Method and apparatus for video coding

1. A method for video decoding in a decoder, comprising:

decoding prediction information of a block from a coded video bitstream, the prediction information of the block indicating a first intra prediction direction mode number for the block, the first intra prediction direction mode number corresponding to a first intra prediction direction angle;

determining a second intra prediction direction mode number based on the indicated first intra prediction direction mode number and a shape of the block being non-square, the second intra prediction direction mode number corresponding to a second intra prediction direction angle that is different from the first intra prediction direction angle; and

reconstructing at least one sample of the block according to the determined second intra prediction direction mode number.

2. The method of claim 1 , wherein an intra prediction direction mode corresponding to the first intra prediction direction mode number in a case that the shape of the block is square is different from an intra prediction direction mode corresponding to the second intra prediction direction mode number in a case that the shape of the block is non-square.

3. The method of claim 1 , wherein

the shape of the block is non-square, and

the determining includes determining the second intra prediction direction mode number from a first set of intra-prediction direction mode numbers that is associated with the non-square block, the first set of intra prediction direction mode numbers including a subset of a second set of intra prediction direction mode numbers that is associated with a square block and at least one additional intra prediction direction mode number that is different from the second set of intra prediction direction mode numbers.

4. The method of claim 3 , wherein a number of the at least one additional intra prediction direction mode number is a fixed number that is independent of the shape of the non-square block, the number being from 1 to 7 when the first set of intra prediction direction mode numbers has 33 intra prediction direction mode numbers, the number being from 2 to 14 when the first set of intra prediction direction mode numbers has 65 intra prediction direction mode numbers, and the number being from 4 to 28 when the first set of intra prediction direction mode numbers has 127 intra prediction direction mode numbers.

5. The method of claim 3 , wherein a number of the at least one additional intra prediction direction mode number is determined based on at least one of a width of the block, a height of the block, a ratio of the width and the height of the block, and an area of the block.

6. The method of claim 3 , further comprising:

decoding a syntax element from the coded video bitstream, the syntax element indicating a number of the at least one additional intra prediction direction mode number, the syntax element being in at least one of a sequence parameter set, a picture parameter set, a slice header, a common syntax element for a region of a picture, and a common parameter for the region of the picture.

7. The method of claim 3 , wherein the determined second intra prediction direction mode number is not in the second set of intra prediction direction mode numbers that is associated with the square block.

8. The method of claim 3 , wherein a number of the at least one additional intra prediction direction mode number is equal to a number M when an aspect ratio of the block is equal to or less than 2.

9. The method of claim 8 , wherein the number M is equal to 3 when the second set of intra prediction direction mode numbers has 33 intra prediction direction mode numbers, and the number M is equal to 6 when the second set of intra prediction direction mode numbers has 65 intra prediction direction mode numbers.

10. The method of claim 3 , wherein a number of the at least one additional intra prediction direction mode number is equal to a number N when an aspect ratio of the block is equal to or more than 4.

11. The method of claim 10 , wherein the number N is equal to 5 when the second set of intra prediction direction mode numbers has 33 intra prediction direction mode numbers, and the number N is equal to 10 when the second set of intra prediction direction mode numbers has 65 intra prediction direction mode numbers.

12. An apparatus, comprising:

processing circuitry configured to:

decode prediction information of a block from a coded video bitstream, the prediction information of the block indicating a first intra prediction direction mode number for the block, the first intra prediction direction mode number corresponding to a first intra prediction direction angle;

determine a second intra prediction direction mode number based on the indicated first intra prediction direction mode number and a shape of the block being non-square, the second intra prediction direction mode number corresponding to a second intra prediction direction angle that is different from the first intra prediction direction angle; and

reconstruct at least one sample of the block according to the determined second intra prediction direction mode number.

13. The apparatus of claim 12 , wherein an intra prediction direction mode corresponding to the first intra prediction direction mode number in a case that the shape of the block is square is different from an intra prediction direction mode corresponding to the second intra prediction direction mode number in a case that the block is non-square.

14. The apparatus of claim 12 , wherein

the shape of the block is non-square, and

the processing circuitry is configured to determine the second intra prediction direction mode number from a first set of intra-prediction direction mode numbers that is associated with the non-square block, the first set of intra prediction direction mode numbers including a subset of a second set of intra prediction direction mode numbers that is associated with a square block and at least one additional intra prediction direction mode number that is different from the second set of intra prediction direction mode numbers.

15. The apparatus of claim 14 , wherein a number of the at least one additional intra prediction direction mode number is a fixed number that is independent of the shape of the non-square block, the number being from 1 to 7 when the first set of intra prediction direction mode numbers has 33 intra prediction direction mode numbers, the number being from 2 to 14 when the first set of intra prediction direction mode numbers has 65 intra prediction direction mode numbers, the number being from 4 to 28 when the first set of intra prediction direction mode numbers has 127 intra prediction direction mode numbers.

16. The apparatus of claim 14 , wherein a number of the at least one additional intra prediction direction mode number is equal to a number M when an aspect ratio of the block is equal to or less than 2.

17. The apparatus of claim 16 , wherein the number M is equal to 3 when the second set of intra prediction direction mode numbers has 33 intra prediction direction mode numbers, and the number M is equal to 6 when the second set of intra prediction direction mode numbers has 65 intra prediction direction mode numbers.

18. The apparatus of claim 14 , wherein a number of the at least one additional intra prediction direction mode number is equal to a number N when an aspect ratio of the block is equal to or more than 4.

19. The apparatus of claim 18 , wherein the number N is equal to 5 when the second set of intra prediction direction mode numbers has 33 intra prediction direction mode numbers, and the number N is equal to 10 when the second set of intra prediction direction mode numbers has 65 intra prediction direction mode numbers.

20. A non-transitory computer-readable medium storing instructions which when executed by a computer for video decoding cause the computer to perform:

decoding prediction information of a block from a coded video bitstream, the prediction information of the block indicating a first intra prediction direction mode number for the block, the first intra prediction direction mode number corresponding to a first intra prediction direction angle;

determining a second intra prediction direction mode number based on the indicated first intra prediction direction mode number and a shape of the block being non-square, the second intra prediction direction mode number corresponding to a second intra prediction direction angle that is different from the first intra prediction direction angle; and

reconstructing at least one sample of the block according to the determined second intra prediction direction mode number.