W3C home > Mailing lists > Public > public-tt@w3.org > January 2013

RE: TTML and aspect ratio

From: John Birch <John.Birch@screensystems.tv>
Date: Wed, 30 Jan 2013 16:40:37 +0000
To: Michael Dolan <mdolan@newtbt.com>, "public-tt@w3.org" <public-tt@w3.org>
Message-ID: <0981DC6F684DE44FBE8E2602C456E8ABAAF02455@SS-IP-EXMB-01.screensystems.tv>
Just FYI,

The aspect ratio issue has already been discussed quite extensively within the EBU-TT group.

One of the specific aims of EBU-TT is to allow authors to write a resolution independent subtitle file for timed text storage.
E.g. Current recommendations include using percentages and cell metrics to allow target resolution independence.

EBU-TT also supports an extension called:

ebuttm:documentTargetAspectRatio (element)
Type xs:string
Cardinality 0..1
The aspect ratio of the video the EBU-TT document was authored for, in width by height.
Sample Value: "4:3"

This is intended to allow the document consumer to process the timed text contents appropriately. For example, knowledge of the aspect ratio that the contents were originally authored for might allow more 'intelligent' processing to adapt the content to other aspect ratio presentations.
Information about any letterbox aspects may also be captured in extension metadata elements similar to the one above. (These are necessary because subtitle content may be positioned 'in the black' for a certain presentations, but may need to be relocated if a different display device is used - e.g. cinema to widescreen TV).

It should be understood that EBU-TT is NOT intended as a delivery format (to the viewer / browser)... and it is anticipated that EBU-TT files would be converted into the relevant format.

Best regards,

John Birch | Screen | Strategic Partnerships Manager
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P Before printing, think about the environment-----Original Message-----
From: Michael Dolan [mailto:mdolan@newtbt.com]
Sent: 30 January 2013 16:20
To: public-tt@w3.org
Subject: RE: TTML and aspect ratio

Well, yes, that would be the logical thing for W3C to do in reaction to SMPTE's request :-)

But that would be a TTML 1.1 enhancement, which may be a bit further out.
Once SDP-US and TTML 1.0 2nd Edition publish, I expect the TTWG to return to working on 1.1.

I suppose instead you can define your own attribute (TTML allows foreign namespaces), but that would not be interoperable of course.


-----Original Message-----
From: David Ronca [mailto:dronca@netflix.com]
Sent: Wednesday, January 30, 2013 7:58 AM
To: public-tt@w3.org
Subject: RE: TTML and aspect ratio

> Today, when dealing with 608 and 708 sourced content, one should rely
> on the SMPTE work.  Except for 2052-11, which is not yet published,
> the work is available for free at www.smpte.org.

We ingest captions from many different formats besides 608 & 708, and thus need a general way to resolve this issue.  The most obvious being <tt tts:aspectRatio>.

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Received on Wednesday, 30 January 2013 16:41:05 UTC

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