Abstract

Distributed partial mixing (DPM) is an approach to creating a distributed audio service that supports optimization of bandwidth utilization across multiple related audio streams (e.g., from concurrently active audio sources) while maintaining fairness to TCP traffic in best-effort networks. Rate adaptation of streamed audio is difficult because of its rate sensitivity, the relatively limited range of encoding bandwidths available, and the potential impact on the end user of rate-adaptation artifacts (such as changes of encoding). This paper describes and demonstrates how our design combines TCP-fairness with the stability that is desirable for streaming audio and other rate-sensitive media. In particular, our design combines: a distributed multi-stream management/mixing architecture, loss-event and round-trip time monitoring, rate limiting based on a TCP rate equation, tuned increase and decrease strategies, and a loss-driven network-probing mode. Experimental validation is performed against TCP and independent DPM traffic. In particular, we summarize and discuss the two contrasting models for deploying DPM within the context of large dynamic environments that we introduced in Radenkovic and Greenhalgh (2002), Proceedings of ACM VRST 2002, 179–185. We argue that the DPM paradigm remains feasible and desirable in such environments.

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