1. A method for decoding a bitstream for a video signal by a decoding apparatus, the method comprising: deriving at least one motion vector candidate from at least one neighboring block of a current block; constructing a motion vector candidate group of the current block, the motion vector candidate group comprising a plurality of motion vector candidates including the derived at least one motion vector candidate; obtaining a motion vector predictor of the current block from the constructed motion vector candidate group; and decoding the current block based on the motion vector predictor, wherein deriving the at least one motion vector candidate includes: selecting a scaled motion vector of the at least one neighboring block as the at least one motion vector candidate when the at least one neighboring block refers to a reference picture having a different picture order count (POC) value than the current block in a different reference picture list than the current block.