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Re: Re: TTML and aspect ratio

From: Glenn Adams <glenn@skynav.com>
Date: Thu, 31 Jan 2013 07:54:24 -0700
Message-ID: <CACQ=j+dGDDeo3KbuBeHzoqzZjcKV2qHG6TOHs+J7+UJat5MmhQ@mail.gmail.com>
To: David Ronca <dronca@netflix.com>
Cc: "public-tt@w3.org" <public-tt@w3.org>
On Thu, Jan 31, 2013 at 7:45 AM, David Ronca <dronca@netflix.com> wrote:

> >The implementer of the client provides it. The implementer might ask the
> >user, or the system platform might define. Or the TTML client might be
> >embedded in a larger context (e.g., an HTML5 browser) that provides its
> own
> >mechanism for defining where to present captions.
>
>  A proprietary model will not work.  We need a method to define a
> consistent layout for *any* well behaved client.  Consider two scenarios:
>  1) we implement a client to present the W3C-tt, 2) we pass the W3C-tt to a
> client that will do the presentation (i.e. game console, etc.).  For both
> of these scenarios, the client *must* present the captions in a proper and
> consistent way.  This is our use case, and it does not work if TT
> presentation is based on an undefined "external authoring context".
>
> We believe that our use case can be accomplished as follows:
> 1) Cell or percentage positioning
> 2) default <tt tts:extent>
> 3) The addition of root container aspect ratio (along with a default
> behavior for centering the root container in the video window rule).
>

Don't take my remarks as meaning I don't support adding new mechanisms to
satisfy your use case. Rather, I was just attempting to explain what is
there now, and to note that this is effectively a new requirement that we
have not previously entertained. That said, I think it quite feasible to
add something to TTML 1.1 that would explicitly support this requirement.
I'm not sure that adding a new root container region aspect ratio parameter
is the best way to achieve this, but it may end up being the case after we
go through the process.
Received on Thursday, 31 January 2013 14:55:13 GMT

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