Multimedia data have specific temporal presentation requirements. For example in video conferencing applications the voice and images of the participants must be delivered and presented synchronously. These requirements can be achieved by scheduling or managing system resources. We present a technique called limited a priori scheduling (LAP) to manage the delivery channel from source to destination for digital multimedia data. By using delay estimation a LAP scheduler can retrieve stored digital media spanning arbitrary networks with unspecified delays. The use of delay estimation also facilitates selective degradation of service in bandwidth and buffer limited situations. Such degradation enables the continuous real-time playout and synchronization of various media arriving from different sources. The performance of the LAP scheduler is described based on implementation and experimentation using Ethernet.

A coherent computer-based multimedia presentation requires the use of real-time scheduling theory applied to system resources including storage devices, the bus, and network. In this paper we present a scheduling technique which is essentially static in nature during periods of network quiescence, but becomes dynamic in response to detection of network load changes of users interaction. This mechanism, called the limited a priori (LAP) scheduler, is an extension of earlier work on scheduling which assumed guaranteed system loading characteristics. The LAP schedules determines network load changes and estimates packet delay using a dynamic filtering algorithm. We show the bounds of accuracy for this technique and describe its suitability with respect to multi-media traffic across an FDDI network.

Video-on-demand represents a key demonstrative application for enabling multimedia technology in communication, database, and interface research.This application requires solving a number of diverse technical problems including the data synchronization problem for time-dependent data delivery.In this paper we describe the general requirements of video-ondemand and introduce a system supporting content-based retrieval and playback for the structure and content of digital motion pictures.In our model we capture domain-specific information for motion pictures and provide access to individual scenes of movies through queries on a temporal database.We describe our implementation of this service using existing workstation and storage technology.