Comments on: A review of the W3C Timed Text Authoring Format http://blog.gingertech.net/2009/06/28/a-review-of-the-w3c-timed-text-authoring-format/ Silvia's blog Sun, 28 Feb 2010 17:51:54 +0000 http://wordpress.org/?v=2.9.1 hourly 1 By: silvia http://blog.gingertech.net/2009/06/28/a-review-of-the-w3c-timed-text-authoring-format/comment-page-1/#comment-989 silvia Sun, 28 Jun 2009 22:27:22 +0000 http://blog.gingertech.net/?p=428#comment-989 Daniel, Thanks for the link to SMIL. I now understand where the extra "dur" attribute comes from - because SMIL allows for example to have repeats on an event, "dur" is a delimiting attribute that provides an upper limit for repeats. Since there are no dynamics in DFXP (thank god!), "dur" is probably surplus and should be let go of. Daniel,

Thanks for the link to SMIL. I now understand where the extra “dur” attribute comes from – because SMIL allows for example to have repeats on an event, “dur” is a delimiting attribute that provides an upper limit for repeats. Since there are no dynamics in DFXP (thank god!), “dur” is probably surplus and should be let go of.

]]> By: Daniel http://blog.gingertech.net/2009/06/28/a-review-of-the-w3c-timed-text-authoring-format/comment-page-1/#comment-988 Daniel Sun, 28 Jun 2009 21:05:43 +0000 http://blog.gingertech.net/?p=428#comment-988 I agree about the "end" and "dur" ambiguity. The problem stems from the fact that TimedText is making an explicit reference to the timing semantics of SMIL 2.1, but overrides the attribute grammar with a format that is very limited (i.e. no synchronization arcs, events, or access keys), without detailing the concrete semantic implications. In SMIL, an author can use "end" and "dur" at the *same time* for an actual purpose (i.e. this is a "feature"): this mechanism offers some interesting timing effects due to precedence order of "end" over "dur" resolved values. In other words, "end" and "dur" are redundant in TimedText, in the sense that they are bound by simple arithmetic (end = begin + dur), which is not the case in SMIL because of more complex timing semantics and the way time values are resolved (e.g. non-deterministic events, animation sandwich model). (just from the top of my mind on Sunday evening...I hope I'm being clear enough :) ) http://www.w3.org/TR/2009/WD-ttaf1-dfxp-20090602/#timing-value-timeExpression http://www.w3.org/TR/SMIL2/smil-timing.html#Timing-TimingAttributeGrammars I agree about the “end” and “dur” ambiguity. The problem stems from the fact that TimedText is making an explicit reference to the timing semantics of SMIL 2.1, but overrides the attribute grammar with a format that is very limited (i.e. no synchronization arcs, events, or access keys), without detailing the concrete semantic implications.

In SMIL, an author can use “end” and “dur” at the *same time* for an actual purpose (i.e. this is a “feature”): this mechanism offers some interesting timing effects due to precedence order of “end” over “dur” resolved values.

In other words, “end” and “dur” are redundant in TimedText, in the sense that they are bound by simple arithmetic (end = begin + dur), which is not the case in SMIL because of more complex timing semantics and the way time values are resolved (e.g. non-deterministic events, animation sandwich model).

(just from the top of my mind on Sunday evening…I hope I’m being clear enough :) )

http://www.w3.org/TR/2009/WD-ttaf1-dfxp-20090602/#timing-value-timeExpression

http://www.w3.org/TR/SMIL2/smil-timing.html#Timing-TimingAttributeGrammars

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