# US 11,909,997 B2 · Image decoding method for chroma component and device therefor

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- Number: US 11,909,997 B2
- Document ID: US11909997B2
- Status: Granted
- Kind: B2
- Application number: 18/117,776
- Filed: 2023-03-06
- Published: 2023-06-29
- Granted: 2024-02-20
- Earliest claimed: 2019-06-11
- Assignees: LG Electronics Inc.
- Applicants: LG Electronics Inc.
- Inventors: Seethal Paluri; Seunghwan Kim; Jie Zhao
- Web page: https://patentgrep.com/patent/US11909997B2

## CPC

- H04N 19/124: Quantisation
- H04N 19/46: Embedding additional information in the video signal during the compression process (H04N19/517, H04N19/68, H04N19/70 take precedence)
- H04N 19/132: Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
- H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/186: the unit being a colour or a chrominance component
- H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An image decoding method performed by a decoding device, according to the present document, comprises the steps of: deriving a chroma quantization parameter table on the basis of quantization parameter data; deriving a quantization parameter for combined chroma coding on the basis of the chroma quantization parameter table; deriving prediction samples of a current chroma block on the basis of prediction information; deriving transform coefficients of the current chroma block on the basis of residual information; deriving residual samples by dequantizing the transform coefficients on the basis of the quantization parameter; and generating a reconstructed picture on the basis of the prediction samples and the residual samples.

## Claims

### Claim 1

An image decoding method, performed by a decoding apparatus, comprising:
obtaining image information including prediction information and residual information for a current chroma block, and a flag representing whether quantization parameter data for combined chroma coding is present, based on a chroma type;
obtaining the quantization parameter data for the combined chroma coding based on the flag;
obtaining quantization parameter data for a chroma cb component and quantization parameter data for a chroma cr component;
deriving a chroma quantization parameter mapping table for the combined chroma coding based on the quantization parameter data for the combined chroma coding;
deriving a chroma quantization parameter mapping table for the chroma cb component and a chroma quantization parameter mapping table for the chroma cr component based on the quantization parameter data for the chroma cb component and the quantization parameter data for the chroma cr component;
deriving a quantization parameter for the combined chroma coding based on the chroma quantization parameter mapping table for the combined chroma coding;
deriving a quantization parameter for the chroma cb component and a quantization parameter for the chroma cr component based on the chroma quantization parameter mapping table for the chroma cb component and the chroma quantization parameter mapping table for the chroma cr component;
deriving prediction samples of the current chroma block based on the prediction information;
deriving transform coefficients of the current chroma block based on the residual information;
deriving residual samples by dequantizing the transform coefficients based on a quantization parameter related to the current chroma block among the quantization parameter for the combined chroma coding, the quantization parameter for the chroma cb component and the quantization parameter for the chroma cr component; and
generating a reconstructed picture based on the prediction samples and the residual samples,
wherein the quantization parameter data for the combined chroma coding includes a syntax element for a starting quantization parameter of the chroma quantization parameter mapping table for the combined chroma coding and a syntax element for a number of quantization parameters in the chroma quantization parameter mapping table for the combined chroma coding,
wherein the quantization parameter for the combined chroma coding is derived based on a quantization parameter corresponding to a quantization parameter of a luma component in the chroma quantization parameter mapping table for the combined chroma coding,
wherein the flag is included in a Sequence Parameter Set (SPS), and
wherein a parsing order of the syntax element for the starting quantization parameter of the chroma quantization parameter mapping table for the combined chroma coding is prior to a parsing order of the syntax element for the number of quantization parameters in the chroma quantization parameter mapping table for the combined chroma coding.

### Claim 2

An image encoding method, performed by an encoding apparatus, comprising:
deriving prediction samples of a current chroma block based on inter prediction or intra prediction;
deriving residual samples of the current chroma block based on the prediction samples;
generating quantization parameter data for combined chroma coding of the residual samples based on a chroma type of the current chroma block;
generating a flag representing whether the quantization parameter data for the combined chroma coding is present;
generating quantization parameter data for a chroma cb component and quantization parameter data for a chroma cr component; and
encoding image information including prediction information and residual information for the current chroma block, the quantization parameter data for the combined chroma coding, the quantization parameter data for the chroma cb component, the quantization parameter data for the chroma cr component and the flag,
wherein the quantization parameter data for the combined chroma coding includes a syntax element for a starting quantization parameter of a chroma quantization parameter mapping table for the combined chroma coding and a syntax element for a number of quantization parameters in the chroma quantization parameter mapping table for the combined chroma coding,
wherein a quantization parameter for the combined chroma coding is derived based on a quantization parameter corresponding to a quantization parameter of a luma component in the chroma quantization parameter mapping table for the combined chroma coding, and
wherein the flag is included in a Sequence Parameter Set (SPS), and
wherein a parsing order of the syntax element for the starting quantization parameter of the chroma quantization parameter mapping table for the combined chroma coding is prior to a parsing order of the syntax element for the number of quantization parameters in the chroma quantization parameter mapping table for the combined chroma coding.

### Claim 3

A transmission method of data for image, the method comprising:
obtaining a bitstream, wherein the bitstream generated based on deriving prediction samples of a current chroma block based on inter prediction or intra prediction, deriving residual samples of the current chroma block based on the prediction samples, generating quantization parameter data for combined chroma coding of the residual samples based on a chroma type of the current chroma block, generating a flag representing whether the quantization parameter data for the combined chroma coding is present, generating quantization parameter data for a chroma cb component and quantization parameter data for a chroma cr component, encoding image information including prediction information and residual information for the current chroma block, the quantization parameter data for the combined chroma coding, the quantization parameter data for the chroma cb component, the quantization parameter data for the chroma cr component and the flag, and generating the bitstream including the image information; and
transmitting the data comprising the bitstream,
wherein the quantization parameter data for the combined chroma coding includes a syntax element for a starting quantization parameter of a chroma quantization parameter mapping table for the combined chroma coding and a syntax element for a number of quantization parameters in the chroma quantization parameter mapping table for the combined chroma coding,
wherein a quantization parameter for the combined chroma coding is derived based on a quantization parameter corresponding to a quantization parameter of a luma component in the chroma quantization parameter mapping table for the combined chroma coding,
wherein the flag is included in a Sequence Parameter Set (SPS), and
wherein a parsing order of the syntax element for the starting quantization parameter of the chroma quantization parameter mapping table for the combined chroma coding is prior to a parsing order of the syntax element for the number of quantization parameters in the chroma quantization parameter mapping table for the combined chroma coding.