Apparatus for performing image coding on basis of ATMVP candidate
A method for image decoding performed by a decoding apparatus according to the present disclosure comprises the steps of: deriving an ATMVP candidate for a current block; deriving merge candidates for the current block; deriving prediction samples for the current block on the basis of the merge candidates and the ATMVP candidate; and deriving reconstruction samples for the current block on the basis of the prediction samples, wherein the ATMVP candidate is a spatial neighboring block spatially adjacent to the current block.
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining information related to a prediction and residual information from a bitstream;
deriving a subblock based temporal merge candidate for a current block based on the information related to the prediction;
deriving affine candidates for the current block based on the information related to the prediction;
deriving a merge candidate list for the current block, wherein the merge candidate list includes the subblock based temporal merge candidate and the affine candidates;
deriving prediction samples for the current block based on the merge candidate list;
deriving residual samples for the current block based on the residual information; and
generating reconstructed samples based on the prediction samples and the residual samples,
wherein deriving the subblock based temporal merge candidate comprises:
deriving the motion vector of a left neighboring block of the current block;
deriving corresponding subblocks in a collocated picture based on the motion vector of the left neighboring block;
deriving subblock motion vectors of the corresponding subblocks; and
deriving the subblock based temporal merge candidate based on the subblock motion vectors,
wherein deriving the subblock based temporal merge candidate further comprises
deriving a base motion vector based on a motion vector related to a below-right center position of the current block, and
wherein based on a motion vector of a corresponding subblock not being available, the base motion vector is used as the subblock motion vector of the corresponding subblock.
2. The method of claim 1 ,
wherein the left neighboring block of which motion vector is used for deriving the subblock based temporal merge candidate is a bottom block among left neighboring blocks adjacent to a left boundary of the current block.
3. The method of claim 1 ,
wherein the left neighboring block of which motion vector is used for deriving the subblock based temporal merge candidate is adjacent to a top boundary of a bottom-left corner neighboring block of the current block.
4. The method of claim 1 ,
wherein the subblock temporal merge candidate is firstly configured in the merge candidate list.
5. The method of claim 1 ,
wherein a configuring order of the subblock temporal merge candidate is prior to a configuring order of each of the affine candidates.
6. An image encoding method performed by an encoding apparatus, the method comprising:
deriving a subblock based temporal merge candidate for a current block;
deriving affine candidates for the current block;
deriving a merge candidate list for the current block, wherein the merge candidate list includes the subblock based temporal merge candidate and the affine candidates;
deriving prediction samples for the current block based on the merge candidate list;
deriving residual samples for the current block based on the prediction samples;
generating information related to a prediction and residual information related to the residual samples; and
encoding image information including the information related to the prediction and the residual information,
wherein deriving the subblock based temporal merge candidate comprises:
deriving the motion vector of a left neighboring block of the current block;
deriving corresponding subblocks in a collocated picture based on the motion vector of the left neighboring block;
deriving subblock motion vectors of the corresponding subblocks; and
deriving the subblock based temporal merge candidate based on the subblock motion vectors,
wherein deriving the subblock based temporal merge candidate further comprises
deriving a base motion vector based on a motion vector related to a below-right center position of the current block, and
wherein based on a motion vector of a corresponding subblock not being available, the base motion vector is used as the subblock motion vector of the corresponding subblock.
7. The method of claim 6 , wherein the left neighboring block of which motion vector is used for deriving the subblock based temporal merge candidate is a bottom block among left neighboring blocks adjacent to a left boundary of the current block.
8. The method of claim 6 , wherein the left neighboring block of which motion vector is used for deriving the subblock based temporal merge candidate is adjacent to a top boundary of a bottom-left corner neighboring block of the current block.
9. A transmission method of data for an image, the method comprising:
obtaining a bitstream for the image, wherein the bitstream is generated based on deriving a subblock based temporal merge candidate for a current block, deriving affine candidates for the current block, deriving a merge candidate list for the current block, wherein the merge candidate list includes the subblock based temporal merge candidate and the affine candidates, deriving prediction samples for the current block based on the merge candidate list, deriving residual samples for the current block based on the prediction samples, generating information related to a prediction and residual information related to the residual samples, and
encoding image information including the information related to the prediction and the residual information; and
transmitting the data comprising the bitstream,
wherein deriving the subblock based temporal merge candidate comprises:
deriving the motion vector of a left neighboring block of the current block;
deriving corresponding subblocks in a collocated picture based on the motion vector of the left neighboring block;
deriving subblock motion vectors of the corresponding subblocks; and
deriving the subblock based temporal merge candidate based on the subblock motion vectors,
wherein deriving the subblock based temporal merge candidate further comprises
deriving a base motion vector based on a motion vector related to a below-right center position of the current block, and
wherein based on a motion vector of a corresponding subblock not being available, the base motion vector is used as the subblock motion vector of the corresponding subblock.
10. The transmission method of claim 9 , wherein the left neighboring block of which motion vector is used for deriving the subblock based temporal merge candidate is a bottom block among left neighboring blocks adjacent to a left boundary of the current block.
11. The transmission method of claim 9 , wherein the left neighboring block of which motion vector is used for deriving the subblock based temporal merge candidate is adjacent to a top boundary of a bottom-left corner neighboring block of the current block.