ASX Scripting Overview

The following section describes how you can control the presentation of your media by using ASX scripting.

Modify the display. Except for the playback controls and status display, the Windows Media Player user interface is open to you for adding text, MoreInfo links, and images. ASX scripting is the tool you use to affect the interface in four main ways:
- Text properties. The user interface and Properties page of Windows Media Player have boxes for displaying Title, Author, Copyright, Rating, and Description text. The text used to populate these areas can be contained in an .asf file, or it can come from ASX scripting in an .asx file. Text that appears in the Show box is also sent to the user interface using ASX scripting. In general, ASX scripting is a better method of passing text properties to Windows Media Player, especially if text elements are likely to change. It is easier to edit text in an .asx file than to redo an .asf file. And because properties read from an .asx file override those contained in the .asf file, you can easily update display text from an .asf file by adding the new text to the corresponding property in an .asx file. For example, the following ASX script overrides author text contained in an .asf file.
```
<Author>Ad Department</Author>
```
- Image properties. An ad banner and small icon images can be added to the user interface of Windows Media Player. The ad banner appears in the lower portion of the video display. Icons appear in the text display.
- MoreInfo properties. Text and image sections of the user interface can be associated with URLs. During playback, a user can click one of these sections to go to the URL associated with it in their Web browser. For example, you can associate an advertiser’s Web site with an ad banner image.
- Abstract properties. Abstract text can also be associated with text and image sections of the user interface. During playback, if a user points to one of these sections, a text box appears beside the mouse pointer displaying the Abstract text associated with the section.
Control playback. With ASX scripting, you can control not only which media is played back, but also which portions of the media are played back. By using ASX scripting tags, Windows Media Player can start playing an .asf file at a set time or marker, and end after a set duration or marker. You can also set a preview duration. If a user enters preview mode on Windows Media Player, the duration you set determines how much of an .asf file is played.

Create a playlist. In ASX scripting, an Entry tag is used to designate one media element (a media file, a live stream, or another .asx file) and any associated elements (such as images, MoreInfo links, and Abstracts). An .asx file can contain one or more Entries. A multiple Entry .asx file is called a playlist. Windows Media Player executes a playlist starting with the first entry and then playing each entry in turn until the list is finished.

An Entry can point to any type of media that Windows Media Player can play. This includes not only .asf, .avi, and .wav files, to name a few, but live ASF streams as well. For example, the playlist can contain two Entries: a standard introduction from an .asf file and a live ASF stream. With ASX scripting, you can assign display properties, start and end times, and markers for each entry as well. For example, the following ASX script shows how you can place an ad banner and the associated MoreInfo link in one Entry, and assign start and end markers in the next.

<ASX version ="3.0">
<Title>Windows Media v4 ASX Demo Two</Title>
<Abstract>Windows Media Technologies</Abstract>
<MoreInfo href = "http://sample.microsoft.com"/>

    <!—This is the first Entry -->
    <Entry>
        <Title>This is the ad</Title>
        <Author>Ad Department</Author>
        <Copyright>1999</Copyright>
        <Abstract>This is a description of the ad</Abstract>
        <MoreInfo href = "http://sample.microsoft.com/"/>
        <Ref href="ad.asf"/>
        <Banner href ="purchase.gif">
           <Abstract>Click here to go to our Web site</Abstract>
           <MoreInfo href = "http://sample.microsoft.com/" />
        </Banner>
     </Entry>        

    <!-- This is the second Entry -->
    <!—The ASF plays from Segment2 to Segment3 -->
    <Entry>
        <Title>Playlist clip number two</Title>
        <Author>Windows Media</Author>
        <Copyright>1999</Copyright>
        <Ref href="show.asf"/>
        <StartMarker Name = "Segment2" />
        <EndMarker Name = "Segment3" />
    </Entry>

</ASX>

Use live Event stream switching. An Event tag looks similar to an Entry tag in ASX scripting, but each handles the playback of media differently. The Entry tag is used to create playlists. Media designated in an Entry starts playing as soon as the media in the previous Entry finishes. The Event tag is usually used in live production. Media designated in an Event plays only when a certain script command is received. For example, when Windows Media Player receives a script command with type string "EVENT" and command string "Adlink", it searches the .asx file for the following script:
```
<EVENT NAME="Adlink" WHENDONE="RESUME"> 
<ENTRYREF HREF=mms://example.microsoft.com/adlink.asf />
</EVENT>
```
Windows Media Player then switches from the live stream to play media contained in the Event, in this case Adlink.asf. The script WHENDONE=”RESUME” instructs Windows Media Player to resume playing the previous media as soon as Adlink.asf is finished.

Event scripting was created to enable personalization in live presentations. The possibilities inherent in Event switching are best appreciated by contrasting how ads reach viewers through standard, over-the-air broadcasting with how ads can reach viewers using Windows Media Technologies. Ads broadcast can only be roughly targeted at viewers, using ratings data as the primary criterion. Ads sent using Windows Media Technologies can be aimed directly at the target user because Events and playlists can be built on the fly based on user input. For more information, see Personalized Media Delivery.

You can create seamless stream switches by using the OpenEvent tag in conjunction with the Event tag. By sending an OpenEvent script command ten seconds prior to the Event command, Windows Media Player is able to preload a portion of the upcoming ASF stream. When Windows Media Player receives a corresponding Event command, the switch to the new ASF stream contains no gaps; presentation is seamless.
Use custom tags and commands. By using the Param tag in your ASX script and the GetMediaParameter method in a Web page containing an embedded Windows Media Player control, you can create custom tags that pass additional information through an .asx file. For example, you can insert the names of the producers of each media file inside the .asx file and display them in HTML near the Windows Media Player window.

For more information, see Using ASX Metafiles in the Windows Media Player Control SDK.

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