Coding escape pixels for palette coding

Patent metadata

Field	Value
Publication number	US-10425659-B2
Application number	US-201615009678-A
Country	US
Kind code	B2
Filing date	Jan 28, 2016
Priority date	Jan 30, 2015
Publication date	Sep 24, 2019
Grant date	Sep 24, 2019

Abstract

In one example, a device includes a memory configured to store video data and a video decoder configured to decode an exponential Golomb codeword representative of at least a portion of a value for an escape pixel of a palette-mode coded block of video data, the video decoder is configured to decode the exponential Golomb codeword using exponential Golomb with parameter 3 decoding, and decode the block using the value for the escape pixel.

First claim

What is claimed is:

1. A method of decoding video data, the method comprising:
obtaining a palette that includes entries representing pixel values for a palette-code coded block of the video data;
determining that the palette-mode coded block of the video data includes an escape pixel that is not associated with any of the entries included in the palette and the entries included in the palette are not used to predict the escape pixel;
decoding an exponential Golomb codeword defining at least a portion of a value for a syntax element defining a chrominance or luminance value for the escape pixel of the palette-mode coded block of the video data, wherein decoding the exponential Golomb codeword comprises decoding the exponential Golomb codeword using exponential Golomb with parameter 3 decoding, and wherein decoding the exponential Golomb codeword using exponential Golomb with parameter 3 decoding comprises decoding the exponential Golomb codeword using a factor of 2 3 ; and
decoding the palette-mode coded block using the value for the syntax element defining the chrominance or luminance value for the escape pixel.

2. The method of claim 1 , further comprising:
determining a quantization step size value for the palette-mode coded block using a quantization parameter for the palette-mode coded block; and
determining a maximum quantized value for the escape pixel of the palette-mode coded block based on the quantization step size value,
wherein decoding the exponential Golomb codeword comprises decoding the exponential Golomb codeword using the maximum quantized value.

3. The method of claim 2 , wherein determining the maximum quantized value comprises determining the maximum quantized value based only on the quantization step size value.

4. The method of claim 2 , wherein determining the maximum quantized value comprises determining the maximum quantized value based on the quantization step size value, a quantization scale value, a right shift offset value, and a right shift parameter value, the method further comprising determining the quantization scale value, the right shift offset value, and the right shift parameter value from a look-up table.

5. The method of claim 4 , wherein determining the maximum quantized value comprises determining the maximum quantized value without performing a clipping operation.

6. The method of claim 2 , wherein determining the maximum quantized value comprises calculating the maximum quantized value without performing a division operation.

7. The method of claim 2 , wherein determining the maximum quantized value comprises retrieving the maximum quantized value from a look-up table indexed by the quantization parameter.

8. The method of claim 7 , further comprising determining the quantization parameter based on a color component that includes the escape pixel.

9. The method of claim 1 , wherein at least the portion of the value comprises a second portion of the value, the method further comprising:
decoding a Golomb rice codeword representative of a first portion of the value for the escape pixel; and
combining the first portion and the second portion to produce the value for the escape pixel.

10. A device for decoding video data, the device comprising:
a memory configured to store video data; and
a video decoder implemented in circuitry and configured to:
obtain a palette that includes entries representing pixel values for a palette-mode coded block of the video data;
determine that the palette-mode coded block of the video data includes an escape pixel that is not associated with any of the entries included in the palette and the entries included in the palette are not used to predict the escape pixel;
decode an exponential Golomb codeword defining at least a portion of a value for a syntax element defining a chrominance or luminance value for the escape pixel of the palette-mode coded block of the stored video data, wherein the video decoder is configured to decode the exponential Golomb codeword using exponential Golomb with parameter 3 decoding, and wherein to decode the exponential Golomb codeword using exponential Golomb with parameter 3 decoding, the video decoder is configured to decode the exponential Golomb codeword using a factor of 2 3 ; and
decode the palette-mode coded block using the value for the syntax element defining the chrominance or luminance value for the escape pixel.

11. The device of claim 10 , wherein the video decoder is further configured to:
determine a quantization step size value for the palette-mode coded block using a quantization parameter for the palette-mode coded block; and
determine a maximum quantized value for the escape pixel of the palette-mode coded block based on the quantization step size value,
wherein the video decoder is configured to decode the exponential Golomb codeword using the maximum quantized value.

12. The device of claim 11 , wherein the video decoder is configured to determine the maximum quantized value based only on the quantization step size value.

13. The device of claim 11 , wherein the video decoder is configured to determine the maximum quantized value based on the quantization step size value, a quantization scale value, a right shift offset value, and a right shift parameter value, and wherein the video decoder is further configured to determine the quantization scale value, the right shift offset value, and the right shift parameter value from a look-up table.

14. The device of claim 13 , wherein the video decoder is configured to determine the maximum quantized value without performing a clipping operation.

15. The device of claim 11 , wherein the video decoder is configured to calculate the maximum quantized value without performing a division operation.

16. The device of claim 11 , wherein the video decoder is configured to retrieve the maximum quantized value from a look-up table indexed by the quantization parameter.

17. The device of claim 10 , wherein at least the portion of the value comprises a second portion of the value, and wherein the video decoder is further configured to:
decode a Golomb rice codeword representative of a first portion of the value for the escape pixel; and
combine the first portion and the second portion to produce the value for the escape pixel.

18. A device for decoding video data, the device comprising:
means for obtaining a palette that includes entries representing pixel values for a palette-mode coded block of the video data;
means for determining that the palette-mode coded block of the video data includes an escape pixel that is not associated with any of the entries included in the palette and the entries included in the palette are not used to predict the escape pixel;
means for decoding an exponential Golomb codeword defining at least a portion of a value for a syntax element defining a chrominance or luminance value for the escape pixel of the palette-mode coded block of the video data, wherein the means for decoding the exponential Golomb codeword comprise means for decoding the exponential Golomb codeword using exponential Golomb with parameter 3 decoding, and wherein the for decoding the exponential Golomb codeword using exponential Golomb with parameter 3 decoding comprise means for decoding the exponential Golomb codeword using a factor of 2 3 ; and
means for decoding the palette-mode coded block using the value for the syntax element defining the chrominance or luminance value for the escape pixel.

19. The device of claim 18 , further comprising:
means for det

Assignees

• Qualcomm Inc

Inventors

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

Classifications

• H04N19/91

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

• H03M7/4075

  Golomb codes · CPC title

• H03M7/40

  Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code · CPC title

• H04N19/44

  Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder · CPC title

• H04N19/105

  Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction · CPC title