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RE: TTML and aspect ratio

From: Michael Dolan <mdolan@newtbt.com>
Date: Mon, 28 Jan 2013 14:51:32 -0800
To: <public-tt@w3.org>
Message-ID: <01df01cdfdaa$063581d0$12a08570$@newtbt.com>
Hi Geoff- 

As you've determined, there is no explicit signaling.  

Probably the closest way to do this today is to specify the origin and
extent on the root element (which then defines the root container) using a
popular video coding format without subsampling - e.g. 640x480 (4:3) or
1920x1080 (16:9). The aspect ratio can then be determined.  For subsampled
video or 21:9, it's less straight-forward, but some conventions could be
adopted.  

If px addressing is used anywhere in the document, then setting origin and
extent is a good idea anyway, else you have to rely on the context of the
companion video. And, if you rely on that, then you probably know the aspect
ratio anyway.

Regards,

	Mike

-----Original Message-----
From: Geoff Freed [mailto:geoff_freed@wgbh.org] 
Sent: Monday, January 28, 2013 2:10 PM
To: public-tt@w3.org
Subject: TTML and aspect ratio


Hi, everybody:

One of NCAM's partners (Netflix) is looking for a way to specify aspect
ratio in a TTML file; however, TTML currently has no way of actually
specifying aspect ratio.  I took a look through the WG archives and saw that
this topic has been discussed recently
(http://lists.w3.org/Archives/Public/public-tt/2012Oct/0061.html) but it
doesn't look like there has been any resolution.  Is this feature under
consideration?

(Netflix has raised the same issue with WebVTT, and it looks like that spec
will be including metadata for specifying aspect ratio:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=20566 .)

Thanks.
Geoff Freed
NCAM/WGBH
Received on Monday, 28 January 2013 22:52:03 GMT

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