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Re: how does EME/DRM effect captioning

From: Mark Watson <watsonm@netflix.com>
Date: Thu, 28 Mar 2013 07:54:48 -0700
Message-ID: <CAEnTvdDQGSYzCk4-GQgmsDS15DORkWfOvCEVg7vSon9UvdD_vQ@mail.gmail.com>
To: Steve Faulkner <faulkner.steve@gmail.com>
Cc: HTMLWG WG <public-html@w3.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>, public-html-media@w3.org
[+HTML Media]

On Thu, Mar 28, 2013 at 2:53 AM, Steve Faulkner <faulkner.steve@gmail.com>wrote:

> HTML5 provides the ability to caption video, is this in anyway negatively
> impacted by the use of the EME feature?

Hi Steve,

First, I think a review of the EME specification by the Accessibility TF
would be a good idea and I would be happy to join a TF meeting to present
the proposal.

With regard to your question, presently, media with content protection
requirements is only delivered on the Web using plugins such as Flash and
Silverlight. In this context HTML5's captioning capabilities are not used
and captions/subtitles are likely not made available to any accessibility
features within the browser. This is certainly also true when media is
delivered using native apps, not in the browser at all.

EME provides the possibility to deliver protected video through the HTML5
video element, opening up the possibility to use unprotected captions
through HTML5's captioning capabilities in conjunction with this video.

So, EME is an improvement over the status quo, because it offers a
possibility to use HTML5's accessibility features which does not exist

Now, one could interpret your question differently: what about an author
who is today using the HTML5 media element without any DRM and chooses to
start using EME in order to add content protection. In this case the author
may have a choice of whether to DRM-protect the captions as well as the
video and audio. I'm not sure if browsers will support DRM-protection of
captions at all - the EME specification does not require them to - but if
they did then in some architectures this could mean the captions were not
available to the accessibility features of the browser. Specifically, this
could happen in architectures where the content protection is provided by
the platform and the decrypted media is not provided back to the browser.
However, AFAIK, the commercial DRM solutions focus on audio and video and
not captions, meaning that the only choice for the author may be to deliver
the captions unprotected (as they did before, in this example), to be
handled by HTML5 with the obvious benefits that brings. So there would be
no negative impact on the use of HTML5 captioning capabilities for this
author. And again, the situation is better with EME than the status quo
where this author would be forced into using plugins or native apps in
order to meet their content protection goals.


> with regards
> --
> SteveF
> HTML 5.1 <http://www.w3.org/html/wg/drafts/html/master/>
>  <http://www.paciellogroup.com/resources/wat-ie-about.html>
Received on Thursday, 28 March 2013 14:55:19 UTC

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