EVENT Element

Artikel
4/26/2023

[The feature associated with this page, Windows Media Player SDK, is a legacy feature. It has been superseded by MediaPlayer. MediaPlayer has been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer instead of Windows Media Player SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The EVENT element defines a behavior or action taken by Windows Media Player when it receives a script command labeled as an event.

<EVENT   
   NAME = "text string"
   WHENDONE = "RESUME" | "NEXT" | "BREAK"
>
</EVENT>

Attributes

NAME (required)

The name of the event.

WHENDONE (required)

A value that defines what Windows Media Player does after playing the referenced content.

The following values are possible.

Value	Description
RESUME	The current entry (the clip interrupted by the event) resumes playing. If the content is stored content, it resumes at the same point where it stopped; if the content is broadcast, it resumes at the current position.
NEXT	The next ENTRY element plays as if the event had not occurred and Windows Media Player had reached the end of the current clip.
BREAK	If the current entry is within a REPEAT loop, the loop terminates as if the repeat count had been completed. Otherwise, Windows Media Player jumps to the end of the playlist as if the final entry had completed as usual.

Parent/Child Elements

Hierarchy	Elements
Parent elements	ASX
Child elements	ENTRY, ENTRYREF

Remarks

This element defines a behavior or action taken by Windows Media Player when it receives a script command labeled as an event. An event is a particular type of script command embedded in a stream sent to Windows Media Player that consists of a double string. The first string is the word "event", and the second string is the event name. The event name in the second string must match the event name defined in the metafile. (The match is not case-sensitive.) Events can be sent to Windows Media Player receiving a real-time stream, or can be saved in an .asf, .wma, or .wmv file that gets delivered as an on-demand unicast stream. When Windows Media Player receives the script command, it processes the event as defined by the EVENT element.

This element defines a scope of ENTRY or ENTRYREF elements that are processed whenever Windows Media Player receives the script command with the named event. The ENTRYREF can be a URL that points to an ASP page. With this element, you can specify a behavior for stream switching in near real time, as opposed to pre-authored stream changes using references to other pieces of content or Windows Media metafiles.

When you use ASP pages to generate playlists, you must specify a value for the Response.ContentType property and the Response.expires property in the ASP page because of latency issues with Windows Media Player. The Response.ContentType must be a valid file name extension for Windows Media metafiles. Valid types include .asf, .asx, .wma, .wax, .wmv, and .wvx.

See the Platform SDK for details about using the Response object in ASP.

This element can appear anywhere within the ASX element. If multiple EVENT elements within an ASX element have identical values for their NAME attributes, Windows Media Player uses the first occurrence within the ASX element, and ignores all others. When EVENT elements have distinct NAME attributes, their order within the ASX element does not matter.

Windows Media Player discards events it receives while processing another event. Nesting of events is not supported. When Windows Media Player is in preview mode, event content is not constrained by the PREVIEWDURATION element; the full length of event content can play even if the preview duration for the active ENTRY element expires prior to the end of the event.

Examples

In this example, when Windows Media Player receives the script command EVENT and command string "Adlink" in the streaming media it is rendering, it searches the playlist for an EVENTNAME "Adlink". Windows Media Player switches from the stream it is rendering and plays the content referenced in the EVENT, "https://example.microsoft.com/adlink.htm".

ENTRY attribute CLIENTSKIP is set to NO to prevent the EVENT clip from being skipped. It must be played.

The script WHENDONE="RESUME" instructs Windows Media Player to resume playing the previous media it switched from as soon as Adlink.asf is finished.

<ASX VERSION="3.0">
<ENTRY CLIENTSKIP="NO">
   <REF HREF="https://example.microsoft.com/clip1.asf" />
</ENTRY>
<EVENT NAME="Adlink" WHENDONE="RESUME">
   <ENTRYREF HREF="https://example.microsoft.com/adlink.htm" 
       CLIENTSKIP="NO" />
</EVENT>
</ASX>

Requirements

Requirement	Value
Version	Windows Media Player version 7.0 or later

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