Method and apparatus for aspect-ratio dependent filtering for intra-prediction
A method, a device, and a computer program product, for aspect-ratio dependent filtering for intra-prediction include obtaining an aspect ratio of a block to be predicted, wherein the aspect ratio is based on a width of the block and a height of the block, and selecting an interpolation filter for the block to be predicted based on the aspect ratio of the block to be predicted.
1. A method for aspect-ratio dependent filtering for intra-prediction, wherein the method comprises:
obtaining an aspect ratio of a block to be predicted, wherein the aspect ratio is based on a width (W) of the block and a height (H) of the block; and
selecting, by comparing a value of a direction of an intra prediction mode of the block with a threshold value, an interpolation filter for the block based on the aspect ratio,
wherein the aspect ratio is calculated using a formula as follows:
R A =log 2 ( W )−log 2 ( H ),
wherein R A is the aspect ratio, and
wherein an angle of the direction is calculated using a formula as follows:
α
T
=
arctan
(
H
W
)
,
wherein a r is the angle.
2. The method of claim 1 , wherein the direction corresponds to an angle of a main diagonal of the block.
3. The method of claim 2 , further comprising determining the angle of the main diagonal of the block based on the aspect ratio.
4. The method of claim 3 , further comprising determining a threshold of the intra prediction mode based on the angle of the main diagonal of the block.
5. The method of claim 1 , further comprising selecting the interpolation filter for prediction of a sample based on a side that a corresponding reference sample belongs to.
6. The method of claim 5 , further comprising dividing the block into two areas using a straight line with an angle corresponding to an intra direction.
7. The method of claim 5 , further comprising predicting reference samples belonging to different areas using different interpolation filters.
8. The method of claim 1 , wherein the interpolation filter comprises a cubic interpolation filter or a Gaussian interpolation filter.
9. A device comprising:
a memory configured to store instructions; and
a processor coupled the memory, wherein the instructions cause the processor to be configured to:
obtain an aspect ratio of a block to be predicted, wherein the aspect ratio is based on a width (W) of the block and a height (H) of the block; and
select, by comparing a value of a direction of an intra prediction mode of the block with a threshold value, an interpolation filter for the block based on the aspect ratio,
wherein the aspect ratio is calculated using a formula as follows:
R A =log 2 ( W )−log 2 ( H ),
wherein R A is the aspect ratio, and
wherein an angle of the direction is calculated using a formula as follows:
α
T
=
arctan
(
H
W
)
,
wherein a T is the angle.
10. The device of claim 9 , wherein the direction corresponds to an angle of a main diagonal of the block.
11. The device of claim 10 , wherein the instructions further cause the processor to be configured to determine the angle of the main diagonal of the block based on the aspect ratio.
12. The device of claim 11 , wherein the instructions further cause the processor to be configured to determine a threshold of the intra prediction mode based on the angle of the main diagonal of the block.
13. A computer program product comprising computer-executable instructions stored on a non-transitory computer-readable medium that, when executed by a processor, cause an apparatus to:
obtain an aspect ratio of a block to be predicted, wherein the aspect ratio is based on a width (W) of the block and a height (H) of the block; and
select, by comparing a value of a direction of an intra prediction mode of the block with a threshold value, an interpolation filter for the block based on the aspect ratio,
wherein the aspect ratio is calculated using a formula as follows:
R A =log 2 ( W )−log 2 ( H ),
wherein R A is the aspect ratio, and
wherein an angle of the direction is calculated using a formula as follows:
α
T
=
arc
tan
(
H
W
)
,
where a r is me angle.
14. The computer program product of claim 13 , wherein the direction corresponds to an angle of a main diagonal of the block.
15. The computer program product of claim 13 , wherein the computer-executable instructions, when executed by the processor, further cause the apparatus to divide the block into two areas using a straight line with an angle corresponding to an intra direction.
16. The computer program product of claim 13 , wherein the computer-executable instructions, when executed by the processor, further cause the apparatus to predict reference samples belonging to different areas using different interpolation filters.
17. The computer program product of claim 13 , wherein the interpolation filter comprises a cubic interpolation filter or a Gaussian interpolation filter.
18. The device of claim 9 , wherein the instructions further cause the processor to be configured to predict reference samples belonging to different areas using different interpolation filters.
19. The device of claim 9 , wherein the instructions further cause the processor to be configured to divide the block into two areas using a straight line with the angle corresponding to an intra direction.
20. The device of claim 9 , wherein the interpolation filter comprises a cubic interpolation filter or a Gaussian interpolation filter.