Design of the data-retrieving engine for distributed multimedia presentations

To provide the smooth progress of a SMIL-based distributed multimedia presentation, the data-retrieving engine for the player must pre-fetch each object before its playback time. In this paper, a smart data-retrieving engine is proposed, which adopts a retrieval policy named the just-in-time policy. The policy requires the retrieval process of an object to be finished right before the playback time of the object. By converting the synchronization relationship of objects in the SMIL document to the Real-Time Synchronization Model, which simplifies the handling of the synchronization relationship, and considering the network condition, the data-retrieving engine could determine the request time for each object. The engine then makes the request to fetch each object for the ongoing presentation according to the pre-computed request time, and provides the player with proper media objects for smooth playback of the presentation.