Chroma block prediction method and apparatus

Patent metadata

Field	Value
Publication number	US-11943451-B2
Application number	US-202117365372-A
Country	US
Kind code	B2
Filing date	Jul 1, 2021
Priority date	Jan 3, 2019
Publication date	Mar 26, 2024
Grant date	Mar 26, 2024

Abstract

This application provides a chroma block prediction method and apparatus. The method includes: obtaining chroma values of chroma samples; obtaining, luma values of luma samples corresponding to the chroma samples; obtaining, from the luma values, a first luma set and a second luma set; grouping the chroma values into a first chroma set and a second chroma set; determining a scaling coefficient in a linear model based on an average value of luma values in the first luma set, an average value of luma values in the second luma set, an average value of chroma values in the first chroma set, and an average value of chroma values in the second chroma set; determining, based on the scaling coefficient, an offset factor in the linear model; and determining prediction information of the chroma block based on the scaling coefficient and the offset factor.

First claim

What is claimed is:

1. A chroma block prediction method, comprising:
obtaining chroma values of chroma samples;
obtaining, based on neighboring samples of a luma block corresponding to a chroma block, luma values of luma samples;
obtaining, from the obtained luma values, a first luma set and a second luma set;
grouping chroma values of chroma samples corresponding to luma samples associated with luma values in the first luma set into a first chroma set, and grouping chroma values of chroma samples corresponding to luma samples associated with luma values in the second luma set into a second chroma set;
determining a scaling coefficient in a linear model corresponding to the chroma block based on an average value of the luma values in the first luma set, an average value of the luma values in the second luma set, an average value of the chroma values in the first chroma set, and an average value of the chroma values in the second chroma set;
determining, based on the scaling coefficient, an offset factor in the linear model corresponding to the chroma block; and
determining prediction information of the chroma block based on the scaling coefficient, the offset factor, and luma reconstruction information corresponding to the chroma block, wherein the luma reconstruction information corresponding to the chroma block comprises downsampling information of a luma reconstructed block corresponding to the chroma block;
wherein the obtaining, from the obtained luma values, a first luma set and a second luma set comprises:
sorting the luma values of the luma samples corresponding to the chroma samples at preset locations in ascending order, to obtain a first luma value queue; and grouping luma values of a first half part in the first luma value queue into the first luma set, and grouping luma values of a second half part in the first luma value queue into the second luma set; or
sorting the luma values of the luma samples corresponding to the chroma samples at the preset locations in descending order, to obtain a second luma value queue; and grouping luma values of a second half part in the second luma value queue into the first luma set, and grouping luma values of a first half part in the second luma value queue into the second luma set.

2. The method according to claim 1 , further comprising:
obtaining indication information, and determining, based on the indication information, an intra prediction mode corresponding to the chroma block, wherein the intra prediction mode comprises at least one of a linear mode (LM), a linear mode above (LMA), or a linear mode left (LML); and
determining preset locations based on the intra prediction mode corresponding to the chroma block.

3. The method according to claim 1 , wherein the obtaining chroma values of chroma samples comprises:
obtaining the chroma values of the chroma samples at preset locations from neighboring samples of the chroma block based on a preset correspondence between an intra prediction mode and a preset location and the intra prediction mode corresponding to the chroma block.

4. The method according to claim 1 , wherein location coordinates of top neighboring samples of the chroma block are (0, −1), (1, −1), . . . , and (X−1, −1), and location coordinates of left neighboring samples of the chroma block are (−1, 0), (−1, 1), . . . , and (−1, Y−1), wherein X represents a width of the chroma block, and Y represents a height of the chroma block; and
if an intra prediction mode corresponding to the chroma block is a cross-component linear mode LM, location coordinates of the chroma samples at the preset locations are (0, −1), (X−1, −1), (−1, 0), and (−1, Y−1).

5. The method according to claim 4 , wherein the location coordinates of the top neighboring samples of the chroma block are (0, −1), (1, −1), . . . , and −(X−1, −1), wherein X represents the width of the chroma block; and
if the intra prediction mode corresponding to the chroma block is a cross-component linear mode above LMA, the location coordinates at the preset locations are (0, −1), (X/4, −1), (X−1−X/4, −1), and (X−1, −1), or (0, −1), (X/4, −1), (3*X/4, −1), and (X−1, −1).

6. The method according to claim 4 , wherein the location coordinates of the left neighboring samples of the chroma block are (−1, 0), (−1, 1), . . . , and (−1, Y−1), wherein Y represents the height of the chroma block; and
if the intra prediction mode corresponding to the chroma block is a cross-component linear mode left LML, the location coordinates at the preset locations are (−1, 0), (−1, Y/4), (−1, Y−1−Y/4), and (−1, Y−1), or (−1, 0), (−1, Y/4), (−1, 3*Y/4), and (−1, Y−1).

7. The method according to claim 1 , wherein the determining, based on an average value of the luma values in the first luma set, an average value of the luma values in the second luma set, an average value of the chroma values in the first chroma set, and an average value of the chroma values in the second chroma set, a scaling coefficient in a linear model corresponding to the chroma block comprises:

α
=

C
Lmean

-

C
Rmean

L
Lmean

-

L
Rmean

,

wherein α is the scaling coefficient in the linear model corresponding to the chroma block, C Lmean is the average value of the chroma values in the first chroma set, C Rmean is the average value of the chroma values in the second chroma set, L Lmean is the average value of the luma values in the first luma set, and L Rmean is the average value of the luma values in the second luma set.

8. The method according to claim 1 , wherein the determining, based on the scaling coefficient, an offset factor in the linear model corresponding to the chroma block comprises:
determining, based on the scaling coefficient, the average value of the chroma values in the first chroma set, and the average value of the luma values in the first luma set, the offset factor in the linear model corresponding to the chroma block.

9. The method according to claim 8 , wherein the determining, based on the scaling coefficient, the average value of the chroma values in the first chroma set, and the average value of the luma values in the first luma set, the offset factor in the linear model corresponding to the chroma block comprises:
β=C Lmean −α*L Lmean , wherein α is the scaling coefficient, β is the offset factor in the linear model corresponding to the chroma block, C Lmean is the average value of the chroma values in the first chroma set, and L Lmean is the average value of the luma values in the first luma set.

10. The method according to claim 1 , wherein the determining, based on the scaling coefficient, an offset factor in the linear model corresponding to the chroma block comprises:
determining, based on the scaling coefficient, an average value of the chroma values of the chroma samples at preset locations, and the average value of the luma values of the luma samples corresponding to the chroma samples, the offset factor in the linear model corresponding to the chroma block.

11. The method according to claim

Assignees

• Huawei Tech Co Ltd

Inventors

• Ma Xiang
• Mu Fan
• Zhao Yin
• Yang Haitao

Classifications

• H04N19/159 Primary

  Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction · CPC title

• H04N19/132

  Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking · CPC title

• H04N19/176 Primary

  the region being a block, e.g. a macroblock · CPC title

• H04N19/186 Primary

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

• H04N19/11 Primary

  among a plurality of spatial predictive coding modes · CPC title