Rice parameter derivation for transform-skip mode used in lossless/lossy video coding
Embodiments are directed to systems and methods of using a Rice code in video coding. In one embodiment includes a method of encoding or decoding video data, e.g., on a video encoder or decoder. In particular, embodiments are directed to determining a Rice parameter for encoding or decoding syntax elements related to coefficient levels.
1. A method of encoding or decoding video data of a transform block, the method comprising:
coding one or more of a significance coefficient flag, a sign coefficient flag, a level greater than 1 flag, and a parity level flag that specifies the parity of the transform coefficient level at scanning position n, in a first pass;
coding one or more flags which specify whether the absolute value of the transform coefficient level at the scanning position n is greater than a specified value, in a second pass;
coding, in a third pass, one or more syntax elements indicating a remaining coefficient level using a Rice-Golomb code, comprising:
determining available residual coefficients neighboring a current position in a transform unit of video data;
determining a sum of at least two of the available residual coefficients;
normalizing the sum based on the number of available residual coefficients;
determining an offset based on a base level value;
determining a rice parameter based on the sum and the offset; and
coding a syntax element indicative of a residual coefficient in the transform block at the current position based on the determined rice parameter.
2. The method of claim 1 , further comprising determining the base level for a specific coefficient based on whether one or both of the first or second pass is skipped for the specific coefficient based on whether a limit to the number of context coded bins for the transform block has been reached before the first or second encoding pass.
3. The method of claim 1 , wherein the transform unit is encoded with a transform skip encoding mode.
4. The method of claim 1 , wherein the transform unit is encoded with a lossless encoding mode.
5. The method of claim 1 , wherein the transform unit is encoded using transform skip residual coding.
6. The method of claim 1 , wherein coding the syntax element comprises encoding the syntax element to a video bitstream.
7. The method of claim 1 , wherein coding the syntax element comprises decoding the syntax element from a video bitstream.
8. An apparatus for encoding or decoding video data of a transform block, the apparatus comprising:
a memory configured to store a transform unit of a picture of video data;
a video processor configured to:
code one or more of a significance coefficient flag, a sign coefficient flag, a level greater than 1 flag, and a parity level flag that specifies the parity of the transform coefficient level at scanning position n, in a first pass;
code one or more flags which specify whether the absolute value of the transform coefficient level at the scanning position n is greater than a specified value, in a second pass;
code, in a third pass, one or more syntax elements indicating a remaining coefficient level using a Rice-Golomb code, wherein to code the one or more syntax elements in the third pass, the processor is further configured to:
determine available residual coefficients neighboring a current position in a transform unit of video data;
determine a sum of at least two of the available residual coefficients;
normalize the sum based on the number of available residual coefficients;
determine an offset based on a base level value;
determine a rice parameter based on the sum and the offset; and
code a syntax element indicative of a residual coefficient in the transform block at the current position based on the determined rice parameter.
9. The apparatus of claim 8 , wherein to determine the base level for a specific coefficient, the processor is configured to determine the base level based on whether one or both of the first or second pass is skipped for the specific coefficient based on whether a limit to the number of context coded bins for the transform block has been reached before the first or second encoding pass.
10. The apparatus of claim 8 , wherein the transform unit is encoded with a transform skip encoding mode.
11. The apparatus of claim 8 , wherein the transform unit is encoded with a lossless encoding mode.
12. The apparatus of claim 8 , wherein the transform unit is encoded using transform skip residual coding.
13. The apparatus of claim 8 , wherein to code the syntax element, the processor is configured to encode the syntax element to a video bitstream.
14. The apparatus of claim 8 , wherein to code the syntax element, the processor is configured to decode the syntax element to a video bitstream.
15. The apparatus of claim 8 , further comprising a display configured to display a picture including the transform block.
16. The apparatus of claim 8 , further comprising a camera configured to capture a picture including the transform block.
17. An apparatus for encoding or decoding video data of a transform block, the apparatus comprising:
a memory configured to store a transform unit of a picture of video data;
a video processor configured to:
code one or more of a significance coefficient flag, a sign coefficient flag, a level greater than 1 flag, and a parity level flag that specifies the parity of the transform coefficient level at scanning position n, in a first pass;
code one or more flags which specify whether the absolute value of the transform coefficient level at the scanning position n is greater than a specified value, in a second pass;
code, in a third pass, one or more syntax elements indicating a remaining coefficient level using a Rice-Golomb code, wherein to code the one or more syntax elements in the third pass, the processor is further configured to:
determine available residual coefficients neighboring a current position in a transform unit of video data;
determine a sum of at least two of the available residual coefficients;
determine a base level based on whether one or both of the first or second pass is skipped for the specific coefficient based on whether a limit to the number of context coded bins for the transform block has been reached before the first or second encoding pass;
determine an offset based on the base level value;
determine a rice parameter based on the sum and the offset; and
code a syntax element indicative of a residual coefficient in the transform block at the current position based on the determined rice parameter.
18. The apparatus of claim 17 , further comprising a display configured to display a picture including the transform block.
19. The apparatus of claim 18 , further comprising a camera configured to capture a picture including the transform block.