Managing context for Internet videoconferences: the multimedia Internet recorder and archive

Multimedia objects are difficult to query since much of the content of the object is beyond the interpretive capabilities of a computer. State-of-the-art multimedia content-based retrieval systems focus on post mortem analysis of the underlying data objects to derive semantic information. With the emergence of inexpensive I/O technology we can shift some of the burden of this content analysis to `smart' devices that can capture context information about a multimedia object. Context information includes the geographical location an object is created or used, identities of users, activities of users and other applications, etc. Such information can be used to index the multimedia objects to perform content-based queries with minimal signal processing. We are concerned with the design and implementation of a context-based retrieval system for IP-multicast videoconferences. The Multimedia Internet Recorder and Archive (MIRA) models a videoconference as a Bayesian network that describes bounds on `cost' and `reliability' for a recording task. Context about a videoconference is derived from monitoring the RTCP control channel and messaging events that occur among meeting participants. MIRA creates an index of context information as an XML document that is used by clients to visualize, browse, and retrieve multimedia objects. MIRA also creates event-based transcripts as summaries of meetings. These transcripts are available over the WWW.