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Re: ISSUE-312 (forcedDisplay should be in ttm): forcedDisplay attribute is metadata so should be in ttm not tts namespace [TTML IMSC 1.0]

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Tue, 27 May 2014 09:58:36 +0000
To: Glenn Adams <glenn@skynav.com>, Michael Dolan <mdolan@newtbt.com>
CC: Timed Text Working Group <public-tt@w3.org>
Message-ID: <CFAA1C92.1E52A%nigel.megitt@bbc.co.uk>
See Issue-230 for further information. On reflection it looks as though this feature is intended to meet requirement R207 'Conditional Content' [1], which is currently not supported in TTML1.

[1] http://www.w3.org/TR/2006/NOTE-ttaf1-req-20060427/#R207

That requirement could potentially be met partially or fully either by:

  *   change proposal 16 [2], in which the value of the tts:visibility property for non-forced content would be determined conditionally by the UA depending on something along the lines of @where='captions visible' and for forced content would be set according to @where='translation subtitles visible OR captions visible' for forced content.
  *   change proposal 23 [3], which relates specifically to Forced Display but as yet describes no solution.

both of these apply to TTML2.

[2] https://www.w3.org/wiki/TTML/changeProposal016
[3] https://www.w3.org/wiki/TTML/changeProposal023

I propose we drop forcedDisplay from IMSC 1, consider how best to implement the requirement in TTML2 and then bring it back into IMSC 2, to allow us to make more rapid progress with IMSC 1.

Kind regards,

Nigel


On 24/05/2014 00:28, "Glenn Adams" <glenn@skynav.com<mailto:glenn@skynav.com>> wrote:

Agreed, this is not metadata. This feature needs discussion and proper motivation.


On Thu, May 22, 2014 at 2:22 AM, Michael Dolan <mdolan@newtbt.com<mailto:mdolan@newtbt.com>> wrote:
This totally alters decoder processing.  Apparently it needs additional explanation, but it is not metadata.

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Sent: Wednesday, May 21, 2014 5:40 AM
To: public-tt@w3.org<mailto:public-tt@w3.org>
Subject: ISSUE-312 (forcedDisplay should be in ttm): forcedDisplay attribute is metadata so should be in ttm not tts namespace [TTML IMSC 1.0]

ISSUE-312 (forcedDisplay should be in ttm): forcedDisplay attribute is metadata so should be in ttm not tts namespace [TTML IMSC 1.0]

http://www.w3.org/AudioVideo/TT/tracker/issues/312

Raised by: Nigel Megitt
On product: TTML IMSC 1.0

The description of tts:forcedDisplay [1] does not define any change in processing behaviour so it appears to be metadata and should therefore be moved to the ttm: namespace.

Incidentally the note in this section references "forcedDisplayMode" which is not defined anywhere.

[1] http://www.w3.org/TR/ttml-imsc1/#tts-forcedDisplay
Received on Tuesday, 27 May 2014 09:59:13 UTC

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