On boundary padding sample filtering in image/video coding

1 . A method for processing video data, comprising:

generating, during a conversion between a first block of a video and a bitstream of the video, padding samples in an extended area of a first picture, wherein a prediction block of the first block is derived from the first picture;

filtering the padding samples within the extended area; and

performing the conversion based on the padding samples in the extended area as filtered,

wherein the method further comprises: filtering one or more second padding samples at one side or both sides of an edge of the padding samples,

wherein a first padding sample from the padding samples is filtered by adding an offset to a sample value of the first padding sample, and

wherein different offset values are applied to different padding samples dependent on color components.

2 . The method of claim 1 , wherein the offset is based on one or more sample differences between a boundary sample within the first picture and one or more prediction samples corresponding to the boundary sample, and

wherein the boundary sample is located at a boundary of the first picture and is adjacent to the first padding sample.

3 . The method of claim 2 , wherein the offset is based on a sample difference between the boundary sample within the first picture and an intra prediction sample corresponding to the boundary sample.

4 . The method of claim 2 , wherein the offset is based on a sample difference between the boundary sample within the first picture and an inter prediction sample corresponding to the boundary sample.

5 . The method of claim 2 , wherein the offset is based on a sample difference between the boundary sample within the first picture and an Intra Block Copy (IBC) prediction sample corresponding to the boundary sample.

6 . The method of claim 1 , wherein a value of the offset added to the sample value of the first padding sample is derived based on a*Func(Diff 0 . . . , Diff i , . . . )+b, wherein a and b are constants, Diff i denotes the sample differences, i is an integer greater than 0, and Func denotes an average operation.

7 . The method of claim 1 , wherein a value of the offset added to the sample value of the first padding sample is derived based on a*Func(Diff 0 . . . , Diff i , . . . )+b, wherein a and b are constants, Diff i denotes the sample differences, i is an integer greater than 0, and Func denotes a minimum operation.

8 . The method of claim 1 , wherein a value of the offset added to the sample value of the first padding sample is derived based on a*Func (Diff 0 . . . , Diff i , . . . )+b, wherein a and b are constants, Diff i denotes the sample differences, i is an integer greater than 0, and Func denotes a maximum operation.

9 . The method of claim 1 , further comprising:

using the padding samples as filtered to generate inter-prediction, wherein the inter-prediction comprises Intra Block Copy (IBC) prediction.

10 . The method of claim 1 , wherein the conversion comprises encoding the first picture into the bitstream.

11 . The method of claim 1 , wherein the conversion comprises decoding the first picture from the bitstream.

12 . An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:

generate, during a conversion between a first block of a video and a bitstream of the video, padding samples in an extended area of a first picture, wherein a prediction block of the first block is derived from the first picture;

filter the padding samples within the extended area; and

perform the conversion based on the padding samples in the extended area as filtered,

wherein the instructions upon execution by the processor, further cause the processor to: filter one or more second padding samples at one side or both sides of an edge of the padding samples,

wherein a first padding sample from the padding samples is filtered by adding an offset to a sample value of the first padding sample, and

wherein different offset values are applied to different padding samples dependent on color components.

13 . The apparatus of claim 12 , wherein the offset is based on one or more sample differences between a boundary sample within the first picture and one or more prediction samples corresponding to the boundary sample, and wherein the boundary sample is located at a boundary of the first picture and is adjacent to the first padding sample,

wherein the offset is based on a sample difference between the boundary sample within the first picture and an intra prediction sample corresponding to the boundary sample,

wherein the offset is based on a sample difference between the boundary sample within the first picture and an inter prediction sample corresponding to the boundary sample, or

wherein the offset is based on a sample difference between the boundary sample within the first picture and an Intra Block Copy (IBC) prediction sample corresponding to the boundary sample, and

wherein a value of the offset added to the sample value of the first padding sample is derived based on a*Func(Diff 0 . . . , Diff i , . . . )+b, wherein a and b are constants, Diff i denotes the sample differences, i is an integer greater than 0, and Func denotes an average operation, a minimum operation or a maximum operation.

14 . The apparatus of claim 12 , wherein the instructions upon execution by the processor, further cause the processor to:

use the padding samples as filtered to generate inter-prediction, wherein the inter-prediction comprises Intra Block Copy (IBC) prediction.

15 . A non-transitory computer-readable storage medium storing instructions that cause a processor to:

generate, during a conversion between a first block of a video and a bitstream of the video, padding samples in an extended area of a first picture, wherein a prediction block of the first block is derived from the first picture;

filter the padding samples within the extended area; and

perform the conversion based on the padding samples in the extended area as filtered,

wherein the instructions further cause the processor to: filter one or more second padding samples at one side or both sides of an edge of the padding samples,

wherein a first padding sample from the padding samples is filtered by adding an offset to a sample value of the first padding sample, and

wherein different offset values are applied to different padding samples dependent on color components.

16 . The non-transitory computer-readable storage medium of claim 15 , wherein the offset is based on one or more sample differences between a boundary sample within the first picture and one or more prediction samples corresponding to the boundary sample, and wherein the boundary sample is located at a boundary of the first picture and is adjacent to the first padding sample,

wherein the offset is based on a sample difference between the boundary sample within the first picture and an intra prediction sample corresponding to the boundary sample,

wherein the offset is based on a sample difference between the boundary sample within the first picture and an inter prediction sample corresponding to the boundary sample, or

wherein the offset is based on a sample difference between the boundary sample within the first picture and an Intra Block Copy (IBC) prediction sample corresponding to the boundary sample, wherein a value of the offset added to the sample value of the first padding sample is derived based on a*Func(Diff 0 . . . , Diff i , . . . )+b, wherein a and b are constants, Diff i denotes the sample differences, i is an integer greater than 0 , and Func denotes an average operation, a minimum operation or a maximum operation, and

wherein the instructions further cause the processor to:

use the padding samples as filtered to generate inter-prediction, wherein the inter-prediction comprises Intra Block Copy (IBC) prediction.

17 . A method for storing bitstream of a video, comprising:

generating, for a first block of the video, padding samples in an extended area of a first picture, wherein a prediction block of the first block is derived from the first picture;

filtering the padding samples within the extended area;

generating the bitstream of the video based on the padding samples in the extended area as filtered; and

storing the bitstream in a non-transitory computer-readable recording medium,

wherein the method further comprises: filtering one or more second padding samples at one side or both sides of an edge of the padding samples,

wherein a first padding sample from the padding samples is filtered by adding an offset to a sample value of the first padding sample, and

wherein different offset values are applied to different padding samples dependent on color components.

18 . The method of claim 17 ,

wherein the offset is based on one or more sample differences between a boundary sample within the first picture and one or more prediction samples corresponding to the boundary sample, and wherein the boundary sample is located at a boundary of the first picture and is adjacent to the first padding sample,

wherein the offset is based on a sample difference between the boundary sample within the first picture and an intra prediction sample corresponding to the boundary sample,

wherein the offset is based on a sample difference between the boundary sample within the first picture and an inter prediction sample corresponding to the boundary sample, or

wherein the offset is based on a sample difference between the boundary sample within the first picture and an Intra Block Copy (IBC) prediction sample corresponding to the boundary sample,

wherein a value of the offset added to the sample value of the first padding sample is derived based on a*Func(Diff 0 . . . , Diff i , . . . )+b, wherein a and b are constants, Diff i denotes the sample differences, i is an integer greater than 0, and Func denotes an average operation, a minimum operation or a maximum operation, and wherein the method further comprises:

using the padding samples as filtered to generate inter-prediction, wherein the inter-prediction comprises Intra Block Copy (IBC) prediction.