Method and apparatus for video coding

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

decoding prediction information of a first block from a coded video bitstream, the first block being a non-square block and the prediction information of the first block being indicative of a first intra prediction direction mode in a first set of intra prediction direction modes that is associated with the non-square block, the first set of intra prediction direction modes including a subset of a second set of intra prediction direction modes that is associated with a square block and at least one additional intra prediction direction mode that is different from the second set of intra prediction direction modes; and

reconstructing at least one sample of the first block according to the first intra prediction direction mode, wherein

the second set of intra prediction direction modes includes at least one intra prediction direction mode that is different from the first set of intra prediction direction modes.

2. The method of claim 1 , wherein a number of the modes in the first set of intra prediction direction modes is equal to a number of the modes in the second set of intra prediction direction modes.

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

4. The method of claim 1 , wherein a number of the at least one additional intra prediction direction mode is determined based on at least one of a width of the first block, a height of the first block, a ratio of the width and the height of the first block, and an area of the first block.

5. The method of claim 1 , further comprising:

decoding a syntax element from the coded video bitstream, the syntax element being indicative of a number of the at least one additional intra prediction direction mode, 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.

6. The method of claim 1 , wherein the first intra prediction direction mode is not in the second set of intra prediction direction modes that is associated with the square block.

7. The method of claim 4 , wherein the number of the at least one additional intra prediction direction mode is equal to a number M when the aspect ratio of the first block is equal to or less than 2.

8. The method of claim 7 , wherein the number M is equal to 2 when the second set of intra prediction direction modes has 33 intra prediction direction modes, and the number M is equal to 6 when the second set of intra prediction direction modes has 65 intra prediction direction modes.

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

10. The method of claim 9 , wherein the number N is equal to 5 when the second set of intra prediction direction modes has 33 intra prediction direction modes, and the number N is equal to 10 when the second set of intra prediction direction modes has 65 intra prediction direction modes.

11. An apparatus, comprising:

processing circuitry configured to:

decode prediction information of a first block from a coded video bitstream, the

first block being a non-square block and the prediction information of the first block being indicative of a first intra prediction direction mode in a first set of intra prediction direction modes that is associated with the non-square block, the first set of intra prediction direction modes including a subset of a second set of intra prediction direction modes that is associated with a square block and at least one additional intra prediction direction mode that is different from the second set of intra prediction direction modes; and

reconstruct at least one sample of the first block according to the first intra prediction direction mode, wherein

the second set of intra prediction direction modes includes at least one intra prediction direction mode that is different from the first set of intra prediction direction modes.

12. The apparatus of claim 11 , wherein a number of the modes in the first set of intra prediction direction modes is equal to a number of the modes in the second set of intra prediction direction modes.

13. The apparatus of claim 11 , wherein a number of the at least one additional intra prediction direction mode is a fixed number that is independent of a shape of the first block, the number being from 1 to 7 when the first set of intra prediction direction modes has 33 intra prediction direction modes, the number being from 2 to 14 when the first set of intra prediction direction modes has 65 intra prediction direction modes, the number being from 4 to 28 when the first set of intra prediction direction modes has 127 intra prediction direction modes.

14. The apparatus of claim 11 , wherein a number of the at least one additional intra prediction direction mode is equal to a number M when the aspect ratio of the first block is equal to or less than 2.

15. The apparatus of claim 14 , wherein the number M is equal to 3 when the second set of intra prediction direction modes has 33 intra prediction direction modes, and the number M is equal to 6 when the second set of intra prediction direction modes has 65 intra prediction direction modes.

16. The apparatus of claim 11 , wherein a number of the at least one additional intra prediction direction mode is equal to a number N when the aspect ratio of the first block is equal to or more than 4.

17. The apparatus of claim 16 , wherein the number N is equal to 5 when the second set of intra prediction direction modes has 33 intra prediction direction modes, and the number N is equal to 10 when the second set of intra prediction direction modes has 65 intra prediction direction modes.

18. 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 first block from a coded video bitstream, the first block being a non-square block and the prediction information of the first block being indicative of a first intra prediction direction mode in a first set of intra prediction direction modes that is associated with the non-square block, the first set of intra prediction direction modes including a subset of a second set of intra prediction direction modes that is associated with a square block and at least one additional intra prediction direction mode that is different from the second set of intra prediction direction modes; and

reconstructing at least one sample of the first block according to the first intra prediction direction mode, wherein

the second set of intra prediction direction modes includes at least one intra prediction direction mode that is different from the first set of intra prediction direction modes.