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RE: Timed Text Authoring Format - Distribution Format Exchange Pr ofile (DFXP) Streaming

From: Glenn A. Adams <gadams@xfsi.com>
Date: Sat, 26 Mar 2005 00:51:57 -0500
Message-ID: <7249D02C4D2DFD4D80F2E040E8CAF37C0E9110@longxuyen.xfsi.com>
To: "Russ Wood" <russ.wood@softel.co.uk>
Cc: <public-tt@w3.org>, <Johnb@screen.subtitling.com>, <shayes@microsoft.com>


I'm not exactly sure what you mean by "a DFXP preload and store
operation on first transmission", but I gather that you are generally
supportive of not having references in DFXP to other resources. Correct?


To follow up on your comment about obsolescence of referenced content,
it was indeed an implicit requirement of DFXP that it should be
completely self-contained, just like a video or audio stream or clip.





From: Russ Wood [mailto:russ.wood@softel.co.uk] 
Sent: Monday, March 21, 2005 10:30 AM
To: Glenn A. Adams; Johnb@screen.subtitling.com; shayes@microsoft.com
Cc: public-tt@w3.org
Subject: RE: Timed Text Authoring Format - Distribution Format Exchange
Pr ofile (DFXP) Streaming


BULK OF MESSAGE DELETED see comment RW> below


"does not require dereferencing (and subsequent loading) of any
resources other than DFXP content (i.e., no embedded URIs);"

Is this just a timeliness issue?


[GA] No. Having to load any other resource may preclude direct streaming
through inline insertion, otherwise, any referenced resources would have
to be inlined and made availabe contemporaneously.


 Loading of a resource (referred to for example by a header section)
would presumably just delay the ability to decode subsequent timed
fragments. A stream decoder may then incur a 'one off' setup period
where referenced resources were dereferenced and loaded. Any timed
fragment in a streaming scenario would need to be sent some (short) time
in advance of its activation period(s) on the timebase.



RW> Another reason why the referencing of non-included resources should
be prevented is the issue of obsolescence.  If a broadcaster purchases a
programme with subtitles, he wants to know that those subtitles will
work today, tomorrow, next year and in a decade.  If a reference is made
to a URI that needs to be fetched then that resource may have moved for
reasons beyond the control of the originator.


I would prefer not to have a DFXP preload and store operation on first





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