Microsoft Windows Media Resource Kit (Pro-Resource Kit)

Your next task is to create the announcement file that will point Windows Media Player to your content. An announcement file is a redirector file with an .asx file name extension. Redirector files are used to transfer the request for content from the browser to Windows Media Player. Because browsers communicate using HTTP, they do not recognize popular streaming protocols and will attempt to download rather than play the referenced content. Once the redirector file sends the content request to Windows Media Player, the Player communicates directly with the Windows Media server to determine the appropriate protocol for delivering the stream. You can post the .asx file on your Web page or put it in an e-mail message to the users you want to target.

During the planning process, the Coho Webmaster decided that she would encode all winery content at multiple bit rates in order to serve a variety of customers: both dial-up and broadband. Even though she encoded the content at multiple bit rates, she still only needs one announcement file to post on the Coho Winery Web site. Using MBR streaming in this way also eliminates the need for users to choose the stream that is appropriate for them—a decision that some users are not comfortable making.

Creating the announcement file is a wizard-based process. The wizard will ask you for the following information:

• URL of the content. The URL should be specified using either the MMS or RTSP protocols (for example, mms://coho01/Winery_Videos). If you use MMS, the Player and server will automatically negotiate and roll over to the most suitable protocol based on the Player version and network conditions. While RTSP can also roll over to the most appropriate protocol, earlier versions of Windows Media Player do not support RTSP and will return an error when the stream request is received.

• The name and location of the .asx file on your server. By default, the .asx file takes the name of your publishing point and is placed in the folder %systemdrive%\inetpub\wwwroot. The Coho .asx file, for example, can be found at c:\inetpub\wwwroot\Winery_Videos.asx.

• The name and location of your multicast information file if your content is to be multicast. The multicast information file contains stream format details that the Player needs to decode the stream. This file will be generated for you by the announcement wizard. Like the announcement file, the multicast information file, which has an .nsc file name extension, is placed in the folder %systemdrive%\inetpub\wwwroot by default.

• Optional metadata about the content. This data includes title, author, and copyright. Because this data is displayed in the captioning area of Windows Media Player when users view the stream, Coho Winery includes a title and copyright, as shown in figure 7.14.

  Figure 7.14: Entering optional metadata for a file or stream.

  Additional metadata entries are possible. If you want a company logo or banner to be displayed in the Player, you can provide the location of that banner in the Banner field. LogURL is used for posting client logs to a Web server. If you have additional metadata that you want to provide, such as the date the content was produced, the company that edited it, and so on, you can add these attributes easily. These attributes will not be displayed in the Player but can be extracted by using search tools or other programs that are built using the Windows Media Format SDK.