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Re: Coments - last call draft [re: timing attributes]

From: John Birch <johnb@screen.subtitling.com>
Date: Sun, 3 Apr 2005 11:36:56 +0100
Message-ID: <007301c53839$108d1560$8d216551@win2000itx>
To: <charles@sidar.org>, <public-tt@w3.org>, "Erik Hodge" <ehodge@real.com>
Erik,

If we allow for extrinsic timing where such a time may not
be resolved yet, then there are use cases where it is
necessary to express both dur and end.  For instance:
"Display this text for 20 seconds unless the extrinsic-
event-based end time resolves before that time, in which
case end when it resolves".

Is this mix of extrinsic and intrinsic timing actually supported within DFXP. I thought that the discontinuous attribute applied to the entire document (I see discontinuous as synonymous with media marker modality)?

Further, I find it a strange balance of features in that DFXP allows such a sophisticated timing model when it only supports a relatively simplistic styling model. 

Note: I do not have any real issue with the inclusion of the ttp parameters for timing model, except that they increase the complexity of a **fully conformant** (non SMIL based) user agent fairly dramatically. I am currently assuming that since DFXP deliberately avoids talking about UAs, that an implementation must clarify what aspects of DFXP timing model it supports. I feel this puts DFXP in an awkward position as a universal distribution format - since originators of content may use features of the timing model that are not supported by transcoders or UAs. So my position is that a simpler timimng model would be more likely to be universally adopted, further sophistication of the type in your example could IMO be handled by any 'container' format e.g. SMIL, and is unneccesary within a 'media track' format (which is how I view DFXP).

best regards

John Birch
Received on Sunday, 3 April 2005 10:26:48 GMT

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