Patent ID: 11902527
Assignee: LG ELECTRONICS INC.
Field: Audio-visual technology (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining image information including prediction information, residual information and information on luma mapping with chroma scaling (LMCS) data from a bitstream;
generating predicted luma samples based on the prediction information;
deriving LMCS codewords based on the information on the LMCS data;
generating mapped predicted luma samples based on the predicted luma samples and the LMCS codewords;
deriving residual samples based on the residual information, wherein the residual samples includes residual luma samples and residual chroma samples;
generating reconstructed luma samples based on the mapped predicted luma samples and the residual luma samples; and
generating modified reconstructed luma samples based on the reconstructed luma samples and the LMCS codewords,
wherein the image information includes LMCS adaptation parameter sets (APSs),
wherein an LMCS APS includes type information indicating that the LMCS APS is an APS including an LMCS data field,
wherein the LMCS APS includes the LMCS data field based on the type information,
wherein the LMCS data field includes the information on the LMCS data,
wherein a maximum number of the LMCS APS is a specific value,
wherein the specific value is 4,
wherein the method further comprises:
deriving a chroma residual scaling factor based on a piece wise index; and
generating scaled residual chroma samples based on the residual chroma samples and the chroma residual scaling factor,
wherein the piecewise index is identified based on the information on the LMCS data.