Quantization in video coding

Patent metadata

Field	Value
Publication number	US-9854275-B2
Application number	US-201213531106-A
Country	US
Kind code	B2
Filing date	Jun 22, 2012
Priority date	Jun 25, 2011
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

In an example, aspects of this disclosure relate to a method of coding video data that includes determining a quantization parameter (QP) for coding residual video data, where the QP is indexed to a quantizer step size. The method also includes determining a quantization scaling value for scaling the quantizer step size, and applying the quantization scaling value scaling to the quantizer step size. The method also includes coding the residual video data using the scaled quantizer step size.

First claim

The invention claimed is:

1. A method of coding video data, the method comprising:
determining, for a block of residual video data, a quantization parameter (QP) from a plurality of QPs for coding the residual video data, wherein each QP of the plurality of QPs is indexed to a predetermined quantizer step size, and wherein the predetermined quantizer step size is fixed;
coding, for the block of the residual video data, one or more syntax elements that indicate a value for a quantization scaling value that is separate from the predetermined quantizer step size for scaling the predetermined quantizer step size indexed to the determined QP;
applying the quantization scaling value to the predetermined quantizer step size to determine a scaled quantizer step size, and wherein:
applying the quantization scaling value to the predetermined quantizer step size causes the predetermined quantizer step size to increase to the scaled quantizer step size, wherein the scaled quantizer step size corresponds to less quantization than an amount of quantization associated with a next higher QP relative to the QP; or
applying the quantization scaling value to the predetermined quantizer step size causes the predetermined quantize step size to decrease to the scaled quantizer step size, wherein the scaled quantizer step size corresponds to more quantization than an amount of quantization associated with a next lower QP relative to the QP; and

de-quantizing one or more transform coefficients of the block of residual video data using the scaled quantizer step size.

2. The method of claim 1 , wherein applying the quantization scaling value to the predetermined quantizer step size comprises applying the quantization scaling value such that the scaled quantizer step size is less than a second quantizer step size indexed to a second QP adjacent to the QP in a range of QPs.

3. The method of claim 1 , further comprising generating the quantization scaling value based on a delta quantization scaling value, wherein the delta quantization scaling value comprises the difference between the value for the quantization scaling value and a reference quantization scaling value.

4. The method of claim 1 , wherein coding the one or more syntax elements comprises decoding the one or more syntax elements from an encoded bitstream that includes the block of video data.

5. The method of claim 4 , wherein decoding the one or more syntax elements that indicate the value for the quantization scaling value comprises decoding a slice header that includes the one or more syntax elements.

6. The method of claim 5 , wherein decoding the one or more syntax elements comprises decoding a plurality of syntax elements, each syntax element of the plurality of syntax elements corresponding to a block type, such that applying the quantization scaling value comprises applying the quantization scaling value based on a block type of the block of residual data, the block type comprising at least one of an intra predicted block, an inter predicted block, a luma block, or a chroma block.

7. The method of claim 4 , wherein decoding the one or more syntax elements that indicate the value for the quantization scaling value comprises decoding syntax associated with a largest coding unit that includes the block of video data.

8. The method of claim 7 , wherein decoding the one or more syntax elements comprises decoding the one or more syntax elements based on a quantization scaling value of a previously coded largest coding unit.

9. The method of claim 1 , further comprising encoding the one or more syntax elements and the one or more transform coefficients, and wherein encoding the one or more transform coefficients comprises quantizing the transform coefficient using the scaled quantizer step size.

10. The method of claim 9 , further comprising encoding the one or more syntax elements that indicate the value for the quantization scaling value in a slice header of an encoded bitstream.

11. The method of claim 9 , further comprising encoding the one or more syntax elements that indicate the value for the quantization scaling value with syntax for a largest coding unit that includes the block of video data.

12. The method of claim 1 , further comprising:
selecting between at least a first quantization granularity and a second, different quantization granularity, wherein quantization granularity comprises an extent to which a predetermined amount of quantization for transform coefficient coding is subdivided; and
coding one or more transform coefficients associated with the residual video data using the selected quantization granularity.

13. The method of claim 1 , wherein applying the quantization scaling value to the predetermined quantizer step size comprises multiplying the predetermined quantizer step size by the quantization scaling value.

14. The method of claim 1 , the method being executable on a wireless communication device, wherein the device comprises:
a memory configured to store the block of residual data;
a processor configured to execute instructions to process the block of residual data stored in said memory; and
a receiver configured to receive the block of residual data.

15. The method of claim 14 , wherein the wireless communication device is a cellular telephone and the block of residual data is received by the receiver and modulated according to a cellular communication standard.

16. An apparatus for coding video data, the apparatus comprising:
a memory configured to store residual video data; and
one or more processors configured to:
determine, for a block of residual video data, a quantization parameter (QP) from a plurality of QPs for coding the residual video data, wherein each QP of the plurality of QPs is indexed to a predetermined quantizer step size, and wherein the predetermined quantizer step size is fixed;
code, for the block of the residual video data, one or more syntax elements that indicate a value for a quantization scaling value that is separate from the predetermined quantizer step size for scaling the predetermined quantizer step size indexed to the determined QP;
apply the quantization scaling value to the predetermined quantizer step size to determine a scaled quantizer step size, and wherein:
to apply the quantization scaling value to the predetermined quantizer step size, the one or more processors cause the predetermined quantizer step size to increase to the scaled quantizer step size, wherein the scaled quantizer step size corresponds to less quantization than an amount of quantization associated with a next higher QP relative to the QP; or
to apply the quantization scaling value to the predetermined quantizer step size, the one or more processors cause the predetermined quantize step size to decrease to the scaled quantizer step size, wherein the scaled quantizer step size corresponds to more quantization than an amount of quantization associated with a next lower QP relative to the QP; and

de-quantize one or more transform coefficients of the block of residual video data using the scaled quantizer step size.

17. The apparatus of claim 16 , wherein to apply the quantization scaling value to the predetermined quantizer step size, the one or more processors are configured to apply the quantization scaling value such that the scaled quantizer step size is less than a quantizer step size indexed to a second QP adjacent to the QP in a range of QPs.

18. The apparatus of claim 16 , wherein the one or more processors are further configured to generate the quantization sca

Assignees

• Joshi Rajan Laxman
• Wang Xianglin
• Van Der Auwera Geert
• Karczewicz Marta
• Qualcomm Inc

Inventors

• Joshi Rajan Laxman
• Wang Xianglin
• Van Der Auwera Geert
• Karczewicz Marta

Classifications

• H04N19/174

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

• H04N19/90 Primary

  using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals · CPC title

• H04N19/172

  the region being a picture, frame or field · CPC title

• H04N19/147

  according to rate distortion criteria (rate-distortion as a criterion for motion estimation H04N19/567) · CPC title

• H04N19/61

  in combination with predictive coding · CPC title