Using internet for media-based real-time collaboration has become widespread activity. In this paper, we present a framework called CoUniverse, designed for building realtime user-empowered collaborative environments to work primarily on high-speed networks with true high-bandwidth applications such as uncompressed high-definition video. The system is designed for unreliable experimental infrastructures and therefore its operation relies heavily on selforganizing principles-this is also useful approach for extending it to larger infrastructures. When media stream bitrate is comparable to capacity of the links, the additive assumption no longer holds and the system needs to have sophisticated scheduling. Concept of scheduler is a flexible plug-in for the CoUniverse framework and in this paper, we present a formal scheduling model based on constraint programming including evaluation of its prototype implementation. CoUniverse is designed to utilize external media application, so that wide variety of existing tools can be used. The whole system has been prototyped and demonstrated, e. g., during international demonstration on GLIF 2007 workshop.

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