A Distributed Recording System for High Quality MBone Archives

Popular multicast applications that allow group communication using real-time audio and video have enabled a wide variety of online meetings, conferences and panel discussions. The ability to record and later replay these sessions is one of the key functionalities required for a complete collaboration system. One of the unsolved problems in archiving these interactive sessions is the lack of any method for recording sessions at the highest possible quality. Since audio and video transmissions are typically sent unreliably, there may be a wide variance in recorded quality depending on where the recorder is placed relative to the various sources. This is especially problematic if multiple sources are active in a single session. In addition, because of congestion control schemes that send high-quality, high-rate data to local receivers, and low-rate data in the wide area, different sets of data may be available in different areas of the network for any given session. In response to these challenges, we have developed a system that uses multiple distributed recorders placed at or near the sources of the session. These recorders serve as data caches that transmit data to archives. The archive systems collate the data from various recorders and create a high-quality recorded session, which is then available for playback.