Playlists

To play numerous streams in a particular order, use a playlist. When the first stream in a playlist ends, the player then moves on to the next one, and so on, until the list is completely traversed. Playlist support for RealMedia, Windows Media, and MP3 is handled by the player application. QuickTime handles playlists differently, implementing this feature within the server. RealMedia, Windows Media, and MP3 use metafiles to define their playlists. QuickTime requires configuration through the QTSS or DSS server administrator program. RealMedia, Windows Media, and MP3 (but not QuickTime) make it easy for playlists to contain streams from disparate servers and also can include live streams in a playlist. Occasionally, a playlist is used when placing a brief audio clip as a station ID before a live stream begins. Playlists are most commonly used, however, for on-demand (as opposed to live) streaming audio.

Sometimes playback of a live stream may become disconnected because of temporary network congestion. Using a playlist allows you to list the same live stream multiple times so that the player will immediately attempt to reconnect to the next entry.

If you have a Web site with lots of streaming audio, you can provide a simple way for listeners to easily access a playlist or even create their own. As the Web master of your site, you can choose a predetermined, a randomly generated, or a user-selected playlist (or a combination of all three) based on any criteria you can imagine. If you're streaming files for which you don't own the rights, then provisions of the DMCA will limit you (see the Appendix).

To create playlists for RealMedia, Windows Media, and MP3, refer to the section on metafiles in Chapter 7. Follow the details to include multiple entries in a single metafile. Technically, any metafile is a playlist, whether it contains a single URL or a hundred URLs. To create playlists for QuickTime, choose Playlist Settings within the Streaming Server Administrator and follow the intuitive selection process from on-demand files you've already uploaded.

You can get creative with playlists. Following are some ideas:

• The Author Scenario Your band has 10 albums but not a "best of" album. You can create a playlist of your favorite material to introduce your music to new listeners. All you need is the encoded files and the server URLs. After you've chosen your songs, simply create a playlist of those URLs in a metafile.

• The Random Scenario Create a playlist containing a randomly generated list of songs (compiled from every song available) on your Web site. Your random playlist generator program creates a different random list each time a listener accesses it. For this scenario, you need to know how to program using a language that can be integrated into your Web server. You can also use JavaScript, which you include as part of your Web page. Common browsers support JavaScript. Most commonly used tools use the standard Common Gateway Interface (CGI) specification that allows Web pages to connect to locally run programs. Perl is the most commonly used language for writing CGI programs. You need to know Perl and also how to configure your Web server to allow access to your program. Remember to create playlists so that they contain only one format and are delivered with the correct MIME type. You can also limit how many (and which) songs are included.

• The Listener Scenario Allow the listener to create a playlist using every song on your Web site. The difference here is that you allow a list based on the listener's own criteria. Like the prior example, you need to know how to program using a language (including JavaScript) that can be integrated into your Web server. This is a more complicated process than before, and you have to provide a Web-based form to the listener in which they can select what they want. You can get very advanced for how you allow listeners to add songs. Listeners could receive a complete list all at once, or they could add items to a playlist as they browse your site.