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Re: ISSUE-154 (endsync behavior): Clarify the endsync behavior [DFXP 1.0]

From: Andreas Tai <tai@irt.de>
Date: Thu, 31 May 2012 11:04:09 +0200
Message-ID: <4FC73409.2020403@irt.de>
To: Timed Text Working Group <public-tt@w3.org>
I would like to propose to make a decision on ISSUE-154 [1] endsync 
behavior. As proposed I would support the change that for (par) time 
container with no specified duration the implicit default value of the 
attribute "endsync" shall be "all" (and not "last"). This change is 
expressed already in the specification of the EBU TTML subset [2]. It 
would be much better to have this clarification in the TTML 1.0 (2nd 
edition). The stable version of the EBU-TT specification will be 
published soon and a hint that the "endync" part could be left out of 
the EBU spec would be highly welcome.

Best regards,


[1] http://www.w3.org/AudioVideo/TT/tracker/issues/154
[2] http://tech.ebu.ch/docs/tech/tech3350.pdf, page 44

Am 15.02.2012 13:39, schrieb Timed Text Working Group Issue Tracker:
> ISSUE-154 (endsync behavior): Clarify the endsync behavior [DFXP 1.0]
> http://www.w3.org/AudioVideo/TT/tracker/issues/154
> Raised by: Sean Hayes
> On product: DFXP 1.0
> Summary:
> Time containers should have a default value of endsync=’all’ rather than the current default endsync=’last’, otherwise marker mode does not work.
> Detail:
> In SMPTE discontinuous mode TTML defines time containers to use the marker mode (event based) timing model of SMIL; however in this mode the elements inside a time container are not waiting for events unless the parent timecontainer is active. However unless the parent duration is explicitly notated, since all of the children are event based they would under SMIL have no resolved active time, which in the default endsync model results in a parent with zero duration.
> I think we can most simply resolve this issue by defining that time containers have a default value of endsync=’all’ rather than the SMIL default endsync=’last’. This means that the parent will stay around until all of the children have completed at least one activation, which is a more intuitive expectation for a caption file anyway.

Andreas Tai
Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
Floriansmuehlstrasse 60, D-80939 Munich, Germany

Phone: +49 89 32399-389 | Fax: +49 89 32399-200
http: www.irt.de | Email: tai@irt.de

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Received on Thursday, 31 May 2012 09:07:58 UTC

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