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Re: TTML and aspect ratio

From: Glenn Adams <glenn@skynav.com>
Date: Wed, 30 Jan 2013 14:56:28 -0700
Message-ID: <CACQ=j+dK_CKC8AonSW1rPH-rPsc6s4fNTD69mX3C=0QaOqOWgQ@mail.gmail.com>
To: David Ronca <dronca@netflix.com>
Cc: "public-tt@w3.org" <public-tt@w3.org>
On Wed, Jan 30, 2013 at 12:51 PM, David Ronca <dronca@netflix.com> wrote:

> > If you avoid specifying extent for the root container, then how does the
> > client know the extent is not full screen? At present, extent defaults to
> > full screen if not specified.
>
> If we could specify the aspect ratio, then the client would default to
> full screen in either a 4:3 or 16:9 presentation area, which is exactly
> what we are asking for.
>

David, could you be more precise? Every time you say "aspect ratio", I have
no idea what you mean.

Are you referring to:

   - physical screen aspect ratio
   - display aspect ratio (DAR), aspect ratio of a displayed frame when
   rendered on a physical screen
   - storage aspect ratio (SAR), aspect ratio of stored/transmitted image
   - pixel aspect ratio (PAR), aspect ratio of storage pixels as relates to
   displayed pixels, i.e., PAR = DAR/SAR

Presumably, you are referring to the aspect ratio of the related media
object, and not necessarily the aspect ratio of the root container region
(top level caption display region). Again, in general, the display aspect
ratio of the related media object is (or may be) distinct from the display
aspect ratio of the root container region.
Received on Wednesday, 30 January 2013 21:57:20 GMT

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