Audio imported into Variations is streamed to clients over RTSP using Darwin Streaming Server and Quicktime for Java.
Darwin Streaming Server is an open-source RTP/RTSP server originally developed by Apple as the Quicktime Streaming Server. Darwin is capable of serving MOV and MP4 files that have been hinted for streaming.
More information as well as instructions on installing and configuring Darwin can be found at Darwin Streaming Server.
This Perl cgi-bin script generates a Quicktime reference movie with links to the derivative files that have been linked into the leases directory. This reference movie allows clients to select the bitrate that best suites their Quicktime bandwidth configuration. Clients make an http request to this script whenever they open a recording.
For more information on usage see this page.