A decoding method performed at least partially by electronic circuitry, comprising:
inputting encoded data comprising at least a target block in a first frame;
decoding a merge flag specifying whether at least a motion vector of an inter prediction mode is inferred from a merging block;
deriving a first candidate motion vector from at least one neighboring block of the target block in the first frame, when the merge flag specifies that at least the motion vector of the inter prediction mode is inferred from the merging block, wherein the at least one neighboring block of the target block comprises at least one of (1) a block on bottom left side of the target block, (2) a block on left side of the target block, (3) a block on upper right side of the target block, (4) a block on upper side of the target block, or (5) a block on upper left side of the target block;
deriving a second candidate motion vector from a collocated block in a second frame different from the first frame, when the merge flag specifies that at least the motion vector of the inter prediction mode is inferred from the merging block, wherein the collocated block is selected according to a center position of the target block or a corner position of the target block, and information specifying whether the collocated block is selected according to the center position of the target block or the corner position of the target block is derived based on at least one of a position or a size of the target block;
decoding a merge index specifying the merging block from the at least one neighboring block and the collocated block; and
deriving a first motion vector for the target block from any one of the first candidate motion vector and the second candidate motion vector according to the merge index.