Reduction of the bitrate of video content is necessary in order to satisfy the different constraints imposed by networks and terminals. A fast and elegant solution for the reduction of the bitrate is requantization, which has been successfully applied on MPEG-2 bitstreams. Because of the improved intra prediction in the H.264/AVC specification, existing transcoding techniques are no longer suitable. In this paper we compare requantization transcoders for H.264/AVC bitstreams. The discussion is restricted to intra 4x4 macroblocks only, but the same techniques are also applicable to intra 16x16 macroblocks. Besides the open-loop transcoder and the transcoder with mode reuse, two architectures with drift compensation are described, one in the pixel domain and the other in the transform domain. Experimental results show that these architectures approach the quality of the full decode and recode architecture for low to medium bitrates. Because of the reduced computational complexity of these architectures, in particular the transform-domain compensation architecture, they are highly suitable for real-time adaptation of video content.

Date Published: 24 August 2006
PDF: 10 pages
Proc. SPIE 6312, Applications of Digital Image Processing XXIX, 63120X (24 August 2006); doi: 10.1117/12.680769

Published in SPIE Proceedings Vol. 6312:
Applications of Digital Image Processing XXIX
Andrew G. Tescher, Editor(s)