Video coding using intra sub-partition coding mode

1. A method of video decoding, comprising:

performing an intra prediction for a plurality of sub-partitions of a coding block in a Intra Sub-Partition (ISP) mode in response to determining that the plurality of sub-partitions meet first conditions for the intra prediction,

wherein performing the intra prediction for the plurality of sub-partitions of the coding block comprises:

merging at least two sub-partitions of the plurality of sub-partitions into one prediction region for the intra prediction, and

generating predicted samples for the one prediction region in the intra prediction based on a plurality of reference samples of the coding block adjacent to the one prediction region,

wherein the first conditions comprise that the plurality of sub-partitions are a plurality of vertical sub-partitions and each of the sub-partitions has a width less than or equal to 2.

2. The method of claim 1 , wherein no reconstructed sample from one sub-partition of the at least two sub-partitions is used to perform the intra prediction for any other sub-partition of the at least two sub-partitions.

3. The method of claim 1 further comprising:

generating a set of predicted samples for the plurality of vertical sub-partitions using a vertical prediction mode with a mode index larger than 50.

4. The method of claim 1 further comprising performing the intra prediction for samples in the one prediction region independently and in parallel.

5. The method of claim 1 , wherein the plurality of sub-partitions includes a last sub-partition, and the method further comprises signaling a coefficients block flag (CBF) value for the last sub-partition.

6. The method of claim 5 , wherein the plurality of sub-partitions includes a last sub-partition, and the method further comprises inferring a coefficients block flag (CBF) value for the last sub-partition at a decoder.

7. The method of claim 6 , wherein the coefficients block flag (CBF) value is inferred as one or zero.

8. The method of claim 1 , wherein multiple prediction samples for the intra prediction are generated in parallel for the plurality of sub-partitions.

9. An apparatus of video decoding, comprising:

one or more processors;

a non-transitory computer-readable memory storing instructions executable by the one or more processors,

wherein the one or more processors are configured to:

perform an intra prediction for a plurality of sub-partitions of a coding block in a Intra Sub-Partition (ISP) mode in response to determining that the plurality of sub-partitions meet first conditions for the intra prediction,

wherein performing the intra prediction for the plurality of sub-partitions of the coding block comprises:

merging at least two sub-partitions of the plurality of sub-partitions into one prediction region for the intra prediction, and

generating predicted samples for the one prediction region in the intra prediction based on a plurality of reference samples of the coding block adjacent to the one prediction region,

wherein the first conditions comprise that the plurality of sub-partitions are a plurality of vertical sub-partitions and each of the sub-partitions has a width less than or equal to 2.

10. The apparatus of claim 9 , wherein no reconstructed sample from one sub-partition of the at least two sub-partitions is used to perform the intra prediction for any other sub-partition of the at least two sub-partitions.

11. The apparatus of claim 9 , wherein, the one or more processors are further configured to:

generate a set of predicted samples for the plurality of vertical sub-partitions using a vertical prediction mode with a mode index larger than 50.

12. The apparatus of claim 9 , wherein, the one or more processors are further configured to: perform the intra prediction for the plurality of vertical sub-partitions independently and in parallel.

13. The apparatus of claim 9 , wherein the plurality of sub-partitions includes a last sub-partition, and the method further comprises signaling a coefficients block flag (CBF) value for the last sub-partition.

14. The apparatus of claim 13 , wherein the plurality of sub-partitions includes a last sub-partition, and the method further comprises inferring a coefficients block flag (CBF) value for the last sub-partition at a decoder.

15. The apparatus of claim 14 , wherein the coefficients block flag (CBF) value is inferred as one or zero.

16. A non-transitory computer-readable storage medium storing a plurality of programs for execution by an apparatus of video decoding having one or more processors, wherein the plurality of programs, when executed by the one or more processors, cause the apparatus of video decoding to perform decoding operations including:

performing an intra prediction for a plurality of sub-partitions of a coding block in a Intra Sub-Partition (ISP) mode in response to determining that the plurality of sub-partitions meet first conditions for the intra prediction,

wherein performing the intra prediction for the plurality of sub-partitions of the coding block comprises:

merging at least two sub-partitions of the plurality of sub-partitions into one prediction region for the intra prediction, and

generating predicted samples for the one prediction region in the intra prediction based on a plurality of reference samples of the coding block adjacent to the one prediction region,

wherein the first conditions comprise that the plurality of sub-partitions are a plurality of vertical sub-partitions and each of the sub-partitions has a width less than or equal to 2.