# US 12,225,214 B2 · Luma mapping and chroma scaling-based video or image coding

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- Number: US 12,225,214 B2
- Document ID: US12225214B2
- Status: Granted
- Kind: B2
- Application number: 18/071,156
- Filed: 2022-11-29
- Published: 2023-04-20
- Granted: 2025-02-11
- Earliest claimed: 2019-07-05
- Assignees: LG Electronics Inc.
- Applicants: LG Electronics Inc.
- Inventors: Jie Zhao; Seunghwan Kim
- Web page: https://patentgrep.com/patent/US12225214B2

## CPC

- H04N 19/11: among a plurality of spatial predictive coding modes
- H04N 19/186: the unit being a colour or a chrominance component
- H04N 19/105: Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/30: using hierarchical techniques, e.g. scalability (H04N19/63 takes precedence)
- H04N 19/593: involving spatial prediction techniques
- H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

According to the disclosure of the present document, a chroma residual scaling factor is derived on the basis of information relating to an absolute value of a chroma residual scaling delta value and information relating to a sign of the chroma residual scaling delta value, and an LMCS procedure can be efficiently performed by applying explicit signaling to information relating to a value(s) of the chroma residual scaling factor.

## Claims

### Claim 1

An image decoding method performed by a decoding apparatus, the method comprising:
obtaining image information including prediction related information and residual information from a bitstream;
deriving an inter prediction mode for a current block based on the prediction related information;
deriving motion information for the current block based on the inter prediction mode;
generating prediction luma samples and prediction chroma samples based on the motion information for the current block;
generating mapped prediction luma samples based on mapping process for the prediction luma samples;
generating residual luma samples and residual chroma samples based on the residual information;
generating reconstructed luma samples based on the mapped prediction luma samples and the residual luma samples;
deriving a chroma residual scaling factor based on the reconstructed luma samples; and
generating reconstructed chroma samples based on the prediction chroma samples and scaled residual chroma samples,
wherein the image information includes luma mapping with chroma scaling (LMCS) related information, 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 LMCS related information includes information on LMCS codewords, information related to a minimum bin index and information related to a maximum bin index,
wherein LMCS codewords are derived based on the information on the LMCS codewords,
wherein an inverse scaling index is derived based on the information related to the minimum bin index, the information related to the maximum bin index and the reconstructed luma samples,
wherein the chroma residual scaling factor is derived based on the LMCS codewords, the inverse scaling index, 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 generated based on the residual chroma samples and the chroma residual scaling factor.

### Claim 2

An image encoding method performed by an encoding apparatus, the method comprising:
deriving an inter prediction mode;
generating motion information for a current block based on the inter prediction mode;
generating prediction luma samples and prediction chroma samples based on the motion information for the current block;
generating prediction related information based on the inter prediction mode;
deriving luma mapping with chroma scaling (LMCS) codewords;
generating LMCS related information based on the LMCS codewords;
generating mapped prediction luma samples based on mapping process for the prediction luma samples;
generating residual luma samples based on the mapped prediction luma samples;
generating reconstructed luma samples based on the mapped prediction luma samples and the residual luma samples;
deriving a chroma residual scaling factor based on the residual luma samples;
generating residual chroma samples based on the prediction chroma samples;
generating scaled residual chroma samples based on the residual chroma samples and the chroma residual scaling factor;
generating residual information based on the residual luma samples and the scaled residual chroma samples; and
encoding image information including the prediction related information, the LMCS related information and the residual information,
wherein the image information includes information on an absolute value of a chroma residual scaling delta value and information on a sign of a chroma residual scaling delta value,
wherein the LMCS related information includes information on the LMCS codewords, information related to a minimum bin index and information related to a maximum bin index,
wherein an inverse scaling index is derived based on the information related to the minimum bin index, the information related to the maximum bin index and the reconstructed luma samples, and
wherein the inverse scaling index, 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 are for deriving the chroma residual scaling factor.

### Claim 3 (depends on 2)

A transmission method of data for an image, performed by a transmission apparatus, the method comprising:
generating a bitstream for the image by performing the image encoding method of claim 2; and
transmitting the data comprising the bitstream.