# US 2025/0159151 A1 · Method and device for encoding/decoding image, and recording medium in which bitstream is stored

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- Number: US 2025/0159151 A1
- Document ID: US20250159151A1
- Status: Published application
- Kind: A1
- Application number: 19/025,680
- Filed: 2025-01-16
- Published: 2025-05-15
- Earliest claimed: 2017-07-06
- Assignees: Lx Semicon Co., Ltd.
- Applicants: LX Semicon Co., Ltd.
- Inventors: Jin Ho LEE; Jung Won KANG; Hyun Suk KO; Sung Chang LIM; Ha Hyun LEE; Dong San JUN; Hui Yong KIM
- Web page: https://patentgrep.com/patent/US20250159151A1

## CPC

- G06T 9/004: {Predictors, e.g. intraframe, interframe coding}
- H04N 19/11: among a plurality of spatial predictive coding modes
- 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 19/117: Filters, e.g. for pre-processing or post-processing (sub-band filter banks H04N19/635)
- 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 19/593: involving spatial prediction techniques
- H04N 19/46: Embedding additional information in the video signal during the compression process (H04N19/517, H04N19/68, H04N19/70 take precedence)
- H04N 19/59: involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An image encoding/decoding method and apparatus for performing intra prediction using a plurality of reference sample lines are provided. The image decoding method can include deriving an intra prediction mode of a current chroma block, selecting one or more luma reference sample lines for a current luma block corresponding to a current chroma block based on the intra prediction mode of the current chroma block being inter-component intra prediction mode, deriving downsampled luma samples of the current luma block, deriving downsampled luma reference samples based on the luma reference sample lines, and deriving chroma reference samples for the current chroma block.

## Claims

### Claim 1

An image decoding method performed by an image decoding apparatus, the image decoding method comprising:
deriving an intra prediction mode of a current chroma block;
selecting one or more luma reference sample lines for a current luma block corresponding to a current chroma block based on the intra prediction mode of the current chroma block being inter-component intra prediction mode;
deriving downsampled luma samples of the current luma block;
deriving downsampled luma reference samples based on the luma reference sample lines;
deriving chroma reference samples for the current chroma block;
deriving prediction parameters for inter-component intra prediction using the downsampled luma reference samples and the chroma reference samples; and
generating a prediction block by performing the inter-component intra prediction for the current chroma block based on the current luma block and the prediction parameters,
wherein the downsampled luma samples are derived based on a color format of the current chroma block,
wherein based on an upper boundary of the current luma block corresponding to an upper boundary of a coding tree block, one upper reference sample line adjacent to the current luma block is selected and three left reference sample lines neighboring of the current luma block are selected,
wherein an upper downsampled luma reference sample for prediction parameters is derived based on three reference samples selected from the one upper reference sample line,
wherein a left downsampled luma reference sample for the prediction parameters is derived based on six reference samples selected from the three left reference sample lines,
wherein the chroma reference samples include an upper chroma reference sample and a left chroma reference sample, and
wherein the prediction parameters are derived by using the upper downsampled luma reference sample derived based on the three reference samples, the left downsampled luma reference sample derived based on the six reference samples, the upper chroma reference sample and the left chroma reference sample.

### Claim 2

An image encoding method performed by an image encoding apparatus, the image encoding method comprising:
determining an intra prediction mode of a current chroma block;
selecting one or more luma reference sample lines for a current luma block corresponding to the current chroma block for inter-component intra prediction of the current chroma block;
deriving downsampled luma samples of the current luma block;
deriving downsampled luma reference samples based on the luma reference sample lines;
deriving chroma reference samples for the current chroma block;
deriving prediction parameters for the inter-component intra prediction using the downsampled luma reference samples and the chroma reference samples;
generating a prediction block by performing the inter-component intra prediction for the current chroma block based on the current luma block and the prediction parameters; and
encoding image information including information related to the inter-component intra prediction,
wherein the downsampled luma samples are derived based on a color format of the current chroma block,
wherein based on an upper boundary of the current luma block corresponding to an upper boundary of a coding tree block, one upper reference sample line adjacent to the current luma block is selected and three left reference sample lines neighboring of the current luma block are selected,
wherein an upper downsampled luma reference sample for prediction parameters is derived based on three reference samples selected from the one upper reference sample line,
wherein a left downsampled luma reference sample for the prediction parameters is derived based on six reference samples selected from the three left reference sample lines,
wherein the chroma reference samples include an upper chroma reference sample and a left chroma reference sample, and
wherein the prediction parameters are derived by using the upper downsampled luma reference sample derived based on the three reference samples, the left downsampled luma reference sample derived based on the six reference samples, the upper chroma reference sample and the left chroma reference sample.

### Claim 3 (depends on 2)

A non-transitory computer-readable recording-medium storing a bitstream which is generated by the image encoding method of claim 2.

### Claim 4

A transmitting method for image data, the method comprising:
obtaining a bitstream of encoded image information, wherein the encoded image information is generated based on determining an intra prediction mode of a current chroma block, selecting one or more luma reference sample lines for a current luma block corresponding to the current chroma block for inter-component intra prediction of the current chroma block, deriving downsampled luma samples of the current luma block, deriving downsampled luma reference samples based on the luma reference sample lines, deriving chroma reference samples for the current chroma block, deriving prediction parameters for the inter-component intra prediction using the downsampled luma reference samples and the chroma reference samples, generating a prediction block by performing the inter-component intra prediction for the current chroma block based on the current luma block and the prediction parameters, and encoding image information including information related to the inter-component intra prediction; and
transmitting the image data comprising the bitstream,
wherein the downsampled luma samples are derived based on a color format of the current chroma block,
wherein based on an upper boundary of the current luma block corresponding to an upper boundary of a coding tree block, one upper reference sample line adjacent to the current luma block is selected and three left reference sample lines neighboring of the current luma block are selected,
wherein an upper downsampled luma reference sample for prediction parameters is derived based on three reference samples selected from the one upper reference sample line,
wherein a left downsampled luma reference sample for the prediction parameters is derived based on six reference samples selected from the three left reference sample lines,
wherein the chroma reference samples include an upper chroma reference sample and a left chroma reference sample, and
wherein the prediction parameters are derived by using the upper downsampled luma reference sample derived based on the three reference samples, the left downsampled luma reference sample derived based on the six reference samples, the upper chroma reference sample and the left chroma reference sample.