Method and apparatus for coding video data in palette mode

1. A palette coding method, comprising:

determining whether a luma component of a coding unit (CU) and chroma components of the CU are coded jointly or separately in a palette mode; and

in response to the luma component and the chroma components being coded jointly in the palette mode,

determining a first maximum joint palette-table size for the CU;

determining a first maximum joint palette-predictor size for the CU; and

predicting the CU based on the first maximum joint palette-table size and the first maximum joint palette-predictor size.

2. The method of claim 1 , wherein determining the first maximum joint palette-table size for the CU comprises:

determining the first maximum joint palette-table size for the CU based on a value of a first syntax element signaled in a video bitstream; and

determining the first maximum joint palette-predictor size for the CU based on the value of the first syntax element and a value of a second syntax element signaled in the video bitstream.

3. The method of claim 2 , wherein determining the first maximum joint palette-predictor size for the CU comprises:

determining the first maximum joint palette-predictor size for the CU to be a sum of the value of the first syntax element and the value of the second syntax element.

4. The method of claim 2 , wherein the first syntax element and second syntax element are signaled in a sequence parameter set (SPS) or a picture header (PH) associated with the CU.

5. The method of claim 1 , further comprising:

in response to the luma component and the chroma components being coded separately in the palette mode,

determining a second maximum palette-table size for the CU based on the first maximum joint palette-table size,

determining a second maximum palette-predictor size for the CU based on the first maximum joint palette-predictor size, and

predicting the CU based on the second maximum palette-table size and the second maximum palette-predictor size.

6. The method of claim 1 , wherein determining the first maximum joint palette-table size for the CU comprises:

determining the first maximum joint palette-table size for the CU to be a first predetermined value; and

determining the first maximum joint palette-predictor size for the CU to be a second predetermined value.

7. The method of claim 6 , wherein:

the first predetermined value is 31 ; and

the second predetermined value is 63 .

8. The method of claim 6 , further comprising:

in response to the luma component and the chroma components being coded separately in the palette mode,

determining a third maximum palette-table size for the CU to be a third predetermined value; and

predicting the CU based on the third maximum palette-table size,

wherein the third predetermined value is smaller than the first predetermined value.

9. The method of claim 8 , wherein the third predetermined value is 15.

10. The method of claim 8 , further comprising:

in response to the luma component and the chroma components being coded separately in the palette mode and the CU being part of a single-tree slice, predicting the CU based on the first maximum joint palette-predictor size.

11. The method of claim 8 , further comprising:

in response to the luma component and the chroma components being coded separately in the palette mode and the CU being not part of a single-tree slice,

determining a third maximum palette-predictor size for the CU to be a fourth predetermined value; and

predicting the CU based on the third maximum palette-predictor size,

wherein the fourth predetermined value is smaller than the second predetermined value.

12. The method of claim 11 , wherein the fourth predetermined value is 31 .

13. The method of claim 1 , further comprising:

determining whether a picture slice comprising the CU is a single-tree slice or a dual-tree slice; and

in response to the picture slice being a single-tree slice,

determining the first maximum joint palette-table size for the CU in the picture slice, based on a value of a third syntax element signaled in a slice header of the picture slice; and

determining the first maximum joint palette-predictor size for the CU, based on the value of the third syntax element and a value of a fourth syntax element signaled in the slice header.

14. The method of claim 13 , further comprising:

in response to the picture slice being a dual-tree slice,

determining a fourth maximum palette-table size for the CU, based on a value of a fifth syntax element signaled in the slice header,

determining a fourth maximum palette-predictor size for the CU, based on the value of the fifth syntax element and a value of a sixth syntax element signaled in the slice header, and

predicting the CU based on the fourth maximum palette-table size and the fourth maximum palette-predictor size.

15. A video processing apparatus, comprising:

at least one memory for storing instructions; and

at least one processor configured to execute the instructions to cause the apparatus to perform:

determining whether a luma component of a coding unit (CU) and chroma components of the CU are coded jointly or separately in a palette mode; and

in response to the luma component and the chroma components being coded jointly in the palette mode,

determining a first maximum joint palette-table size for the CU;

determining a first maximum joint palette-predictor size for the CU; and

predicting the CU based on the first maximum joint palette-table size and the first maximum joint palette-predictor size.

16. A non-transitory computer readable storage medium storing a set of instructions that are executable by one or more processing devices to cause a video processing apparatus to perform a method comprising:

determining whether a luma component of a coding unit (CU) and chroma components of the CU are coded jointly or separately in a palette mode; and

in response to the luma component and the chroma components being coded jointly in the palette mode,

determining a first maximum joint palette-table size for the CU;

determining a first maximum joint palette-predictor size for the CU; and

predicting the CU based on the first maximum joint palette-table size and the first maximum joint palette-predictor size.

17. The non-transitory computer readable storage medium of claim 16 , wherein the set of instructions are executable by the one or more processing devices to cause the video processing apparatus to perform:

determining the first maximum joint palette-table size for the CU based on a value of a first syntax element signaled in a video bitstream; and

determining the first maximum joint palette-predictor size for the CU based on the value of the first syntax element and a value of a second syntax element signaled in the video bitstream.

18. The non-transitory computer readable storage medium of claim 16 , wherein the set of instructions are executable by the one or more processing devices to cause the video processing apparatus to perform:

in response to the luma component and the chroma components being coded separately in the palette mode,

determining a second maximum palette-table size for the CU based on the first maximum joint palette-table size,

determining a second maximum palette-predictor size for the CU based on the first maximum joint palette-predictor size, and

predicting the CU based on the second maximum palette-table size and the second maximum palette-predictor size.

19. The non-transitory computer readable storage medium of claim 16 , wherein the set of instructions are executable by the one or more processing devices to cause the video processing apparatus to perform:

determining the first maximum joint palette-table size for the CU to be a first predetermined value; and

determining the first maximum joint palette-predictor size for the CU to be a second predetermined value.

20. The non-transitory computer readable storage medium of claim 19 , wherein the set of instructions are executable by the one or more processing devices to cause the video processing apparatus to perform:

in response to the luma component and the chroma components being coded separately in the palette mode,

determining a third maximum palette-table size for the CU to be a third predetermined value; and

predicting the CU based on the third maximum palette-table size,

wherein the third predetermined value is smaller than the first predetermined value.