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Re: Track kinds

From: David Singer <singer@apple.com>
Date: Fri, 29 Apr 2011 09:52:52 -0400
Cc: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-id: <D3699776-E612-455B-A3BC-AE3FCFEF831A@apple.com>
To: Mark Watson <watsonm@netflix.com>

On Apr 29, 2011, at 1:43 , Mark Watson wrote:

> This is a more general question about how to signal whether a track is "additive" or "alternative". I think we discussed this before (or maybe that was a different list, I forget).

I don't think we are designing SMIL, or other mixing systems, in general.  I think we need to say at the HTML or DASH level 'pick this source if you need clearaudio or repetitivestimulussafe', and leave to the media engine underneath any necessary configuring of the media resource to provide that experience.

That is, it's a two-step process; select at the DASH/HTML level, configure at the media engine level.

Putting the tag on all sources mean that the program content naturally has this characteristic.  Putting it on some indicates a choice.  Not mentioning it means the content author didn't think about it (typically).

In the case of a built-up audio experience, it's the media engine's problem to adjust the build to respond to 'I need clearaudio' (perhaps by adjusting relative volumes, perhaps by disabling some audio completely).

> In the context of audio descriptions I've seen it stated that sometimes an audio description track is a replacement for the main audio track and in other cases it's intended to be mixed in (i.e. the descriptions fit somehow into gaps in the main audio track.)
> Does anyone on this list know whether that is true ?
> As with the repetitive stimulus question there are three approaches:
> (a) treat it as a new property (additive vs alternative)
> (b) allow multiple kinds (so we wold have "alternate clearaudio" and just "clearaudio")
> (c) define separate kinds for the different cases, where it makes sense ("clearaudio-alt" and "clearaudio-mix")
> Personally, I prefer (c) as I don't think the concept is universal enough to warrant a separate property.
> ...Mark
>> Cheers,
>> Silvia.

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Friday, 29 April 2011 13:53:23 UTC

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