Cross-component adaptive loop filter

Patent metadata

Field	Value
Publication number	US-11765368-B2
Application number	US-202217879956-A
Country	US
Kind code	B2
Filing date	Aug 3, 2022
Priority date	Feb 3, 2020
Publication date	Sep 19, 2023
Grant date	Sep 19, 2023

Abstract

Methods, systems and apparatus for video processing including coding or decoding are described. One example method of video processing includes determining, for a conversion between a video region of a chroma component of a video and a bitstream of the video, a manner of applying a cross-component adaptive loop filtering (CC-ALF) operation to a first sample of the chroma component based on a position of a second sample associated with the first sample. The method also includes performing the conversion based on the determining.

First claim

What is claimed is:

1. A method of processing video data, comprising:
determining, for a conversion between a video region of a chroma component of a video and a bitstream of the video, a filter strength used in a cross-component loop filtering operation for a first sample of the video region, wherein the filter strength is determined based on a first distance between the first sample and a chroma virtual boundary and a second distance between a corresponding luma sample of the first sample and a luma virtual boundary; and
performing the conversion based on the filter strength,
wherein in the cross-component loop filtering operation, reconstructed luma picture samples prior to a luma adaptive loop filtering process and a filtered reconstructed chroma picture sample after a chroma adaptive loop filtering process of the first sample are used to derive the cross-component filtered value of the first sample, and the filter strength is applied to the reconstructed luma picture samples.

2. The method of claim 1 , wherein the first sample is located at (x, y) relative to a top-left sample of the video region, and the corresponding luma sample of the first sample is located at (x×subWidthC, y×subHeightC), and wherein subWidthC and subHeightC are chroma subsampling rates in horizontal direction and vertical direction and the chroma subsampling rates are determined based on a color format of the video.

3. The method of claim 1 , wherein the video region satisfies that a bottom boundary of the video region is not a bottom boundary of a current picture including the video region, or a difference between a height of the current picture in units of luma samples and a vertical location of a corresponding luma sample of a top-left sample of the video region is greater than a size of a coding tree block in units of luma samples minus 4.

4. The method of claim 2 , wherein the cross-component loop filtering operation has a 4×3 filter shape, −yP1, yL, yP1, yP2 are y-coordinates of four sample rows in the 4×3 filter shape, whereby −yP1=−1, yL=0, yP1=1, yP2=2 and the corresponding luma sample of the first sample is in a row yL=0.

5. The method of claim 4 , wherein, in a case that a vertical location of the corresponding luma sample of the first sample is at CtbSizeY−3 or CtbSizeY−6 of a coding tree block, a luma sample (x, yP2) in a row at yP2 is padded using a luma sample (x, yP1) in a row at yP1, and wherein CtbSizeY is a size of the coding tree block in units of luma samples.

6. The method of claim 4 , wherein, in a case that a vertical location of the corresponding luma sample of the first sample is at CtbSizeY−4 or CtbSizeY−5, a luma sample (x, −yP1) in a row at −yP1 is padded using a luma sample (x, yL) in a row of the corresponding luma sample of the first sample, a luma sample (x, yP1) in a row at yP1 is padded using a luma sample (x, yL) in a row of the corresponding luma sample of the first sample, and a luma sample (x, yP2) in a row at yP2 is padded using a luma sample (x, yL) in a row of the corresponding luma sample of the first sample, and wherein CtbSizeY is a size of a coding tree block in units of luma samples.

7. The method of claim 1 , wherein the conversion comprises decoding the video from the bitstream.

8. The method of claim 1 , wherein the conversion comprises encoding the video into the bitstream.

9. An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
determine, for a conversion between a video region of a chroma component of a video and a bitstream of the video, a filter strength used in a cross-component loop filtering operation for a first sample of the video region, wherein the filter strength is determined based on a first distance between the first sample and a chroma virtual boundary and a second distance between a corresponding luma sample of the first sample and a luma virtual boundary; and
perform the conversion based on the filter strength,
wherein in the cross-component loop filtering operation, reconstructed luma picture samples prior to a luma adaptive loop filtering process and a filtered reconstructed chroma picture sample after a chroma adaptive loop filtering process of the first sample are used to derive the cross-component filtered value of the first sample, and the filter strength is applied to the reconstructed luma picture samples.

10. The apparatus of claim 9 , wherein the first sample is located at (x, y) relative to a top-left sample of the video region, and the corresponding luma sample of the first sample is located at (x×subWidthC, y×subHeightC), and wherein subWidthC and subHeightC are chroma subsampling rates in horizontal direction and vertical direction and the chroma subsampling rates are determined based on a color format of the video.

11. The apparatus of claim 9 , wherein the video region satisfies that a bottom boundary of the video region is not a bottom boundary of a current picture including the video region, or a difference between a height of the current picture in units of luma samples and a vertical location of a corresponding luma sample of a top-left sample of the video region is greater than a size of a coding tree block in units of luma samples minus 4.

12. The apparatus of claim 10 , wherein the cross-component loop filtering operation has a 4×3 filter shape, −yP1, yL, yP1, yP2 are y-coordinates of four sample rows in the 4×3 filter shape, whereby −yP1=−1, yL=0, yP1=1, yP2=2 and the corresponding luma sample of the first sample is in a row yL=0;
wherein, in a case that a vertical location of the corresponding luma sample of the first sample is at CtbSizeY−3 or CtbSizeY−6 of a coding tree block, a luma sample (x, yP2) in a row at yP2 is padded using a luma sample (x, yP1) in a row at yP1, and wherein CtbSizeY is a size of the coding tree block in units of luma samples; or
wherein, in a case that a vertical location of the corresponding luma sample of the first sample is at CtbSizeY−4 or CtbSizeY−5, a luma sample (x, −yP1) in a row at −yP1 is padded using a luma sample (x, yL) in a row of the corresponding luma sample of the first sample, a luma sample (x, yP1) in a row at yP1 is padded using a luma sample (x, yL) in a row of the corresponding luma sample of the first sample, and a luma sample (x, yP2) in a row at yP2 is padded using a luma sample (x, yL) in a row of the corresponding luma sample of the first sample, and wherein CtbSizeY is a size of a coding tree block in units of luma samples.

13. A non-transitory computer-readable storage medium storing instructions that cause a processor to:
determine, for a conversion between a video region of a chroma component of a video and a bitstream of the video, a filter strength used in a cross-component loop filtering operation for a first sample of the video region, wherein the filter strength is determined based on a first distance between the first sample and a chroma virtual boundary and a second distance between a corresponding luma sample of the first sample and a luma virtual boundary; and
perform the conversion based on the filter strength,
wherein in the cross-component loop filtering operation, reconstructed luma picture samples prior to a luma adaptive loop filtering process and a filtered reconstructed chroma picture sample after a chroma adaptive loop filtering process of the first sample are used to derive the cross-component filtered value of the first sample, and the filter strength is applied to the reconstructed luma picture samples.

14. The non-transitory computer-readable storage med

Assignees

• Beijing Bytedance Network Tech Co Ltd
• Bytedance Inc

Inventors

• Zhang Li
• Zhang Kai
• Wang Yue

Classifications

• H04N19/117 Primary

  Filters, e.g. for pre-processing or post-processing (sub-band filter banks H04N19/635) · CPC title

• H04N19/186 Primary

  the unit being a colour or a chrominance component · CPC title

• H04N19/82

  involving filtering within a prediction loop · CPC title

• H04N19/174

  the region being a slice, e.g. a line of blocks or a group of blocks · CPC title

• H04N19/70

  characterised by syntax aspects related to video coding, e.g. related to compression standards · CPC title