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

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 16 Feb 2011 13:31:47 +1100
Message-ID: <AANLkTimdnGettUaeLAJ7m_5zmmxOxDZ1JGJ6P9jEx=GW@mail.gmail.com>
To: Jonas Sicking <jonas@sicking.cc>
Cc: Mark Watson <watsonm@netflix.com>, Philip Jägenstedt <philipj@opera.com>, public-html <public-html@w3.org>
On Wed, Feb 16, 2011 at 12:08 PM, Jonas Sicking <jonas@sicking.cc> wrote:
> On Tue, Feb 15, 2011 at 4:19 PM, Silvia Pfeiffer
> <silviapfeiffer1@gmail.com> wrote:
>> On Wed, Feb 16, 2011 at 5:36 AM, Mark Watson <watsonm@netflix.com> wrote:
>>> Hi Philip,
>>>
>>> Just a quick note that the "alternative" vs "additional" distinction is not always completely clear. Video with different camera angles (gimmiky or not) could be considered as an alternative, or could be rendered as picture-in-picture, or multiple thumbnail videos could show beside the main video (some sports sites already do this kind of thing).
>>>
>>> If you have the output capabilities (e.g. wireless headphones plus regular speakers) then simultaneous output of different audio languages might make sense.
>>>
>>> Not to say these are compelling use-cases, just that the markup should indicate what the media actually is such that the player can decide what to do, without any hard "alternative" vs "additional" distinction.
>>
>> I think I generally agree.
>
> Is there anything that prevents an implementation from displaying
> multiple "alternative" streams at the same time? Even if they are
> explicitly labelled and in spec called "alternative" I wouldn't think
> there is. Compare to how there are currently alternative CSS
> stylesheets. There is nothing preventing an implementation from
> displaying multiple windows which have different alternative
> stylesheets applied, as long as the DOM acts as though a specific one
> is applied (you can only return one value for .offsetTop). This is a
> model that works quite well IMHO since it doesn't require page authors
> to keep more exotic UAs in mind, allowing UAs to freely experiment.

I think it all burns down to what the user/UA select to activate. If
there are multiple tracks that should really be alternative but are
presented together, then it's up to the user to deactivate the one
they don't want to see/hear. Even with <track> elements there is
nothing prohibiting multiple tracks from being active at the same
time. It's up to the UA to present these and up to the user to decide
if that is the presentation they would like to see. So, I don't
actually think we need to put an attribute on the media track for
alternative/additional, since the UA will not actually use it as input
IMHO.

I used to think that alternative/additional was a big thing, too, and
it made sense to tell the UA about it so it can act appropriately, but
it becomes very complex very quickly: which group of tracks is
alternative to which other (e.g. all the English tracks a+v+t plus
original video against all the German tracks plus original video?) and
the logic becomes almost impossible to represent, and even worse to
interpret. So, I would think it's easiest if the browser just tries to
display them and leaves the choice of managing the active tracks to
the user.

Silvia.
Received on Wednesday, 16 February 2011 02:32:40 UTC

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