This project is supported in part by grants from ARPA and the National Science Foundation, and donations from Tektronix, Hewlett-Packard and the Portland Trail Blazers.
Multimedia systems - Design, Streaming technology (Telecommunications), Adaptive computing systems
This paper describes problems and solutions for delivering real-time, multi-media presentations across the Internet. A key characteristic of presentations of continuous media datatypes, such as digital video and audio, is their need for predictable real-time data delivery. For example, an NTSC quality video presentation requires video frames to be displayed every 1/30th of a second. Variations in this display rate can be observable as stalls or glitches in the video stream and reduce the quality of the presentation . Delivering such presentations across the Internet is difficult because highly variable band- width and latency make it difficult to predict the arrival time of network packets containing video or audio data. Our solution is for distributed multimedia systems to adapt dynamically to these changing network conditions. This paper describes the use of software feedback to make multimedia presentations adaptive, and shows how video can be played across an unpredictable network such as the Internet without benefit of resource reservations. The Internet's unpredictable latency and bandwidth characteristics arise because different links in the network have performance that varies by several orders of magnitude. Hence, the location of a video client relative to its video server influences the performance characteristics of the connection. Furthermore, even if the capability of the hardware in question can be established, the available bandwidth varies wildly from moment to moment because the Internet is a shared resource: just a few concurrent large data transfers can easily take up most of a connection's bandwidth. In this environment, adaptive methods are essential to maintaining video quality.
Cowan, Crispin, Shanwei Cen, Jonathan Walpole, and Calton Pu. "Adaptive Methods for Distributed Video Presentation," December 1995.