A Motion Vector Prediction Scheme for MPEG-2 to H.264 Transcoding Based on Smoothness of Motion Vector Field

In MPEG-2 to H.264 transcoding, MPEG-2 motion vector (MV) is often reused as search center to simplify H.264 motion estimation (ME) module. In this paper, we show that motion vector predictor (MVP) from neighboring sub-blocks is more accurate than MPEG-2 MV as search center when MPEG-2 MV field is non-smooth. A criterion based on relative motion is proposed to evaluate smoothness of MPEG-2 MV field. And a hardware oriented MV prediction scheme is also proposed. Experiment results show that the proposed MV prediction scheme with a relative small search range can approach the performance of full search algorithm. Comparing with the method only utilizing MPEG-2 M V, the proposed approach can achieve significant improvement on accuracy of motion prediction, especially in sequences with fast motion and complicate background.