[Bug 25218] Allow license management directly via MediaKeySession

https://www.w3.org/Bugs/Public/show_bug.cgi?id=25218

--- Comment #14 from Joe Steele <steele@adobe.com> ---
(In reply to Mark Watson from comment #12)
> (In reply to David Dorwin from comment #11)
> > (In reply to Mark Watson from comment #10)
> I should say that my understanding is that any additional state is really
> just an optimization. We should assume that a CDM in a 'cold state' can
> always perform the necessary message exchanges with its server peer to get
> the content keys needed to decrypt the content. What I understood Joe was
> asking for was to avoid repeating exchanges every time when they can be done
> once and the resulting state persisted. The application doesn't even need to
> know this is happening.

To say this is just an "optimization" is understating it quite a bit. In the
same sense, taking a car on a 100mile trip is an optimization over walking.
Both methods will get you there, but there is a huge difference in experience.

In the case where a web application is using a CDM for the first time, there
may be bootstrapping keys unique to that origin that need to be downloaded. Why
unique? Because in our earlier discussions on key sharing it was determined
that keys should not be shared across origins. 

If the CDM is using software-based key hiding mechanisms, the bootstrapping
process is slow. On the order of seconds. This is not a problem when it happens
once, and can be managed to happen while the application is occupied with other
things (like displaying video thumbnails for selection) but a HUGE problem if
it happens on every download. 

This is the key exchange I do not want to repeat. This key exchange should be
subject to the same-origin constraints all other CDM communication is. To me
this implies it must go through the keyrequest/update() mechanism. Or we must
introduce an alternate mechanism which looks essentially the same, but is
specific to this purpose.

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Received on Wednesday, 30 April 2014 18:01:53 UTC