Editing RealAudio (section)

==Streaming audio==
RealAudio was developed as a [[streaming media]] format, meaning that it can be played while it is downloaded. It is possible to stream RealAudio using [[HTTP]]. In this case, the RealAudio file is retrieved similarly to a normal web page, but playback begins as soon as the first part is received and continues while the rest of the file is downloaded.  Using HTTP streaming works best with pre-recorded files so some alternative protocols have been developed which work better for live broadcasts.

The first version of RealAudio used a proprietary protocol called PNA or PNM to send streaming audio data. RealNetworks later switched to the [[IETF]] standardized [[Real Time Streaming Protocol]] (RTSP) but they use RTSP only to manage the connection. The actual audio data is sent with their own proprietary [[RDT stream transport|RDT]] protocol, which they initially kept secret. Recently, some specifications for the RDT protocol have been made public through the [[Helix Community]] project. By around 2004 the open-source MPlayer project developed a means of playing the RDT streams.<ref>[[MPlayer]] {{better citation|date=November 2011}}</ref>

In many cases, web pages do not [[hyperlink|link]] directly to a RealAudio file. Instead, they link to a .ram (Real Audio Metadata) or [[Synchronized Multimedia Integration Language|SMIL]] file. This is a small [[text file]] containing a link to the audio stream. When a user clicks on such a link, the user's web browser downloads the .ram or .smil file and launches the user's media player. The media player reads the PNM or RTSP [[Uniform Resource Locator|URL]] from the file and then plays the stream.<ref>{{cite web|author=David Fiedler|title=RealAudio|url=http://homerecording.com/realaudio.html|work=HomeRecording.com|access-date=August 20, 2011|year=2008}}</ref>

With [[RealPlayer SP]], it is now possible to save an audio stream to a file. Other programs, including [[MPlayer]], [[RM Downloader]], [[VLC media player]], [[StreamBox VCR]], [[HiDownload]] and [[Real7ime Converter]] can also save streams to a file.