Method and apparatus for encoding/decoding video, and recording medium storing bit stream
The present invention relates to an image encoding/decoding method and apparatus. The image decoding method according to the present invention may comprise reconstructing an intra prediction mode of a current block, determining a reference sample for intra prediction of the current block, and generating a prediction block of the current block by performing the intra prediction on the current block on the basis of the intra prediction mode and the reference sample. The determining of the reference sample or the intra prediction may be performed on the basis of a shape of the current block.
1. An image decoding method performed by an image decoding apparatus, the method comprising:
deriving an intra prediction mode of a current block;
selecting a reference sample line among a plurality of reference sample lines of the current block;
deriving reference samples of the current block based on the reference sample line; and
generating a prediction block of the current block by performing intra prediction for the current block based on the intra prediction mode and the reference sample,
wherein, in response to a first reference sample line being selected as the reference sample line among the plurality of reference sample lines, the reference samples are derived by filtering the reference sample line, the first reference sample line being immediately adjacent to the current block,
wherein, in response to the first reference sample line not being selected as the reference sample line among the plurality of reference sample lines, the reference samples are derived without filtering the reference sample line,
wherein the reference sample line is selected based on whether a top boundary of the current block corresponds to a boundary of a current coding tree block, the current block being obtained by dividing the current coding tree block,
wherein, in response to the top boundary of the current block not corresponding to the boundary of the current coding tree block, the reference sample line is selected based on an indicator signaled from a bitstream, the indicator indicating one of the plurality of reference sample lines, and
wherein, in response to the top boundary of the current block corresponding to the boundary of the current coding tree block, the first reference sample line is selected as the reference sample line without signaling the indicator from the bitstream.
2. The method of claim 1 ,
wherein the intra prediction mode of the current block is derived using an MPM list determined based on intra prediction modes of neighboring blocks of the current block, and
wherein the neighboring blocks are a left block and a top block of the current block.
3. The method of claim 2 ,
wherein the MPM list comprises MPM candidates derived using statistic values of the intra prediction modes of the neighboring blocks, and
wherein the statistic values are a maximum value and a minimum value.
4. The method of claim 1 ,
wherein the intra prediction mode of the current block is derived using an MPM list determined based on a flag signaled from the bitstream among a plurality of MPM lists.
5. The method of claim 4 ,
wherein, in response to the determined MPM list including only one MPM candidate, the intra prediction mode of the current block is derived as the one MPM candidate, and
wherein, in response to the determined MPM list including a plurality of MPM candidates, the intra prediction mode of the current block is derived as an MPM candidate selected based on an index indicating one among the plurality of MPM candidates.
6. The method of claim 1 ,
wherein, in response to the current block being non-square and the intra prediction mode being a DC mode, the intra prediction for the current block is performed by a weighted sum of reference samples adjacent to a longer side among a width and height of the current block.
7. The method of claim 6 ,
wherein the weighted sum is calculated using a right-shift operation based on a length of the longer side among the width and height of the current block.
8. An image encoding method performed by an image encoding apparatus, the method comprising:
determining an intra prediction mode of a current block;
selecting a reference sample line among a plurality of reference sample lines of the current block;
deriving reference samples of the current block based on the reference sample line; and
generating a prediction block of the current block by performing intra prediction for the current block based on the intra prediction mode and the reference sample,
wherein, in response to a first reference sample line being selected as the reference sample line among the plurality of reference sample lines, the reference samples are derived by filtering the reference sample line, the first reference sample line being immediately adjacent to the current block,
wherein, in response to the first reference sample line not being selected as the reference sample line among the plurality of reference sample lines, the reference samples are derived without filtering the reference sample line,
wherein the reference sample line is selected based on whether a top boundary of the current block corresponds to a boundary of a current coding tree block, the current block being obtained by dividing the current coding tree block,
wherein, in response to the top boundary of the current block not corresponding to the boundary of the current coding tree block, the reference sample line is selected as one of the plurality of reference sample lines, and an indicator indicating the one of the plurality of reference sample lines is encoded into a bitstream, and
wherein, in response to the top boundary of the current block corresponding to the boundary of the current coding tree block, the first reference sample line is selected as the reference sample line, and the indicator is not encoded into the bitstream.
9. The method of claim 8 ,
wherein the intra prediction mode of the current block is encoded using an MPM list determined based on intra prediction modes of neighboring blocks of the current block, and
wherein the neighboring blocks are a left block and a top block of the current block.
10. The method of claim 9 ,
wherein the MPM list comprises MPM candidates derived using statistic values of the intra prediction modes of the neighboring blocks, and
wherein the statistic values are a maximum value and a minimum value.
11. The method of claim 8 ,
wherein a flag related to which an MPM list, among a plurality of MPM lists, the intra prediction mode of the current block is included in, is encoded into the bitstream.
12. The method of claim 11 ,
wherein, in response to the MPM list including a plurality of MPM candidates, an index indicating one MPM candidate representing the same prediction mode as the intra prediction mode of the current block among the plurality of MPM candidates is encoded into the bitstream, and
wherein, in response to the MPM list including only one MPM candidate, the index is not encoded into the bitstream.
13. The method of claim 8 ,
wherein, in response to the current block being non-square and the intra prediction mode being a DC mode, the intra prediction for the current block is performed by a weighted sum of reference samples adjacent to a longer side among a width and height of the current block, in response to the current block being non-square and the intra prediction mode being a DC mode.
14. The method of claim 13 ,
wherein the weighted sum is calculated using a right-shift operation based on a length of the longer side among the width and height of the current block.
15. A method for storing a bitstream associated with video data, the method comprising:
generating the bitstream containing encoded data fora current block; and
storing the bitstream in a non-transitory computer-readable medium,
wherein the generating of the bitstream comprises:
determining an intra prediction mode of the current block;
selecting a reference sample line among a plurality of reference sample lines of the current block;
deriving reference samples of the current block based on the filtered reference sample line; and generating a prediction block of the current block by performing intra prediction for the current block based on the intra prediction mode and the reference sample,
wherein, in response to a first reference sample line being selected as the reference sample line among the plurality of reference sample lines, the reference samples are derived by filtering the reference sample line, the first reference sample line being immediately adjacent to the current block,
wherein, in response to the first reference sample line not being selected as the reference sample line among the plurality of reference sample lines, the reference samples are derived without filtering the reference sample line,
wherein the reference sample line is selected based on whether a top boundary of the current block corresponds to a boundary of a current coding tree block, the current block being obtained by dividing the current coding tree block,
wherein, in response to the top boundary of the current block not corresponding to the boundary of the current coding tree block, the reference sample line is selected as one of the plurality of reference sample lines, and an indicator indicating the one of the plurality of reference sample lines is encoded into a bitstream, and
wherein, in response to the top boundary of the current block corresponding to the boundary of the current coding tree block, the first reference sample line is selected as the reference sample line, and the indicator is not encoded into the bitstream.