High-Performance Prefetching ProtocoIs for VB R Prerecorded Video

We describe several high-performance prefetching protocols for the transport of VBR prerecorded video over a shared channel. The protocols are particular1 well suited for offering video on demand over a residential cable network, a resiJential ADSL network, or over a shared satellite channel. W e advocate the use of VBR-encoded video instead of CBR video because, for the same image quality, VBR-encoded video can have a significantly lower average rate. However, in order to exploit the efficiency of VBR encoding, it is necessary that the VBR scheme multi-plex and prefetch streams so that near 100 percent link utilizations are achieved. Our protocols are based on the observation that there are frequent periods of time during which the network bandwidth i s underutilized. D u r i n these periods the server can prefetch frames from any of the ongoing videos a n i send the frames to the buffers in the appropriate clients. Simulation results based on MPEG-encoded traces show that the discussed prefetching protocols compare favorably with other VBR transport protocols