APA WG Feedback on the Encrypted Media Extensions Working Draft

REFERENCE: Encrypted Media Extensions (https://www.w3.org/TR/encrypted-media/) 

 

Colleagues,

 

As part of our ongoing work at the APA WG (Accessible Platform Architecture Working Group) to review emergent specifications at the W3C, I would like to take this opportunity to provide some final feedback on this extension, as well as a request.

 

Our Working Group has monitored the work of your group for quite some time, and the majority of the outstanding questions we had were answered at a W3C Face-to-Face meeting in 2013, minuted here: https://www.w3.org/2013/04/23-html-wg-minutes.html#item12  

 

We appreciate that the Media Encryption API coming from your group has no apparent impact on the final user-agent and related assistive technologies that Persons With Disabilities might use in the task of watching Premium Digital Content on the web, restricting itself to the encryption and decryption of the video stream only. 

 

Today, as in 2013, the only possible scenario we could envision where there *MAY* be an issue is the use-case where the principle media content is encrypted using one encryption scheme, and yet the supporting accessibility materials (captions, transcripts, audio description, etc.) would be encrypted using a second, different encryption scheme. Much of the concern focused on the potential complexity of decrypting 2 streams simultaneously and still keeping them in synchronized playback.

During our meetings in 2013 however, all agreed that this was an extreme possible edge case, and representatives in your group representing content owners indicated an extremely low probability of this happening, and that currently today this type of accessibility support content is provided un-encrypted to the end user.

 

APA’s request however focuses on this potential scenario. We would like to request that your Working Group included non-normative author guidance in the extension specification that cautions content creators from following this particular course of action. It was agreed by all at our meetings that should supporting accessibility content require encryption, that the content owners would be best served by including such materials in-band of the video stream (i.e. inside an .mp4 wrapper), which would then be encrypted at source, and decrypted at the same time as the primary media stream, mitigating the possible concern brought forward.

 

APA WG would be happy to review any draft language you might bring forward, or, upon request, provide you with some draft text for your consideration.

 

Thank you, and congratulations on your work well done.

 

This email satisfies apa-ACTION-2006

 

JF

​-- 

John Foliot

Principal Accessibility Strategist

Austin, TX

 

Deque Systems Inc.
2121 Cooperative Way, Suite 210,  
Herndon, VA 20171-5344

Office: 703-225-0380 

 <mailto:john.foliot@deque.com> john.foliot@deque.com

 

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