Efficient Motion Estimation in H.264 Reverse Transcoding

In this paper, we propose a fast reverse motion estimation algorithm with efficient mode decision for reverse transcoding of H.264 bitstream. By analyzing the motion vectors and modes decoded from the forward bitstream, the best mode and motion vector for each backward transcoded macroblock are estimated. A remarkable reduction of computational complexity involved in reverse motion estimation can be achieved by the proposed algorithm with only negligible impact on the rate-distortion performance.