Fast H.264/AVC to HEVC transcoding using mode merging and mode mapping

A fast H.264/AVC to HEVC transcoding algorithm using motion vector based mode merging and conditional probability based mode mapping is proposed in this paper. Reusing the incoming H.264 block modes directly does not give the best Rate Distortion performance in HEVC. Motion vector variance is used to predict the possible merge of the H.264 blocks at coding depths 0 and 1 in HEVC. A conditional probability based mathematical model is developed to predict the two most probable modes at coding depths 2 and 3 of the HEVC encoding stage. Results show around 50 percent complexity reduction with negligible rate distortion loss.