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[Bug 13357] Additional AudioTrack.kind categories are needed to identify tracks where audio descriptions are premixed with main dialogue.

From: <bugzilla@jessica.w3.org>
Date: Tue, 30 Aug 2011 01:34:55 +0000
To: public-html-a11y@w3.org
Message-Id: <E1QyDE7-0005kB-Pu@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=13357

--- Comment #7 from Bob Lund <b.lund@cablelabs.com> 2011-08-30 01:34:54 UTC ---
(In reply to comment #6)
> Bob, you are referring to the "pass-through" rule and references to the use of
> secondary audio programming in the FCC ruling. What this refers to is the use
> of multichannel video programming distributors (MVPDs), which provide a second
> and separate audio channel to the main one in which additional audio content
> can be distributed. Most of the concerns raised in the FCC document are about
> the current use of the secondary channel for a second language audio track and
> that a requirement to provide audio descriptions would require stopping that
> service which is not acceptable for a different part of the MVPDs audience. All
> of the discussion in the FCC document are about MVPDs, i.e. about distributing
> audio descriptions in a secondary audio track. Nowhere do I see a discussion
> about a mixed audio tracks. The only mixing that happens is in the receiving
> device for display purposes.

No, this is not the case. There are only two audio channels - main and
secondary. Audio descriptions are mixed with the main dialogue by the
programmer and carried in the secondary audio channel. This channel is a mix of
dialogue and description. Receivers only tune one of the audio channels. There
is no mixing in the receiver.

> 
> So, I don't really follow your argument that this is a reason for introducing a
> new @kind value.

The current @kind does not support identification of an audio channel with
dialogue and descriptions.

Bob
> 
> 
> In contrast, the ATSC Digital Television specification indeed allows an
> associated visually impaired service to the main service to be either a single
> channel (which is what is typically implemented) or a complete mix of all
> program elements (i.e. main and audio description). See
> 
> http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf (6.6.2.3, 6.6.4.3)
> and
> http://www.atsc.org/cms/index.php/standards/document-download/doc_download/13-a52b-digital-audio-compression-standard-ac-3-e-ac-3-revision-b
> (p. 117, full_svc flag)
> However, it seems that most implementations only do a single channel. Do you
> know if there are actual implementations out there that do such a mixed
> delivery? And do they actually mix the channels or do they dedicate, for
> example, the center channel to audio descriptions, thus retaining the
> separation?

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Received on Tuesday, 30 August 2011 01:34:57 GMT

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