Constraint of intra mode for geometric partition mode with inter and intra prediction

1. A method of video decoding performed in a video decoder, the method comprising:

receiving coded information of a current block in a current picture of a video from a coded video bitstream;

partitioning the current block into at least a first partition and a second partition based on a geometric partition mode (GPM);

determining a first prediction mode for the first partition of the current block based on a first number of neighboring reconstructed samples adjacent to the first partition being larger than a threshold value, the threshold value indicating a minimum number of the neighboring reconstructing samples adjacent to the first partition that is required to allow an intra prediction mode for the first partition;

in response to the first number of neighboring reconstructed samples adjacent to the first partition being smaller than the threshold value,

determining that a flag indicating whether the current block is intra coded or inter coded is not signaled in the coded video bitstream; and

inferring that the first prediction mode is inter prediction mode without decoding the flag indicating whether the current block is intra coded or inter coded in the coded video bitstream; and

reconstructing the first partition of the current block based on the first prediction mode.

2. The method of claim 1 , wherein the neighboring reconstructed samples adjacent to the first partition include at least one of left neighboring reconstructed samples, top neighboring reconstructed samples, a top-left neighboring reconstructed sample, or a top-right neighboring reconstructed sample.

3. The method of claim 1 , wherein the threshold value is one of a value based on a size of the current block and a value based on a shape of the current block.

4. The method of claim 1 , wherein the threshold value includes one of W/4, H/4, and (W+H)/4, the W being a width of the current block, and the H being a height of the current block.

5. The method of claim 2 , further comprising:

determining a second prediction mode for the second partition of the current block based on a second number of neighboring reconstructed samples adjacent to the second partition being larger than the threshold value; and

reconstructing the second partition of the current block based on the second prediction mode.

6. The method of claim 5 , wherein

the determining the first prediction mode includes determining that the first prediction mode for the first partition is a first inter prediction mode based on the first number of the neighboring reconstructed samples adjacent to the first partition being equal to or less than the threshold value; and

the determining the second prediction mode includes determining that the second prediction mode for the first partition is a second inter prediction mode based on the second number of the neighboring reconstructed samples adjacent to the second partition being equal to or less than the threshold value.

7. The method of claim 2 , wherein the determining the first prediction mode further comprises:

in response to the first number of the left neighboring reconstructed samples adjacent to the first partition being equal to or less than the threshold value, determining that the first prediction mode for the first partition is not an intra prediction mode based on the left neighboring reconstructed samples adjacent to the first partition.

8. The method of claim 2 , wherein the determining the first prediction mode further comprises:

in response to the first number of the top neighboring reconstructed samples adjacent to the first partition being equal to or less than the threshold value, determining that the first prediction mode for the first partition is not an intra prediction mode based on the top neighboring reconstructed samples adjacent to the first partition.

9. The method of claim 2 , wherein the coded information further comprises:

a first flag that indicates whether the first prediction mode for the first partition corresponds to intra prediction based on the top neighboring reconstructed samples adjacent to the first partition, and

a second flag that indicates whether the first prediction mode for the first partition corresponds to intra prediction based on the left neighboring reconstructed samples adjacent to the first partition.

10. The method of claim 9 , further comprising:

in response to the first flag indicating that the first prediction mode for the first partition is not an intra prediction mode based on the top neighboring reconstructed samples adjacent to the first partition,

based on a height of the current block being greater than a width of the current block, determining that the first prediction mode is equal to (i) a pre-defined intra prediction mode minus six based on a ratio of the width of the current block and the height of the current block being equal to or less than one, and (ii) the pre-defined intra prediction mode−(6+2*the ratio of the width of the current block and the height of the current block) based on the ratio of the width of the current block and the height of the current block being larger than one; and

based on the pre-defined intra prediction mode being less than zero, determining that the first prediction mode is equal to the pre-defined intra prediction mode plus 67.

11. The method of claim 9 , further comprising:

in response to the first flag indicating that the first prediction mode for the first partition corresponds to intra prediction based on the top neighboring reconstructed samples adjacent to the first partition, and the second flag indicating that the first prediction mode for the first partition is not an intra prediction mode based on the left neighboring reconstructed samples adjacent to the first partition,

based on a width of the current block being greater than a height of the current block, determining that the first prediction mode is equal to (i) a sum of a pre-defined intra prediction mode, 33, and 8 based on a ratio of the width of the current block and the height of the current block being equal to or less than one, and (ii) a sum of the pre-defined intra prediction mode, 33, and (8+2*the ratio of the width of the current block and the height of the current block) based on the ratio of the width of the current block and the height of the current block being larger than one;

based on the width of the current block being equal to or less than the height of the current block, determining that the first prediction mode is equal to the pre-defined intra prediction mode plus 33; and

based on the pre-defined intra prediction mode being larger than 66, determining that the first prediction mode is equal to the pre-defined intra prediction mode minus 65.

12. An apparatus, comprising:

processing circuitry configured to:

receive coded information of a current block in a current picture of a video from a coded video bitstream;

partition the current block into at least a first partition and a second partition based on a geometric partition mode (GPM);

determine a first prediction mode for the first partition of the current block based on a first number of neighboring reconstructed samples adjacent to the first partition being larger than a threshold value, the threshold value indicating a minimum number of the neighboring reconstructing samples adjacent to the first partition that is required to allow an intra prediction mode for the first partition;

in response to the first number of neighboring reconstructed samples adjacent to the first partition being smaller than the threshold value,

determine that a flag indicating whether the current block is intra coded or inter coded is not signaled in the coded video bitstream; and

infer that the first prediction mode is inter prediction mode without decoding the flag indicating whether the current block is intra coded or inter coded in the coded video bitstream; and

reconstruct the first partition of the current block based on the first prediction mode.

13. The apparatus of claim 12 , wherein:

the neighboring reconstructed samples adjacent to the first partition include at least one of left neighboring reconstructed samples, top neighboring reconstructed samples, a top-left neighboring reconstructed sample, or a top-right neighboring reconstructed sample, and

the threshold value is one of a value based on a size of the current block and a value based on a shape of the current block.

14. The apparatus of claim 13 , wherein the processing circuitry is configured to:

determine that the first prediction mode for the first partition is a first inter prediction mode based on the first number of the neighboring reconstructed samples adjacent to the first partition being equal to or less than the threshold value; and

determine that the second prediction mode for the first partition is a second inter prediction mode based on a second number of the neighboring reconstructed samples adjacent to the second partition being equal to or less than the threshold value.

15. The apparatus of claim 13 , wherein the processing circuitry is configured to:

in response to the first number of the left neighboring reconstructed samples adjacent to the first partition being equal to or less than the threshold value, determine that the first prediction mode for the first partition is not an intra prediction mode based on the left neighboring reconstructed samples adjacent to the first partition.

16. The apparatus of claim 13 , wherein the processing circuitry is configured to:

in response to the first number of the top neighboring reconstructed samples adjacent to the first partition being equal to or less than the threshold value, determine that the first prediction mode for the first partition is not an intra prediction mode based on the top neighboring reconstructed samples adjacent to the first partition.

17. The apparatus of claim 13 , wherein the coded information further comprises:

a first flag that indicates whether the first prediction mode for the first partition corresponds to intra prediction based on the top neighboring reconstructed samples adjacent to the first partition, and

a second flag that indicates whether the first prediction mode for the first partition corresponds to intra prediction based on the left neighboring reconstructed samples adjacent to the first partition.

18. The apparatus of claim 17 , wherein the processing circuitry is configured to:

in response to the first flag indicating that the first prediction mode for the first partition is not an intra prediction mode based on the top neighboring reconstructed samples adjacent to the first partition,

based on a height of the current block being greater than a width of the current block, determine that the first prediction mode is equal to (i) a pre-defined intra prediction mode minus six based on a ratio of the width of the current block and the height of the current block being equal to or less than one, and (ii) the pre-defined intra prediction mode−(6+2*the ratio of the width of the current block and the height of the current block) based on the ratio of the width of the current block and the height of the current block being larger than one; and

based on the pre-defined intra prediction mode being less than zero, determine that the first prediction mode is equal to the pre-defined intra prediction mode plus 67.

19. The apparatus of claim 17 , wherein the processing circuitry is further configured to:

in response to the first flag indicating that the first prediction mode for the first partition corresponds to intra prediction based on the top neighboring reconstructed samples adjacent to the first partition, and the second flag indicating that the first prediction mode for the first partition is not an intra prediction mode based on the left neighboring reconstructed samples adjacent to the first partition,

based on a width of the current block being greater than a height of the current block, determine that the first prediction mode is equal to (i) a sum of a pre-defined intra prediction mode, 33, and 8 based on n a ratio of the width of the current block and the height of the current block being equal to or less than one, and (ii) a sum of the pre-defined intra prediction mode, 33, and (8+2*the ratio of the width of the current block and the height of the current block) based on the ratio of the width of the current block and the height of the current block being larger than one;

based on the width of the current block being equal to or less than the height of the current block, determine that the first prediction mode is equal to the pre-defined intra prediction mode plus 33; and

based on the pre-defined intra prediction mode being larger than 66, determine that the first prediction mode is equal to the pre-defined intra prediction mode minus 65.

20. A non-transitory computer readable storage medium storing instructions which when executed by at least one processor cause the at least one processor to perform:

receiving coded information of a current block in a current picture of a video from a coded video bitstream;

partitioning the current block into at least a first partition and a second partition based on a geometric partition mode (GPM);

determining a first prediction mode for the first partition of the current block based on a first number of neighboring reconstructed samples adjacent to the first partition being larger than a threshold value, the threshold value indicating a minimum number of the neighboring reconstructing samples adjacent to the first partition that is required to allow an intra prediction mode for the first partition;

in response to the first number of neighboring reconstructed samples adjacent to the first partition being smaller than the threshold value,

determining that a flag indicating whether the current block is intra coded or inter coded is not signaled in the coded video bitstream; and

inferring that the first prediction mode is inter prediction mode without decoding the flag indicating whether the current block is intra coded or inter coded in the coded video bitstream; and

reconstructing the first partition of the current block based on the first prediction mode.