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Re: Encrypted Media proposal (was RE: ISSUE-179: av_param - Chairs Solicit Alternate Proposals or Counter-Proposals)

From: Mark Watson <watsonm@netflix.com>
Date: Mon, 27 Feb 2012 23:27:42 +0000
To: Kornel Lesiński <kornel@geekhood.net>
CC: "HTML WG (public-html@w3.org)" <public-html@w3.org>, Adrian Bateman <adrianba@microsoft.com>, David Dorwin <ddorwin@google.com>
Message-ID: <404BE010-CE98-431D-8BEA-492C27D6A7A8@netflix.com>

On Feb 27, 2012, at 3:15 PM, Kornel Lesiński wrote:

> On Tue, 21 Feb 2012 23:16:42 -0000, Adrian Bateman <adrianba@microsoft.com> wrote:
> 
>> We'd like to get people's feedback on the proposal. It is posted here:
>> http://dvcs.w3.org/hg/html-media/raw-file/tip/encrypted-media/encrypted-media.html

> 
> 
> In section 5.1. of the proposal there are steps:
> 
> 2. Detect whether the frame is encrypted.
> 	 If the frame is encrypted
> 	 Run the steps above. ([...] Use handler to Decrypt the block [...])
> 
> 3. Decode the frame.
> 
> 4. Provide the frame for rendering.
> 
> 
> Do I understand correctly that once user is authorized CDM gives browser access to the decrypted bitstream of the media being played?

It's not as clear as it could be, but the intention is that all three of the following are possible, depending on the CDM:

(1) The CDM returns the decrypted frame to the browser
(2) The CDM handles decryption and decoding and returns the decoded (raw pixels) frame to the browser
(3) The CDM handles decryption, decoding and rendering and (possibly) returns some kind of reference to the decoded frame to the browser

(3) for example might be what happens on a TV that includes a secure media pipeline as part of the platform. In that case the CDM doesn't itself implement the decrypt/decode/render operations but makes use of platform capabilities to achieve these.

...Mark

> 
> -- 
> regards, Kornel Lesiński
> 

Received on Monday, 27 February 2012 23:28:11 UTC

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