The lower attribute specifies the behavior of the media elements within a priorityClass element when they are interrupted by media elements of a lower priorityClass.
You can assign the following values to the lower attribute.
||Specifies that an attempt by a lower-priority media element to interrupt playback is deferred. Playback of the interrupting media element begins when the higher-priority media element ends. This is the default behavior.|
||Specifies that an attempt by a lower-priority media element to interrupt playback is denied. The interrupting media element does not play.|
Priority is determined by the order in which priorityClass elements are declared in an excl element. The first priorityClass element in an excl element has the highest priority, and the last priorityClass element has the lowest priority.
A media element will be interrupted if the begin attribute value of another media element is set to start while the first is still playing. You can also interrupt a media element by initiating a server event that triggers the start of another element. Server events can be initiated by using a script command that is embedded in a stream from an encoder or by using the server object model. For more information about server events, see the Windows Media Services Software Development Kit (SDK). For more information about stream switching using script commands, see priorityClass element.
The following example shows three priorityClass elements
which each contain one media element. Playback begins with
the media element named Intro1 in the priorityClass
element named P1. Music2 in P2 is set to start playing at 10
seconds. However, because the lower attribute value in P1 is
defer, Music2 cannot start playing until Intro1
finishes. Music3 in P3 is set to start playing 10 seconds after
Music2 begins. However, because the lower attribute value in
P2 is set to
never, Music3 cannot interrupt Music2 and
therefore never plays.
<?wsx version="1.0"?> <smil> <excl> <priorityClass id="P1" lower="nefer"> <media id="Intro1" src="Intro1.wmv" begin="0s"/> </priorityClass> <priorityClass id="P2" lower="never"> <media id="Music2" src="Music2.wmv" begin="10s"/> </priorityClass> <priorityClass id="P3"> <media id="Music3" src="Music3.wmv" begin="Music2.begin+10s"/> </priorityClass> </excl> </smil>
The lower attribute can be specified for the following playlist element: