Method and apparatus of improved intra luma prediction mode coding utilizing block size of neighboring blocks

1. A method of video coding using intra prediction for a block of video data, the method comprising:

determining one or more tables ranking first intra prediction modes according to a first priority order for a first neighboring block having a first block size and second intra prediction modes according to a second priority order for a second neighboring block having a second block size, wherein the first block size is different from the second block size, and wherein the first priority order is different from the second priority order;

receiving a current intra prediction mode corresponding to a current block;

receiving two or more neighboring intra prediction modes corresponding to two or more neighboring blocks, wherein one of said two or more neighboring block has a neighboring block size corresponding to the first block size and the other one of said two or more neighboring block has a neighboring block size corresponding to the second block size;

determining a mode priority for each of said two or more neighboring intra prediction modes according to each neighboring intra prediction mode and each neighboring block size of said two or more neighboring blocks using said one or more tables;

determining a highest-priority mode among said two or more neighboring intra prediction modes as a most probable mode by identifying a neighboring intra prediction mode with a lowest index relative to all of the two or more neighboring intra prediction modes ranked in their respective tables corresponding to different block sizes; and

encoding the current mode using the most probable mode as a predictor.

2. The method of claim 1 , wherein said two or more neighboring blocks correspond to an above block located above the current block and a left block located at a left side of the current block.

3. The method of claim 1 , wherein the first block corresponds to a 4×4 or 8×8 block.

4. The method of claim 3 , wherein Vertical intra prediction mode has a highest priority in said one or more tables, wherein the Vertical intra prediction mode predicts the block in a vertical direction using neighboring reconstructed samples.

5. The method of claim 4 , wherein the Vertical intra prediction mode is assigned mode index 0.

6. The method of claim 1 , wherein the second block corresponds to a 16×16, 32×32 or 64×64 block.

7. The method of claim 6 , wherein DC intra prediction mode has a highest priority in said one or more tables, wherein the DC intra prediction mode predicts the block using a constant value.

8. The method of claim 7 , wherein the DC intra prediction mode is assigned mode index 2.

9. The method of claim 6 , wherein Planar intra prediction mode has different priorities for different block sizes.

10. The method of claim 1 , wherein the block of video data corresponds to a prediction unit (PU).

11. A method of video decoding using intra prediction for a block of video data, the method comprising:

receiving one or more tables ranking first intra prediction modes according to a first priority order for a first neighboring block having a first block size and second intra prediction modes according to a second priority order for a second neighboring block having a second block size, wherein the first block size is different from the second block size, and wherein the first priority order is different from the second priority order;

receiving coded data of a current intra prediction mode of a current block;

receiving two or more neighboring intra prediction modes corresponding to two or more neighboring blocks, wherein one of said two or more neighboring block has a neighboring block size corresponding to the first block size and the other one of said two or more neighboring block has a neighboring block size corresponding to the second block size;

determining a mode priority for each of said two or more neighboring intra prediction modes according to each neighboring intra prediction mode and each neighboring block size of said two or more neighboring blocks using said one or more tables;

determining a highest-priority mode among said two or more neighboring intra prediction modes as a most probable mode by identifying a neighboring intra prediction mode with a lowest index relative to all of the two or more neighboring intra prediction modes ranked in their respective tables corresponding to different block sizes; and

decoding the current intra prediction mode based on the coded data of the current intra prediction mode and the most probable mode.

12. The method of claim 11 , wherein said two or more neighboring blocks correspond to an above block located above the current block and a left block located at a left side of the current block.

13. The method of claim 11 , wherein the first block corresponds to a 4×4 or 8×8 block.

14. The method of claim 13 , wherein Vertical intra prediction mode has a highest priority in said one or more tables, wherein the Vertical intra prediction mode predicts the block in a vertical direction using neighboring reconstructed samples.

15. The method of claim 14 , wherein the Vertical intra prediction mode is assigned mode index 0.

16. The method of claim 11 , wherein the second block corresponds to a 16×16, 32×32 or 64×64 block.

17. The method of claim 16 , wherein DC intra prediction mode has a highest priority in said one or more tables, wherein the DC intra prediction mode predicts the block using a constant value.

18. The method of claim 17 , wherein the DC intra prediction mode is assigned mode index 2.

19. The method of claim 16 , wherein Planar intra prediction mode has different priorities for different block sizes.

20. The method of claim 11 , wherein the block of video data corresponds to a prediction unit (PU).