The following information contains general information about RealAudio. Specific questions about its features and functions should be addressed to firstname.lastname@example.org.
What is RealAudio?
RealAudio refers to a client-server based system which allows web sites to deliver (or "stream") pre-recorded and live compressed audio data to multimedia computers with a RealAudio Player. The Player continuously decompresses the audio stream and plays it in real time, on demand. Unique flow control technology allows computer users with sound cards to listen to whole clips, or just sections, when they want, as often as they want.
Not counting the player, the system has two components, the RealAudio Encoder and the RealAudio Server.
RealAudio Encoder The encoder is a software only solution (no proprietary hardware required) and is used to convert the live or prerecorded content into the RealAudio or RealVideo formats. The 3.0 Encoder will encode .wav, .au and live raw audio data including sound from CD players, tuners, microphones and mixing boards. Download RealAudio Encoder from:
RealAudio Server RealAudio 3.0 features broadcast quality audio over the Internet for the first time. RealAudio 3.0 technology introduces stereo sound to 28.8 Kbps modem users. Version 3.0 also introduces scaleable bandwidths between 28.8 Kbps connections and ISDN connections and above, producing near CD quality sound at ISDN connections and beyond. Content providers can select from multiple codecs at the same bandwidths to enable them to customize RealAudio sound for different content types.
The delivery system has been enhanced by improving the communication reliability with Robust UDP and other features designed to improve sound quality, including PerfectPlay (with the RealAudio Player Plus) and Bandwidth Negotiation. Download a RealAudio 3.0 Server license from:
How Does the System Work?
RealAudio technology utilizes an interactive system between the RealAudio Server and the RealAudio Player to enable real-time audio delivery over the Internet. When the user clicks on a link on a Web page, the audio buffers and then begins to play, all within a few seconds. This gives the deceiving impression that the RealAudio file is linked directly to the Web page. In reality, information is passing between the Web server supporting the Web page, the RealAudio Server supporting the audio file, and the RealAudio Player. When the user clicks on the RealAudio link, it is actually activating a metafile, which in turn sends the location of the RealAudio file to the Player. The Player then sends a signal to the RealAudio Server requesting that file. The file is sent to the Player and played as it is received. The entire process is completed within seconds.
How Does One Deliver Live Content?
The RealAudio and Video system will allow you to stream prerecorded files on demand from your web pages. It will also allow streaming of live content in realtime. Real-time encoding and serving technology allows organizations to broadcast live events including breaking news stories, sporting events, corporate meetings, and more, live, as they're happening, without time delays.
In a live situation, the RealAudio or video encoder must be connected to the Real server so that the incoming audio or video can be compressed into the Real format and be streamed over the internet (or intranet). Clearly, this assumes you'll need two machines...one for the encoder and one for the server. Generally, when doing live encoding, the encoder should be run on its own dedicated machine! Additionally, the encoder may be at a remote location apart from the server (perhaps at the live event or radio station in question) or it may be on the same network as the RealAudio/Video server. In situations where the RA/RV encoder will be remote you may send the newly created RA/RV stream from the RA encoder to the RA/RV server simply by specifying the destination of the server. The stream will then be sent over the Internet via TCP/IP to be received by the server...and then multiplied and streamed out to the listners. When the encoder is remote, you can send the stream to the server via:
a dedicated internet connection (min. 56kbs or 64k ISDN)
The experienced audio technician may seek professional results by experimenting with a number of different techniques including compression, noise gating, equalization and normalization equipment. A list of such equipment as well as other hints for getting the best sound with RealAudio can be found here:
The RealAudio server allows you to freely stream your live content without saving it to hard disk, thus making for a maintenance free system that wont fill your hard drive with large files on a daily basis. However, in some instances you may want to archive live content for play back at a later time. The RealAudio server provides such an option.
Audio Storage Depending upon the level of audio compression, RealAudio files require hard disk space equal to approximately 1.1 - 2.4 kilobytes per second of audio. Sound Requirements RealAudio will encode most common monaural PC formats. RealAudio 2.0 comes with two audio encoding algorithms. The RealAudio 14.4 algorithm provides AM sound quality, while the 28.8 algorithm offers FM sound quality. EXAMPLES OF AUDIO FILE STORAGE REQUIREMENTS: