Method and apparatus for video coding

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

decoding first prediction information of a current region in a current picture and second prediction information of a current block of plural blocks included in the current region from a coded video bitstream, the first prediction information indicating a first set of default vectors in a set of vectors such that individual candidate lists for each of two or more of the plural blocks of the current region are filled using the same first set of default vectors, and the second prediction information indicating that a prediction mode for reconstructing the current block is one of: an inter prediction mode and an intra block copy (IBC) mode, the first set of default vectors being different from a zero vector;

in response to a determination that a number of candidates in a candidate list for the current block is less than a threshold, selecting one or more default vectors from the first set of default vectors indicated by the first prediction information of the current region in which the current block is located;

adding the selected one or more default vectors from the first set of default vectors indicated by the first prediction information of the current region to the candidate list for the current block; and

reconstructing at least one sample in the current block based on the candidate list including the selected one or more default vectors.

2. The method of claim 1 , wherein

the method further includes determining the number of candidates in the candidate list.

3. The method of claim 1 , wherein

the current region is one of: a slice, a tile, and a tile group; and

the first prediction information is signaled in a header, the header being one of: a slice header, a tile header, and a tile group header.

4. The method of claim 1 , wherein the first prediction information includes the first set of default vectors.

5. The method of claim 1 , wherein

the first prediction information includes indices pointing to first vectors in the set of vectors; and

the method further includes determining the first vectors to be the first set of default vectors.

6. The method of claim 1 , wherein

the method includes obtaining a second set of default vectors for a previously reconstructed region; and

the first set of default vectors for the current region further includes vectors determined based on the second set of default vectors and the first prediction information.

7. The method of claim 6 , wherein

the first prediction information includes at least one index and at least one new vector to replace at least one of the second set of default vectors, the at least one index indicating the at least one of the second set of default vectors to be replaced; and

the method further includes:

replacing the at least one of the second set of default vectors with the at least one new vector to form the vectors included in the first set of default vectors.

8. The method of claim 1 , wherein the adding the selected one or more default vectors further comprises:

adding the selected one or more default vectors from the first set of default vectors to a last entry in the candidate list.

9. The method of claim 1 , wherein the adding the vector further comprises:

prior to adding the selected one or more default vectors, determining whether at least one candidate in the candidate list is invalid for the current block;

when the at least one candidate in the candidate list is determined to be invalid,

removing the at least one candidate from the candidate list to prune the candidate list; and

adding the selected one or more default vectors from the first set of default vectors to a last entry in the pruned candidate list.

10. The method of claim 1 , wherein the selected one or more default vectors are block vectors and the prediction mode is the IBC mode.

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

decoding prediction information of a current block in a current picture from a coded video bitstream, the prediction information indicating that a prediction mode for reconstructing the current block is one of: an inter prediction mode and an intra block copy (IBC) mode;

selecting a candidate from a candidate list for the current block as a base vector;

selecting, based on the decoded prediction information, an offset vector to be added to the base vector from a set of offset vectors, the set of offset vectors being one of: a first set of (+1, 0), (−1, 0), (0, +1), and (0, −1) or a second set of (+2, 0), (−2, 0), (0, +2), and (0, −2), the decoded prediction information signaling whether the first set or the second set is to be used as the set of offset vectors;

adding the selected offset vector to the base vector to determine a vector;

adding, to the candidate list, the vector generated by adding the base vector and the offset vector; and

reconstructing at least one sample in the current block based on the candidate list after the vector is added to the candidate list.

12. An apparatus for video decoding, comprising processing circuitry configured to:

decode first prediction information of a current region in a current picture and second prediction information of a current block of plural blocks included in the current region from a coded video bitstream, the first prediction information indicating a first set of default vectors in a set of vectors such that individual candidate lists for each of two or more of the plural blocks of the current region are filled using the same first set of default vectors, and the second prediction information indicating that a prediction mode for reconstructing the current block is one of: an inter prediction mode and an intra block copy (IBC) mode, the first set of default vectors being different from a zero vector;

in response to a determination that a number of candidates in a candidate list for the current block is less than a threshold, select one or more default vectors from the first set of default vectors indicated by the first prediction information of the current region in which the current block is located;

add the selected one or more default vectors from the first set of default vectors indicated by the first prediction information of the current region to the candidate list for the current block; and

reconstruct at least one sample in the current block based on the candidate list including the selected one or more default vectors.

13. The apparatus of claim 12 , wherein the processing circuitry is further configured to:

determine the number of candidates in the candidate list.

14. The apparatus of claim 12 , wherein

the current region is one of: a slice, a tile, and a tile group; and

the first prediction information is signaled in a header, the header being one of: a slice header, a tile header, and a tile group header.

15. The apparatus of claim 12 , the first prediction information includes the first set of default vectors.

16. The apparatus of claim 12 , wherein

the first prediction information includes indices pointing to first vectors in the set of vectors; and

the processing circuitry is further configured to determine the first vectors to be the first set of default vectors.

17. The apparatus of claim 12 , wherein

the processing circuitry is further configured to:

obtain a second set of default vectors for a previously reconstructed region; and

the first set of default vectors for the current region further includes vectors determined based on the second set of default vectors and the first prediction information.

18. The apparatus of claim 17 , wherein

the first prediction information includes at least one index and at least one new vector to replace at least one of the second set of default vectors, the at least one index indicating the at least one of the second set of default vectors to be replaced; and

the processing circuitry is further configured to:

replace the at least one of the second set of default vectors with the at least one new vector to form the vectors included in the first set of default vectors.

19. The apparatus of claim 12 , wherein the processing circuitry is further configured to:

add the selected one or more default vectors from the first set of default vectors to a last entry in the candidate list.