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Re: AES-CTR inside vs. outside the media container (was: Re: Encrypted Media proposal: Summary of the discussion so far)

From: Leonard Rosenthol <lrosenth@adobe.com>
Date: Wed, 7 Mar 2012 07:53:53 -0800
To: Henri Sivonen <hsivonen@iki.fi>, Mark Watson <watsonm@netflix.com>
CC: Tab Atkins <jackalmage@gmail.com>, Christian Kaiser <kaiserc@google.com>, HTML WG <public-html@w3.org>
Message-ID: <CB7CEE37.1A270%lrosenth@adobe.com>
On 3/7/12 7:54 AM, "Henri Sivonen" <hsivonen@iki.fi> wrote:
>(Presumably in non-streaming cases, it might be useful to be able to
>read embedded metadata even if the media is unrenderable, but in the
>streaming Web case, that doesn't seem like an important benefit.)

Remember that streaming does NOT simply mean "start at byte 0 and go to
byte n".  The byte-range feature of HTTP allows the client to fetch any
specific set of byte ranges from the stream in whatever order it wishes.
Thus a smart media player could leverage selective encryption on the MP4
blocks to read the (unencrypted) metadata and display it to the user if
they couldn't read the rest of the package.

Received on Wednesday, 7 March 2012 15:55:08 UTC

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