Recording and Playing Back Mbone Sessions

Experiences of interactive Internet multimedia applications, especially conferencing, indicate that there is a need for a mechanism to record and playback the media of these conferences [#!mice!#] [#!remsem!#].

When recording, both audio and video streams need to be archived, and possibly the shared workspace, with the possibility of having stream synchronisation. As some conferences only require a subset of the conferees to be recorded, the record mechanism should allow a selection of the streams to be specified. The retrieval of recorded material needs to be easy for users to access, either for direct playback to the user or for inclusion in another multicast multimedia conference. Users also need to see which conferences have been recorded and are online for access in order to select streams to play. As real-time multimedia applications generate vast amounts of data, any recording system must therefore be fully equipped with large storage capabilities.

To meet the above requirements, the objectives of a recording and playback system need to be:

• the ability to record multicast session data whose source may be any of the conferees;
• the ability to playback recorded material either directly to one user or into another multicast session;
• to provide synchronisation between streams from each source;
• to allow users to create their own segments of recorded material, and create their own material for playback;
• to provide a single point of contact for recording and playback;
• to supply a large repository of archive space which is accessible to authorised network users who wish to record or playback multimedia data;

In the next section we discuss previous attempts at recording and playback of multimedia conferences, and see how they meet the above objectives. Then the design of a system to achieve the above objectives is presented, showing what is actually required for recording, playback, and editing of multimedia streams. As the media streams are large, it is pertinent to provide indexes into these streams. Multimedia indexes are a novel approach to accessing such data, and these techniques will be discussed later.

After this, we describe the Real Time Streaming Protocol, which is becoming the standard for remote control facilities for multimedia servers.