1. A method for encoding a video signal comprising: deriving, based on a position and a size of a coding block, at least one merging candidate relating to a first prediction block, the coding block comprising the first prediction block and a second prediction block; generating a first merging candidate list for the first prediction block based on the merging candidate; and obtaining prediction samples of the first prediction block based on the first merging candidate list, wherein the first merging candidate list for the first prediction block is equivalent to a second merging candidate list for the second prediction block included in the coding block with the first prediction block.