Motion Re-estimation for MPEG-2 to MPEG-4 Simple Profile Transcoding

Since its emerging in mid 90’s, MPEG-2 [1] has been widely accepted by the digital video industry. There have been huge amount of video content stored in MPEG-2 format. MPEG4 [2] is the latest video coding standard out of MEPG targeted at network video applications. The Simple Profile (SP) of MPEG-4 is often used in practical applications. Thus, it is often necessary to perform MPEG-2 to MPEG-4 SP transcoding for the transmission of MPEG-2 coded video content over networks. Such transcoding usually requires hybrid spatial/temporal resolution down-sampling. Since MPEG-4 SP does not support bi-directional prediction, the B-pictures in the MPEG-2 bit-stream need to be changed into P-pictures. In addition, the transcoder needs to be able to deal with interlaced input video supported by MPEG-2 standard. In this paper, we propose techniques to perform motion vector re-estimation that effectively handles the hybrid spatial/temporal resolution reduction with picture type conversion, as well as the interlaced MEPG-2 input video.