Constrained and general dynamic rate shaping of compressed digital video

We introduce the concept of dynamic rate shaping, a technique to adapt the rate of compressed video bitstreams (MPEG-1, MPEG-2, H.261, as well as JPEG) to dynamically varying bit rate constraints. The approach provides an interface (or filter) between the encoder and the network, with which the encoder´s output can be perfectly matched to the network´s quality of service characteristics. Since the presented algorithms do not require interaction with the encoder, they are fully applicable to precoded, stored video (e.g., video-on-demand systems). By decoupling the encoder and the network, universal interoperability can be achieved. In essence, DRS bridges the gap between CBR and VBR video, allowing a continuum of possibilities between the two. A set of low-complexity algorithms for so-called unconstrained dynamic rate shaping are presented, and both optimal and extremely fast designs are discussed. Experimental results are provided using actual MPEG-2 bitstreams