Re: TTML and aspect ratio

On Wed, Jan 30, 2013 at 11:53 AM, David Ronca <dronca@netflix.com> wrote:

> > If the extent is specified, then it cannot be ignored by a compliant
> > client. A compliant client is obligated to respect that extent
> > specification.
>
> Agreed, which means that extent is not useful for indicating the aspect
> ratio of the root container if the frame size will vary.
>
> > It is sounding to me like you want to avoid specifying root container
> > extent at all,
>
> Definitely want to avoid specifying the root container extent.
>
> >but have a way to automatically determine it in the client
> > based on an a specified aspect ratio and possibly a safe area
> >specification, is that correct?
>
> If the client knows the aspect ratio of the root container, it can scale
> presentation for any frame size or display size.
>
> > If so, would other length specifications always use non-pixel metrics or
> > percentages? e.g., to specify non-root region origin and extent, use
> cells
> > or percentages, but not pixels?
>
> Percentage could work if the specified behavior for an extent that was not
> full screen is to center the root container in the display area
>

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.