Re: begin/end (events or syncbase?)

On Tue, Sep 24 2002 "Sigurd Lerstad" wrote:

> 
> Hello,
> 
> The SMIL timing model are talking about syncbase elements, e.g
> 
> begin="video1.begin"
> 
> and they're talking about events, e.g
> 
> begin="video1.someevent"
> 
> But the syncbase values begin/end are also events (DOM events)
> 
> Reading up on the TimeGraph model, they set slightly different rules for
> handling syncbases and events
> 
> Is it correct that an implementation MUST differ between these two (instead
> of also treating begin/end as events?)
> (The statement above seems to indicate this, but I just want to make sure
> (because it would be simpler if one could treat them the same :)

Yes, an implementation must distinguish between events and syncbases.
For one thing, a syncbase can be predicted, so if you use a negative
offset to a syncbase.  E.g. if you have begin="foo.begin - 5s", you can
actually begin 5 seconds before foo begins.
Events on the other hand cannot be predicted, so if you have
begin="foo.activateEvent - 5s", the elements starts when the
activateEvent happens, but 5 seconds *into* the element.

> Is it correct that it's IMPOSSIBLE to specify e.g begin="video1.begin" and
> tell the implementation to treat it as an event? (since the syntax for
> syncbase would be the same?

You can use begin="video1.beginEvent" which refers to the evens of
video1 beginning and is an event in the SMIL sense and not a
syncbase.  This event triggers when video1 actually begins.

-- Sjoerd Mullender <sjoerd@acm.org>

Received on Monday, 23 September 2002 07:21:22 UTC