Re: Re: TTML and aspect ratio

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.