Intra block copy with an adaptive local reference range

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

reconstructing an area in a block in a current picture from a coded video bitstream, the block including one or more coding blocks (CBs) in the current picture;

after the reconstructing, determining whether to update a previous local reference search range for an intra block copy (IBC) mode with reconstructed samples in the reconstructed area based on (i) a content of the reconstructed area and/or (ii) prediction information of the reconstructed area that indicates the previous local reference search range is to be updated; and

in response to a determination not to update the previous local reference search range for the IBC mode with the reconstructed samples in the reconstructed area,

the previous local reference search range for the IBC mode is not updated, and

decoding a coding block (CB) in the current picture using the IBC mode that is based on the previous local reference search range, which does not include the reconstructed area.

2. The method of claim 1 , wherein the determining whether to update the previous local reference search range comprises:

determining the content of the reconstructed area based on the reconstructed samples in the reconstructed area, the content of the reconstructed area indicating a percentage of a texture content and/or a percentage of a screen content in the reconstructed area; and

determining whether to update the previous local reference search range for the IBC mode based on the percentage of the texture content and/or the percentage of the screen content in the reconstructed area.

3. The method of claim 2 , wherein

the content of the reconstructed area includes no screen content; and

the determining whether to update the previous local reference search range includes determining that the previous local reference search range for the IBC mode is not to be updated.

4. The method of claim 1 , wherein the determining whether to update the previous local reference search range comprises:

decoding the prediction information of the area, which indicates a prediction mode of the area; and

determining whether to update the previous local reference search range for the IBC mode based on whether the prediction mode is in a set of pre-defined prediction modes.

5. The method of claim 1 , wherein the determining whether to update the previous local reference search range comprises:

decoding the prediction information of the area, which indicates whether to update the previous local reference search range with the reconstructed samples in the reconstructed area; and

determining whether to update the previous local reference search range for the IBC mode based on the indication, in the prediction information, of whether to update the previous local reference search range with the reconstructed samples in the reconstructed area.

6. The method of claim 5 , wherein

whether to update the previous local reference search range with the reconstructed samples in the reconstructed area is indicated by a flag included in the prediction information of the area; and

the determining whether to update the previous local reference search range includes determining whether to update the previous local reference search range for the IBC mode based on the flag.

7. The method of claim 6 , wherein

the flag indicates whether any reconstructed samples in the block are to be used in updating the local reference search range in the IBC mode.

8. The method of claim 1 , wherein

the previous local reference search range for the IBC mode is determined to be updated;

the previous local reference search range includes multiple areas stored in a reference sample memory (RSM), the multiple areas including reference samples; and

the method further includes:

ranking the multiple areas based on contents of the multiple areas, each of the contents corresponding to a respective one of the multiple areas;

selecting an area in the multiple areas to be replaced by the reconstructed samples in the reconstructed area based on the ranking of the multiple areas; and

generating a current local reference search range by replacing the selected area in the previous local reference search range with the reconstructed samples in the reconstructed area.

9. The method of claim 8 , wherein

each of the contents corresponding to the respective one of the multiple areas is indicated by a percentage of a screen content or a percentage of a texture content in the corresponding area; and

the ranking the multiple areas includes ranking the multiple areas based on the respective percentages of the screen contents or the respective percentages of the texture contents of the multiple areas.

10. The method of claim 1 , wherein

the previous local reference search range for the IBC mode is determined to be updated;

the previous local reference search range includes multiple areas stored in a reference sample memory (RSM);

each area of the multiple areas includes a number of specially coded reference samples in the respective area that are coded with one or more prediction modes in a set of pre-defined prediction modes; and

the method further includes:

ranking the multiple areas based on the respective numbers of specially coded reference samples in the multiple areas;

selecting an area in the multiple areas to be replaced by the reconstructed samples in the reconstructed area based on the ranking of the multiple areas; and

generating a current local reference search range by replacing the selected area in the previous local reference search range with the reconstructed samples in the reconstructed area.

11. The method of claim 1 , wherein

the previous local reference search range for the IBC mode is determined to be updated;

the previous local reference search range includes multiple areas stored in a reference sample memory (RSM);

a reference frequency associated with each area of the multiple areas indicates a number of times that the respective area is referenced by block vectors used to predict CBs in the current picture; and

the method further includes:

ranking the multiple areas based on the respective reference frequencies of the multiple areas;

selecting an area in the multiple areas to be replaced by the reconstructed samples in the reconstructed area based on the ranking of the multiple areas; and

generating a current local reference search range by replacing the selected area in the previous local reference search range with the reconstructed samples in the reconstructed area.

12. The method of claim 1 , wherein

the previous local reference search range includes multiple areas;

reconstructed samples of the multiple areas except reconstructed samples of a sub-area in one of the multiple areas are stored in a reference sample memory (RSM); and

the reconstructed samples of the sub-area in the one of the multiple areas are replaced by a padding process that stores padded samples corresponding to the sub-area in the one of the multiple areas in the RSM.

13. The method of claim 1 , wherein

the reconstructed area is a reconstructed coding block, or

a size of the reconstructed area is a size of a memory update area unit.

14. An apparatus for video decoding, comprising:

processing circuitry configured to:

reconstruct an area in a block in a current picture from a coded video bitstream, the block including one or more coding blocks (CBs) in the current picture;

after the reconstructing, determine whether to update a previous local reference search range for an intra block copy (IBC) mode with reconstructed samples in the reconstructed area based on (i) a content of the reconstructed area and/or (ii) prediction information of the reconstructed area that indicates the previous local reference search range is to be updated; and

in response to a determination not to update the previous local reference search range for the IBC mode with the reconstructed samples in the reconstructed area,

the previous local reference search range for the IBC mode is not updated, and

decode a coding block (CB) in the current picture using the IBC mode that is based on the previous local reference search range, which does not include the reconstructed area.

15. The apparatus of claim 14 , wherein the processing circuitry is configured to:

determine the content of the reconstructed area based on the reconstructed samples in the reconstructed area, the content of the reconstructed area indicating a percentage of a texture content and/or a percentage of a screen content in the reconstructed area; and

determine whether to update the previous local reference search range for the IBC mode based on the percentage of the texture content and/or the percentage of the screen content in the reconstructed area.

16. The apparatus of claim 15 , wherein

the content of the reconstructed area includes no screen content; and

the processing circuitry is configured to determine that the previous local reference search range for the IBC mode is not to be updated.

17. The apparatus of claim 14 , wherein the processing circuitry is configured to:

decode the prediction information of the area, which indicates whether to update the previous local reference search range with the reconstructed samples in the reconstructed area; and

determine whether to update the previous local reference search range for the IBC mode based on the indication, in the prediction information, of whether to update the previous local reference search range with the reconstructed samples in the reconstructed area.

18. The apparatus of claim 17 , wherein

whether to update the previous local reference search range with the reconstructed samples in the reconstructed area is indicated by a flag included in the prediction information of the area; and

the processing circuitry is configured to determine whether to update the previous local reference search range for the IBC mode based on the flag.

19. The apparatus of claim 18 , wherein

the flag indicates whether any reconstructed samples in the block are to be used in updating the local reference search range in the IBC mode.

20. A non-transitory computer-readable storage medium storing a program executable by at least one processor to perform:

reconstructing an area in a block in a current picture from a coded video bitstream, the block including one or more coding blocks (CBs) in the current picture;

after the reconstructing, determining whether to update a previous local reference search range for an intra block copy (IBC) mode with reconstructed samples in the reconstructed area based on (i) a content of the reconstructed area and/or (ii) prediction information of the reconstructed area that indicates the previous local reference search range is to be updated; and

in response to a determination not to update the previous local reference search range for the IBC mode with the reconstructed samples in the reconstructed area,

the previous local reference search range for the IBC mode is not updated, and

decoding a coding block (CB) in the current picture using the IBC mode that is based on the previous local reference search range, which does not include the reconstructed area.