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Re: Meaning of audio track kind 'descriptions'

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 16 Jun 2011 14:55:30 +1000
Message-ID: <BANLkTik34WwODAqLpRmdnc0-sJpy0gJT8Q@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>
Note that I haven't yet seen a use case that absolutely requires us to
know if a track is additional or alternative. If we do, we can always
use a data-* attribute for this right now. If we see the data-*
attribute being required to solve use cases, then we can ask for the
introduction of an additional marker.

Bob: what was your use case?

Cheers,
Silvia.

On Thu, Jun 16, 2011 at 2:53 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com> wrote:
> 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:
> http://www.longtailvideo.com/support/addons/audio-description/15136/audio-description-reference-guide
> .
>
> 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
> separate.
>
>
> Cheers,
> Silvia.
>
Received on Thursday, 16 June 2011 04:56:18 GMT

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