A Fast MPEG-2 to H.264 Downscaling Transcoder

In MPEG-2 to H.264 cascaded transcoder, the transcoding speed is mainly affected by computational complexity of H.264 encoder. Especially, motion estimation module of the encoder costs much time due to multiple motion-compensated prediction modes of H.264. In this paper, in order to speed up the transcoding and achieve good video quality, we propose a new motion vector composition scheme for MPEG-2 to H.264 transcoder. In this scheme, the multiple partition modes in H.264 are considered. Then we suggest a motion vector refinement method to improve the picture quality. In order to further improve the composited motion vector, we also combine the motion vector mapping scheme with the H.264 FME algorithm. The experiments results show that the proposed method reduces computation complexity of downscale transcoding while maintaining similar PSNR performance.