Delivering Audio/Video on the 'Net

Let's face it. Delivering multimedia over the network on campus is great, but it's dismal over modems. Digital video and audio files are huge, and the traditional method of delivering it -- downloading the entire file, then playing it -- just takes too long.

The Solution: Use streaming instead of downloading.

A file containing just one minute of useable compressed video -- a quarter of the screen and of decent quality -- can be as large as four to eight megabytes. A file containing a minute of stereo-quality audio is about one megabyte. Thus, under typical conditions, one minute of video, which would take 20 to 40 seconds to download on campus, could take from 24 to 48 minutes to download using a 28.8 Kbps modem. Similarly, one minute of audio would take 5 seconds to download in a lab on campus and could take as much as 6 to 12 minutes to download using a modem.

That's a looong time.

Streaming gets around this problem by playing the clip as it is being received. The streaming client begins to play an audio or video clip just a few seconds after it starts receiving it from the streaming server, and continues to play the stream as it receives it. Because the streamed clip is never stored on the receiving computer, even people with limited available disk space can play it; thus there's little penalty in using longer or more detailed clips.

The Client and Server: RealMedia Streaming Server and the RealPlayer client.

The RealMedia Streaming Server and the RealPlayer client are from RealNetworks (formerly Progressive Networks). We picked the RealMedia server because of its features, maturity, and scalability, and also because the RealAudio and RealVideo formats (for streaming audio and video, respectively) are de facto standards.

The RealPlayer client runs stand alone and as a helper application for your Web browser. There are versions for MacOS 7/8, for all varieties of Microsoft Windows, for OS/2, and for several flavors of UNIX. It is free for individual download and use; you can download it from RealNetworks at: http://www.real.com/products/player/index.html

Return to Contents

The quality of RealVideo, however, is not quite so good, particularly when it is transferred over modems. If fine detail is not a problem, you can deliver useful clips of decent quality if you make them smaller, say 1/16 of the screen. Clips can be digitized from standard composite video sources like VHS tape, laserdisc, or camcorder tape.

In addition to the usual animation and talking heads, videos can be used to illustrate medical procedures or show excerpts from a documentary film or a simulation. Streaming video is often used for previewing the content of video clips that are stored in larger, more detailed formats such as MPEG, QuickTime, AVI, or ActiveMovie, so you can decide whether to spend the time downloading the full clip for high-quality playback.

Return to Contents

This is easier than it sounds. With the proper hardware -- and we've got it in the ITL -- even the digitizing and encoding steps are easy. What generally takes the most time is selecting the appropriate content and, if the original analog sources were of poor quality, editing the clip to improve its quality. If you're interested, please visit us at the ITL; we'll be glad to help you.

Return to Contents

In the long run, however, the standard for streaming audio/video will probably be Advanced Streaming Format. The ASF standard is supported by all the major players in the streaming industry, including RealNetworks, VDOnet, and Microsoft. It will provide added quality and functionality, and the ASF standard requires that an ASF client must play streaming content from different servers.

Also the new Synchronized Multimedia Integration Language (SMIL) proposed by the World Wide Web Consortium promises to simplify the integration of multimedia into Web applications by synchronizing the use of audio, video, images, text, and other multimedia via a simple HTML-like markup language.

Return to Contents

URLs for Steaming Audio/Video:

Return to Contents