# US 12,003,773 B2 · Transform-based video coding method, and device therefor

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- Number: US 12,003,773 B2
- Document ID: US12003773B2
- Status: Granted
- Kind: B2
- Application number: 18/086,422
- Filed: 2022-12-21
- Published: 2023-04-27
- Granted: 2024-06-04
- Earliest claimed: 2019-09-21
- Assignees: LG Electronics Inc.
- Applicants: LG Electronics Inc.
- Inventors: Moonmo Koo; Seunghwan Kim; Jaehyun Lim
- Web page: https://patentgrep.com/patent/US12003773B2

## CPC

- H04N 19/61: in combination with predictive coding
- 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 19/11: among a plurality of spatial predictive coding modes
- H04N 19/122: Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
- H04N 19/127: Prioritisation of hardware or computational resources
- 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 19/18: the unit being a set of transform coefficients
- H04N 19/186: the unit being a colour or a chrominance component
- H04N 19/1883: {the unit relating to sub-band structure, e.g. hierarchical level, directional tree, e.g. low-high [LH], high-low [HL], high-high [HH]}
- H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A video decoding method according to the present document comprises a step of deriving a modified transform coefficient, and the step of deriving the transform coefficient may comprise the steps of: determining whether an LFNST can be applied to the height and width of a current block on the basis of the tree type and color format of the current block; parsing an LFNST index if the LFNST can be applied; and deriving the modified transform coefficient on the basis of the LFNST index and an LFNST matrix.

## Claims

### Claim 1

A decoding apparatus for image decoding, the decoding apparatus comprising:
a memory; and
at least one processor connected to the memory, the at least one processor configured to:
receive information on quantized transform coefficients from a bitstream;
derive quantized transform coefficients for a current block based on the information on the quantized transform coefficients;
derive transform coefficients for the current block by performing a dequantization on the quantized transform coefficients;
derive modified transform coefficients by applying a low-frequency non-separable transform (LFNST) to the transform coefficients based on an LFNST matrix related to an LFNST index;
derive residual samples for the current block by applying an inverse primary transform on the modified transform coefficients; and
generate a reconstructed picture based on the residual samples,
wherein in a case a tree-type of the current block is a dual-tree chroma, based on a height and a width of a chroma component block for the current block being equal to 4 or more, the LFNST index is parsed, and
wherein the height and the width of the chroma component block for the current block is determined based on a color format of the current block.

### Claim 2

An encoding apparatus for image encoding, the encoding apparatus comprising:
a memory: and
at least one processor connected to the memory, the at least one processor configured to:
derive prediction samples for a current block;
derive residual samples for the current block based on the prediction samples;
derive transform coefficients for the current block based on a primary transform for the residual samples;
derive modified transform coefficients from the transform coefficients based on a low-frequency non-separable transform (LFNST) matrix for an LFNST;
derive quantized transform coefficients for the current block by performing a quantization on the modified transform coefficients; and
encode information on the quantized transform coefficients and an LFNST index related to the LFNST matrix,
wherein in a case a tree-type of the current block is a dual-tree chroma, based on a height and a width of a chroma component block for the current block being equal to 4 or more, the LFNST index is encoded, and
wherein the height and the width of the chroma component block for the current block is determined based on a color format of the current block.

### Claim 3 (depends on 2)

A non-transitory computer-readable digital storage medium storing a bitstream generated by the encoding apparatus of claim 2.

### Claim 4

An apparatus for transmitting data for an image, the apparatus comprising:
at least one processor configured to obtain a bitstream for the image, wherein the bitstream is generated based on deriving prediction samples for a current block, deriving residual samples for the current block based on the prediction samples, deriving transform coefficients for the current block based on a primary transform for the residual samples, deriving modified transform coefficients from the transform coefficients based on a low-frequency non-separable transform (LFNST) matrix for an LFNST, deriving quantized transform coefficients for the current block by performing a quantization on the modified transform coefficients, and encoding information on the quantized transform coefficients and an LFNST index related to the LFNST matrix; and
a transmitter configured to transmit the data comprising the bitstream,
wherein in a case a tree-type of the current block is a dual-tree chroma, based on a height and a width of a chroma component block for the current block being equal to 4 or more, the LFNST index is encoded, and
wherein the height and the width of the chroma component block for the current block is determined based on a color format of the current block.