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Understanding sources and source groups

With Windows Media Encoder, you can encode content from three different sources: audio, video, or script. You can capture audio and video from a card installed in your computer or from a file. And you can type scripts directly in the main window of the encoder during an encoding session.

The combination of audio, video, and script sources is known as a source group. A source group represents the stream that is displayed in a player. Although only one source group streams at a time, as you encode, you can switch between source groups to stream different content. For example, before broadcasting a live event, such as company meeting, you can set up source groups for the main event as well as for welcome, intermission, and goodbye videos. When you broadcast the event, you could start with the welcome source group, switch to the main speaker when appropriate, switch to the intermission source group during a break, and then switch to the goodbye source group when the event finishes.

A source group must consist of at least one audio source; it can also include one video source and one script source. You can add an unlimited number of source groups to an encoding session, either before or after encoding has begun, but they must contain the same combination of source types (audio, video, and script). You can use capture cards only once. For example, let’s say that you create two sources. One source is a live event in which a speaker is introducing a new video. The second source is the video. When setting up the sources, you would need a separate card for each one. 

A script can be either a URL or a caption. A URL is the path to a Web page; a caption is a text string. When a player receives a script, it transmits it to an application that can run the command. URLs are transmitted to the Web browser, and captions are displayed in a player. When a URL is inserted into a stream, the default browser opens and the requested URL loads into the browser. If you have embedded the player within a browser, the requested URL replaces the player, and you cannot view the rest of the stream. You can get around this either by displaying the requested URL in a separate frame in the same browser instance or by opening an additional instance of the browser on your screen.

When you set up an encoding session, the New Session Wizard helps you create three source groups. To add more source groups, use the Session Properties dialog box.

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