Method and apparatus for decoding video, and method and apparatus for coding video

1. A video decoding method comprising:

determining neighboring pixels of a current block to be used for performing intra prediction on the current block;

acquiring, from a bitstream, information indicating one of a plurality of filtering methods used on the neighboring pixels;

selecting one of the plurality of filtering methods according to the acquired information;

filtering the neighboring pixels by using the selected filtering method; and

performing the intra prediction on the current block by using the filtered neighboring pixels,

wherein the plurality of filtering methods comprise a spatial domain filtering method and a frequency domain filtering method, wherein the spatial domain filtering method filters the neighboring pixels in a spatial domain, and the frequency domain filtering method filters the neighboring pixels in a frequency domain.

2. The video decoding method of claim 1 , wherein the spatial domain filtering method comprises:

partitioning the neighboring pixels into predetermined pixel units;

obtaining an average value of pixel values with respect to each of the predetermined pixel units; and

substituting the average value for a pixel value of pixels included in each of the predetermined pixel units.

3. The video decoding method of claim 2 , wherein the partitioning of the neighboring pixels into the predetermined pixel units comprises partitioning the neighboring pixels into the predetermined pixel units, based on image characteristics of the neighboring pixels.

4. The video decoding method of claim 2 , wherein the partitioning of the neighboring pixels into the predetermined pixel units comprises:

generating a histogram with respect to a pixel value of the neighboring pixels;

setting sections of a pixel value in the histogram, based on at least one threshold value; and

determining, as one pixel unit, pixels adjacent to each other and having a pixel value belonging to the same section of the histogram.

5. The video decoding method of claim 2 , wherein the partitioning of the neighboring pixels into the predetermined pixel units comprises:

generating a gradient value of the neighboring pixels by performing a gradient operation on the neighboring pixels; and

determining a boundary between the predetermined pixel units by using one or more of the neighboring pixels having a gradient value greater than or equal to a threshold value.

6. The video decoding method of claim 2 , wherein the partitioning of the neighboring pixels into the predetermined pixel units comprises:

extracting edge information included in the neighboring pixels; and

partitioning the neighboring pixels into the predetermined pixel units, based on the extracted edge information.

7. The video decoding method of claim 2 , wherein the spatial domain filtering method further comprises filtering a boundary between the predetermined pixel units.

8. The video decoding method of claim 1 , wherein the frequency domain filtering method comprises:

transforming the neighboring pixels into the frequency domain;

filtering the transformed neighboring pixels; and

inverse-transforming the filtered neighboring pixels into the spatial domain.

9. The video decoding method of claim 8 , wherein the filtering of the transformed neighboring pixels comprises filtering the transformed neighboring pixels by using a low-pass filter.

10. The video decoding method of claim 1 , wherein

the spatial domain filtering method and the frequency domain filtering method filter a block including the neighboring pixels, and

a region corresponding to the neighboring pixels in the filtered block is used for performing the intra prediction on the current block.

11. A video decoding apparatus comprising:

a neighboring pixel determiner configured to determine neighboring pixels of a current block to be used for performing intra prediction on the current block;

an information acquirer configured to acquire, from a bitstream, information indicating one of a plurality of filtering methods used on the neighboring pixels; and

a decoder configured to select one of the plurality of filtering methods according to the acquired information, filter the neighboring pixels by using the selected filtering method, and perform the intra prediction on the current block by using the filtered neighboring pixels,

wherein the plurality of filtering methods comprise a spatial domain filtering method and a frequency domain filtering method, wherein the spatial domain filtering method filters the neighboring pixels in a spatial domain, and the frequency domain filtering method filters the neighboring pixels in a frequency domain.

12. The video decoding apparatus of claim 11 , wherein the spatial domain filtering method comprises:

partitioning the neighboring pixels into predetermined pixel units;

obtaining an average value of pixel values with respect to each of the predetermined pixel units; and

substituting the average value for a pixel value of pixels included in each of the predetermined pixel units.

13. The video decoding apparatus of claim 11 , wherein the frequency domain filtering method comprises:

transforming the neighboring pixels into the frequency domain;

filtering the transformed neighboring pixels; and

inverse-transforming the filtered neighboring pixels into the spatial domain.

14. A video encoding method comprising:

determining neighboring pixels of a current block to be used for performing intra prediction on the current block;

selecting one of a plurality of filtering methods used for the neighboring pixels;

filtering the neighboring pixels by using the selected filtering method; and

performing the intra prediction on the current block by using the filtered neighboring pixels,

wherein the plurality of filtering methods comprise a spatial domain filtering method and a frequency domain filtering method, wherein the spatial domain filtering method filters the neighboring pixels in a spatial domain, and the frequency domain filtering method filters the neighboring pixels in a frequency domain.

15. The video encoding method of claim 14 , wherein the selecting comprises:

filtering the neighboring pixels by using each of the plurality of filtering methods;

performing the intra prediction on the current block by using the filtered neighboring pixels; and

selecting one of the plurality of filtering methods, based on a cost according to a result of the intra prediction.