Local illumination compensation in video coding

1. A method of coding video data, the method comprising:

selecting, by one or more processors, a set of a plurality of neighboring samples of a current block in a current picture, wherein the plurality of neighboring samples includes a row of samples adjacent to a top row of the current block in the current picture and a column of samples adjacent to a left column of the current block in the current picture, wherein selecting the sub-set of the plurality of neighboring samples comprises:

determining that a particular sample is reconstructed based on other samples in the current picture comprises determining that the particular sample is included in a block coded with one of a plurality of specified prediction modes that includes combined intra and inter prediction (CIIP) mode, and current picture referencing (CPR) mode;

excluding, from the set of neighboring samples, samples in the row of samples adjacent to the top row of the current block that are reconstructed based on other samples in the current picture; and

excluding, from the set of neighboring samples, samples in the column of samples adjacent to the left column of the current block that are reconstructed based on other samples in the current picture;

deriving, by the one or more processors and based on the set of the plurality of neighboring samples in the current picture, local illumination compensation (LIC) parameters for the current block; and

performing, by the one or more processors and based on the LIC parameters, LIC on samples of the current block to generate compensated samples of the current block.

2. The method of claim 1 , further comprising:

coding, from a video bitstream, one or more syntax elements that indicate the plurality of specified prediction modes.

3. The method of claim 1 , wherein deriving the LIC parameters for the current block comprises deriving the LIC parameters for the current block based on the set of the plurality of neighboring samples of the current block in the current picture and a set of a plurality of neighboring samples of a reference block in a reference picture, the reference block used to predict the samples of the current block, wherein the method further comprises:

selecting, by the one or more processors, the set of the plurality of neighboring samples of the reference block in the reference picture, wherein the plurality of neighboring samples of the reference block includes a row of samples adjacent to a top row of the reference block in the reference picture and a column of samples adjacent to a left column of the reference block in the reference picture.

4. The method of claim 3 , wherein selecting the set of neighboring samples of the reference block comprises:

excluding, from the set of neighboring samples of the reference block, samples of the plurality of neighboring samples of the reference block located at relative positions corresponding to samples of the plurality of neighboring samples of the current block that are excluded from the set of neighboring samples of the current block.

5. The method of claim 1 , wherein performing LIC comprises performing LIC in response to determining to perform LIC for the current block.

6. The method of claim 5 , wherein determining to perform LIC for the current block comprises inferring whether to perform LIC for the current block.

7. The method of claim 6 , wherein inferring whether to perform LIC for the current block comprises determining whether to perform LIC for the current block based on whether the current block is coded using skip mode.

8. The method of claim 6 , wherein inferring whether to perform LIC for the current block comprises determining whether to perform LIC for the current block based on a value of a coded block flag for the current block.

9. The method of claim 1 , wherein the one or more processors are included in a video decoder.

10. The method of claim 1 , wherein the one or more processors are included in a video encoder.

11. An apparatus for processing video data, the apparatus comprising:

one or more storage media; and

one or more processors implemented in circuitry and configured to:

select a set of a plurality of neighboring samples of a current block in a current picture, wherein the plurality of neighboring samples includes a row of samples adjacent to a top row of the current block in the current picture and a column of samples adjacent to a left column of the current block in the current picture, wherein, to select the sub-set of neighboring samples, the one or more processors are configured to:

determine that a particular sample is reconstructed based on other samples in the current picture comprises determining that the particular sample is included in a block coded with one of a plurality of specified prediction modes that includes combined intra and inter prediction (CIIP) mode, and current picture referencing (CPR) mode;

exclude, from the set of neighboring samples, samples in the row of samples adjacent to the top row of the current block that are reconstructed based on other samples in the current picture; and

exclude, from the set of neighboring samples, samples in the column of samples adjacent to the left column of the current block that are reconstructed based on other samples in the current picture;

derive, based on the set of the plurality of neighboring samples in the current picture, local illumination compensation (LIC) parameters for the current block; and

perform, based on the LIC parameters, LIC on samples of the current block to generate compensated samples of the current block.

12. The apparatus of claim 11 , wherein the one or more processors are further configured to:

code, from a video bitstream, one or more syntax elements that indicate the plurality of specified prediction modes.

13. The apparatus of claim 11 , wherein, to derive the LIC parameters for the current block, the one or more processors configured to derive the LIC parameters for the current block based on the set of the plurality of neighboring samples of the current block in the current picture and a set of a plurality of neighboring samples of a reference block in a reference picture, the reference block used to predict the samples of the current block, wherein the one or more processors are further configured to:

select the set of the plurality of neighboring samples of the reference block in the reference picture, wherein the plurality of neighboring samples of the reference block includes a row of samples adjacent to a top row of the reference block in the reference picture and a column of samples adjacent to a left column of the reference block in the reference picture.

14. The apparatus of claim 13 , wherein, to select the set of neighboring samples of the reference block, the one or more processors are configured to:

exclude, from the set of neighboring samples of the reference block, samples of the plurality of neighboring samples of the reference block located at relative positions corresponding to samples of the plurality of neighboring samples of the current block that are excluded from the set of neighboring samples of the current block.

15. The apparatus of claim 11 , wherein, to perform LIC, the one or more processors are configured to perform LIC in response to determining to perform LIC for the current block.

16. The apparatus of claim 15 , wherein, to determine to perform LIC for the current block, the one or more processors are configured to infer whether to perform LIC for the current block.

17. The apparatus of claim 16 , wherein, to infer whether to perform LIC for the current block, the one or more processors are configured to determine whether to perform LIC for the current block based on whether the current block is coded using skip mode.

18. The apparatus of claim 16 , wherein, to infer whether to perform LIC for the current block, the one or more processors are configured to determine whether to perform LIC for the current block based on a value of a coded block flag for the current block.

19. The apparatus of claim 11 , wherein the one or more processors are included in a video decoder.

20. The apparatus of claim 11 , wherein the one or more processors are included in a video encoder.

21. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to:

select a set of a plurality of neighboring samples of a current block in a current picture, wherein the plurality of neighboring samples includes a row of samples adjacent to a top row of the current block in the current picture and a column of samples adjacent to a left column of the current block in the current picture, wherein the instructions that cause the one or more processors to select the sub-set of neighboring samples comprise instructions that cause the one or more processors to:

determine that a particular sample is reconstructed based on other samples in the current picture comprises determining that the particular sample is included in a block coded with one of a plurality of specified prediction modes that includes combined intra and inter prediction (CIIP) mode, and current picture referencing (CPR) mode;

exclude, from the set of neighboring samples, samples in the row of samples adjacent to the top row of the current block that are reconstructed based on other samples in the current picture; and

exclude, from the set of neighboring samples, samples in the column of samples adjacent to the left column of the current block that are reconstructed based on other samples in the current picture;

derive, based on the set of the plurality of neighboring samples in the current picture, local illumination compensation (LIC) parameters for the current block; and

perform, based on the LIC parameters, LIC on samples of the current block to generate compensated samples of the current block.

22. A device for coding video data, the device comprising:

means for selecting a set of a plurality of neighboring samples of a current block in a current picture, wherein the plurality of neighboring samples includes a row of samples adjacent to a top row of the current block in the current picture and a column of samples adjacent to a left column of the current block in the current picture, wherein the means for selecting comprise:

means for determining that a particular sample is reconstructed based on other samples in the current picture comprises determining that the particular sample is included in a block coded with one of a plurality of specified prediction modes that includes combined intra and inter prediction (CIIP) mode, and current picture referencing CPR) mode;

means for excluding, from the set of neighboring samples, samples in the row of samples adjacent to the top row of the current block that are reconstructed based on other samples in the current picture; and

means for excluding, from the set of neighboring samples, samples in the column of samples adjacent to the left column of the current block that are reconstructed based on other samples in the current picture;

means for deriving, based on the set of the plurality of neighboring samples in the current picture, local illumination compensation (LIC) parameters for the current block; and

means for performing, based on the LIC parameters, LIC on samples of the current block to generate compensated samples of the current block.