Video encoding/decoding method and device, and recording medium having bitstream stored therein
An image encoding/decoding method and apparatus for performing intra prediction are provided. An image decoding method of the present invention comprises deriving an intra-prediction mode for a current block, determining whether or not a left boundary or an upper boundary of the current block is a boundary of a predetermined image region, configuring a reference sample by using at least one reconstructed sample included in at least one reconstructed sample line adjacent to the current block based on the determination result, and performing intra-prediction for the current block based on the intra-prediction mode and the reference sample.
1. An image decoding method comprising:
deriving an intra prediction mode of a current block;
deriving a reference sample of intra prediction for the current block from a plurality of reference sample lines; and
generating a prediction block by performing intra prediction for the current block based on the intra prediction mode and the reference sample,
wherein the deriving the reference sample of intra prediction for the current block comprises:
determining whether an upper boundary of the current block is an upper boundary of a current coding tree block or not; and
selecting a reference sample line for deriving the reference sample among the plurality of reference sample lines based on the determination, and
wherein, in response to the upper boundary of the current block being the upper boundary of the current coding tree block, the reference sample is derived using a first reference sample line adjacent to the current block among the plurality of reference sample lines, and
wherein the current block is obtained by dividing the current coding tree block using at least one of a quad-tree division method or a binary-tree division method.
2. The method of claim 1 ,
wherein different number of reference samples lines are available according to whether the boundary of the current block is the boundary of the current coding tree block.
3. The method of claim 1 ,
wherein, in response to the boundary of the current block not being the boundary of the current coding tree block, the reference sample is derived using a second reference sample line of the current block among the plurality of reference sample lines, and
wherein the second reference sample line is adjacent to the first reference sample line.
4. The method of claim 1 ,
wherein the intra prediction mode of the current block is derived based on an intra prediction mode of a left neighboring block and an intra prediction mode of an upper neighboring block, the left neighboring block being a block adjacent to a lower-left side of the current block and the upper neighboring block being a block adjacent to a upper-right side of the current block.
5. The method of claim 4 ,
wherein the intra prediction mode of the current block is derived based on a statistic value of the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block.
6. The method of claim 5 ,
wherein all of a maximum value and a minimum value are used as the statistic value.
7. The method of claim 1 ,
wherein the deriving the intra prediction mode of the current block comprises
decoding a first flag indicating whether the intra prediction mode is identical to a mode included in a first Most Probable Mode (MPM) list including at least one mode; and
determining the mode included in the first MPM list as the intra prediction mode in response to the first flag being a first value.
8. The method of claim 7 ,
wherein the deriving the intra prediction mode of the current block comprises:
configuring a second MPM list including at least one mode in response to the first flag being a second value;
decoding index information indicating a mode identical to the intra prediction mode of the current block; and
deriving the intra prediction mode of the current block using the second MPM list and the index information.
9. An image encoding method comprising:
determining an intra prediction mode of a current block;
deriving a reference sample of intra prediction for the current block from a plurality of reference sample lines; and
generating a prediction block by performing intra prediction for the current block based on the intra prediction mode and the reference sample,
wherein the deriving the reference sample of intra prediction for the current block comprises:
determining whether an upper boundary of the current block is an upper boundary of a current coding tree block or not; and
selecting a reference sample line for deriving the reference sample among the plurality of reference sample lines based on the determination, and
wherein, in response to the upper boundary of the current block being the upper boundary of the current coding tree block, the reference sample is derived using a first reference sample line adjacent to the current block among the plurality of reference sample lines, and
wherein the current block is obtained by dividing the current coding tree block using at least one of a quad-tree division method or a binary-tree division method.
10. The method of claim 9 ,
wherein different number of reference samples lines are available according to whether the boundary of the current block is the boundary of the current coding tree block.
11. The method of claim 9 ,
wherein, in response to the boundary of the current block not being the boundary of the current coding tree block, the reference sample is derived using a second reference sample line of the current block among the plurality of reference sample lines, and
wherein the second reference sample line is adjacent to the first reference sample line.
12. The method of claim 9 ,
wherein the intra prediction mode of the current block is encoded based on an intra prediction mode of a left neighboring block and an intra prediction mode of an upper neighboring block, the left neighboring block being a block adjacent to a lower-left side of the current block and the upper neighboring block being a block adjacent to an upper-right side of the current block.
13. The method of claim 12 ,
wherein the intra prediction mode of the current block is encoded based on a maximum value and a minimum value of the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block.
14. The method of claim 9 , further comprising
encoding the intra prediction mode of the current block,
wherein the encoding the intra prediction mode comprises:
determining whether the intra prediction mode is identical to a mode included in a first Most Probable Mode (MPM) list including at least one mode; and
encoding a first flag having a first value in response to the intra prediction mode being identical to a mode included in the first MPM list.
15. The method of claim 14 ,
wherein the encoding the intra prediction mode comprises:
configuring a second MPM list including at least one mode in response to the intra prediction mode not being identical to a mode included in the first MPM list;
determining an index indicating a mode identical to the intra prediction mode of the current block among modes included in the second MPM list; and
encoding the first flag having a second value and the index.
16. A method of transmitting a bitstream, the method comprising:
determining an intra prediction mode of a current block;
deriving a reference sample of intra prediction for the current block from a plurality of reference sample lines;
generating a prediction block by performing intra prediction for the current block based on the intra prediction mode and the reference sample; and
transmitting the bitstream generated based on the prediction block,
wherein the deriving the reference sample of intra prediction for the current block comprises:
determining whether an upper boundary of the current block is an upper boundary of a current coding tree block or not; and
selecting a reference sample line for deriving the reference sample among the plurality of reference sample lines based on the determination, and
wherein, in response to the upper boundary of the current block being the upper boundary of the current coding tree block, the reference sample is derived using a first reference sample line adjacent to the current block among the plurality of reference sample lines, and
wherein the current block is obtained by dividing the current coding tree block using at least one of a quad-tree division method or a binary-tree division method.