A generic video transcoder for MPEG streams by arbitrary frame dropping

In video transcoding, the new motion vectors are composed by reusing incoming motion vectors to reduce transcoding latency. Currently available motion vector composition techniques for temporal transcoding work for progressive video comprising I and P-frames. Since I-frames do not carry any motion vector, such techniques do not handle their dropping. In this paper, we propose a motion vector composition scheme for arbitrarily dropping any frame from incoming video bit-stream comprising I, B and P frames. The proposed scheme handles progressive as well as interlaced video. The scheme is shown to work for MPEG videos. To further reduce transcoding latency, we proposed an adaptive motion vector refinement method using a variability measure. The transcoding results are presented and compared with other schemes.