| CPC H04N 19/186 (2014.11) [H04N 19/157 (2014.11); H04N 19/176 (2014.11); H04N 19/46 (2014.11)] | 4 Claims |
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1. An image decoding method performed by a decoding apparatus, the image decoding method comprising:
obtaining image information including prediction related information, residual information and information on luma mapping with chroma scaling (LMCS) data from a bitstream;
generating prediction chroma samples for a current block in a current picture based on the prediction related information;
generating residual chroma samples for the current block based on the residual information;
deriving LMCS codewords based on the information on the LMCS data;
generating scaled residual chroma samples based on the residual chroma samples and the LMCS codewords; and
generating reconstructed chroma samples for the current block based on the prediction chroma samples and the scaled residual chroma samples,
wherein the image information includes a sequence parameter set (SPS), information on an absolute value of a chroma residual scaling delta value and information on a sign of the chroma residual scaling delta value,
wherein the SPS includes an LMCS enabled flag representing whether an LMCS data field is enabled,
wherein the information on the LMCS data includes information on the LMCS codewords,
wherein the LMCS codewords are derived based on the information on the LMCS codewords,
wherein the information on the sign of the chroma residual scaling delta value is included in the image information based on the information on the absolute value of the chroma residual scaling delta value,
wherein a chroma residual scaling factor is derived based on the information on the absolute value of the chroma residual scaling delta value and the information on the sign of the chroma residual scaling delta value, and
wherein the scaled residual chroma samples are derived based on the chroma residual scaling factor.
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