Method and apparatus for encoding motion information, and method and apparatus for decoding same

A method of decoding an image, the method comprising:

• obtaining, by a decoder comprising a processor, a prediction mode of a current block, from a bitstream;
• when the prediction mode of the current block is inter-prediction, obtaining a spatial motion vector predictor candidate of the current block by using a motion vector of an available spatial block spatially related to the current block;
• obtaining a temporal motion vector predictor candidate of the current block by using a motion vector of an available temporal block temporally related to the current block;
• adding, when a number of the spatial motion vector predictor candidate and the temporal motion vector predictor candidate is smaller than a predetermined number n, where n is an integer equal to two or greater, a zero vector to be a motion vector predictor candidate so that a number of motion vector predictor candidates is to be the predetermined number n;
• and
• obtaining a motion vector predictor of the current block based on information indicating a motion vector predictor among the motion vector predictor candidates,
• wherein the spatial motion vector predictor candidate is obtained from neighboring blocks including a first block and a second block, the first block located on the left of a leftmost block among lower blocks adjacent to a lower side of the current block, and the first block located below a lowermost block among left blocks adjacent to a left side of the current block, the second block located on the right of a rightmost block among upper blocks adjacent to an upper side of the current block, and the second block located above an uppermost block among right blocks adjacent to a right side of the current block, and
• wherein, when a first spatial motion vector predictor candidate is equal to a second spatial motion vector predictor candidate, the second spatial motion vector candidate is removed from the motion vector predictor candidates.