Fast transcoding of intra frames between H.263 and H.264

In this paper we present algorithms developed for transcoding predicted intra macroblocks between H.263 and H.264. It can be used in video servers for fast adaption of video content in networks supplying different coding standards, e.g. Internet and UMTS. It is shown that due to basic pattern similarities between frequency domain prediction of H.263 and spatial prediction of H.263 it is possible to reuse predictor side information. This side information is used to simplify the mode and direction decision for intra prediction. It results in a high reduction of complexity for mode and direction estimation at comparable PSNR and a slightly increased rate.