Palette coding for screen content coding
Sketch copy mode may be used to code blocks comprising irregular lines, syntax redundancy may be removed from blocks with special characteristics, and/or run value coding may be simplified. The parsing dependencies in palette coding design may be removed. For example, the context modeling dependency of the syntax element palette_transpose_flag may be removed, for example, by simplifying the corresponding context model. The context modeling of the syntax element palette_mode may be removed, for example, by using run-length coding without using context. The syntax parsing dependencies and/or the syntax signaling dependencies that are related with escape color signaling may be removed. A palette table generation process may handle input screen content video with high bit depths, for example, at the encoder side.
1. A method for palette decoding, the method comprising:
receiving a first scan direction indication for a first coding unit (CU) in video data, wherein the first scan direction indication is coded with a single context that does not depend on a value of a second scan direction indication for a second CU, wherein the first scan direction indication indicates a scan direction for palette coding; and
parsing the first CU based on the first scan direction indication.
2. The method of claim 1 , wherein the first scan direction indication for the first CU is a scan direction flag.
3. The method of claim 1 , wherein the second CU is a neighboring CU of the first CU, and the second scan direction indication indicates a scan direction for the neighboring CU.
4. The method of claim 1 , wherein the first scan direction indication for the first CU is a palette_transpose_flag.
5. A device for palette decoding, the device comprising:
a processor configured to:
receive a first scan direction indication for a first coding unit (CU) in video data, wherein the first scan direction indication is coded with a single context that does not depend on a value of a second scan direction indication for a second CU, wherein the first scan direction indication indicates a scan direction for palette coding; and
parse the first CU based on the first scan direction indication.
6. The device of claim 5 , wherein the first scan direction indication for the first CU is a scan direction flag.
7. The device of claim 5 , wherein the second CU is a neighboring CU of the first CU, and the second scan direction indication indicates a scan direction for the neighboring CU.
8. The device of claim 5 , wherein the first scan direction indication for the first CU is a palette_transpose_flag.
9. A method for palette encoding, the method comprising:
determining a first coding unit (CU) of video data; and
including a first scan direction indication for the first CU in the video data, wherein the first scan direction indication is coded with a single context that does not depend on a value of a second scan direction indication for a second CU, wherein the first scan direction indication indicates a scan direction for palette coding.
10. The method of claim 9 , wherein the first scan direction indication of the palette mode for the first CU is a scan direction flag.
11. The method of claim 9 , wherein the second CU is a neighboring CU of the first CU, and the second scan direction indication indicates a scan direction for the neighboring CU.
12. The method of claim 9 , wherein the first scan direction indication for the first CU is a palette_transpose_flag.
13. A device for palette encoding, the device comprising:
a processor, the processor configured to:
determine a first coding unit (CU) of video data; and
include a first scan direction indication for the first CU in the video data, wherein the first scan direction indication is coded with a single context that does not depend on a value of a second scan direction indication for a second CU, wherein the first scan direction indication indicates a scan direction for palette coding.
14. The device of claim 13 , wherein the first scan direction indication of the palette mode for the first CU is a scan direction flag.
15. The device of claim 13 , wherein the second CU is a neighboring CU of the first CU, and the second scan direction indication indicates a scan direction for the neighboring CU.
16. The device of claim 13 , wherein the first scan direction indication for the first CU is a palette_transpose_flag.
17. The method of claim 1 , further comprising:
determining that an escape color presence flag for the first CU is not signaled in video data;
inferring that a value of the escape color presence flag for the first CU is equal to a value that indicates that the first CU contains at least one escape color coded sample, wherein the value of the escape color presence flag for the first CU is inferred based on the escape color presence flag for the first CU not being signaled in the video data; and
parsing the first CU based on the value of the escape color presence flag.
18. The device of claim 5 , wherein the processor is further configured to:
determine that an escape color presence flag for the first CU is not signaled in video data;
infer that a value of the escape color presence flag for the first CU is equal to a value that indicates that the first CU contains at least one escape color coded sample, wherein the value of the escape color presence flag for the first CU is inferred based on the escape color presence flag for the first CU not being signaled in the video data; and
parse the first CU based on the value of the escape color presence flag.
19. The method of claim 9 , further comprising:
determining the first CU that contains an escape color coded sample;
determining that a value of an escape color presence flag for the first CU indicates that the first CU contains the escape color coded sample;
determining that the value of the escape color presence flag for the first CU can be inferred by a decoder when the escape color presence flag for the first CU is not signaled in video data; and
preventing the escape color presence flag for the first CU from being signaled in the video data.
20. The device of claim 13 , wherein the processor is further configured to:
determine the first CU that contains an escape color coded sample;
determine that a value of an escape color presence flag for the first CU indicates that the first CU contains the escape color coded sample;
determine that the value of the escape color presence flag for the first CU can be inferred by a decoder when the escape color presence flag for the first CU is not signaled in video data; and
prevent the escape color presence flag for the first CU from being signaled in the video data.
21. A non-transitory computer readable medium comprising instructions for implementing, when executed by at least one processor, steps comprising:
receiving a first scan direction indication for a first coding unit (CU) in video data, wherein the first scan direction indication is coded with a single context that does not depend on a value of a second scan direction indication for a second CU, wherein the first scan direction indication indicates a scan direction for palette coding; and
parsing the first CU based on the first scan direction indication.
22. A non-transitory computer readable medium comprising instructions for implementing, when executed by a processor, steps comprising:
determining a first coding unit (CU) of video data; and
including a first scan direction indication for the first CU in the video data, wherein the first scan direction indication is coded with a single context that does not depend on a value of a second scan direction indication for a second CU, wherein the first scan direction indication indicates a scan direction for palette coding.