Filtering mode for intra prediction inferred from statistics of surrounding blocks
View Patent ↗The present invention relates to intra prediction which may be performed during encoding and/or decoding of an image signal. In particular, the present invention relates to intra prediction of a current block, during which filtering is applied to the prediction signal and/or to signal used for the prediction. The filtering is applied in accordance with a decision based on characteristics of image signal included in block(s) spatially adjacent to the current block.
1. A method for encoding, on a block-by-block basis, image data partitioned into a plurality of blocks, said method comprising:
deriving characteristics between image data of each of plurality of previously processed blocks spatially adjacent to a current block, the previously processed blocks being used for intra prediction of the current block;
deciding on the basis of the derived characteristics whether first filtering is to be applied or not to the previously processed blocks; and
predicting a corresponding prediction block to the current block from the image data of the previously processed blocks by intra prediction,
wherein in said predicting of the corresponding prediction block to the current block, intra prediction is performed using filtered image data of the previously processed blocks to which the first filtering is applied, when said deciding decides that the first filtering is to be applied to the previously processed blocks.
2. The method according to claim 1 , wherein said deriving of the characteristics includes calculating a variance between the image data of each of the plurality of the previously processed blocks.
3. The method according to claim 2 ,
wherein said deciding decides that the first filtering is to be applied to the previously processed blocks when the variance is below a predefined threshold, and
wherein said deciding decides that no filtering is to be applied to the previously processed blocks when the variance is above the predefined threshold.
4. The method according to claim 1 , wherein in said predicting of the corresponding prediction block to the current block, intra prediction is performed using filtered image data of the previously processed blocks to which second filtering is applied, when said deciding decides that no filtering is to be applied to the previously processed blocks.
5. The method according to claim 1 , further comprising detecting an edge,
wherein said deciding includes deciding, according to the detected edge and a position of a pixel, which one of the first filtering and a second filtering is to be applied to the previously processed blocks, and
wherein in said predicting of the corresponding prediction block to the current block, intra prediction is performed using the filtered image data of the previously processed blocks to which the decided one of the first filtering and the second filtering is applied.
6. A computer program product comprising a non-transitory computer-readable medium having a computer-readable program code embodied thereon, the program code being adapted to carry out the method according to claim 1 .
7. An apparatus for encoding, on a block-by-block basis, image data partitioned into a plurality of blocks, said apparatus comprising:
a processor; and
a non-transitory memory having stored thereon executable instructions, which when executed, cause the processor to perform:
deriving characteristics between image data of each of plurality of previously processed blocks spatially adjacent to a current block, the previously processed blocks being used for intra prediction of the current block;
deciding on the basis of the derived characteristics whether first filtering is to be applied or not to the previously processed blocks; and
predicting a corresponding prediction block to the current block from the image data of the previously processed blocks by intra prediction,
wherein in said predicting of the corresponding prediction block to the current block, intra prediction is performed using filtered image data of the previously processed blocks to which the first filtering is applied, when said deciding decides that the first filtering is to be applied to the previously processed blocks.
8. The apparatus according to claim 7 , wherein the deriving of the characteristics includes calculating a variance between the image data of each of the plurality of the previously processed blocks.
9. The apparatus according to claim 8 ,
wherein the deciding decides that the first filtering is to be applied to the previously processed blocks when the variance is below a predefined threshold, and
wherein the deciding decides that no filtering is to be applied to the previously processed blocks when the variance is above the predefined threshold.
10. The apparatus according to claim 7 , wherein in the predicting of the current block, intra prediction is performed using filtered image data of the previously processed blocks to which second filtering is applied, when the deciding decides that no filtering is to be applied to the previously processed blocks.
11. The apparatus according to claim 7 ,
wherein the executable instructions, when executed, further cause the processor to perform detecting an edge,
wherein the deciding includes deciding, according to the detected edge and a position of a pixel, which one of the first filtering and a second filtering is to be applied to the previously processed blocks, and
wherein in the predicting of the corresponding prediction block to the current block, intra prediction is performed using the filtered image data of the previously processed blocks to which the decided one of the first filtering and the second filtering is applied.