Method for decoding image by using block partitioning in image coding system, and device therefor
The method for decoding an image by a decoding device according to the present document may comprise the steps of: acquiring image information comprising partitioning information for a current block; determining, on the basis of the size of the current block, whether to partition the current block; partitioning the current block into subblocks on the basis of the partitioning information, if it is determined that the current block is to be partitioned, and decoding the subblocks; and not partitioning the current block, if it is determined that the current block is not to be partitioned, and decoding the current block, wherein, if the current block is a chroma block, and the size of the current block is at most the minimum size of a chroma block, then it is determined that the current block is not to be partitioned.
1. A video decoding method performed by a decoding apparatus, comprising:
obtaining image information including partitioning information;
determining whether a current block is partitioned based on a number of samples of the current block; and
decoding the current block based on whether the determined current block is partitioned,
wherein the partitioning information includes a first flag indicating whether the current block is partitioned as quad-tree (QT) type, and
based on a value of the first flag being 0, the partitioning information includes a second flag and a third flag, the second flag indicates a partitioning direction of the current block, and the third flag indicates whether a partition type of the current block is a binary-tree (BT) type or ternary-tree (TT) type.
2. The video decoding method of claim 1 , wherein when the current block is a chroma block and a size of a sub-block partitioned and derived from the current block is 2×2, it is determined that the current block is not partitioned.
3. The video decoding method of claim 1 , wherein a minimum chroma block size is 16.
4. The video decoding method of claim 3 , wherein the image information includes information indicating the minimum chroma block size, and the minimum chroma block size is derived based on information indicating the minimum chroma block size.
5. The video decoding method of claim 1 , wherein when the current block is a luma block and the number of the samples of the current block is equal to or smaller than a minimum luma block size, it is determined that the current block is not partitioned.
6. The video decoding method of claim 5 , wherein the image information includes information indicating the minimum luma block size, and the minimum luma block size is derived based on information indicating the minimum luma block size.
7. The video decoding method of claim 6 , wherein the information indicating the minimum luma block size is signaled as a sequence parameter set (SPS).
8. The video decoding method of claim 1 , wherein the current block is partitioned into sub-blocks based on the partition type of the current block derived based on the second flag and the third flag.
9. The video decoding method of claim 8 , wherein
when the value of the second flag is 0 and the value of the third flag is 0, the partition type is derived as a horizontal ternary type,
when the value of the second flag is 0 and the value of the third flag is 1, the partition type is derived as a horizontal binary type,
when the value of the second flag is 1 and the value of the third flag is 0, the partition type is derived as a vertical ternary type, and
when the value of the second flag is 1 and the value of the third flag is 1, the partition type is derived as a vertical binary type.
10. A video encoding method performed by an encoding apparatus, the video encoding method comprising:
determining a partition type for a current block;
determining whether the current block is partitioned based on a number of samples of the current block;
partitioning the current block into sub-blocks based on the partition type based on determination that the current block is partitioned; and
encoding image information including partitioning information indicating the partition type for the current block,
wherein the partitioning information includes a first flag indicating whether the current block is partitioned as quad-tree (QT) type, and
based on a value of the first flag being 0, the partitioning information includes a second flag and a third flag, the second flag indicates a partitioning direction of the current block, and the third flag indicates whether a partition type of the current block is a binary-tree (BT) type or ternary-tree (TT) type.
11. The video encoding method of claim 10 , wherein, when the current block is a chroma block and a size of a sub-block partitioned and derived from the current block is 2×2, it is determined that the current block is not partitioned.
12. The video encoding method of claim 10 , wherein a minimum chroma block size is 16.
13. A non-transitory computer-readable storage medium storing a bitstream generated by a method, the method comprising:
determining a partition type for a current block;
determining whether the current block is partitioned based on a number of samples of the current block;
partitioning the current block into sub-blocks based on the partition type based on determination that the current block is partitioned; and
encoding image information including partitioning information indicating the partition type for the current block; and
generating the bitstream including the image information,
wherein the partitioning information includes a first flag indicating whether the current block is partitioned as quad-tree (QT) type, and
based on a value of the first flag being 0, the partitioning information includes a second flag and a third flag, the second flag indicates a partitioning direction of the current block, and the third flag indicates whether a partition type of the current block is a binary-tree (BT) type or ternary-tree (TT) type.