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ISSUE-306 (Fractional time expressions in N.2 media timeBase): Appendix N.2 omits fractional time expressions [TTML 1.0]

From: Timed Text Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Fri, 02 May 2014 09:32:25 +0000
Message-Id: <E1Wg9pR-0001iz-9x@stuart.w3.org>
To: public-tt@w3.org
ISSUE-306 (Fractional time expressions in N.2 media timeBase): Appendix N.2 omits fractional time expressions [TTML 1.0]

http://www.w3.org/AudioVideo/TT/tracker/issues/306

Raised by: Nigel Megitt
On product: TTML 1.0

Appendix N.2 [1] describes the cases when time expressions include frames and subframes, and when it includes ticks, but not when it includes fractions of seconds. This usage is present in EBU-TT-D [2].

[1] http://www.w3.org/TR/ttml1/#time-expression-semantics-media
[2] https://tech.ebu.ch/docs/tech/tech3380.pdf

This could be fixed by adding the following alternative equation for M in the green box in this section immediately after the equation that uses frames and subFrames:

++++
OR

M = referenceBegin + 3600 * hours + 60 * minutes + seconds + fraction
++++

and changing

----
the hours, minutes, seconds, frames, subFrames components are extracted from time expression if present, or zero if not present;
----

to 

====
the hours, minutes, seconds, frames, subFrames, fraction components are extracted from time expression if present, or zero if not present;
====

One could argue that this interpretation is obvious and does not require elaboration however I think it should be present for completeness. Otherwise when this appendix is made normative it could be interpreted that fractions of seconds are not permitted in time expressions when the timeBase is media, which I believe would be an error.
Received on Friday, 2 May 2014 09:32:29 UTC

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