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

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