A CONTROL-THEORETIC APPROACH TO ADAPTING VBR COMPRESSED VIDEO FOR TRANSPORT OVER A CBR COMMUNICATIONS CHANNEL

Future broad-band communications networks are expected to be dominated by video and image traffic. Variable bit-rate (VBR) video compression is generally preferred to constant bit-rate (CBR) compression because constant image quality can be provided, In contrast, CBR transport is preferred to VER transport from the networking standpoint because of its simplicity, This paper studies the important issue of adapting VBR -compressed video for transport over a CBR channel, We focus on tempor al traffic smoothing using an elastic buffer, The target image quality and the output rate of the video encoder is controlled by feedback ba sed, on the buffer-occupancy level, previous adaptation schemes are no t readily analyzable, an analyzable control-theoretic adaptation frame work is proposed. It allows systematic and quantitative investigation of issues such as stability, robustness against scene changes, robustn ess against image-quality oscillations due to coding-mode switching, a nd tradeoffs between image-quality and buffer-occupancy (delay) fluctu ations. Perhaps more importantly, the framework opens up many new poss ibilities for further research.