan direction.
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