H.264 to MPEG-4 Resolution Reduction Transcoding

In this paper, we propose a heterogeneous transcoding method of converting an H.264 video bitstream into an MPEG-4 video bitstream. The proposed method reduces the spatial resolution for mobile terminals which support only low resolution video bitstreams. When the H.264 video bitstream is transformed into the MPEG-4 video bitstream, the conversions between the H.264 block types and the MPEG-4 block types are performed by minimizing the distortion, and 4 times 4 block-based motion vector mapping is performed. The proposed transcoding method runs on average 5.5 times faster than the cascaded transcoding methods, for a degradation of the PSNR (peak-signal- to-noise ratio) of less than 0.5 dB.