Transcoding of video into different encoding formats

In this paper, transcoding of pre-encoded MPEG-1,2 video into lower bit rates is realized through altering the coding algorithm into H.261/H.263 standards with lower spatial resolutions. We extract and compose a set of candidate motion vectors, from the incoming bit stream, to comply with the encoding format of the output bit stream. For the spatial resolution reduction, we generate one motion vector out of a set of input motion vectors operating on the higher spatial resolution image. We discuss the impact of motion estimation refinement on the new motion vectors and show that for all cases a simple half-pixel refinement is sufficient for near-optimum results