Image processing method and apparatus therefor

1. A video decoding method performed by a video decoding apparatus, the video decoding method comprising:

obtaining an intra prediction mode of a current block;

obtaining a reference sample for intra prediction based on a neighboring sample of the current block;

filtering on the reference sample based on a filtering being determined to be performed on the reference sample; and

generating a prediction block of the current block based on the intra prediction mode and the reference sample, which is filtered or not,

wherein, whether to perform the filtering on the reference sample is determined based on a distance between the current block and the reference sample and based on a first parameter representing a size of the current block, the size including a length of a horizontal edge of the current block and a length of a vertical edge of the current block, and

wherein the filtering on the reference sample is skipped when the intra prediction mode is a horizontal mode or is a vertical mode, independent of the size of the current block.

2. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on a second parameter related to a neighboring block of the current block.

3. The video decoding method of claim 1 ,

whether to perform filtering on a left reference sample of the current block is determined further based on the length of the horizontal edge of the current block,

whether to perform filtering on an upper reference sample of the current block is determined further based on the length of the vertical edge of the current block, and

each of the left reference sample and the upper reference sample is filtered independently.

4. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on a first square block or a second square block satisfies a predefined filtering performance condition,

the first square block is a square block having a pixel number identical with a pixel number of the current block, and

the second square block is a greatest square block among square blocks having a pixel number smaller than the pixel number of the current block.

5. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on whether a first quantization parameter related to a quantization rate of the current block is greater than a first threshold.

6. The video decoding method of claim 1 ,

wherein the distance includes at least one of a vertical distance between a prediction sample within the current block and an upper reference sample of the current block, or a horizontal distance between a prediction sample within the current block and a left reference sample of the current block, and

wherein, whether to perform the filtering on the reference sample is determined further based on whether at least one of a first filtering performance condition or a second filtering performance condition is satisfied,

the first filtering performance condition is that the vertical distance is greater than a second threshold, and

the second filtering performance condition is that the horizontal distance is greater than a third threshold.

7. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on whether a second quantization parameter related to a quantization rate of a neighboring block of the current block is greater than a fourth threshold.

8. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on whether a number of residual coefficients of a neighboring block of the current block is greater than a fifth threshold.

9. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on a flag specifying whether a residual coefficient is present in a neighboring block of the current block.

10. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on an edge parameter specifying whether one or more of upper and left reference samples of the current block are configured with samples belonging to different neighboring blocks of the current block.

11. The video decoding method of claim 1 ,

wherein, whether to perform the filtering on the reference sample is determined further based on whether a number of different neighboring blocks of the current block to which one or more of upper and left reference samples of the current block belong is greater than a sixth threshold.

12. The video decoding method of claim 1 , further comprising:

determining whether an upper reference sample and a left reference sample of the current block are available for reference,

wherein, when one of the upper reference sample and the left reference sample is available for reference, whether to perform the filtering on the reference sample is determined further based on a length of an edge adjacent to the available reference sample among a horizontal edge and a vertical edge of the current block,

otherwise, whether to perform the filtering on the reference sample is determined further based on a length of a longer or shorter edge among the horizontal edge and the vertical edge, or independently determined for each of the upper reference sample and the left reference sample, further based on a length of the horizontal edge and a length of the vertical edge.

13. A video encoding method performed by a video encoding apparatus, the video encoding method comprising:

determining an intra prediction mode of a current block;

obtaining a reference sample for intra prediction based on a neighboring sample of the current block;

filtering on the reference sample based on the filtering on the reference sample being determined to be performed; and

generating a prediction block of the current block based on the intra prediction mode and the reference sample, which is filtered or not,

wherein, whether to perform the filtering on the reference sample is determined based on a distance between the current block and the reference sample and based on a first parameter representing a size of the current block, the size including a length of a horizontal edge of the current block and a length of a vertical edge of the current block, and

wherein the filtering on the reference sample is skipped when the intra prediction mode is a horizontal mode or is a vertical mode, independent of the size of the current block.

14. A non-transitory computer-readable recording medium storing a bitstream generated by a video encoding method, the video encoding method comprising:

determining an intra prediction mode of a current block;

obtaining a reference sample for intra prediction based on a neighboring sample of the current block;

filtering on the reference sample based on the filtering on the reference sample being determined to be performed; and

generating a prediction block of the current block based on the intra prediction mode and the reference sample, which is filtered or not,

wherein, whether to perform the filtering on the reference sample is determined based on a distance between the current block and the reference sample and based on a first parameter representing a size of the current block, the size including a length of a horizontal edge of the current block and a length of a vertical edge of the current block, and

wherein the filtering on the reference sample is skipped when the intra prediction mode is a horizontal mode or is a vertical mode, independent of the size of the current block.

15. The method of claim 1 , wherein the size of the current block is a square shape.