| CPC H04N 19/159 (2014.11) [H04N 19/105 (2014.11); H04N 19/126 (2014.11); H04N 19/13 (2014.11); H04N 19/176 (2014.11); H04N 19/463 (2014.11); H04N 19/513 (2014.11); H04N 19/593 (2014.11); H04N 19/96 (2014.11)] | 3 Claims |

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1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining a plurality of sub-blocks by dividing the current block into sub-block units;
deriving a plurality of co-located sub-blocks for the plurality of sub-blocks;
deriving sub-block-based temporal merge candidates of the current block based on the plurality of co-located sub-blocks; and
generating a predicted block of the current block based on the sub-block-based temporal merge candidates,
wherein the co-located sub-blocks are located in a collocated picture which is one of reference pictures,
wherein deriving sub-block-based temporal merge candidates of the current block based on the plurality of co-located sub-blocks comprises:
based on that motion information of a co-located sub-block for a sub-block is available, motion information of the sub-block is derived by using motion information of the co-located sub-block,
based on that the motion information of the co-located sub-block for the sub-block is not available, the motion information of the sub-block is derived by using motion information of a center sub-block in a co-located block comprising the co-located sub-block, and
wherein the co-located block and co-located sub-blocks are derived by using a predefined motion vector, and
wherein a reference picture for the sub-block-based temporal merge candidates is selected as a firstly-ordered picture in a reference picture list for the current block.
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