Method and device for encoding/decoding image, and recording medium in which bitstream is stored
An image encoding/decoding method and apparatus for performing intra prediction using a plurality of reference sample lines are provided. An image decoding method may comprise configuring a plurality of reference sample lines, reconstructing an intra prediction mode of a current block, and performing intra prediction for the current block based on the intra prediction mode and the plurality of reference sample lines.
1. An image decoding method performed by an image decoding apparatus, the method comprising:
determining at least one reference sample line for intra prediction of a current block among a plurality of reference sample lines,
wherein based on an upper boundary of the current block corresponding to an upper boundary of a current coding tree block including the current block, only a first reference sample line among the plurality of reference sample lines is determined as the at least one reference sample line for intra prediction of the current block,
wherein the first reference sample line includes upper reference samples immediately adjacent to the current block and left reference samples immediately adjacent to the current block,
deriving reference samples for intra prediction of the current block based on the determined at least one reference sample line and an intra prediction mode; and
performing intra prediction for the current block based on the intra prediction mode and the reference samples,
wherein the performing the intra prediction for the current block comprises:
determining an interpolation filter for the intra prediction; and
performing the intra prediction for the current block based on the interpolation filter, and
wherein filter coefficients of the interpolation filter are determined differently depending on whether the determined at least one reference sample line is the first reference sample line.
2. The method of claim 1 ,
wherein the first reference sample line is selected among the plurality of reference sample lines based on a color component of the current block.
3. The method of claim 1 ,
wherein a number of the plurality of reference sample lines available for intra prediction of the current block is determined differently based on the intra prediction mode of the current block.
4. The method of claim 1 ,
wherein the deriving the reference samples further comprises filtering reference samples, and
the reference samples are filtered when the determined at least one reference sample line is the first reference sample line, among the plurality of reference sample lines.
5. The method of claim 1 ,
wherein the interpolation filter is determined further based on a size of the current block, the intra prediction mode of the current block, and a color component of the current block.
6. The method of claim 5 , wherein:
based on the color component of the current block being a luma component, the interpolation filter is a 4-tap filter, and
based on the color component of the current block being a chroma component, the interpolation filter is a 2-tap filter.
7. An image encoding method performed by an image encoding apparatus, the method comprising:
determining at least one reference sample line for intra prediction of a current block among a plurality of reference sample lines,
wherein based on an upper boundary of the current block corresponding to an upper boundary of a current coding tree block including the current block, only a first reference sample line among the plurality of reference sample lines is determined as the at least one reference sample line for intra prediction of the current block,
wherein the first reference sample line includes upper reference samples immediately adjacent to the current block and left reference samples immediately adjacent to the current block,
determining an intra prediction mode of the current block;
deriving reference samples for intra prediction of the current block based on the determined at least one reference sample line and an intra prediction mode; and
performing intra prediction for the current block based on the intra prediction mode and the reference samples,
wherein the performing the intra prediction for the current block comprises:
determining an interpolation filter for the intra prediction; and
performing the intra prediction for the current block based on the interpolation filter, and
wherein filter coefficients of the interpolation filter are determined differently depending on whether the determined at least one reference sample line is the first reference sample line.
8. The method of claim 7 ,
wherein a number of the plurality of reference sample lines available for intra prediction of the current block is determined differently based on the intra prediction mode of the current block.
9. The method of claim 7 ,
wherein the deriving the reference samples further comprises filtering reference samples, and
the reference samples are filtered when the determined at least one reference sample line is the first reference sample line, among the plurality of reference sample lines.
10. The method of claim 7 ,
wherein the interpolation filter is determined further based on a size of the current block, the intra prediction mode of the current block, and a color component of the current block.
11. The method of claim 10 , wherein:
based on the color component of the current block being a luma component, the interpolation filter is a 4-tap filter, and
based on the color component of the current block being a chroma component, the interpolation filter is a 2-tap filter.
12. A non-transitory computer-readable recording medium storing a bitstream that is generated by an image encoding method, the image encoding method comprising:
determining at least one reference sample line for intra prediction of a current block among a plurality of reference sample lines,
wherein based on an upper boundary of the current block corresponding to an upper boundary of a current coding tree block including the current block, only a first reference sample line among the plurality of reference sample lines is determined as the at least one reference sample line for intra prediction of the current block,
wherein the first reference sample line includes upper reference samples immediately adjacent to the current block and left reference samples immediately adjacent to the current block,
determining an intra prediction mode of the current block;
deriving reference samples for intra prediction of the current block based on the determined at least one reference sample line and an intra prediction mode; and
performing intra prediction for the current block based on the intra prediction mode and the reference samples,
wherein the performing the intra prediction for the current block comprises:
determining an interpolation filter for the intra prediction; and
performing the intra prediction for the current block based on the interpolation filter, and
wherein filter coefficients of the interpolation filter are determined differently depending on whether the determined at least one reference sample line is the first reference sample line.