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Re: Audio Description requirements document

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 6 Oct 2016 13:43:08 +0000
To: Janina Sajka <janina@rednote.net>, "public-apa@w3.org" <public-apa@w3.org>
Message-ID: <D41C1188.2C418%nigel.megitt@bbc.co.uk>
Following this up, I have updated the TTML2 AD requirements document to include references to the supported MAUR requirements, and this is now available on the TTML2 wiki at https://github.com/w3c/ttml2/wiki/Audio-Description-Requirements for further review and input.

In my view at the moment the TTML2 AD requirements support all of the MAUR requirements for Descriptions that it would be reasonable to include, excluding those requirements that would need to be handled "out of band": for example DV-1 is "Provide an indication that descriptions are available, " and that would be a UI implementation requirement independent of the means of carriage of the descriptions data, so that is not included.

Similarly the EVD requirements for pausing and resuming playback of video and audio to allow for enough time to play a lengthy description are in my view "out of band" in that the overriding requirement for a media timeline in TTML2 is to match the originating media timeline. Any decision to pause and resume the media is knowledge that by definition cannot be available when authoring a TTML2 document.

Conversely there are some data format requirements that are not included in MAUR at all, but which are relevant for TTML2, for example the requirement for a processor to be able to generate a set of directives to control an audio mixer, which is a pre-requisite for meeting the MAUR requirements at all.

Many thanks,


From: Nigel Megitt <nigel.megitt@bbc.co.uk<mailto:nigel.megitt@bbc.co.uk>>
Date: Friday, 23 September 2016 at 17:37
To: Janina Sajka <janina@rednote.net<mailto:janina@rednote.net>>
Cc: "public-apa@w3.org<mailto:public-apa@w3.org>" <public-apa@w3.org<mailto:public-apa@w3.org>>
Subject: Re: Audio Description requirements document

Thank you for the reminder Janina. Indeed I recall reviewing MAUR and feeding back, though not specifically on audio description.

These requirements should be complementary in that they describe what is needed to support the production of AD.

I have just double checked and the requirements I have circulated would support TVDs and "ordinary" video descriptions but not EVDs. It appears to me that there is strong if not complete alignment between the two documents for all of the DV requirements, assuming we begin with a TTML2 starting point and add the additional requirements from my recent document.

I am actually unclear about how the requirement for EVDs can be met by simple extensions to TTML2 so I would prefer to leave those requirements out of scope for the time being.

Kind regards,


On 23 Sep 2016, at 16:12, Janina Sajka <janina@rednote.net<mailto:janina@rednote.net>> wrote:

Thanks for the heads up, Nigel.

We actually developed requirements on audio description during our work
on HTML 5. These are published in a W3C Note known as the Media
Accessibility User Requirements (MAUR) available at:


We should also note that ISO SC35 WG6 has a document in this area, but I
don't have its URI immediately at hand.


Nigel Megitt writes:
Dear APA,

[blame John Foliot for suggesting to me that you would be interested!]

TTWG is considering requirements for supporting audio descriptions (also known as video descriptions) in a document format e.g. TTML. I have proposed a draft requirements document for this use case which can be found attached to the email archived at https://lists.w3.org/Archives/Public/public-tt/2016Sep/0034.html which describes the workflow being supported and a short list of requirements.

Feedback is welcome either directly to me or to the TTWG public reflector; the intent is to add features to TTML2 to support these requirements.

kind regards,



Nigel Megitt
Executive Product Manager, BBC Design & Engineering
Telephone : +44 (0)3030807996
BC2 C1 Broadcast Centre, Media Village, 201 Wood Lane, London W12 7TP


Janina Sajka,    Phone:    +1.443.300.2200
       Email:    janina@rednote.net<mailto:janina@rednote.net>

Linux Foundation Fellow
Executive Chair, Accessibility Workgroup:    http://a11y.org

The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
Chair, Accessible Platform Architectures    http://www.w3.org/wai/apa
Received on Thursday, 6 October 2016 13:44:29 UTC

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