Method and an apparatus for processing a video signal

1. A method of processing a video signal, comprising:

obtaining residual information of a current block from the video signal, the current block being coded in an intra prediction mode, the intra prediction mode corresponding to predicting a current sample of the current block within a current picture comprising the current block;

obtaining an intra prediction reference sample from interpolation of at least one boundary sample of a neighbor block and at least one boundary sample of the current block, the neighbor block being adjacent to the at least one boundary sample of the current block within the current picture and including at least one of a left block, an upper block, an upper right block, or an upper left block; and

reconstructing the current sample of the current block using the intra prediction reference sample and the residual information of the current block,

wherein the intra prediction reference sample is located in a sub-pixel position between the at least one boundary sample of the current block and the at least one boundary sample of the neighbor block within the current picture,

wherein based on a relative position of an upper left corner sample of the current block being (0, 0), a relative position of the intra prediction reference sample is (m/c, n/c), and

wherein at least one of the m or the n is −1 and the c is a constant.

2. The method of claim 1 , wherein the intra prediction mode corresponds to at least one of a vertical direction mode, a horizontal direction mode, a DC direction mode, a diagonal down right mode, and a diagonal down left mode.

3. The method of claim 1 , wherein the intra prediction mode indicates direction information for predicting the current sample of the current block within the current picture.

4. The method of claim 2 , wherein based on the intra prediction mode corresponding to the vertical direction mode, the intra prediction reference sample is obtained only by a vertical filtering of a boundary sample of the neighboring block and a boundary sample of the current block,

based on the intra prediction mode corresponding to the horizontal direction mode, the intra prediction reference sample is obtained only by a horizontal filtering of a boundary sample of the neighboring block and a boundary sample of the current block, or

based on the intra prediction mode corresponding to a prediction mode other than the vertical direction mode and the horizontal direction mode, the intra prediction reference sample is obtained by vertical and horizontal filtering of two boundary samples of the neighboring block and two boundary samples of the current block.

5. The method of claim 2 , wherein based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the vertical direction mode, the relative position of the intra prediction reference sample is (x, −½), or

based on the relative position of the current sample being (x, y) and the intra prediction mode corresponding to the horizontal direction mode, the relative position of the intra prediction reference sample is (−½, y).

6. The method of claim 2 , wherein based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the diagonal down right mode, the relative position of the intra prediction reference sample is (x−m/2, −½) or (−½, y−m/2), or

based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the diagonal down left mode, the relative position of the intra prediction reference sample is (x+m/2, −½),

wherein m is an odd integer.

7. The method of claim 4 , wherein based on the intra prediction mode corresponding to the vertical direction mode, the intra prediction reference sample is obtained only by a vertical filtering of a boundary sample of the neighboring block and a boundary sample of the current block.

8. The method of claim 4 , wherein based on the intra prediction mode corresponding to the horizontal direction mode, the intra prediction reference sample is obtained only by a horizontal filtering of a boundary sample of the neighboring block and a boundary sample of the current block.

9. The method of claim 4 , wherein based on the intra prediction mode corresponding to a prediction mode other than the vertical direction mode and the horizontal direction mode, the intra prediction reference sample is obtained by vertical and horizontal filtering of two boundary samples of the neighboring block and two boundary samples of the current block.

10. The method of claim 5 , wherein based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the vertical direction mode, the relative position of the intra prediction reference sample is (x, −½).

11. The method of claim 5 , wherein based on the relative position of the current sample is (x, y) and the intra prediction mode corresponds to the horizontal direction mode, the relative position of the intra prediction reference sample is (−½, y).

12. The method of claim 6 , wherein based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the diagonal down right mode, the relative position of the intra prediction reference sample is (x−m/2, −½) or (−½, y−m/2), wherein m is an odd integer.

13. The method of claim 6 , wherein based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the diagonal down left mode, the relative position of the intra prediction reference sample is (x+m/2, −½), wherein m is an odd integer.

14. An apparatus for processing a video signal, comprising:

an entropy decoding unit configured to obtain residual information of a current block from the video signal, the current block being coded in an intra prediction mode, the intra prediction mode corresponding to predicting a current sample of the current block within a current picture comprising the current block;

an intra prediction unit configured to obtain an intra prediction reference sample from interpolation of at least one boundary sample of a neighbor block and at least one boundary sample of the current block, the neighbor block being adjacent to the at least one boundary sample of the current block within the current picture and including at least one of a left block, an upper block, an upper right block, or an upper left block; and

a current block reconstructing unit configured to reconstruct the current sample of the current block using the intra prediction reference sample and the residual information of the current block,

wherein the intra prediction reference sample is located in a sub-pixel position between the at least one boundary sample of the current block and the at least one boundary sample of the neighbor block within the current picture,

wherein based on a relative position of an upper left corner sample of the current block being (0, 0), a relative position of the intra prediction reference sample is (m/c, n/c), and

wherein at least one of the m or the n is −1 and the c is a constant.

15. The apparatus of claim 14 , wherein the intra prediction mode corresponds to at least one of a vertical direction mode, a horizontal direction mode, a DC direction mode, a diagonal down right mode, and a diagonal down left mode.

16. The apparatus of claim 14 , wherein the intra prediction mode indicates direction information for predicting the current sample of the current block within the current picture.

17. The apparatus of claim 15 , wherein based on the intra prediction mode corresponding to the vertical direction mode, the intra prediction reference sample is obtained only by a vertical filtering of a boundary sample of the neighboring block and a boundary sample of the current block,

based on the intra prediction mode corresponding to the horizontal direction mode, the intra prediction reference sample is obtained only by a horizontal filtering of a boundary sample of the neighboring block and a boundary sample of the current block, or

based on the intra prediction mode corresponding to a prediction mode other than the vertical direction mode and the horizontal direction mode, the intra prediction reference sample is obtained by vertical and horizontal filtering of two boundary samples of the neighboring block and two boundary samples of the current block.

18. The apparatus of claim 15 , wherein based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the vertical direction mode, the relative position of the intra prediction reference sample is (x, −½), or

based on the relative position of the current sample being (x, y) and the intra prediction mode corresponding to the horizontal direction mode, the relative position of the intra prediction reference sample is (−½, y).

19. The apparatus of claim 15 , wherein based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the diagonal down right mode, the relative position of the intra prediction reference sample is (x−m/2, −½) or (−½, y−m/2), or

based on a relative position of the current sample being (x, y) and the intra prediction mode corresponding to the diagonal down left mode, the relative position of the intra prediction reference sample is (x+m/2, −½),

wherein m is an odd integer.