Intra-prediction mode-based image processing method and device therefor

1. A method of processing video based on an intra prediction mode, the method comprising:

configuring, by a processor, a reference sample to be used for prediction of a current block based on width and height information of the current block;

deriving, by the processor, an intra prediction mode of the current block from a plurality of intra prediction modes applicable to the current block; and

generating, by the processor, a prediction sample of the current block using the reference sample based on the intra prediction mode of the current block,

wherein, based on the current block being a non-square block, one or more first intra prediction modes in the plurality of intra prediction modes applicable to the current block are replaced by one or more second intra prediction modes, the one or more second intra prediction modes covering a specific angle range determined based on a ratio of the width and height information of the current block.

2. The method of claim 1 ,

wherein when the width of the current block is N and the height of the current block is M, the reference sample is configured with one sample neighboring a top left of the current block, M samples neighboring a left of the current block, N samples neighboring a bottom left of the current block, N samples neighboring a top of the current block and M samples neighboring a top right of the current block.

3. The method of claim 1 ,

wherein the plurality of intra prediction modes applicable to the current block is determined as intra prediction modes in which prediction directions are differentially distributed based on the ratio of the width and height information of the current block.

4. The method of claim 1 ,

wherein when the width is greater among the width and height of the current block, the plurality of intra prediction modes applicable to the current block is determined as intra prediction modes in which a number of prediction directions is more distributed between a prediction direction of an angle of 45° and a prediction direction of an angle of 135° than between a prediction direction of an angle of 135° and a prediction of an angle of 225°.

5. The method of claim 1 ,

wherein when the height is greater among the width and height of the current block, the plurality of intra prediction modes applicable to the current block is determined as intra prediction modes in which a number of prediction directions is more distributed between a prediction direction of an angle of 135° and a prediction of an angle of 225° than between a prediction direction of an angle of 45° and a prediction direction of an angle of 135°.

6. The method of claim 1 ,

wherein the plurality of intra prediction modes applicable to the current block is determined by sub-sampling a prediction direction of the specific angle range based on the ratio of the width and height information of the current block.

7. The method of claim 1 ,

wherein a number of the first intra prediction modes is the same as a number of the second intra prediction modes.

8. The method of claim 1 , further comprising:

determining, by the processor, whether to split the current block into a plurality of square sub-blocks based on the ratio of the width and height information of the current block,

wherein if the current block is not split into a plurality of square sub-blocks, the prediction sample of the current block is generated in a current block unit,

wherein if the current block is split into a plurality of square sub-blocks, the prediction sample of the current block is generated in a sub-block unit, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.

9. The method of claim 1 , further comprising:

splitting, by the processor, the current block into a plurality of square sub-blocks when the width is greater among the width and height of the current block and an angle of the intra prediction mode of the current block is greater than 180°,

wherein the prediction sample of the current block is generated in a sub-block unit using the reference sample based on the intra prediction mode of the current block, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.

10. The method of claim 1 , further comprising:

splitting, by the processor, the current block into a plurality of square sub-blocks when the height is greater among the width and height of the current block and an angle of the intra prediction mode of the current block is smaller than 90°,

wherein the prediction sample of the current block is generated in a sub-block unit using the reference sample based on the intra prediction mode of the current block, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.

11. The method of claim 1 , further comprising:

splitting, by the processor, the current block into a plurality of square sub-blocks,

wherein the prediction sample of the current block is generated in a sub-block unit using the reference sample based on the intra prediction mode of the current block, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.

12. An apparatus processing video based on an intra prediction mode, comprising:

a processor configured to:

configure a reference sample to be used for prediction of a current block based on width and height information of the current block;

derive an intra prediction mode of the current block from a plurality of intra prediction modes applicable to the current block; and

generate a prediction sample of the current block using the reference sample based on the intra prediction mode of the current block; and

a memory configured to exchange data with the processor,

wherein, based on the current block being a non-square block, one or more first intra prediction modes in the plurality of intra prediction modes applicable to the current block are replaced by one or more second intra prediction modes, the one or more second intra prediction modes covering a specific angle range determined based on a ratio of the width and height information of the current block.

13. The apparatus of claim 12 ,

wherein the processor is configured to determine the plurality of intra prediction modes applicable to the current block as intra prediction modes in which prediction directions are differentially distributed based on the ratio of the width and height information of the current block.

14. The apparatus of claim 12 ,

wherein a number of the first intra prediction modes is the same as a number of the second intra prediction modes.

15. The apparatus of claim 12 ,

wherein the specific angle range of the second prediction modes corresponds inversely to an angle range of the first prediction modes.

16. The method of claim 7 ,

wherein the specific angle range of the second prediction modes corresponds inversely to an angle range of the first prediction modes.

17. The apparatus of claim 12 ,

wherein the processor is configured to determine whether to split the current block into a plurality of square sub-blocks based on the ratio of the width and height information of the current block,

wherein if the current block is not split into a plurality of square sub-blocks, the prediction sample of the current block is generated in a current block unit,

wherein if the current block is split into a plurality of square sub-blocks, the prediction sample of the current block is generated in a sub-block unit, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.

18. The apparatus of claim 12 ,

wherein the processor is configured to split the current block into a plurality of square sub-blocks when the width is greater among the width and height of the current block and an angle of the intra prediction mode of the current block is greater than 180°,

wherein the prediction sample of the current block is generated in a sub-block unit using the reference sample based on the intra prediction mode of the current block, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.

19. The apparatus of claim 12 ,

wherein the processor is configured to split the current block into a plurality of square sub-blocks when the height is greater among the width and height of the current block and an angle of the intra prediction mode of the current block is smaller than 90°,

wherein the prediction sample of the current block is generated in a sub-block unit using the reference sample based on the intra prediction mode of the current block, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.

20. The apparatus of claim 12 ,

wherein the processor is configured to split the current block into a plurality of square sub-blocks,

wherein the prediction sample of the current block is generated in a sub-block unit using the reference sample based on the intra prediction mode of the current block, and

wherein the sub-block is identical with a transform unit transforming a residual signal of the current block.