Re: Roll-up captions in WebVTT

On Tue, Feb 28, 2012 at 6:49 PM, David Singer <singer@apple.com> wrote:

> I am simply saying that the choice between jump-scroll and smooth-scroll
> is a presentational one, and not semantic; the text ends up in the same
> place in either case.  Given that, it seems it should be under control of
> the (a) presentational system and (b) the user and chosen user-agent.
>

But 1: transitions would be a poor, brittle mechanism for authors to
implement this, and 2: if viewers really do want to see roll-up captions,
they shouldn't be dependent on authors baking roll-ups into the caption
files manually, since almost nobody will actually do that.  The choice to
view roll-ups or not--if the decision is available at all--should be a user
(not an author) preference, and always work.

I don't understand the resistance to allowing UAs to render roll-ups on
their own.  It would work much more reliably, and due to not needing
special authoring work it would work on most files instead of almost none.
It would be much more flexible; UAs could, for example, vary the number of
displayed lines and scrolling speed based on screen usage with the chosen
font.  (I doubt that there's actually any demand for roll-ups, so it would
probably never be implemented, but that's how it's supposed to work.)

-- 
Glenn Maynard