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This paper describes the design and initial implementation of the Rapport multimedia conferencing system, which supports interactive, real-time, distributed conferences among two or more users. Using computers connected by data and voice networks, this system creates an environment in which many sorts of meetings can take place, including telephone conversations, discussions among colleagues, and lectures. Rapport provides new opportunities for meetings, allowing a user to interact with distant colleagues and to participate in several conferences concurrently at his or her workstation. The system allows many existing computer programs to be used, unmodified, within its conferencing environment. Thus computer-generated data and displays are available to the conferees for manipulation and editing, enhancing the exchange of information during meetings. Although Rapport does not encourage a particular methodology of meeting conduct, such specialized support can be built using Rapport.The paper outlines Rapport's conference abstraction and the model on which it is based -the "virtual meeting room." It then presents an overview of Rapport's architecture, discusses the system's environmental requirements, and concludes by mentioning some of our plans for future work with Rapport.

Desktop conferencing is a term used to describe real-time, computer-based conferences in which users may share data through their personal computers. In these conferences, the participants may access user-level programs, called application programs, which produce common displays (screens or windows) on their computers. Because each participant may give input to the application program and sees its resulting output as though the program were executing on his or her local computer, these applications retain their own look and feel as they form a shared environment for the conference. We compare some methods of sharing application programs during real-time, computer-based conferencing. In particular, we have explored different methods in three versions of Rapport, a multimedia conferencing system. We examine the qualitative and quantitative differences of these implementations using some typical shared applications and find that one method possesses good semantic characteristics as well as good performance in several network environments.

This paper discusses ways to incorporate video displays into virtual environments. It focuses on the virtual worlds created by a distributed multi-user simulator. Still images or video streams represent spaces within these three-dimensional worlds. The paper introduces techniques to deal with avatar movement into and out of video regions. In one technique-media melding-when an object moves from one region to another, the media used to represent that object correspondingly change. In a second technique-object tracing-when an object moves from one region to another, its actions in the second region are represented by a trace object in the first region. Pyramidic panels provide a means of dealing with viewpoint changes so that two-dimensional images and video clips can successfully simulate threedimensional spaces. The paper concludes by suggesting ways to extend our techniques and by listing possible future studies.

Desktop conferencing is a term used to describe real-time, computer-based conferences in which users may share data through their personal computers.In these conferences, the participants may access user-level programs, called application programs, which produce common displays (screens or windows) on their computers. Because each participant may give input to the application program and sees its resulting output as though