Draft for summary of an HTMLCue proposal

Dear all,

One open task I had was to draft a summary for the HTMLCue proposal. 
This summary is intended as a base for discussion with other standard 
groups or with developers from the browser communities.

The proposal could be discussed in tomorrows TTWG meeting (see agenda 
topic 9a)

Best regards,

Andreas

"""
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What?
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We propose to specify an implementation of the text track cue API where 
the format of the cue data is HTML. The "cue type" is called in the 
following HTMLCue.

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Why?
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Different file formats are used for the distribution of subtitles and 
captions in the HTML ecosystem. Currently only WebVTT has a defined Cue 
Concept that is implemented by Web Browsers. It would extend the reach 
of accessible content a lot if the text track API can be used by any 
subtitle format.

Options for a solution:

1) Mapping of other formats to VTTCues
Although this maybe a short-term option a lossless mapping is often not 
feasible and requires considerable knowledge of the source and the 
destination format. It would also need continuous alignment of each of 
the subtitle formats with WebVTT and vice versa.

2) Define a cue type for every subtitle format
Even if these different cue type specifications would exist it is 
unlikely that browsers will support all different cue "specializations".

3) Define a generic cue type
This cue type should be easy to implement by browsers and it should be 
possible to map the semantic the scope of different existing formats.

We think an HTML cue as a variant of the third option is the best solution.

The strength of a  generic  HTML cue type is that, assuming that the way 
to render these cues is clearly defined somewhere, basically any kind of 
subtitle format that can be translated into HTML could be supported, as 
long as the browser, a client side JS   or a server based solution does 
the translation work somewhere. One way to make use of the doc fragment 
is to place the doc fragment as an overlay over the video.

The HTMLCue could be defined as HTML extension. The HTML Spec itself 
does not need to be changed.

It may be worth noting that under the hood some browsers already 
translate WebVTT to HTML and some client side JS solutions translate 
TTML to HTML.

=> Next Steps?
We would appreciate to hear your opinion about this so that this 
activity can be started during TPAC in October 2015.
"""

-- 
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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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registration court&  managing director:
Munich Commercial, RegNo. B 5191
Dr. Klaus Illgner-Fehns
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Received on Wednesday, 12 August 2015 20:05:42 UTC