Efficient block size selection for MPEG-2 to H.264 transcoding

In this paper, an efficient block size mode selection algorithm for the variable-sizes block-matching (VSBM) in the MPEG-2 to H.264 transcoding is presented. Depending on leveraging the available motion information carried by the MPEG-2 bit-streams, the proposed algorithm is used to determine which one of the 16x16, 16x8, 8x16, and 8x8 block size modes should be used for each macroblock (MB). The simulation results show that the performance of the proposed algorithm is close to that of a cascaded pixel-domain transcoder (CPDT) when all the seven block size modes are enabled and the exhaustively full search method is used to determine the best block size modes. The whole transcoding time can be efficiently reduced by 22% on the average while the bit rate is slightly increased (2.9%).