Online Smoothing of Live, Variable-Bit-Rate Video

Bandwidth smoothing techniques are eeective at reducing the burstiness of a compressed, pre-recorded video stream by prefetching frames into the client playback buuer in advance of each burst. In contrast to stored video, live applications typically have limited knowledge of frame sizes and often require bounds on the delay between the source and the client(s). This paper addresses bandwidth smoothing for a growing number of live video applications, such as videocasts of courses or television news, where many clients may be willing to tolerate a playback delay of several seconds or minutes in exchange for a smaller through-put requirement. Extending techniques for smoothing pre-recorded video, we develop online, window-based smoothing algorithms for these delay-tolerant applications. Experiments with MPEG traces demonstrate that the new algorithms signiicantly reduce the peak rate, coeecient of variation, and eeective bandwidth of variable-bit-rate video streams using fairly small window sizes (1{10 seconds), closely approximating the performance of the optimal ooine algorithm 1].