Method for encoding and decoding image information and device using same

A method for an inter prediction, the method comprising:

• receiving, by a decoding apparatus, inter prediction mode information and merge index information for a current block;
• determining, by the decoding apparatus, a merge mode is used as an inter prediction mode for the current block based on the inter prediction mode information;
• configuring, by the decoding apparatus, merge candidates including spatial merge candidates and a temporal merge candidate based on spatial neighboring blocks and a temporal neighboring block of the current block, wherein the temporal neighboring block is located in a collocated picture;
• selecting, by the decoding apparatus, a merge candidate from the configured merge candidates for the merge mode based on the merge index information;
• deriving, by the decoding apparatus, motion information for the selected merge candidate as motion information of the current block, wherein the motion information of the current block includes a motion vector and a reference picture index;
• and
• generating, by the decoding apparatus, prediction samples of the current block using the motion vector and a reference picture indicated by the reference picture index,
• wherein motion information for a spatial merge candidate is derived from motion information of a spatial neighboring block of the current block,
• wherein a motion vector for the temporal merge candidate is derived from a motion vector of the temporal neighboring block,
• wherein a reference picture index for the temporal merge candidate is set equal to 0 regardless of any of values of reference picture indexes of the spatial neighboring blocks and the temporal neighboring block.