Low-latency delivery of multiple video streams over a wireless channel.

摘要

An emerging application for wireless local area networks is the distribution of high-quality video from so-called home media gateways to receivers throughout a local area. The challenge is to deliver streams reliably over a time-varying, error-prone wireless channel while meeting stringent latency constraints. It is also desirable to maximize the quality of concurrent streams that must share network resources.; To address the problem of how to share network resources among streams, we introduce an algorithm for optimal channel-time allocation. An optimal allocation is one that maximizes the overall video quality of the streams given the transmission speed that is available to each receiver and the rate-distortion properties of each video sequence. We present solutions for several optimization objectives and show how the rate-distortion information needed for optimal allocation can be estimated on the fly from previous outputs of transcoders used in our system to control encoded rates.; To address the problem of reliably delivering streams over an error-prone wireless channel when a latency constraint limits the amount of protective playout buffering that can be used, we introduce a scheduling algorithm that prioritizes packet transmissions. Transmissions are scheduled in order to maximize overall video quality when conditions make it unlikely that already-transcoded frames can all be delivered by their deadlines. We also show how Adaptive Media Playout (AMP), can be used to increase protective buffering without affecting user-perceived start-up latency. With the results of Markov chain analysis and simulation experiments we show how AMP can be used to greatly improve the reliability of a streaming system without adding perceived latency.