Chroma quantization in video coding

Patent metadata

Field	Value
Publication number	US-9294766-B2
Application number	US-201414452494-A
Country	US
Kind code	B2
Filing date	Aug 5, 2014
Priority date	Sep 9, 2013
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

A method of signaling additional chroma QP offset values that are specific to quantization groups is provided, in which each quantization group explicitly specifies its own set of chroma QP offset values. Alternatively, a table of possible sets of chroma QP offset values is specified in the header area of the picture, and each quantization group uses an index to select an entry from the table for determining its own set of chroma QP offset values. The quantization group specific chroma QP offset values are then used to determine the chroma QP values for blocks within the quantization group in addition to chroma QP offset values already specified for higher levels of the video coding hierarchy.

First claim

What is claimed is:

1. A method comprising:
receiving a plurality of sets of chroma quantization parameter (QP) offset values associated with an encoded video picture, wherein an encoded video picture includes a plurality of quantization groups, each quantization group comprising at least one coding unit;
selecting one set of chroma QP offset values from the plurality of sets of chroma QP offset values for a particular quantization group from the plurality of quantization groups; and
computing a set of chroma quantization parameters for a coding unit in the particular quantization group based on the selected set of chroma QP offset values and a luma QP value associated with the coding unit.

2. The method of claim 1 , wherein computing the set of chroma quantization parameters comprises adding the selected set of chroma QP offset values to the luma QP value.

3. The method of claim 2 further comprising identifying the luma QP value for the coding unit.

4. The method of claim 2 , wherein the selected set of chroma QP offset values is a first set of chroma QP offset values, the method further comprising adding a second set of chroma QP offset values associated with the video picture to the luma QP value and the first set of chroma QP offset values.

5. The method of claim 2 , wherein the selected set of chroma QP offset values is a first set of chroma QP offset values, the method further comprising adding a second set of chroma QP offset values associated with a slice to the luma QP value and the first set of chroma QP offset values, wherein the slice comprises the particular quantization group.

6. The method of claim 1 , wherein each set of chroma QP offset values in the plurality of sets of chroma QP offset values is associated with an index, wherein selecting a set chroma QP offset value from the plurality of sets of chroma QP offset values comprises using an index to retrieve the selected set of chroma QP offset values.

7. The method of claim 1 , wherein a header for the encoded video picture comprises parameters for identifying a level in the video coding hierarchy for the quantization group.

8. The method of claim 7 , wherein a first quantization group in a first video picture is at a different level of the video coding hierarchy than a second quantization group in a second video picture.

9. The method of claim 7 , wherein a first quantization group in a first video picture is at a different level of a coding quad tree than a second quantization group in a second video picture.

10. The method of claim 1 , wherein the selected set of chroma QP offset values is for determining chroma quantization parameters for two chroma components, wherein a first chroma QP offset value for a first chroma component is predicted from a second chroma QP offset value for the second chroma component.

11. A video device comprising:
a set of processing units; and

a non-transitory machine readable medium storing a program for execution by at least of the processing units, the program comprising sets of instructions for:
receiving a plurality of sets of chroma quantization parameter (QP) offset values associated with an encoded video picture, wherein an encoded video picture includes a plurality of quantization groups, each quantization group comprising at least one coding unit;
selecting one set of chroma QP offset values from the plurality of sets of chroma QP offset values for a particular quantization group from the plurality of quantization groups; and
computing a set of chroma quantization parameters for a coding unit in the particular quantization group based on the selected set of chroma QP offset values and a luma QP value associated with the coding unit.

12. The video device of claim 11 , wherein the set of instructions for computing the set of chroma quantization parameters comprises a set of instructions for adding the selected set of chroma QP offset values to the luma QP value.

13. The video device of claim 12 , wherein the program further comprises a set of instructions for identifying the luma QP value for the coding unit.

14. The video device of claim 12 , wherein the selected set of chroma QP offset values is a first set of chroma QP offset values, the program further comprising a set of instructions for adding a second set of chroma QP offset values associated with the video picture to the luma QP value and the first set of chroma QP offset values.

15. The video device of claim 12 , wherein the selected set of chroma QP offset values is a first set of chroma QP offset values, the program further comprising a set of instructions for adding a second set of chroma QP offset values associated with a slice to the luma QP value and the first set of chroma QP offset values, wherein the slice comprises the particular quantization group.

16. The video device of claim 11 , wherein each set of chroma QP offset values in the plurality of sets of chroma QP offset values is associated with an index, wherein the set of instructions for selecting a set chroma QP offset value from the plurality of sets of chroma QP offset values comprises a set of instructions for using an index to retrieve the selected set of chroma QP offset values.

17. The video device of claim 11 , wherein a header for the encoded video picture comprises parameters for identifying a level in the video coding hierarchy for the quantization group.

18. The video device of claim 17 , wherein a first quantization group in a first video picture is at a different level of the video coding hierarchy than a second quantization group in a second video picture.

19. The video device of claim 17 , wherein a first quantization group in a first video picture is at a different level of a coding quad tree than a second quantization group in a second video picture.

20. The video device of claim 11 , wherein the selected set of chroma QP offset values is for determining chroma quantization parameters for two chroma components, wherein a first chroma QP offset value for a first chroma component is predicted from a second chroma QP offset value for the second chroma component.

21. A computing device comprising:
a set of processing units; and
a Non-transitory machine readable medium storing a program for execution by at least one of the processing units, the program comprising:
a module for receiving a plurality of sets of chroma quantization parameter (QP) offset values associated with an encoded video picture, wherein an encoded video picture includes a plurality of quantization groups, each quantization group comprising at least one coding unit;
a module for selecting one set of chroma QP offset values from the plurality of sets of chroma QP offset values for a particular quantization group from the plurality of quantization groups; and
a module for computing a set of chroma quantization parameters for a coding unit in the particular quantization group based on the selected set of chroma QP offset values and a luma QP value associated with the coding unit.

22. The computing device of claim 21 , wherein the module for computing the set of chroma quantization parameters adds the selected set of chroma QP offset values to the luma QP value.

23. The computing device of claim 22 further comprises a module for identifying the luma QP value for the coding unit.

24. The computing device of claim 22 , wherein the selected set of chroma QP offset values is a first set of chroma QP offset values, wh

Assignees

• Apple Inc

Inventors

• Tourapis Alexandros
• Cote Guy

Classifications

• H04N19/865

  with detection of the former encoding block subdivision in decompressed video · CPC title

• H04N19/463

  by compressing encoding parameters before transmission · CPC title

• H04N19/174

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

• H04N19/70 Primary

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

• H04N19/61

  in combination with predictive coding · CPC title