An efficient intra prediction mode decision algorithm for H.263 to H.264 transcoding

Video transcoding comprises the necessary operations for the conversion of a compressed video stream from one syntax to another one for inter-network communications, without the need of any further decoding and re-encoding process. The two most recent and popular standard video coders are H.263 and H.264. In this paper, we present tools to enable low complexity intra transcoding from H.263 to H.264 using a novel fast intra prediction mode decision algorithm that does not require extra computation. It is shown that due to basic similarities of H.263 and H.264 it is possible to reuse predictor side information, so this side information is used to simplify the mode and direction decision for intra prediction. Also, as it is shown the proposed algorithm is improved by using temporal correlation between the intra predicted block in the current frame and the motion-compensated block in its reference. This novel transcoding algorithm reduces the computational complexity, for mode and direction estimation, while maintaining similar PSNR and bitrate.