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[encrypted-media] Explicitly handle potentially-encrypted media data that does not contain Initialization Data

From: ddorwin via GitHub <sysbot+gh@w3.org>
Date: Mon, 19 Sep 2016 23:16:28 +0000
To: public-html-media@w3.org
Message-ID: <issues.opened-177922930-1474326986-sysbot+gh@w3.org>
ddorwin has just created a new issue for 
https://github.com/w3c/encrypted-media:

== Explicitly handle potentially-encrypted media data that does not 
contain Initialization Data ==
The spec currently handles "implementation [that require] 
specification of a MediaKeys object before decoding 
potentially-encrypted media data" in the [Initialization Data 
Encountered](https://w3c.github.io/encrypted-media/#initdata-encountered)
 algorithm. However, it is possible for a stream to be encrypted 
without it containing Initialization Data. Specifically, as pointed 
out in 
https://github.com/w3c/web-platform-tests/issues/3721#issuecomment-247526640,
 it is possible for CENC files to not contain `'pssh'` boxes.

The actual trigger for this step in CENC files is covered in the 
[Detection](http://w3c.github.io/encrypted-media/format-registry/stream/mp4.html#detect-format)
 section of the stream registry entry but not for this purpose.

I think we need to expand the registry entries to state that the 
Detection sections define encountering encrypted stream [data] then 
add a new algorithm for "Encrypted Stream Encountered" (or something 
similar) and move the step referenced in the first section to this 
algorithm. I don't think we need to duplicate it in the Initialization
 Data Encountered algorithm since I don't think Initialization Data 
should be encountered before it is determined that the stream is 
encrypted.

Please view or discuss this issue at 
https://github.com/w3c/encrypted-media/issues/333 using your GitHub 
account
Received on Monday, 19 September 2016 23:16:35 UTC

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