Motion vector refinement for MPEG-2 to H.264 video transcoding

A method for transcoding that includes (A) generating a decoded frame by decoding an MPEG-2 input video stream, the decoded frame including decoded macroblocks; (B) determining a search center for encoding a current macroblock corresponding to a pair of the decoded macroblocks on consecutive macroblock rows, when (i) the encoding uses a predictive field mode and (ii) a current field being encoded is a second field of a current frame that has a first field as a reference field, the search center is a temporally scaled version of a decoded motion vector from an upper or a lower macroblock in the pair; (C) generating a refined motion vector by searching in a temporal search direction about the search center; and (D) generating an H.264 output video stream by encoding the current macroblock based on the refined motion vector.