Chroma block prediction method and apparatus

Patent metadata

Field	Value
Publication number	US-11595669-B2
Application number	US-202117303976-A
Country	US
Kind code	B2
Filing date	Jun 11, 2021
Priority date	Dec 13, 2018
Publication date	Feb 28, 2023
Grant date	Feb 28, 2023

Abstract

This application provides a chroma block prediction method and apparatus. The method includes: obtaining a maximum luma value and a minimum luma value based on luma samples corresponding to neighboring samples of a target chroma block, and calculating a first difference between the maximum luma value and the minimum luma value; if the first difference is not equal to 0, processing the first difference based on a quantity of significant bits of the first difference and a first preset bit depth to obtain a second difference; and determining, based on a first chroma value, a second chroma value, and the second difference, an intra prediction model parameter corresponding to the target chroma block, and determining prediction information of the target chroma block based on the intra prediction model parameter and luma reconstruction information corresponding to the target chroma block.

First claim

What is claimed is:

1. A chroma block prediction method, comprising:
obtaining a maximum luma value and a minimum luma value based on luma samples corresponding to neighboring samples of a target chroma block;
if a first difference between the maximum luma value and the minimum luma value is not equal to 0, processing the first difference based on a quantity of significant bits of the first difference and a first preset bit depth to obtain a second difference;
determining, based on a first chroma value, a second chroma value, and the second difference, an intra prediction model parameter corresponding to the target chroma block, wherein the first chroma value and the second chroma value are determined based on the neighboring samples of the target chroma block; and
determining prediction information of the target chroma block based on the intra prediction model parameter and luma reconstruction information corresponding to the target chroma block.

2. The method according to claim 1 , wherein the obtaining a maximum luma value and a minimum luma value based on luma samples corresponding to neighboring samples of a target chroma block comprises:
dividing a preset quantity of luma samples corresponding to a preset quantity of neighboring samples of the target chroma block into a first luma sample set and a second luma sample set, wherein a quantity of luma samples in the first luma sample set is the same as a quantity of luma samples in the second luma sample set, and luma values of the luma samples in the first luma sample set are greater than or equal to luma values of the luma samples in the second luma sample set; and
determining the maximum luma value based on the first luma sample set, and determining the minimum luma value based on the second luma sample set.

3. The method according to claim 1 , wherein the processing the first difference to obtain a second difference comprises:
shifting the first difference to the right to obtain the second difference, wherein a bit depth of the second difference is not larger than a preset value.

4. The method according to claim 3 , wherein the processing the first difference based on a quantity of significant bits of the first difference and a first preset bit depth to obtain a second difference comprises:
determining a third difference between the quantity of significant bits of the first difference and the first preset bit depth; and
shifting the first difference to the right by bits of the third difference to obtain the second difference, wherein the third difference is greater than 0.

5. The method according to claim 1 , wherein the determining, based on a first chroma value, a second chroma value, and the second difference, an intra prediction model parameter corresponding to the target chroma block comprises:
determining, based on the first chroma value, the second chroma value, a preset value of a normalized shift parameter, the second difference, and the minimum luma value, the intra prediction model parameter corresponding to the target chroma block.

6. The method according to claim 5 , wherein the determining, based on the first chroma value, the second chroma value, a preset value of a normalized shift parameter, the second difference, and the minimum luma value, the intra prediction model parameter corresponding to the target chroma block comprises:
determining, based on the first chroma value, the second chroma value, the second difference, and the preset value of the normalized shift parameter, a scaling coefficient in the intra prediction model parameter corresponding to the target chroma block; and
determining, based on the scaling coefficient, the second chroma value, the preset value of the normalized shift parameter, and the minimum luma value, an offset factor in the intra prediction model parameter corresponding to the target chroma block.

7. The method according to claim 6 , wherein the determining, based on the scaling coefficient, the second chroma value, the preset value of the normalized shift parameter, and the minimum luma value, an offset factor in the intra prediction model parameter corresponding to the target chroma block comprises:
determining, based on the scaling coefficient, the second chroma value, a target value of the normalized shift parameter, and the minimum luma value, the offset factor in the intra prediction model parameter corresponding to the target chroma block, wherein the target value of the normalized shift parameter is determined based on the preset value of the normalized shift parameter.

8. The method according to claim 6 , wherein the scaling coefficient a in the intra prediction model parameter is determined based on (maxC−minC) and a value from a lookup table, wherein maxC is the first chroma value, minC is the second chroma value, and the value from the lookup table is determined based on the second difference.

9. The method according to claim 6 , wherein the determining, based on the first chroma value, the second chroma value, the second difference, and the preset value, a scaling coefficient in the intra prediction model parameter corresponding to the target chroma block comprises:
determining, based on the first chroma value, the second chroma value, the preset value, and the second difference, an initial scaling coefficient in the intra prediction model parameter corresponding to the target chroma block; and
when a fourth difference between a quantity of significant bits of the initial scaling coefficient and a second preset bit depth is greater than 0, shifting the initial scaling coefficient to the right based on the fourth difference to obtain the scaling coefficient in the intra prediction model parameter corresponding to the target chroma block.

10. The method according to claim 9 , wherein the shifting the initial scaling coefficient to the right based on the fourth difference to obtain the scaling coefficient in the intra prediction model parameter corresponding to the target chroma block comprises:
shifting the initial scaling coefficient to the right by bits of the fourth difference to obtain the scaling coefficient in the intra prediction model parameter corresponding to the target chroma block.

11. The method according to claim 9 , further comprising:
if the fourth difference is greater than 0, determining a difference between the fourth difference and a sum of the preset value of the normalized shift parameter and a third difference as a target value of the normalized shift parameter.

12. The method according to claim 7 , wherein the determining, based on the scaling coefficient, the second chroma value, a target value, and the minimum luma value, the offset factor in the intra prediction model parameter corresponding to the target chroma block comprises:
b=minC−((a*minY)>>k), wherein b is the offset factor, a is the scaling coefficient, minC is the second chroma value, minY is the minimum luma value, and k is the target value.

13. The method according to claim 1 , further comprising:
if the first difference is not equal to 0, determining that a scaling coefficient in the intra prediction model parameter is 0, and determining that an offset factor in the intra prediction model parameter is the second chroma value.

14. The method according to claim 5 , wherein the preset value of the normalized shift parameter is a bit depth of the first difference, a bit depth of luma samples, a sum of the bit depth of the first difference and a second preset value, a product of the bit depth of the first difference and a third preset value, or a bit depth of one byte.

15. The method according to c

Assignees

• Huawei Tech Co Ltd

Inventors

• Ma Xiang
• Chen Jianle
• Yang Haitao

Classifications

• H04N19/149

  by estimating the code amount by means of a model, e.g. mathematical model or statistical model · 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

• H04N19/159

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