US 12,309,399 B2
Luma mapping- and chroma scaling-based video or image coding
Jie Zhao, Seoul (KR); and Seunghwan Kim, Seoul (KR)
Assigned to LG Electronics Inc., Seoul (KR)
Filed by LG Electronics Inc., Seoul (KR)
Filed on Dec. 6, 2023, as Appl. No. 18/530,716.
Application 18/530,716 is a continuation of application No. 17/423,667, granted, now 11,876,984, previously published as PCT/KR2020/007834, filed on Jun. 17, 2020.
Claims priority of provisional application 62/862,648, filed on Jun. 17, 2019.
Prior Publication US 2024/0121412 A1, Apr. 11, 2024
This patent is subject to a terminal disclaimer.
Int. Cl. H04N 19/186 (2014.01); H04N 19/109 (2014.01); H04N 19/132 (2014.01); H04N 19/70 (2014.01)
CPC H04N 19/186 (2014.11) [H04N 19/109 (2014.11); H04N 19/132 (2014.11); H04N 19/70 (2014.11)] 3 Claims
OG exemplary drawing
 
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining image information including prediction mode information and luma mapping with chroma scaling (LMCS) related information from a bitstream;
deriving an inter prediction mode for a current block in a current picture based on the prediction mode information;
deriving motion information for the current block based on the inter prediction mode;
generating a prediction luma sample for the current block based on the motion information for the current block;
generating a mapped prediction luma sample based on a mapping process for the prediction luma sample; and
generating a modified reconstructed luma sample based on an inverse mapping process for luma samples,
wherein the LMCS related information includes information on bins for LMCS,
wherein a minimum bin index and a maximum bin index are derived based on the information on the bins,
wherein a mapped value indexed by 0 is equal to 0 and mapped values indexed by indices from 1 to 16 are derived based on LMCS codewords,
wherein in the mapping process for the prediction luma sample, a mapping index is derived based on the prediction luma sample, and the mapped prediction luma sample is generated by using a mapped value indexed by the mapping index,
wherein in the inverse mapping process for the luma samples, an inverse mapping index is derived based on the mapped values indexed by bin indices from the minimum bin index to the maximum bin index, and the modified reconstructed luma sample is generated by using a mapped value indexed by the inverse mapping index,
wherein, for deriving the inverse mapping index, the inverse mapping process for the luma samples comprises:
determining whether a mapped value, based on a case that the inverse mapping index is equal to the minimum bin index, is greater than a value of a reconstructed luma sample;
determining whether a mapped value, based on a case that the inverse mapping index is equal to maximum bin index−1, is greater than the value of the reconstructed luma sample; and
determining whether a mapped value, based on a case that the inverse mapping index is equal to the maximum bin index, is greater than the value of the reconstructed luma sample based on a determination that the mapped value, based on the case that the inverse mapping index is equal to maximum bin index−1, is not greater than the value of the reconstructed luma sample, and
wherein, based on a determination that the mapped value, based on the case that the inverse mapping index is equal to the maximum bin index, is greater than the value of the reconstructed luma sample, the inverse mapping index is derived as the maximum bin index.