W3C home > Mailing lists > Public > public-html@w3.org > March 2011

Re: Tech Discussions on the Multitrack Media (issue-152)

From: David Singer <singer@apple.com>
Date: Wed, 2 Mar 2011 17:27:34 -0800
Cc: Frank Olivier <Frank.Olivier@microsoft.com>, Philip Jägenstedt <philipj@opera.com>, "public-html@w3.org" <public-html@w3.org>
Message-Id: <C3739477-5923-485F-985C-857A683D3643@apple.com>
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>

On Mar 2, 2011, at 13:36 , Silvia Pfeiffer wrote:

> On Thu, Mar 3, 2011 at 6:39 AM, David Singer <singer@apple.com> wrote:
>> On Mar 2, 2011, at 10:01 , Frank Olivier wrote:
>>> "About multiple text track formats, my working assumption is that we will be able to agree on a single format that everyone supports as there is not really any of the legal of business issues that we have for audio and video."
>>> Yes, this would be a very desirable outcome. However, it would still be prudent to have the ability to reference multiple text track formats for the same content, as some user agents may have the ability to display more-complex-than-baseline text track formats.
>> Also, looking ahead, we should not assume that even if we pick a default and mandate now, it'll be the best for all time. If we (or someone) introduces a new, better, format, there will be a need for a while to offer both.
> All of these concerns are fair enough. However, I also wonder if this
> necessarily means to have <source> elements for them. The <img> tag
> supports multiple formats without needing a <source> selection.

I think this is one of the reasons that it's so hard to get new image formats to take off.  If I adopt a new format, some people get better pictures, but the majority get no picture at all :-(

> surely would be better marked up as:
>  <video id="v1" poster=“video.png” controls>
>     <track kind="captions"  srclang="en" label="Captions" src="captions.vtt">
>     <track kind="captions"  srclang="en" label="Captions" src="captions.xml">
>  </video>

the number of users who want captions in all possible formats is probably vanishingly small...

On Mar 2, 2011, at 13:49 , Silvia Pfeiffer wrote:
> Actually, when we have replacement and the replacement resource
> changes the timing of the whole virtually multitracked resource, it
> makes no sense to have that as part of this construct, since it
> influences all tracks.

Yes. I am working on a separate suggestion on how to handle the cases where re-authoring the primary source is needed, or beneficial, for meeting a particular accessibility need.

> The timing of all tracks would change and thus
> other resources for all tracks would need to be loaded. For this case,
> a complete replacement <video> element would be much better IMHO. I am
> in particular thinking about extended audio description recordings
> here.

one of the top use-cases for re-authoring, IMHO.

> Overall, I think that the requirements for "addition" are much more
> common than for "replacement".

Yes, probably, but not non-existent.

> Since replacement of resources can
> already be achieved through JavaScript, I wonder if there is really a
> need for inclusion of a markup solution for this. Is it really on the
> 80% side of the 80:20 use cases?

I'm not sure.  If we can cleanly address it, then I would like to.

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Thursday, 3 March 2011 01:28:38 UTC

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