Re: More comments on updated timed-text document

At 14:50 03/13/2002 +0100, Chris Lilley wrote:
>I understand what point II.2 is getting at, but speaking of 'erasure'
>is problematic unless it is assumed that all text will be displayed
>against its own rectangular, opaque background. Rather than thinking
>of text overwriting other text, I suggest thinking more along the SMIL
>model that elements have a duration. Between their start and end
>times, they are visible. Thus, having an old caption disappear and no
>new caption displayed simply arises as a natural consequence of the
>architecture.  Thuis would help simplify and define buth II.1 and II.2

Agreed; if you don't assign an end time to text, you may run into many 
problems.  For the user agent to figure out what is visible versus what is 
covered at a particular time is nearly impossible without it having to 
render all prior text (in possibly varying font sizes and faces) in 
temporal order.  Seeking from t1 to t1+d would require all text from t1 to 
t1+d to have to be rendered just in case there is still any of this older 
text not completely occluded by the t1+d text.  SMIL 2.0 has a "dur" and an 
"end" attribute, the latter of which can be based on an event or be 
relative to a timing attribute of another element.

The problem, however, with having to give an end time to a block of text is 
that we want to be able to do "live" TT (III.3) in which case you might not 
know the end time of that block of text until some new text comes along to 
replace it (as in the case of live sports scores, for instance).  The SMIL 
2.0 "excl" element allows for this type of "interrupt" timing.  We should 
be sure not to preclude being able to specify a live-text wire format that 
is inter-operable with the final TT file format.

         - Erik

Received on Wednesday, 13 March 2002 13:59:04 UTC