24.7.1. A Simple Link

<A HREF="audio/song.wav">Play the song (3.5 MB)</A>
<A HREF="groovy.mp3"><IMG SRC="buttons/playme.gif"></A>

When the reader clicks on the linked text or graphic, the browser retrieves the audio file from the server and launches a helper application (or plug-in, if the browser is so configured) to play the file. Files accessed in this manner are typically downloaded to the user's hard drive (stored in cache).

If the browser uses an external player, a new small window from the helper application opens with the controls for playing the audio. If the browser is configured to use a plug-in player (such as the popular QuickTime plug-in), a control panel may load right in the browser window, replacing the original web page. You may want to advise readers to use the Back button to return to the original page should this happen.

It is also good web etiquette to warn readers of the size of an audio file so they can make an informed decision as to whether they want to spend the time downloading the file.

24.7.2. Background Sound

To add a background sound to a web page, try these methods:

24.7.3. Adding RealMedia

RealMedia (including RealAudio) files can be added to a web page via two methods. The first triggers the browser to launch RealPlayer as an external application. The second plays the media file in a player embedded directly in the browser window using the RealPlayer plug-in.

In either case, you do not create a link directly to the RealMedia file itself, but rather to a special reference file, called a metafile. The metafile is a simple text document that contains the URL of the RealMedia file. These reference files are generally kept in the same directories as the HTML documents, although that is not a requirement.

There is a three-step process from click to playback. First, clicking the HTML link downloads the metafile from the server to the browser. Once it arrives at the browser, the metafile tells the browser to launch the RealPlayer and provides the player with URL information. Finally, the player uses the URL to request the actual media file from the server and begins playing the stream.

Metafiles are useful for maintenance and control purposes. To change the audio, all you have to do is change the tiny metafile, rather than having to dig through HTML source code. You can also do things like calling multiple streaming media files from one metafile. One link to the metafile plays all the files.

This indirect linking process is demonstrated in the following two examples.

24.7.4. Adding Windows Media

To link to a downloadable (nonstreaming) Windows Media Audio file (.wma), use a simple link directly to the audio file:

<A HREF="song.wma">Link to the song</A>

Linking to streaming Windows Media works much like the process described for RealAudio above. Streaming Windows Media use a go-between reference file called an "active stream redirector" file (.asx), similar to RealAudio's metafile. The ASX file contains the URL information that points the player to the actual media file. This method of providing a single stream to a single user on demand is called unicasting. In the HTML document, create a link to the redirector file as shown in this example:

<A HREF="streamingsong.asx">Stream the song</A>

The content of the .asx file looks like this:

<ASX version="3">
	<Entry>
		<ref href="path/streamingsong.asf" />
	</Entry>
</ASX>

Change the path in the <ref> tag so that it points to your Windows Media file. The .asx file should be saved in the same directory as the Windows Media file.