Pre-Coded Video Transcoding into H.264 with Arbitrary Resolution Change

This paper describes a new transcoding algorithm, able to transcode any coded (e.g. MPEG-2) bit-stream into an H.264 sequence with arbitrary spatial resolution change. The visual quality at a given input and output bit-rate is close or equal to full decoding followed by a full encoding (0.5 dB-to-2 dB less in PSNR than that of re-encoding the stream at the target resolution) while, from the complexity point of view, the proposed transcoding approach is at least ten times faster than re-encoding. The experimental results show that this H.264 transcoder always gives about 20 to 60% better compression than that of the size of the original MPEG2 sequence scaled by the target resolution ratio at equal subjective quality. Using constant quantization parameters both in the transcoding and re-encoding, transcoding gives 20 to 40% lesser compression than re-encoding.