Method and device for encoding/decoding image, and recording medium having stored bitstream
The present invention relates to an image encoding/decoding method. The image decoding method includes splitting a coding tree unit (CTU) into at least one coding unit (CU) according to a block splitting structure and performing CU-based decoding, in which the block partition structure is configured such that at least one of binary tree splitting and ternary tree splitting is performed after quadtree splitting is performed.
1. An image decoding method comprising:
splitting a coding tree unit (CTU) into at least one coding unit (CU) according to a block splitting structure; and
performing CU-based decoding, and
wherein the block splitting structure is configured such that:
at least one of binary tree splitting and ternary tree splitting is performed after quadtree splitting is performed,
when a size of the coding unit is larger than a predefined size, an implicit quadtree splitting is performed, and
when the size of the coding unit is equal to or smaller than the predefined size, an explicit splitting is performed, wherein the explicit splitting is performed based on signaled information,
wherein the block splitting structure is configured such that, when the coding unit crosses both a lower boundary and a right boundary of a picture and the coding unit is larger than a minimum size of a quadtree leaf node, quadtree splitting is implicitly performed.
2. The image decoding method according to claim 1 , wherein the predetermined size is 64.
3. The image decoding method according to claim 1 , wherein the block splitting structure is configured such that, after performing ternary tree splitting, binary tree splitting in the same direction as the ternary tree splitting for a center block among the blocks, which are divided by the ternary tree splitting, is not allowed.
4. The image decoding method according to claim 1 , wherein the block splitting structure is determined on the basis of at least one of the first flag, a second flag indicating whether or not binary/ternary tree splitting needs to be performed, a third flag indicating either a vertical split or a horizontal split, and a fourth flag indicating either the binary tree splitting or the ternary tree splitting.
5. The image decoding method according to claim 4 , wherein the first flag and the third flag are entropy-decoded using at least one of a size and a depth of a neighboring block.
6. The image decoding method according to claim 1 , wherein the block splitting structure is configured such that, when the height of the coding unit is greater than a predetermined size and the width of the coding unit is same as the predefined size, vertical binary tree splitting is not allowed.
7. The image decoding method according to claim 1 , wherein the block splitting structure is configured such that, when the width of the coding unit is greater than a predetermined size and the height of the coding unit is same as the predefined size, horizontal binary tree splitting is not allowed.
8. The image decoding method according to claim 1 , wherein when the coding tree unit is included in an intra slice, the block splitting structure of a luma signal of the coding tree unit and the block splitting structure of a chroma signal of the coding tree unit are independently determined of each other.
9. An image encoding method comprising:
splitting a coding tree unit (CTU) into at least one coding unit (CU) according to a block splitting structure; and
performing CU-based encoding, and
wherein the block splitting structure is configured such that:
quadtree splitting is performed first and at least one of binary tree splitting and ternary tree splitting is then performed,
when a size of the coding unit is larger than a predefined size, an implicit quadtree splitting is performed and splitting information for the block splitting structure is not signaled, and
when the size of the coding unit is equal to or smaller than the predefined size, an explicit splitting is performed and the splitting information for the explicit splitting is signaled,
wherein the block splitting structure is configured such that, when the coding unit crosses both a lower boundary and a right boundary of a picture and the coding unit is lamer than a minimum size of a quadtree leaf node, quadtree splitting is implicitly performed.
10. The image encoding method according to claim 9 , wherein the block splitting structure is determined on the basis of at least one of a first flag, a second flag indicating whether or not binary/ternary tree splitting needs to be performed, a third flag indicating either a vertical split or a horizontal split, and a fourth flag indicating either the binary tree splitting or the ternary tree splitting.
11. The image encoding method according to claim 9 , wherein when the coding tree unit is included in an intra slice, the block splitting structure of a luma signal of the coding tree unit and the block splitting structure of a chroma signal of the coding tree unit are independently determined of each other.
12. A non-transitory computer readable storage medium storing commands that, when executed by a processor, causes the processor to:
split a coding tree unit (CTU) into at least one coding unit (CU) according to a block splitting structure; and
perform CU-based encoding, and
wherein the block splitting structure is configured such that:
quadtree splitting is performed first and then at least one of binary tree splitting and ternary tree splitting is performed,
when a size of the coding unit is larger than a predefined size, an implicit quadtree splitting is performed and splitting information for the block splitting structure is not signaled, and
when the size of the coding unit is equal to or smaller than the predefined size, an explicit splitting is performed and the splitting information for the explicit splitting is signaled,
wherein the block splitting structure is configured such that, when the coding unit crosses both a lower boundary and a right boundary of a picture and the coding unit is larger than a minimum size of a quadtree leaf node, quadtree splitting is implicitly performed.
13. The image decoding method according to claim 1 , wherein the quadtree splitting is performed based on minimum size information of a quadtree leaf node obtained from a bitstream.
14. The image decoding method according to claim 1 , wherein the minimum size information of a quadtree leaf node is obtained for each of a luma signal and a chroma signal.
15. The image decoding method according to claim 1 , wherein the method further comprises obtaining maximum size information of a transform block from a bitstream.