Method and device for encoding/decoding image and recording medium having bitstream stored thereon
The present invention relates to an image decoding method. The image decoding method comprises deriving initial motion information of a current block from at least one of motion information of a spatial neighbor block, motion information of a temporal neighbor block, and pre-defined motion information, generating refined motion information by performing motion information refinement for the initial motion information and generating a prediction block of the current block by using the refined motion information.
1. A method of decoding an image, the method comprising:
obtaining information indicating a co-located image of a current block;
determining the co-located image of the current block based on the information;
determining whether a merge candidate in a sub-block unit is derived based on a size of the current block;
based on a determination that the merge candidate in the sub-block unit is derived, determining a co-located block in the co-located image by using motion information of a block that is spatially adjacent to the current block, wherein the motion information of the block that is spatially adjacent to the current block is derived based on the co-located image of the current block;
deriving the merge candidate in the sub-block unit from a sub-block within the co-located block; and
generating a merge candidate list by using the merge candidate in the sub-block unit,
wherein the sub-block within the co-located block is determined based on a center location of a current sub-block within the current block,
wherein based on the size of the current block being equal to or greater than a preset value, it is determined that the merge candidate in the sub-block unit is derived, and
wherein based on a picture order count of a reference picture indicated by the motion information of the block that is spatially adjacent to the current block being the same as a picture order count of the co-located image of the current block, the motion information of the block that is spatially adjacent to the current block is derived as motion information to determine the co-located block in the co-located image.
2. The method of claim 1 , wherein the information indicating the co-located image is signaled in at least one unit of a sequence, picture, slice or a tile group.
3. The method of claim 1 , wherein the preset value is 8×8 block size.
4. A method of encoding an image, the method comprising:
determining a co-located image of a current block;
determining whether a merge candidate in a sub-block unit is derived based on a size of the current block;
based on a determination that the merge candidate in the sub-block unit is derived, determining a co-located block in the co-located image by using motion information of a block that is spatially adjacent to the current block, wherein the motion information of the block that is spatially adjacent to the current block is derived based on the co-located image of the current block;
deriving the merge candidate in the sub-block unit from a sub-block within the co-located block; and
generating a merge candidate list by using the merge candidate in the sub-block unit,
wherein the co-located image of the current block is encoded as information and the information is signaled in at least one unit of a sequence, picture, slice or a tile group,
wherein the sub-block within the co-located block is determined based on a center location of a current sub-block within the current block,
wherein based on the size of the current block being equal to or greater than a preset value, it is determined that the merge candidate in the sub-block unit is derived, and
wherein based on a picture order count of a reference picture indicated by the motion information of the block that is spatially adjacent to the current block being the same as a picture order count of the co-located image of the current block, the motion information of the block that is spatially adjacent to the current block is derived as motion information to determine the co-located block in the co-located image.
5. A non-transitory computer readable storage medium including a bitstream, wherein the bitstream is generated by using an image encoding method including:
determining a co-located image of a current block;
determining whether a merge candidate in a sub-block unit is derived based on a size of the current block;
based on a determination that the merge candidate in the sub-block unit is derived, determining a co-located block in the co-located image by using motion information of a block that is spatially adjacent to the current block, wherein the motion information of the block that is spatially adjacent to the current block is derived based on the co-located image of the current block;
deriving the merge candidate in the sub-block unit from a sub-block within the co-located block; and
generating a merge candidate list by using the merge candidate in the sub-block unit,
wherein the co-located image of the current block is encoded as information and the information is signaled in at least one unit of a sequence, picture, slice or a tile group,
wherein the sub-block within the co-located block is determined based on a center location of a current sub-block within the current block,
wherein based on the size of the current block being equal to or greater than a preset value, it is determined that the merge candidate in the sub-block unit is derived, and
wherein based on a picture order count of a reference picture indicated by the motion information of the block that is spatially adjacent to the current block being the same as a picture order count of the co-located image of the current block, the motion information of the block that is spatially adjacent to the current block is derived as motion information to determine the co-located block in the co-located image.
6. The method of claim 1 , wherein a location of the sub-block within the co-located block is derived based on the center location of the current sub-block within the current block and the motion information of the block that is spatially adjacent to the current block.
7. The method of claim 4 , wherein a location of the sub-block within the co-located block is derived based on the center location of the current sub-block within the current block and the motion information of the block that is spatially adjacent to the current block.
8. The non-transitory computer readable storage medium of claim 5 , wherein a location of the sub-block within the co-located block is derived based on the center location of the current sub-block within the current block and the motion information of the block that is spatially adjacent to the current block.