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Re: how does EME/DRM effect captioning

From: Glenn Adams <glenn@skynav.com>
Date: Thu, 28 Mar 2013 08:59:00 -0600
Message-ID: <CACQ=j+e783t1XNz18eH+G-ypa1QaO9Zdc+JXKTy4HDJpsEp7bw@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>
On Thu, Mar 28, 2013 at 3:53 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?

Expressing my personal opinion, there are regulatory requirements, at least
in the U.S. (and probably elsewhere), to present captions when present.
Given there are two modes for caption deliver, in-band and out-of-band,
then the mode that is used may intersect with encrypted content. In
particular, if caption data is embedded in-band in an encrypted video
elementary stream, then a CDM may be obligated (for regulatory reasons) to
make the plain text form of this caption data available to the UA (even in
the case that the CDM does not otherwise expose the plain text form of the
embedding stream to the UA).

I expect that CDM providers will be aware of these requirements and work
with UA vendors to ensure that external requirements on accessibility are
met. In addition, content providers have the ability to deliver captions in
HTML5 using multiple sources. For example, they could choose to provide
both captions embedded in an encrypted video stream and out-of-band
(non-embedded) captions in a separate, unencrypted resource, such as TTML
or WebVTT.
Received on Thursday, 28 March 2013 14:59:48 UTC

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