Method and device of intra predicting chroma block of video picture, and storage medium

1 . A method of intra predicting a chroma block of a video picture, comprising:

deriving a first predictor of the chroma block based on a first non-linear-model based mode;

in response to deriving a chroma predictor based on a linear-model based mode being disabled, deriving a second predictor of the chroma block based on a second non-linear-model based mode; and

determining a final predictor of the chroma block by blending the first and second predictors,

wherein the method further comprises:

encoding a video picture block into a bitstream of encoded video picture data, wherein the video picture block comprises predicting the chroma block of the video picture,

wherein the method further comprises:

writing into the bitstream a data indicating whether deriving a chroma predictor based on a linear-model based mode is enabled,

wherein the data indicating whether deriving the chroma predictor based on the linear-model based mode is enabled is written into the bitstream by a syntax element equal to 0 to indicate that blending the first and second predictors is disabled, equal to 1 to indicate the first predictor is blended with predictor derived from a linear-model based mode, equal to 2 to indicate the first predictor is blended with the second predictor when the first and second non-linear-model based predictors are different.

2 . The method of claim 1 , wherein the first and second non-linear-model based mode are selected among a set of non-linear-model based modes by minimization of a rate-distortion trade-off.

3 . The method of claim 1 , wherein the first predictor is derived from a first non-linear-model based mode based on at least one of co-located reconstructed luma samples or neighboring reconstructed chroma samples.

4 . The method of claim 1 , wherein the blending of the first and second predictors is a weighted combination between the first predictor and second predictor and weights of the weighted combination are derived according to presence in top, left or top-left neighbours of the chroma block of samples predicted by either the first predictor, or the second predictor.

5 . The method of claim 1 , wherein the first non-linear-model based mode is a non-angular intra prediction mode and the second non-linear-model based mode is an angular intra prediction mode.

6 . A non-transitory computer-readable storage medium carrying instructions that, when being executed by a processor of an electronic device, cause the device to perform the method of claim 1 .

7 . An electronic device of intra predicting a chroma block of a video picture, comprising:

a processor; and

a memory for storing instructions executable by the processor;

wherein the processor is configured to:

derive a first predictor of the chroma block based on a first non-linear-model based mode;

in response to deriving a chroma predictor based on a linear-model based mode being disabled, derive a second predictor of the chroma block based on a second non-linear-model based mode; and

determine a final predictor of the chroma block by blending the first and second predictors,

wherein the processor is further configured to:

encode a video picture block into a bitstream of encoded video picture data, wherein the video picture block comprises predicting the chroma block of the video picture,

wherein the processor is further configured to:

write into the bitstream a data indicating whether deriving a chroma predictor based on a linear-model based mode is enabled,

wherein the data indicating whether deriving the chroma predictor based on the linear-model based mode is enabled is written into the bitstream by a syntax element equal to 0 to indicate that blending the first and second predictors is disabled, equal to 1 to indicate the first predictor is blended with predictor derived from a linear-model based mode, equal to 2 to indicate the first predictor is blended with the second predictor when the first and second non-linear-model based predictors are different.

8 . The device of claim 7 , wherein the first and second non-linear-model based mode are selected among a set of non-linear-model based modes by minimization of a rate-distortion trade-off.

9 . The device of claim 7 , wherein the first predictor is derived from a first non-linear-model based mode based on at least one of co-located reconstructed luma samples or neighboring reconstructed chroma samples.

10 . The device of claim 7 , wherein the blending of the first and second predictors is a weighted combination between the first predictor and second predictor and weights of the weighted combination are derived according to presence in top, left or top-left neighbors of the chroma block of samples predicted by either the first predictor, or the second predictor.

11 . The device of claim 7 , wherein the first non-linear-model based mode is a non-angular intra prediction mode and the second non-linear-model based mode is an angular intra prediction mode.

12 . A method of intra predicting a chroma block of a video picture, comprising:

deriving a first predictor of the chroma block based on a first non-linear-model based mode;

in response to deriving a chroma predictor based on a linear-model based mode being disabled, deriving a second predictor of the chroma block based on a second non-linear-model based mode; and

determining a final predictor of the chroma block by blending the first and second predictors,

wherein the method further comprises:

decoding a video picture block from a bitstream of encoded video picture data, wherein the video picture block comprises predicting the chroma block of the video picture,

wherein the method further comprises:

reading from the bitstream a data indicating whether deriving a chroma predictor based on a linear-model based mode is enabled,

wherein the data indicating whether deriving the chroma predictor based on the linear-model based mode is enabled is read from the bitstream by a syntax element equal to 0 to indicate that blending the first and second predictors is disabled, equal to 1 to indicate the first predictor is blended with predictor derived from a linear-model based mode, equal to 2 to indicate the first predictor is blended with the second predictor when the first and second non-linear-model based predictors are different.

13 . The method of claim 12 , wherein the first and second non-linear-model based mode are selected among a set of non-linear-model based modes by minimization of a rate-distortion trade-off.

14 . The method of claim 12 , wherein the first predictor is derived from a first non-linear-model based mode based on at least one of co-located reconstructed luma samples or neighboring reconstructed chroma samples.

15 . The method of claim 12 , wherein the blending of the first and second predictors is a weighted combination between the first predictor and second predictor and weights of the weighted combination are derived according to presence in top, left or top-left neighbors of the chroma block of samples predicted by either the first predictor, or the second predictor.

16 . The method of claim 12 , wherein the first non-linear-model based mode is a non-angular intra prediction mode and the second non-linear-model based mode is an angular intra prediction mode.

17 . A non-transitory computer-readable storage medium carrying instructions that, when being executed by a processor of an electronic device, cause the device to perform the method of claim 12 .

18 . An electronic device of intra predicting a chroma block of a video picture, comprising:

a processor; and

a memory for storing instructions executable by the processor;

wherein the processor is configured to perform the method of claim 12 .