RealAudio: Make Your Site Sing  pwp home  >   Reference Library  >   Advanced  >  RealAudio

A common technique being utilized in website design today is the sending of streaming audio and video via the Internet. Before streaming technology, sound and video had to be downloaded to the hard drive before it could be played back and heard. A dial-up connection may have a transfer ratio of 5-to-1; it will take approximately five minutes to download a one minute audio file. Taking advantage of compression tools, the streaming audio or video file usually only takes a few seconds to spool and start playing. The focus of this article is on ways of implementing RealAudio within Prodigy Internet. Installation of the Real server on various platforms and RealAudio's ability to serve streaming video will not be discussed in this article.

While several companies have developed streaming technology, Progressive Networks' RealAudio comes as close to a standard as any available. The player and encoder, the software used to playback and compress the .wav or .au files into .ra files, is available from http://www.real.com. Progressive also includes links to third-party developers who have designed software that will encode or compress to the .ra specification.

What do I do first?: Assuming you have a .wav, .au, .pcm, .snd, .sd2, .aiff, or other supported file, the first step is to encode it to the .ra specification. If you have not already done so, download the encoder from the RealAudio site and install it on your computer. Encoding is straightforward; the screen on the encoder is split in half, one side showing the file to be encoded and the other showing sound and file options. Select the file you want to encode, rename it with the .ra extension, and choose the bandwidth you would like to encode. Options are available for enabling or disabling Select Record, which will allow users of the commercially available Player Plus, to save the RealAudio files to hard disc, and Perfect Play, which partially downloads a file before starting to play, in order help users with slower connections play files encoded for a higher bandwidth.

How do I make it stream?: First, you will have to create a META file. A META file is nothing more than a file made with notepad, or any text editor, and saved with the .ram or .rpm extension. It will contain the information needed to establish a connection between the server and the player or plug-in so it can start playback . If you referenced the file as a link (i.e. <a href="file.ra">play file</a>) the file would download to your hard drive and not stream.

Prodigy Internet takes advantage of HTTP streaming that was first introduced in version 3.0. While not as robust as the Real Server it is an acceptable way of providing streaming content. The META file for Prodigy Internet, would be written like this: "http://pages.prodigy.net/yourusername/filename.ra" and saved, in this case, as filename.ram or, if you are embedding controls in your page, filename.rpm. You will then upload both files to your PWP directory and reference the file in your page as:

<a href="http://pages.prodigy.net/your user name/filename.ram">Play this file</a>

RealAudio can play files in sequence. To achieve this you would construct your meta file to look like this:

<a href="pages.prodigy.net/your user name/filename1.ra"> <a href="pages.prodigy.net/your user name/filename2.ra">

Save the file in the Text Only no Line Breaks format.

RealAudio allows for multiple bandwidth files to be available for different connections. For instance, you could compress the same file in different compression choices and have RealAudio select the correct version to play for your visitor. This is accomplished by creating a directory named filename.ra. The separate files are then named to the bandwidth size and placed in the directory. For example:

RealAudio 1.0 and above 14.4 files would be named to 14_4.18.ra
RealAudio 2.0 28.8 mono files would be named 28_8.36.ra
RealAudio 3.0 28.8 stereo files would be named dnet20.ra
RealAudio 3.0 28.8 stereo files would be named dnet25.ra
RealAudio 3.0 ISDN stereo files would be named dnet50.ra
RealAudio 3.0 dual ISDN stereo files would be named dnet100.ra
The .ram file is then called by creating a link to the filename.ram file.

The lowest common file type is 14_4.18 which can be accessed by all versions of the RealAudio player including the latest version 8. Using this choice would allow all visitors to experience your RealAudio file. By using bandwidth negotiation you will provide more options and a richer listening experience for everyone.

ToolVox (http://www.voxware.com), StreamWorks (http://www.xingtech.com) and Shockwave Audio (http://www.macromedia.com) are other streaming content solutions that have their own strengths and spin on streaming technology. More information on these products can be found at their respective sites.