Coding escape pixels for palette mode coding

Patent metadata

Field	Value
Publication number	US-10057587-B2
Application number	US-201615009609-A
Country	US
Kind code	B2
Filing date	Jan 28, 2016
Priority date	Jan 31, 2015
Publication date	Aug 21, 2018
Grant date	Aug 21, 2018

Abstract

In one example, a device for decoding video data includes a memory configured to store video data and a video decoder configured to determine that a value for a right shift parameter for an escape-mode coded pixel of a palette-mode coded block of the video data is less than zero, based on the value for the right shift parameter being less than zero, set a value for a left shift parameter to a positive value having an absolute value equal to an absolute value of the right shift parameter, and inverse quantize the escape-mode coded pixel using the value of the left shift parameter.

First claim

What is claimed is:

1. A method of decoding video data, the method comprising:
obtaining, by a video decoder, an escape-mode coded pixel of a palette-mode coded block of video data, the palette-mode coded block comprising palette index values mapping pixel values for the palette-mode coded block to respective entries of a color palette, the escape-mode coded pixel corresponding to a pixel value that is not in the color palette; and
inverse quantizing, by the video decoder, the escape-mode coded pixel using a value of a left shift parameter, wherein inverse quantizing comprises calculating a value for the escape-mode coded pixel (deQuantEspValue) according to a formula comprising:
deQuantEspValue=EspValue*invQuantScale[qPrem]<<invQuantLeftShift,

wherein EspValue represents a coded quantized escape value coded for the escape-mode coded pixel, invQuantScale represents an array of inverse quantization scale values, qPrem represents a quantization parameter remainder value, invQuantLeftShift represents the value of the left shift parameter, and << represents the bitwise left shift operator.

2. The method of claim 1 , further comprising determining the value for the left shift parameter based on a value of a quantization parameter (qP) for the block.

3. The method of claim 2 , further comprising determining the value of qP based on a color component index (cIdx) of a color component including the escape-mode coded pixel.

4. The method of claim 2 , wherein determining the value for the left shift parameter comprises:
calculating a quantization ratio (qPper) according to the formula qPper=qP/6, wherein qP represents the value of the qP; and
calculating the value for the left shift parameter using qPper.

5. The method of claim 1 , wherein the array of inverse quantization scale values represented by invQuantScale comprises {40, 45, 51, 57, 64, 72}.

6. The method of claim 1 , further comprising:
decoding the color palette for the palette-mode coded block;
decoding at least one of the pixel values of the block using the color palette; and
reconstructing the block using the escape-mode coded pixel and the decoded at least one of the pixel values.

7. A device for decoding video data, the device comprising:
a memory configured to store video data; and
a video decoder configured to:
obtain an escape-mode coded pixel of a palette-mode coded block of the video data, the palette-mode coded block comprising palette index values mapping pixel values for the palette-mode coded block to respective entries of a color palette, the escape-mode coded pixel corresponding to a pixel value that is not in the color palette; and
inverse quantize the escape-mode coded pixel using the value of a left shift parameter, wherein to inverse quantize the escape-mode coded pixel, the video decoder is configured to calculate a value for the escape-mode coded pixel (deQuantEspValue) according to a formula comprising:
deQuantEspValue=EspValue*invQuantScale[qPrem]<<invQuantLeftShift,

wherein EspValue represents a coded quantized escape value coded for the escape-mode coded pixel, invQuantScale represents an array of inverse quantization scale values, qPrem represents a quantization parameter remainder value, invQuantLeftShift represents the value of the left shift parameter, and << represents the bitwise left shift operator.

8. The device of claim 7 , wherein the video decoder is further configured to determine the value for the left shift parameter based on a value of a quantization parameter (qP) for the block.

9. The device of claim 8 , wherein the video decoder is further configured to determine the value of the qP based on a color component index (cIdx) of a color component including the escape-mode coded pixel.

10. The device of claim 8 , wherein to determine the value for the left shift parameter, the video decoder is configured to:
calculate a quantization ratio (qPper) according to the formula qPper=qP/6, wherein qP represents the value of the qP; and
calculate the value for the left shift parameter using qPper.

11. The device of claim 7 , wherein the array of inverse quantization scale values represented by invQuantScale comprises {40, 45, 51, 57, 64, 72}.

12. The device of claim 7 , wherein the video decoder is further configured to:
decode the palette for the palette-mode coded block;
decode at least one of the pixel values of the block using the color palette; and
reconstruct the block using the escape-mode coded pixel and the decoded at least one of the pixel values.

13. The device of claim 7 , wherein the device comprises at least one of:
an integrated circuit;
a microprocessor; or
a wireless communication device.

14. A device for decoding video data, the device comprising:
means for obtaining an escape-mode coded pixel of a palette-mode coded block of video data, the palette-mode coded block comprising palette index values mapping pixel values for the palette-mode coded block to respective entries of a color palette, the escape-mode coded pixel corresponding to a pixel value that is not in the color palette; and
means for inverse quantizing the escape-mode coded pixel using the value of the left shift parameter, wherein the means for inverse quantizing comprise means for calculating a value for the escape-mode coded pixel (deQuantEspValue) according to a formula comprising:
deQuantEspValue=EspValue*invQuantScale[qPrem]<<invQuantLeftShift,

wherein EspValue represents a coded quantized escape value coded for the escape-mode coded pixel, invQuantScale represents an array of inverse quantization scale values, qPrem represents a quantization parameter remainder value, invQuantLeftShift represents the value of the left shift parameter, and << represents the bitwise left shift operator.

15. The device of claim 14 , further comprising means for determining the value for the left shift parameter based on a value of a quantization parameter (qP) for the block.

16. The device of claim 15 , further comprising means for determining the value of the qP based on a color component index (cIdx) of a color component including the escape-mode coded pixel.

17. The device of claim 15 , wherein the means for determining the value for the left shift parameter comprises:
means for calculating a quantization ratio (qPper) according to the formula qPper=qP/6, wherein qP represents the value of the qP; and
means for calculating the value for the left shift parameter using qPper.

18. The device of claim 14 , wherein the array of inverse quantization scale values represented by invQuantScale comprises {40, 45, 51, 57, 64, 72}.

19. The device of claim 14 , further comprising:
means for decoding the color palette for the palette-mode coded block;
means for decoding at least one of the pixel values of the block using the color palette; and
means for reconstructing the block using the escape-mode coded pixel and the decoded at least one of the pixel values.

20. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a device for decoding video data to:
obtain an escape-mode coded pixel of a palette-mode coded block of the video data, the palette-mode coded block comprising palette index values mapping pixel values for the palette-mode coded block to respective entries of a color palette, the escape-mode coded pixel corresponding to a pixel value that is not in the color palette; and
inverse quantize the escape-mode coded pixel using the value of the l

Assignees

• Qualcomm Inc

Inventors

• Zou Feng
• Seregin Vadim
• Karczewicz Marta
• Pu Wei
• Joshi Rajan Laxman

Classifications

• H04N19/96

  Tree coding, e.g. quad-tree coding · CPC title

• H04N19/61 Primary

  in combination with predictive coding · CPC title

• H04N19/593

  involving spatial prediction techniques · CPC title

• H04N19/577

  Motion compensation with bidirectional frame interpolation, i.e. using B-pictures · CPC title

• H04N19/52

  by predictive encoding · CPC title