Rice parameter initialization for coefficient level coding in video coding process

Patent metadata

Field	Value
Publication number	US-10021419-B2
Application number	US-201414327398-A
Country	US
Kind code	B2
Filing date	Jul 9, 2014
Priority date	Jul 12, 2013
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

Techniques are described for initializing a Rice parameter used to define codes for coefficient level coding. According to the techniques, the initial value of the Rice parameter is determined for a coefficient group (CG) in a transform block of video data based on statistics of coefficient levels that are gathered for previously coded coefficients of the video data. The statistics may be statistics of absolute values of coefficient levels or remaining absolute values of coefficient levels of previously coded coefficients. A value of the statistics may be initialized to zero at a beginning of a video slice and updated based on coefficient levels coded in each CG of the slice. The statistics may be updated once per CG. In some cases, statistics may be gathered separately for each of a plurality of different categories of CGs that are defined based on characteristics of transform blocks that include the CGs.

First claim

What is claimed is:

1. A method of decoding coefficients in a video decoding process, the method comprising:
determining statistics of coefficient levels for previously decoded coefficients of residual video data for each of a plurality of different categories of coefficient groups, wherein the different categories are defined based on characteristics of transform blocks that include the coefficient groups, and wherein the characteristics of the transform blocks of the previously decoded coefficients include whether the transform blocks are luma blocks and whether the transform blocks are transform skip blocks, the previously decoded coefficients being decoded prior to decoding a current coefficient group in a transform block of the residual video data;
determining a category of the current coefficient group from the plurality of different categories based on characteristics of the transform block that includes the current coefficient group, wherein the characteristics of the transform block that includes the current coefficient group include whether the transform block is a luma block and whether the transform block is a transform skip block;
prior to decoding any coefficients in the current coefficient group, determining an initial value of a Rice parameter for the current coefficient group based on the statistics for the determined category of the current coefficient group; and
decoding a remaining absolute value of a coefficient level for at least one of the coefficients in the current coefficient group using codes defined by the initial value of the Rice parameter.

2. The method of claim 1 , wherein the statistics comprise statistics of one of absolute values of the coefficient levels or remaining absolute values of the coefficient levels for the previously decoded coefficients.

3. The method of claim 1 , wherein the statistics comprise statistics of the coefficient levels for the previously decoded coefficients in previous coefficient groups that are included in one or more of the same transform block as the current coefficient group or different transform blocks than the current coefficient group.

4. The method of claim 1 , wherein determining the statistics comprises:
comparing a coefficient level for at least one of the previously decoded coefficients to a function of the statistics; and
determining whether to increase or decrease the value of the statistics based on the comparison.

5. The method of claim 4 , wherein the function of the statistics comprises a first constant value left-shifted by a value of the statistics divided by a second constant value.

6. The method of claim 1 , further comprising initializing a value of the statistics to zero at a beginning of each slice of the residual video data.

7. The method of claim 1 , wherein determining the statistics comprises determining the statistics once per coefficient group.

8. The method of claim 7 , wherein determining the statistics once per coefficient group comprises determining the statistics when one of a first absolute value of a coefficient level or a first remaining absolute value of a coefficient level is decoded in each of a plurality of previous coefficient groups.

9. The method of claim 1 , further comprising receiving a syntax element indicating which characteristics of the transform blocks are used to define the different categories of coefficient groups, wherein the syntax element is received in one of a sequence parameter set (SPS) or a picture parameter set (PPS) for the residual video data.

10. The method of claim 1 , wherein determining the initial value of the Rice parameter for the current coefficient group comprises mapping a value of the statistics to the initial value of the Rice parameter according to a function of the statistics.

11. The method of claim 10 , wherein the function of the statistics comprises a selection of a minimum of either a maximum value of the Rice parameter or the value of the statistics divided by a constant value.

12. The method of claim 1 , further comprising updating the initial value of the Rice parameter based on the initial value of the Rice parameter and an absolute value of the coefficient level for the at least one of the coefficients being decoded in the current coefficient group.

13. The method of claim 1 , wherein the codes defined by the Rice parameter comprise one of Golomb-Rice codes or Exponential-Golomb codes.

14. The method of claim 1 , wherein the current coefficient group comprises either transform coefficients or coefficients for which a transform is not applied.

15. The method of claim 1 , wherein the characteristics of the transform blocks used to define the different categories of coefficient groups further include positions of the coefficient groups within the transform blocks used to define the different categories of coefficient groups, and wherein the characteristics of the transform block that includes the current coefficient group used to determine the category of the current coefficient group further includes the position of the current coefficient groups within the transform block that includes the current coefficient group.

16. A method of encoding coefficients in a video encoding process, the method comprising:
determining statistics of coefficient levels for previously encoded coefficients of residual video data for each of a plurality of different categories of coefficient groups, wherein the different categories are defined based on characteristics of transform blocks that include the coefficient groups, and wherein the characteristics of the transform blocks of the previously encoded coefficients include whether the transform blocks are luma blocks and whether the transform blocks are transform skip blocks, the previously encoded coefficients being encoded prior to encoding a current coefficient group in a transform block of the residual video data;
determining a category of the current coefficient group from the plurality of different categories based on characteristics of the transform block that includes the current coefficient group, wherein the characteristics of the transform block that includes the current coefficient group at least include whether the transform block is a luma block and whether the transform block is a transform skip block;
prior to encoding any coefficients in the current coefficient group, determining an initial value of a Rice parameter for the current coefficient group based on the statistics for the determined category of the current coefficient group; and
encoding a remaining absolute value of a coefficient level for at least one of the coefficients in the current coefficient group using codes defined by the initial value of the Rice parameter.

17. The method of claim 16 , wherein the statistics comprise statistics of one of absolute values of the coefficient levels or remaining absolute values of the coefficient levels for the previously encoded coefficients.

18. The method of claim 16 , wherein the statistics comprise statistics of the coefficient levels for the previously encoded coefficients in previous coefficient groups that are included in one or more of the same transform block as the current coefficient group or different transform blocks than the current coefficient group.

19. The method of claim 16 , wherein determining the statistics comprises:
comparing a coefficient level for at least one of the previously encoded coefficients to a function of the statistics; and
determining whether to increase or decrease the value of the statistics based on the

Assignees

• Qualcomm Inc
• Qualcomm Incorported

Inventors

• Karczewicz Marta
• Sole Rojals Joel
• Joshi Rajan Laxman
• Guo Liwei

Classifications

• H04N19/60 Primary

  using transform coding · CPC title

• H04N19/176 Primary

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

• H04N19/136

  Incoming video signal characteristics or properties · CPC title

• H04N19/91

  Entropy coding, e.g. variable length coding [VLC] or arithmetic coding · CPC title

• H04N19/13

  Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC] · CPC title