EP-4736427-A1 - POSITION DEPENDENT PIXEL COMBINATION (PDPC) FOR NEGATIVE INTRA PREDICTION DIRECTIONS

Abstract

Systems, methods, and instrumentalities are disclosed for video encoding. An initial prediction value may be determined based on a primary reference sample of a target pixel of a target block in a negative prediction direction. A secondary reference position may be identified on the right or at the bottom of the target block by extending the negative prediction direction. A secondary reference sample may be estimated at the identified secondary reference position. The initial prediction value of the target pixel may be modified based on the secondary reference sample with a prediction difference-based pixel coding. The secondary reference position may be identified based on at least one of a block size of the target block, a luminance gradient associated with the target block, or an intra prediction mode associated with the target block.

Inventors

• RATH, Gagan Bihari
• CHEN, Ya
• DUMAS, Thierry
• RADOSAVLJEVIC, Milos

Assignees

• InterDigital CE Patent Holdings, SAS

Dates

Publication Date

20260506

Application Date

20240610

Claims (20)

1. 1 . A method for video encoding, comprising: determining an initial prediction value, based on a primary reference sample of a target pixel of a target block in a negative prediction direction; identifying a secondary reference position on the right or at the bottom of the target block by extending the negative prediction direction; estimating a secondary reference sample at the identified secondary reference position; modifying the initial prediction value of the target pixel based on the secondary reference sample with a prediction difference-based pixel coding; and encoding the target block based on the modified prediction value of the target pixel.
2. 2. The method of claim 1 , wherein the method further comprises determining whether to identify the secondary reference position based on at least one of a block size of the target block, a luminance gradient associated with the target block, or an intra prediction mode associated with the target block.
3. 3. The method of claim 1 , wherein the secondary reference sample comprises at least a first reference sample on the right of the target block, or a second reference sample on the bottom of the target block.
4. 4. The method of claim 3, wherein the method further comprises determining the first reference sample by repeating a top-right reference sample on the right of the target block.
5. 5. The method of any one of claims 3 to 4, wherein the method further comprises determining the second reference sample by repeating a bottom-left reference sample at the bottom of the target block.
6. 6. The method of any one of claims 3 to 5, wherein a bottom-right sample is estimated as a weighted average of the top-right and bottom-left reference samples, and the secondary reference sample on the right is determined by interpolating between the top-right sample and the bottom-right sample, and the secondary reference sample at the bottom is determined by interpolating between the bottom-left sample and the bottom-right sample.
7. 7. The method of claim 6, wherein the bottom-right sample is estimated using a template.
8. 8. The method of any one of claims 2 to 5, wherein a value representing a bottom-right sample is encoded, and then the secondary reference sample on the right is determined by interpolating between the top-right sample and the encoded bottom-right sample, and the secondary reference sample at the bottom is determined by interpolating between the bottom-left sample and the encoded bottom-right sample.
9. 9. The method of claim 8, wherein a value representing a prediction error between the bottom-right sample and its predictor sample is encoded.
10. 10. The method of any of claims 1 to 9, wherein an initial prediction value based on a primary reference sample comprises at least one secondary reference sample on the right or at the target bottom provided a condition is satisfied.
11. 11 . The method of any of claims 1 to 9, wherein the modification of an initial prediction value based on a primary reference sample and at least one secondary reference sample on the right or at the bottom of a target block is signaled with a flag.
12. 12. The method of any of claims 1 to 9, wherein the modification of an initial prediction value based on a primary reference sample and at least one secondary reference sample on the right or at the bottom of a target block is determined using a template for the target block.
13. 13. A method for video decoding, comprising: determining an initial prediction value, based on a primary reference sample of a target pixel of a target block in a negative prediction direction; identifying a secondary reference position on the right or at the bottom of the target block by extending the negative prediction direction; estimating a secondary reference sample at the identified secondary reference position; modifying the initial prediction value of the target pixel based on the secondary reference sample with a prediction difference-based pixel coding; and decoding the target block based on the modified prediction value of the target pixel.
14. 14. The method of claim 13, wherein the method further comprises determining whether to identify the secondary reference position based on at least one of a block size of the target block, a luminance gradient associated with the target block, or an intra prediction mode associated with the target block.
15. 15. The method of claim 13, wherein the secondary reference sample comprises at least a first reference sample on the right of the target block, or a second reference sample on the bottom of the target block.
16. 16. The method of claim 15, wherein the method further comprises determining the first reference sample by repeating a top-right reference sample on the right of the target block.
17. 17. The method of claim 16, wherein the method further comprises determining the second reference sample by repeating a bottom-left reference sample at the bottom of the target block.
18. 18. The method of any one of claims 16 to 17, wherein a bottom-right sample is estimated as a weighted average of the top-right and bottom-left reference samples, and the secondary reference sample on the right is determined by interpolating between the top-right sample and the bottom-right sample and the secondary reference sample at the bottom is determined by interpolating between the bottom-left sample and the bottom-right sample.
19. 19. The method of claim 18, wherein the bottom-right sample is estimated using a template.
20. 20. The method of any one of claims 15 to 17, wherein a value representing a bottom-right sample is encoded, and then the secondary reference sample on the right is determined by interpolating between the top-right sample and the encoded bottom-right sample, and the secondary reference sample at the bottom is determined by interpolating between the bottom-left sample and the encoded bottom-right sample.

Description

POSITION DEPENDENT PIXEL COMBINATION (PDPC) FOR NEGATIVE INTRA PREDICTION DIRECTIONS CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of European Provisional Application No. EP23306106.8, filed June 30, 2023, the contents of which are hereby incorporated by reference herein. BACKGROUND [0002] Video coding systems may be used to compress digital video signals, e.g., to reduce the storage and/or transmission bandwidth needed for such signals. Video coding systems may include, for example, block-based, wavelet-based, and/or object-based systems. SUMMARY [0003] Systems, methods, and instrumentalities are disclosed for video encoding. A prediction value of a target pixel of a target block for a prediction in bottom-right direction may be determined. A primary reference sample of the target pixel for the prediction value may be determined. A secondary reference sample on the right or at the bottom of the target block may be estimated by extending a prediction direction, wherein the prediction direction is associated with the target block. The initial prediction value of the target pixel may be modified using the secondary reference sample with a prediction difference-based pixel coding. The target block may be encoded based on the modified prediction value of the target pixel. [0004] Systems, methods, and instrumentalities are disclosed for video decoding. A prediction value of a target pixel of a target block for a prediction in bottom-right direction may be determined. A primary reference sample of the target pixel for the prediction value may be determined. A secondary reference sample on the right or at the bottom of the target block may be estimated by extending a prediction direction, wherein the prediction direction is associated with the target block. The initial prediction value of the target pixel may be modified using the secondary reference sample with a prediction difference-based pixel coding. The target block may be decoded based on the modified prediction value of the target pixel. [0005] Systems, methods, and instrumentalities described herein may involve a decoder. In some examples, the systems, methods, and instrumentalities described herein may involve an encoder. In some examples, the systems, methods, and instrumentalities described herein may involve a signal (e.g., from an encoder and/or received by a decoder). A computer-readable medium may include instructions for causing one or more processors to perform methods described herein. A computer program product may include instructions which, when the program is executed by one or more processors, may cause the one or more processors to carry out the methods described herein. [0006] An initial prediction value may be determined based on a primary reference sample of a target pixel of a target block in a negative prediction direction. A secondary reference position may be identified on the right or at the bottom of the target block by extending the negative prediction direction. A secondary reference sample may be estimated at the identified secondary reference position. The initial prediction value of the target pixel may be modified based on the secondary reference sample with a prediction difference-based pixel coding. The target block may be encoded based on the modified prediction value of the target pixel. [0007] Whether to identify the secondary reference position may be determined based on at least one of a block size of the target block, a luminance gradient associated with the target block, or an intra prediction mode associated with the target block. The secondary reference sample may include at least a first reference sample on the right of the target block, or a second reference sample on the bottom of the target block. The first reference sample may be determined by repeating a top-right reference sample on the right of the target block. The second reference sample may be determined by repeating a bottom-left reference sample at the bottom of the target block. [0008] A bottom-right sample may be estimated as a weighted average of the top-right and bottom-left reference samples. The secondary reference sample on the right may be determined by interpolating between the top-right sample and the bottom-right sample. The secondary reference sample at the bottom may be determined by interpolating between the bottom-left sample and the bottom-right sample. The bottom-right sample may be estimated using a template. [0009] A value representing a bottom-right sample may be encoded. The secondary reference sample on the right may be determined by interpolating between the top-right sample and the encoded bottom-right sample. The secondary reference sample at the bottom may be determined by interpolating between the bottom-left sample and the encoded bottom-right sample. [0010] A value representing a prediction error between the bottom-right sample and its predictor sample may be encoded. An initial predi