Reduced Complexity H.264 to MPEG-2 Transcoder

This paper presents techniques for reducing the complexity of H.264/MPEG-2 transcoding through reuse of information gathered during the H.264 decoding stage. The H.264 macro block (MB) coding modes and the motion vectors are used for mode mapping and motion estimation in MPEG-2. We present a reduced complexity transcoder based on MB mode mapping, dynamic search range, and a dynamic search window. The proposed transcoder reduces the transcoding time by over 60% compared with the baseline cascaded transcoder with a negligible loss in PSNR.