1. A method of encoding video data, the method comprising: determining a candidate motion vector for each of one or more candidate portions of a video frame; determining a current motion vector for a current portion of a current video frame, wherein the current motion vector identifies a portion of a reference video frame; calculating a motion vector difference between the current motion vector and each of the candidate motion vectors; selecting one of the candidate motion vectors based on the calculated motion vector differences; signaling an index identifying the candidate portion having the selected one of the candidate motion vectors; and signaling the motion vector difference calculated with respect to the selected one of the candidate motion vectors.