W3C home > Mailing lists > Public > public-html-a11y@w3.org > February 2010

Re: [media] Moving forward with captions / subtitles

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Tue, 16 Feb 2010 18:46:00 +1100
Message-ID: <2c0e02831002152346s7a205505m65224eca88197bb4@mail.gmail.com>
To: Philip Jägenstedt <philipj@opera.com>
Cc: Geoff Freed <geoff_freed@wgbh.org>, Eric Carlson <eric.carlson@apple.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
On Tue, Feb 16, 2010 at 6:37 PM, Philip Jägenstedt <philipj@opera.com> wrote:
> On Tue, 16 Feb 2010 04:36:09 +0800, Geoff Freed <geoff_freed@wgbh.org>
> wrote:
>> GF:  I prefer <trackgroup><track> as well--  grouping tracks by role makes
>> the most sense to me. But I'm still confused about one thing after reading
>> today's thread.  From this markup, it looks to me like <trackgroup><track>
>> also would permit multiple tracks of the same role to appear simultaneously.
>>  True?  Playing simultaneous tracks of the same role is still what I'd
>> prefer (in addition to playing simultaneous tracks of differing roles, of
>> course).
> My idea is that <trackgroup> be used to group mutually exclusive tracks,
> independently of their roles. I struggle to come up with an example when you
> would want it, but if you wrap each <track> in its own <trackgroup> then
> *all* tracks can be enabled simultaneously. It is of course up to the author
> to make groups that make sense. Power users could override this using user
> JavaScript or other browser extensions if they really want to.

I'd actually prefer the opposite functionality - and that would also
be much more like what is in a media resource:

<track>s in a list without <trackgroup> can be activated in parallel -
they are like non-grouped MP4 tracks.

<track>s inside a <trackgroup> are mutually exclusive - only one of
them can be activated at any point in time.

IIUC, that's how grouping works in MP4 and QuickTime and thus applying
this same principle here seems to make sense to me. Thus, if you
didn't want tracks to be active together, you'd pack them in a
trackgroup. Much easier than having to package each single <track> in
a <trackgroup> to enable them to be active in parallel.

Received on Tuesday, 16 February 2010 07:46:52 UTC

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