Multimedia conferencing in the Etherphone environment

The latest extension of the Etherphone project is described. It creates a powerful conferencing system that lets users control their participation in multiple conferences across multimedia networks. The emphasis is on the software mechanisms that support its new features: first, a Sparcstation facility called Phoenix that extends the Etherphone software architecture to permit more flexible conferencing and to control Sparcstation-based Ethernet audio transmission, and, second, the integration of the Phoenix capabilities with Macaw, the earlier video extensions. Also described is a multicast packet protocol for audio transmission, which reimplements and extends the earlier special-purpose protocols, adding per-channel volume control and full support for the extended conferencing modes