Chroma mode video coding

1. A method of video decoding, executable by a processor, the method comprising:

receiving video data comprising a chroma component having a first nominal angle and first delta angles and a luma component having a second nominal angle and second delta angles, wherein the first delta angles are dependent on the second delta angles;

parsing or deriving first delta angle values corresponding to the first delta angles based at least on second delta values corresponding to the second delta angles, wherein the first delta angle values are derived from one or more nominal angles associated with one or more sample positions corresponding to one or more luma blocks;

entropy-coding of a prediction mode associated with the chroma component based on a nominal mode of a corresponding luma block; and

decoding the video data based on the first delta angle values corresponding to the first delta angles.

2. The method of claim 1 , further comprising entropy-coding of the first delta angles based on one or more delta angles associated with the one or more sample positions corresponding to one or more luma blocks.

3. The method of claim 1 , wherein the entropy-coding of the prediction mode associated with the chroma component comprises:

determining whether a current mode is a chroma-from-luma mode;

based on determining that the current mode is the chroma-from-luma mode, signaling parameters from the chroma-from-luma mode;

based on determining that the current mode is not the chroma-from-luma mode, determining that the current mode is equal to the nominal mode of the corresponding luma block; and

based on determining that the current mode is equal to the nominal mode of the corresponding luma block, signaling an index of delta angles.

4. The method of claim 1 , wherein the entropy-coding of the prediction mode associated with the chroma component comprises:

determining whether a current mode is equal to the nominal mode of the corresponding luma block;

based on determining that the current mode is equal to the nominal mode of the corresponding luma block, signaling a flag indicating which mode is the current mode; and

based on a value of the flag, signaling one of an index of the first delta angles or parameters from a chroma-from-luma mode.

5. The method of claim 1 , wherein the one or more sample positions corresponding to one or more luma blocks includes at least one of co-located luma blocks or neighboring luma blocks.

6. The method of claim 1 , wherein a context of the first delta angles is different from a context of the second delta angles.

7. The method of claim 2 , wherein the first delta angle values are entropy-coded based on using a delta angle of neighboring chroma blocks as a context.

8. The method of claim 2 , wherein the first delta angle values are entropy-coded based on using a delta angle of co-located luma blocks as a context.

9. The method of claim 1 , wherein the first delta angle values are entropy-coded based on using a delta angle of neighboring chroma blocks as a context based on determining that a nominal mode of the chroma component is equal to a nominal mode of the luma component.

10. The method of claim 1 , wherein an absolute difference between the first delta angle values and second delta angle values signals an entropy-coding of a chroma intra prediction mode instead of signaling delta angles of a current chroma block.

11. A computer system for decoding video data, the computer system comprising:

one or more computer-readable non-transitory storage media configured to store computer program code; and

one or more computer processors configured to access said computer program code and operate as instructed by said computer program code, said computer program code including:

receiving code configured to cause the one or more computer processors to receive video data comprising a chroma component having a first nominal angle and first delta angles and a luma component having a second nominal angle and second delta angles, wherein the first delta angles are dependent on the second delta angles;

parsing or deriving code configured to cause the one or more computer processors to parse or derive first delta angle values corresponding to the first delta angles based at least on second delta values corresponding to the second delta angles, wherein the first delta angle values are derived from one or more nominal angles associated with one or more sample positions corresponding to one or more luma blocks;

entropy code configured to cause the one or more computer processors to entropy-code a prediction mode associated with the chroma component based on a nominal mode of a corresponding luma block; and

decoding code configured to cause the one or more computer processors to decode the video data based on the first delta angle values corresponding to the first delta angles.

12. The computer system of claim 11 , said computer program code further including performing code configured to cause the one or more computer processors to perform entropy-coding of the first delta angles based on one or more delta angles associated with one or more sample positions corresponding to one or more luma blocks.

13. The computer system of claim 11 , wherein the entropy code is configured to cause the one or more computer processors to:

determine whether a current mode is a chroma-from-luma mode;

based on determining that the current mode is the chroma-from-luma mode, signal parameters from the chroma-from-luma mode;

based on determining that the current mode is not the chroma-from-luma mode, determine that the current mode is equal to the nominal mode of the corresponding luma block; and

based on determining that the current mode is equal to the nominal mode of the corresponding luma block, signal an index of delta angles.

14. The computer system of claim 11 , wherein the entropy code is configured to cause the one or more computer processors to:

determine whether a current mode is equal to the nominal mode of the corresponding luma block;

based on determining that the current mode is equal to the nominal mode of the corresponding luma block, signal a flag indicating which mode is the current mode; and

based on a value of the flag, signal one of an index of the first delta angles or parameters from a chroma-from-luma mode.

15. The computer system of claim 11 , wherein a context of the first delta angles is different from a context of the second delta angles.

16. The computer system of claim 11 , wherein the first delta angle values are entropy-coded based on using a delta angle of neighboring chroma blocks as a context.

17. The computer system of claim 12 , wherein the first delta angle values are entropy-coded based on using a delta angle of neighboring chroma blocks as a context.

18. The computer system of claim 12 , wherein the first delta angle values are entropy-coded based on using a delta angle of co-located luma blocks as a context.

19. A non-transitory computer readable medium having stored thereon a computer program for decoding video data, the computer program configured to cause one or more computer processors to:

receive video data comprising a chroma component having a first nominal angle and first delta angles and a luma component having a second nominal angle and second delta angles, wherein the first delta angles are dependent on the second delta angles;

parse or derive first delta angle values corresponding to the first delta angles based at least on second delta values corresponding to the second delta angles, wherein the first delta angle values are derived from one or more nominal angles associated with one or more sample positions corresponding to one or more luma blocks;

entropy-code of a prediction mode associated with the chroma component based on a nominal mode of a corresponding luma block; and

decode the video data based on the first delta angle values corresponding to the first delta angles.

20. The non-transitory computer readable medium of claim 19 , the computer program configured to further cause the one or more computer processors to entropy-code the first delta angles based on one or more delta angles associated with the one or more sample positions corresponding to one or more luma blocks.