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Re: ISSUE-151 Clarify syncbase in SMPTE continuous mode - Draft Change Applied

From: Glenn Adams <glenn@skynav.com>
Date: Sun, 27 May 2012 11:53:53 -0600
Message-ID: <CACQ=j+cFWUkzO=BsdqXF-D8c1wHqy2B8pCPCKkwhubM_yLzmZA@mail.gmail.com>
To: Andreas Tai <tai@irt.de>
Cc: public-tt <public-tt@w3.org>
On Sun, May 27, 2012 at 6:10 AM, Andreas Tai <tai@irt.de> wrote:

> The edit of ttp:markerMode with the value "continuous" implies that all
> time expression in markerMode "continuous" are "labeled synchronization
> events (markers)".
>
> I have two questions with the reference to the last example on the
> discussion page on issue 151 (http://www.w3.org/wiki/TTML/**
> Issue151Discussion <http://www.w3.org/wiki/TTML/Issue151Discussion>):
>
> <p region='r' begin='00:00:27:00' end='00:00:38:00'>
> <span begin='00:00:28:00'>A</span>
> <span begin='00:00:29:00'>B</span>
> <span begin='00:00:30:00'>C</span>
> </p>
>
> Assumption: timebase = "smpte" + markerMode = "continuous"
>
> 1) Are the time expressions of the span elements valid?
>

yes


> 2) Is the begin of the first span element timed when some external
> synchronization context emits the event "00:00:28:00" or is it timed 28s
> after the begin of the parent p (so at "00:00:55:00")?
>

the former, since, by default, all TTML elements are parallel time
containers; the more interesting question is whether it is valid to specify
the use of a sequential time container when timeBase is smpte; at present,
i don't think we have any language that covers this case

if we do allow sequential time containment for smpte time base, then it
would be possible to interpret "00:00:28:00" as a relative time (as opposed
to absolute marker) only in the case that markerMode is continuous, since
it is feasible to convert relative smpte time coordinate expressions to
media time deltas (i.e., offset time) in continuous mode (even in the case
of drop frame)


> Thanks and best regards,
>
> Andreas
>
> Am 26.04.2012 06:31, schrieb Glenn Adams:
>
>
>> I've taken a stab at addressing ISSUE-151 [1] (ACTION-51 [2]). See
>> updated ED [3] and changeset [4].
>>
>> The relevant changes are under Sections 6.2.11 (ttp:timeBase) and 6.2.6
>> (ttp:markerMode).
>>
>> [1] http://www.w3.org/AudioVideo/**TT/tracker/issues/151<http://www.w3.org/AudioVideo/TT/tracker/issues/151>
>> [2] http://www.w3.org/AudioVideo/**TT/tracker/actions/51<http://www.w3.org/AudioVideo/TT/tracker/actions/51>
>> [3] http://dvcs.w3.org/hg/ttml/**raw-file/tip/ttml10/spec/**
>> ttaf1-dfxp.html<http://dvcs.w3.org/hg/ttml/raw-file/tip/ttml10/spec/ttaf1-dfxp.html>
>> [4] http://dvcs.w3.org/hg/ttml/**rev/2bde2e2c5507<http://dvcs.w3.org/hg/ttml/rev/2bde2e2c5507>
>>
>
>
> --
> ------------------------------**------------------
> Andreas Tai
> Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
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> Floriansmuehlstrasse 60, D-80939 Munich, Germany
>
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Received on Sunday, 27 May 2012 17:54:45 UTC

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