Announcement Files and Playlists

While it is possible for Windows Media Player to connect directly to a server or encoder to receive a stream, generally it connects to content by using a link in an e-mail message or on a Web page. These links are metafiles that tell the Player how to connect to a Windows Media server to receive content.

Windows Media playlist files are Extensible Markup Language (XML) documents with .wsx or .asx file name extensions. You can create playlist files by using the Windows Media Services 9 Series Playlist Editor, Windows Media Player, or any text editor.

Note

See appendix A for more information about constructing server-side playlists using SMIL elements and attributes.

Announcement Files

Known as redirector files, these files contain instructions and references that direct Windows Media Player to the server that is distributing your stream. The announcement contains the URL of the content and information about the content, including author, title, and copyright. The .asx and .wvx files refer to Windows Media streams that contain both audio and video. The .wax extension is reserved for streams containing audio only.

Windows Media Services 9 Series uses two different types of announcement file: unicast announcements and multicast announcements. The multicast announcement is slightly different because it also includes a multicast information file (a Windows Media metafile with an .nsc extension), which contains information the Player needs to decode a multicast stream. This information includes:

• Multicast IP address

• Multicast port

• Time-to-live value

• Default error correction span

• Multicast logging URL

• Unicast rollover URL

• Stream formats used by the content being delivered

Two wizards are available in Windows Media Services 9 Series that can help you create an announcement file. One wizard creates a unicast announcement, and the other creates a multicast announcement. The wizards can also help you create a Web page that has Windows Media Player embedded into it, and they can provide the code to embed a Player ActiveX control in your own Web page. (For more information about embedding Windows Media Player in a Web page, see chapter 4.)

Playlists

Playlists provide a means of organizing different pieces of digital media content into a single stream. They are a set of instructions that specify what to play and the order in which to play it. These instructions can be carried out either on the client side or the server side.

Client-side playlists are Windows Media metafiles with an .asx file name extension. You can use Windows Media Player to create a client-side playlist that includes a selection of your favorite songs. You can then set the playlist to loop or shuffle to suit your preferences. A client-side playlist might also be a script that resides on a Web server.

In a server-side playlist, you use Windows Media Services 9 Series to stream a sequence of content, such as digital media files, encoder URLs, advertisements, and even content from other servers to users from a publishing point. Using server-side playlists, you can create your sequence of content and manage it from the server, even while clients are receiving the content. A server-side playlist has a .wsx file name extension. Server-side playlists are based on the Synchronized Multimedia Integration Language (SMIL) 2.0 language specification.