DECspin: A Networked Desktop Videoconferencing Application

1 Abstract The Sound Picture Information Networks (SPIN) technology that is part of the DECspin Version 1.0 product takes digitized audio and video from desktop computers and distributes this data over a network to form real-time conferences. SPIN uses standard local and wide area data networks, adjusting to the various latency and bandwidth differences, and does not require a dedicated bandwidth allocation. A high-level SPIN protocol was developed to synchronize audio and video data and thus alleviate network congestion. SPIN performance on Digital's hardware and software platforms results in sound and pictures suitable for carrying on personal communications over a data network. The Society of Technical Communication chose the DECspin Version 1.0 application as a first-place recipient of the Distinguished Technical Communication Award in 1992. 2 Introduction In late 1990, we began to design a software product that would allow people to see and hear one another from their desktop computers. The resulting DECspin Version 1.0 application takes digitized audio and video data from two to eight desktops and distributes this data over a network to form real-time conferences. The product name represents the four major communication elements that unite into one cohesive desktop application, namely, sound, picture, information, and networks. The overall technology is referred to as SPIN. This paper first presents an introduction to conferencing and gives a brief overview of the framework on which SPIN was developed. The paper then details SPIN's graphical user interface. Although the high-level protocol (which is the application layer of the International Organization for Standardization/Open Systems Interconnection [ISO/OSI] model) that SPIN uses to synchronize distributed audio and video is proprietary, a general discussion of how SPIN uses standard data networks for conferencing is presented. Performance data for DECspin Version 1.0 running on a DECstation 5000 Model 200 workstation with DECvideo and DECaudio hardware follows the discussion of network considerations. Finally, the paper summarizes the future direction of desktop conferencing. 3 Introduction to Conferencing When the SPIN project started, standalone teleconferencing products were available but not for desktop computers. Typically, the products offered cost as much as $150,000, required scheduled conference rooms and operators, and needed leased telephone lines. These systems did not operate as part of a corporate computer data network but instead required