Candidate list size for intra block copy

1. A method of video decoding, comprising:

receiving a coded video bitstream including a current picture;

determining whether a current block included in the current picture is coded in an intra block copy (IBC) mode;

in response to determining that the current block is coded in the IBC mode, determining a maximum number of IBC predictor candidates associated with the current block based on a maximum of (i) a predetermined integer M and (ii) a maximum number of candidates MaxNumMergeCand in a merge mode list, wherein the maximum number of IBC predictor candidates is equal to a value of max (M, MaxNumMergeCand);

constructing an IBC predictor candidate list based on the maximum number of IBC predictor candidates;

determining a block vector associated with the current block based on a block vector predictor included in the IBC predictor candidate list; and

reconstructing the current block based on the block vector.

2. The method according to claim 1 , wherein the predetermined integer M is equal to 2.

3. The method according to claim 2 , wherein the predetermined integer M is equal to 2 based on the current block being coded in an IBC Advanced Motion Vector Prediction (AMVP) mode.

4. The method according to claim 1 , wherein signaling of a motion vector predictor index for the IBC mode is not dependent on the maximum number of candidates MaxNumMergeCand.

5. The method according to claim 1 , wherein a motion vector predictor index for the IBC mode is not signaled based on the maximum number of IBC predictor candidates being equal to 1.

6. The method according to claim 1 , wherein the determining the maximum number of IBC predictor candidates comprises:

determining the maximum number of IBC predictor candidates by processing circuitry of a video decoder.

7. An apparatus for performing video decoding, comprising:

processing circuitry configured to:

receive a coded video bitstream including a current picture;

determine whether a current block included in the current picture is coded in an intra block copy (IBC) mode;

in response to the current block being determined as coded in the IBC mode, determine a maximum number of IBC predictor candidates associated with the current block based on a maximum of (i) a predetermined integer M and (ii) a maximum number of candidates MaxNumMergeCand in a merge mode list, wherein the maximum number of IBC predictor candidates is equal to a value of max(M, MaxNumMergeCand);

construct an IBC predictor candidate list based on the maximum number of IBC predictor candidates;

determine a block vector associated with the current block based on a block vector predictor included in the IBC predictor candidate list; and

reconstruct the current block based on the block vector.

8. The apparatus according to claim 7 , wherein the predetermined integer M is equal to 2.

9. The apparatus according to claim 8 , wherein the predetermined integer M is equal to 2 based on the current block being coded in an IBC Advanced Motion Vector Prediction (AMVP) mode.

10. The apparatus according to claim 7 , wherein signaling of a motion vector predictor index for the IBC mode is not dependent on the maximum number of candidates MaxNumMergeCand.

11. The apparatus according to claim 7 , wherein a motion vector predictor index for the IBC mode is not signaled based on the maximum number of IBC predictor candidates being equal to 1.

12. A non-transitory computer readable medium storing instructions which when executed by a processor cause the processor to perform:

receiving a coded video bitstream including a current picture;

determining whether a current block included in the current picture is coded in an intra block copy (IBC) mode;

in response to determining that the current block is coded in the IBC mode, determining a maximum number of IBC predictor candidates associated with the current block based on a maximum of (i) a predetermined integer M and (ii) a maximum number of candidates MaxNumMergeCand in a merge mode list, wherein the maximum number of IBC predictor candidates is equal to a value of max(M, MaxNumMergeCand);

constructing an IBC predictor candidate list based on the maximum number of IBC predictor candidates;

determining a block vector associated with the current block based on a block vector predictor included in the IBC predictor candidate list; and

reconstructing the current block based on the block vector.

13. The non-transitory computer readable medium according to claim 12 , wherein the predetermined integer M is equal to 2.

14. The non-transitory computer readable medium according to claim 13 , wherein the predetermined integer M is equal 2 based on the current block being coded in an IBC Advanced Motion Vector Prediction (AMVP) mode.

15. The non-transitory computer readable medium according to claim 12 , wherein signaling of a motion vector predictor index for the IBC mode is not dependent on the maximum number of candidates MaxNumMergeCand.

16. The non-transitory computer readable medium according to claim 12 , wherein a motion vector predictor index for the IBC mode is not signaled based on the maximum number of IBC predictor candidates being equal to 1.

17. The method according to claim 1 , further comprising:

determining the maximum number of candidates MaxNumMergeCand in the merge mode list based on a predetermined constant and a syntax element signaled in the coded video bitstream.

18. The method according to claim 17 , wherein

the predetermined constant is 6;

the syntax element in the coded video bitstream is six_minus_max_num_merge_cand; and

the determining the maximum number of candidates MaxNumMergeCand includes determining the maximum number of candidates MaxNumMergeCand in the merge mode list being equal to (6−six_minus_max_num_merge_cand).

19. The method according to claim 4 , wherein the motion vector predictor index for the IBC mode is signaled.