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Re: Meaning of audio track kind 'descriptions'

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 16 Jun 2011 14:53:29 +1000
Message-ID: <BANLkTi=nVCju6ZZ2bfvtZ4VSn+40O2cuzA@mail.gmail.com>
To: Mark Watson <watsonm@netflix.com>
Cc: Bob Lund <B.Lund@cablelabs.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
On Thu, Jun 16, 2011 at 1:07 PM, Mark Watson <watsonm@netflix.com> wrote:
> I had a different understanding.
> We keep coming back to these cases where we can imagine both "alternative" and "additional" tracks as solutions to some problem.
> I've argued at length before that it doesn't work to have a blanket mechanism whereby any track can be labeled as either "alternative" or "additional" - and indeed we have no such mechanism: it's implicit in the track kind - you need to understand the kind to know whether it is alternative or additional.
> I actually thought that all our audio kinds were alternatives. I'm no expect, but I would guess that it's hard to create a descriptions track which can be freely mixed with the original audio.

I've done so before. It's not hard at all. You listen to the original
track and you speak into the microphone. It is easier to record it in
this way because the quality of the original audio doesn't degrade. It
is also the way in which for example the jwplayer works:

It would be bad if you have to mix in the original audio because that
both degrades the quality of that track, increases the required
bandwidth (because compressed silence is smaller than compressed
sound), requires re-recording the original content (which might end up
in copyright trouble), and requires switching between tracks rather
than just adding and removing a track. Switching between tracks will
be a lot more perceptible than adding/removing a second track.

So, I can only see advantages to having an audio description provided
as a separate track.

> If both kinds exists (alternative descriptions and additive descriptions), then we need two kind values. Given that it's an accessibility requirement it would be nice for it to be explicit, so I would expect to have two "descriptions" kinds e.g. descriptions-add and descriptions-alt.

I've only ever seen audio descriptions that come as separate tracks.
In the TV case you would have had to mix it for transmission because
there was only one channel available for transmission, but I believe
that is the artificial case. The more natural case is to have them

Received on Thursday, 16 June 2011 04:54:17 UTC

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