Methods and apparatus of video coding using palette mode

1 . A method of encoding video data, comprising:

determining a coding tree type of a coding unit, and whether a local dual tree mode is enabled for the coding unit;

signaling a plurality of syntax elements associated with the coding unit, wherein the plurality of syntax elements are used to derive a plurality of variables which indicate a coding tree type of the coding unit, and whether a local dual tree mode is enabled for the coding unit; and

in accordance with a determination that the coding tree type of the coding unit is a single tree, and the local dual tree mode is enabled for the coding unit:

disabling palette mode for the coding unit when the coding unit has a size equal to or less than a first predefined threshold; and

disabling the palette mode for chroma component of the coding unit when the coding unit has a size greater than a second predefined threshold.

2 . The method according to claim 1 , wherein the disabling palette mode for the coding unit comprises:

disabling the palette mode for both luma component and chroma component of the coding unit.

3 . The method according to claim 1 , wherein the disabling the palette mode for the chroma component of the coding unit comprises:

determining whether a video component of the coding unit is the chroma component or a luma component; and

in accordance with a determination that the video component of the coding unit is the chroma component:

disabling the palette mode for the chroma component of the coding unit.

4 . The method according to claim 1 , wherein the disabling the palette mode for the chroma component of the coding unit comprises:

determining whether a video component of the coding unit is the chroma component or a luma component; and

at least in accordance with a determination that the video component of the coding unit is the luma component:

signaling a palette mode enable flag associated with the luma component of the coding unit;

wherein the coding unit is decoded in accordance with the palette mode enable flag.

5 . The method according to claim 1 , wherein the first predefined threshold is 16.

6 . An electronic apparatus comprising:

one or more processing units;

a memory coupled to the one or more processing units; and

a plurality of programs stored in the memory that, when executed by the one or more processing units, cause the electronic apparatus to perform a method of encoding video data comprising:

determining a coding tree type of a coding unit, and whether a local dual tree mode is enabled for the coding unit;

signaling a plurality of syntax elements associated with the coding unit, wherein the plurality of syntax elements are used to derive a plurality of variables which indicate a coding tree type of the coding unit, and whether a local dual tree mode is enabled for the coding unit; and

in accordance with a determination that the coding tree type of the coding unit is a single tree, and the local dual tree mode is enabled for the coding unit:

disabling palette mode for the coding unit when the coding unit has a size equal to or less than a first predefined threshold; and

disabling the palette mode for only chroma component of the coding unit when the coding unit has a size greater than a second predefined threshold; or

when executed by the one or more processing units, cause the electronic apparatus to perform a method of decoding video data comprising:

receiving a bitstream;

determining, from the bitstream, a plurality of variables associated with a coding unit, wherein the plurality of variables indicates a coding tree type of the coding unit, and whether a local dual tree mode is enabled for the coding unit; and

decoding the coding unit based on the coding tree type of the coding unit and whether the local dual tree mode is enabled for the coding unit,

wherein in accordance with a determination that the coding tree type of the coding unit is a single tree, and the local dual tree mode is enabled for the coding unit:

palette mode is disabled for the coding unit when the coding unit has a size equal to or less than a first predefined threshold; and

the palette mode is disabled for chroma component of the coding unit when the coding unit has a size greater than a second predefined threshold.

7 . The method according to claim 1 , wherein a chroma format of the video data is 4:2:2.

8 . The method according to claim 1 , wherein a chroma format of the video data is 4:4:4.

9 . A method of decoding video data, comprising:

receiving a bitstream;

determining, from the bitstream, a plurality of variables associated with a coding unit, wherein the plurality of variables indicate a coding tree type of the coding unit, and whether a local dual tree mode is enabled for the coding unit; and

decoding the coding unit based on the coding tree type of the coding unit and whether the local dual tree mode is enabled for the coding unit,

wherein in accordance with a determination that the coding tree type of the coding unit is a single tree, and the local dual tree mode is enabled for the coding unit:

palette mode is disabled for the coding unit when the coding unit has a size equal to or less than a first predefined threshold; and

the palette mode is disabled for chroma component of the coding unit when the coding unit has a size greater than a second predefined threshold.

10 . The method according to claim 9 , wherein the disabling palette mode for the coding unit comprises:

disabling the palette mode for both luma component and chroma component of the coding unit.

11 . The method according to claim 9 , wherein the disabling the palette mode for the chroma component of the coding unit comprises:

determining from at least one of the plurality of variables whether a video component of the coding unit is the chroma component or a luma component; and

in accordance with a determination that the video component of the coding unit is the chroma component:

disabling the palette mode for the chroma component of the coding unit.

12 . The method according to claim 9 , wherein the disabling the palette mode for the chroma component of the coding unit comprises:

determining from at least one of the plurality of variables whether a video component of the coding unit is the chroma component or a luma component; and

at least in accordance with a determination that the video component of the coding unit is the luma component:

receiving, from the bitstream, a palette mode enable flag associated with luma component of the coding unit; and

decoding the coding unit in accordance with the palette mode enable flag.

13 . The method according to claim 12 , further comprising:

deriving, from the bitstream, a local dual tree flag; and

updating a palette prediction for the luma component of the coding unit in response to the local dual tree flag being 1.

14 . The method according to claim 9 , wherein the first predefined threshold is 16.

15 . The method according to claim 9 , wherein a chroma format of the video data is 4:2:2.

16 . The method according to claim 9 , wherein a chroma format of the video data is 4:4:4.

17 . A non-transitory computer readable storage medium storing a bitstream generated by the method of encoding video data of claim 1 .

18 . The non-transitory computer readable storage medium according to claim 17 , wherein a chroma format of the video data is 4:2:2.

19 . The non-transitory computer readable storage medium according to claim 17 , wherein a chroma format of the video data is 4:4:4.