Transcoding of MPEG-2 video in the frequency domain

Video transcoding techniques offer the possibility of matching coded video to transmission channels of lower capacity by reducing the bit rate of compressed bit streams. In this paper we propose a new frequency domain video transcoder for bit rate reduction of compressed bit streams. A motion compensation (MC) loop, operating in the frequency domain, is used for drift compensation at reduced computational complexity. We derive approximate matrices for fast computation of the MC blocks in the frequency domain. By using the Lagrangian optimisation in calculating the best quantiser scales for transcoding, we show that transcoded pictures from a high quality bit stream are better than those encoded from original frames at the same reduced bit rates