Pubilcation of the TTML Subset "EBU-TT Part 1 v.0.9"

Dear all,

First let me introduce myself:

I am working in the EBU-Group "Subtitles in XML" and since this year I 
took over the chair of the group from Larissa Goerner.

Since Tuesday the XML Subtitling format definition EBU Timed Text Part 1 
(EBU-TT) is published:

http://tech.ebu.ch/ebu-tt

The spec builds on the W3C TTML spec.and through the collaboration with 
Sean Hayes we have tried to be as TTML conformant as possible.

The group chose to use TTML because we saw a big advantage in building 
on an existing standard and we are aware TTML already has other 
"subsets/supersets" too (e.g. SMPTE Timed Text). The EBU Group is 
therefore very interested in the further development of the TTML 
specification.

I see the following main TTML topics from the perspective of the EBU 
Subtitle group:

- It?s in the interest of existing TTM "subsets/supersets" that the spec 
stays stable.

- Some errors/inconsistencies in the spec have to be amended (e.g. 
through an errata document).

- The relationship between the TTML spec and the TTML XML Schema has to 
clarified. Both spec and XML Schema are declared as normative. As we 
found out in our work, only the spec text is normative, so the XML 
Schema should be informative.

- There has been some confusion about the extensibility of TTML. TTML 
has an open content model approach but this is, from my view, more 
implicit than explicit. There are some contradictions in the prose, the 
formal definition and the XML schema. A clarification would be useful.

So what could be the next steps?

We kicked of a TTML community group because we saw the need for further 
"maintenance" of the W3C TTML spec. Since then the community group did 
not really start off. From my point of view either the community group 
has to begin with the work or -- what seems a good solution as well -- 
the TTML working group is re-chartered. In any case the process should 
be transparent.

Additionally, better communication between the standardization bodies 
and other groups that define subtitling formats would be great. This is 
not only important for "TTML formats ", but also for other formats, such 
as WebVTT. I think from the "subtitling community" there is some 
confusion about the relationship of the available formats and when to 
use which one. I think we can provide some clarification.

A further note on EBU-TT:

EBU-TT is meant to "tailor" TTML to broadcast operation. The version 0.9 
is similar to a W3C candidate recommendation, so comments are still 
welcome. Although there are two TTML extensions, EBU-TT should be 
regarded more as a subset than as a superset. It uses only a 
well-defined subset of the TTML vocabulary.

It would be great to hear any comments on this and to get the TTML 
community group start working soon.

Best regards,

Andreas Tai


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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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