Web Design in a Nutshell, 3rd Edition

RealMedia/RealAudio (.rm, .ra)

RealNetworks was a pioneer in producing a viable technology for bringing streaming audio to the Web. Despite heavy competition, it continues to lead the pack in terms of widespread use and popularity, and it has grown to be the standard for streaming audio, including live broadcasts.

RealAudio is a server-based streaming audio solution. Real’s Helix server offers advanced features for streaming audio delivery, including bandwidth negotiation (the proper bit rate version is delivered based on the speed of the connection), RTSP transmission for smooth playback, and administrative tools for tracking usage and minimizing server load. Using the SureStream feature, the bandwidth can be adjusted on the fly (while the file is streaming) to accommodate bit rate fluctuations.

A robust Helix system can allow thousands of simultaneous listeners. The server software requires a large investment, and RealNetworks charges licensing fees for the number of streams. There is, however, a free version that allows five simultaneous listeners. For more information, see the RealNetworks site at http://www.realnetworks.com.

If you aren’t ready to commit to Helix, RealMedia and RealAudio files can be pseudostreamed from an ordinary HTTP server for sites with a limited amount of traffic.

To listen to RealAudio files, users must have RealPlayer, which is available for Windows, Mac, and Unix systems. The RealPlayer plug-in comes installed with most systems and makes it possible to ...