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

We have a number of comments related to the potential need for using
continuous durations in the context of (potentially) discontinuous event
(marker) based  timing, i.e., SMPTE markers. This matter will be
discussed at an upcoming F2F.

 

G.

 

  _____  

From: John Birch [mailto:johnb@screen.subtitling.com] 
Sent: Sunday, April 03, 2005 6:37 AM
To: charles@sidar.org; public-tt@w3.org; Erik Hodge
Subject: Re: Coments - last call draft [re: timing attributes]

 

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