Image encoding/decoding method and device, and recording medium in which bitstream is stored
The present invention relates to an image encoding/decoding method and apparatus. An image decoding method performing intra prediction according to the present invention may comprise dividing a current block into at least one sub-block; deriving an intra prediction mode for the at least one sub-block; constructing a reference sample for the intra prediction; and performing intra prediction for the at least one sub-block based on the derived intra prediction mode.
1. An image decoding method comprising:
obtaining a current block by dividing an image;
deriving an intra prediction mode of the current block;
determining a reference sample line from a plurality of reference sample lines without obtaining the reference sample line index information from a bitstream in response to that the intra prediction mode is a predetermined mode;
determining the reference sample line from the plurality of reference sample lines based on reference sample line index information of the current block that is obtained from the bitstream in response to that the intra prediction mode is not the predetermined mode;
deriving a reference sample of intra prediction for the current block from the determined reference sample line; and
generating a prediction block by performing intra prediction for the current block.
2. The method of claim 1 ,
wherein, in case a size of the current block is greater than a predetermined size, the current block is divided by quadtree only.
3. The method of claim 1 ,
wherein, among the plurality of reference sample lines, a reference sample line for deriving the reference sample is determined based on whether an upper boundary of the current block corresponds to a boundary of a coding tree block.
4. The method of claim 1 ,
wherein the deriving the reference sample comprises filtering the reference sample, and
the filtering of the reference sample is performed only for a first reference sample line among the plurality of reference sample lines,
the first reference sample line is immediately above or left to the current block.
5. The method of claim 1 ,
wherein, among the plurality of reference sample lines, a reference sample line for deriving the reference sample is determined based on the intra prediction mode of the current block.
6. The method of claim 1 ,
wherein availability determination for a sample outside of a predetermined range among samples of the plurality of reference sample lines is not performed, and the sample outside of the predetermined range is substituted by an adjacent sample inside of the predetermined range.
7. An image encoding method comprising:
obtaining a current block by dividing an image;
determining an intra prediction mode of the current block;
determining a reference sample line from a plurality of reference sample lines without encoding the reference sample line index information in response to that the intra prediction mode is a predetermined mode;
determining the reference sample line from the plurality of reference sample lines and encoding reference sample line index information of the current block based on the reference sample line in response to that the intra prediction mode is not the predetermined mode;
deriving a reference sample of intra prediction for the current block from the determined reference sample line; and
generating a prediction block by performing intra prediction for the current block.
8. The method of claim 7 ,
wherein, among the plurality of reference sample lines, a reference sample line for deriving the reference sample is determined based on whether an upper boundary of the current block corresponds to a boundary of a coding tree block.
9. The method of claim 7 ,
wherein the deriving the reference sample comprises filtering the reference sample, and
the filtering of the reference sample is performed only for a first reference sample line among the plurality of reference sample lines,
the first reference sample line is immediately above or left to the current block.
10. The method of claim 7 ,
wherein, among the plurality of reference sample lines, a reference sample line for deriving the reference sample is determined based on the intra prediction mode of the current block.
11. The method of claim 7 ,
wherein availability determination for a sample outside of a predetermined range among samples of the plurality of reference sample lines is not performed, and the sample outside of the predetermined range is substituted by an adjacent sample inside of the predetermined range.
12. A non-transitory computer-readable recording-medium storing a bitstream which is generated by an image encoding method,
the method comprising:
obtaining a current block by dividing an image;
determining an intra prediction mode of the current block;
determining a reference sample line from a plurality of reference sample lines without obtaining the reference sample line index information from a bitstream in response to that the intra prediction mode is a predetermined mode;
determining the reference sample line from the plurality of reference sample lines based on reference sample line index information of the current block that is obtained from the bitstream in response to that the intra prediction mode is not the predetermined mode;
deriving a reference sample of intra prediction for the current block from the determined reference sample line; and
generating a prediction block by performing intra prediction for the current block.