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The begin attribute specifies the timing value used to start or activate an element.
The begin attribute works differently depending on the element it is used with. If used with a media element, the begin attribute value specifies when the content source begins playing.
Child elements of seq or smil elements begin automatically and play sequentially, so they do not require a begin attribute value to start. You can add a begin value if you do not want an element in a seq or smil container to start immediately after the previous element. Offset values are the only supported timing values for child elements of seq or smil containers, and the value for the begin attribute must be positive.
The begin attribute is most useful for activating elements in excl or priorityClass elements. Unlike the immediate children of seq or smil containers, child elements of an excl or priorityClass element have no default start time, and will therefore not start without a begin attribute value.
An element can be activated relative to the timing of other
elements in the playlist or by a server event. You can use the
begin attribute with a list of semicolon-delimited event
values to identify multiple times when the element should be
played; for example begin="event1;event2;event3".
Negative time values and time values that are shorter in duration
than the length of the element are ignored. For complete
information about the supported begin attribute values, see
Timing values.
In the following example, the media element Intro.wma
starts the playlist because it has begin attribute value of
0s. When a begin attribute value uses an offset
timing value without a SyncBase timing value, such as in this
example, the currently active element (excl) is the implied
SyncBase, or point of time reference. When the playlist starts, the
excl element becomes the first active element because it has
a media element that has a begin value of
0s.
Ten seconds into the playlist named Prog, the third media
element in the priorityClass element, interrupts playback of
Intro.wma because it has a begin attribute value of
10s. After Prog has played for 10 seconds, the
media element Comml1 interrupts because it has a
begin attribute value of prog.begin+10s. Note
that Comml1 has a begin attribute value that is relative to
the media element Prog instead of relative to the time
container. Similarly, when Comml1 ends, Comml2 plays because it has
a begin attribute value of comml1.end. Because
the priorityClass element has a peers attribute value
of pause, Prog will continue playing when Comml2
ends.
<?wsx version="1.0"?>
<smil>
<excl>
<media src="Intro.wma" begin="0s"/>
<priorityClass peers="pause">
<media id="Comml1" src="Commercial1.wma"
begin="prog.begin+10s"/>
<media id="Comml2" src="Commercial2.wma"
begin="comml1.end"/>
<media id="Prog" src="Program.wma" begin="10s"/>
</priorityClass>
</excl>
</smil>
The begin attribute can be specified for the following playlist elements:
Notes