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We consider multi-rate peer-to-peer multiparty video conferencing applications, where different receivers in the same group can receive videos at different rates using, for example, scalable layered coding. The quality of video received by each receiver can be modeled as a concave utility function of the video bitrate. We study and address the unique challenges introduced by maximizing utility in the multi-rate setting as compared to the single-rate case. We first determine an optimal set of tree structures for routing multi-rate content using scalable layered coding. We then develop Primal and Primal-dual based distributed algorithms to maximize aggregate utility of all receivers in all groups by multi-tree routing and show their convergence. These algorithms can be easily implemented and deployed on today's Internet. We have built a prototype video conferencing system to show that this approach converges to optimal bitrates to improve user experience and offers automatic adaptation to network conditions and user preferences.
Date of Publication: Oct. 2011