[Bug 17202] Explicitly document how keys are to be shared

https://www.w3.org/Bugs/Public/show_bug.cgi?id=17202

Mark Watson <watsonm@netflix.com> changed:

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--- Comment #1 from Mark Watson <watsonm@netflix.com> 2012-06-05 19:57:58 UTC ---
(In reply to comment #0)
> While the algorithms probably cover this, it would be helpful to explicitly
> state how keys may be shared. We want to prevent different behavior that could
> lead to pages that make assumptions that are not true for all implementations.
> 
> The current intent is that keys/licenses are shared for all streams (i.e. audio
> and video) in a single media element but are NOT shared between media elements
> (whether in a given page or different pages). CDMs should ensure that keys
> don't leak between elements.
> 
> Bug 16615 proposes a specific scenario where sharing might be allowed.

There are certainly scenarios where keys/licenses should be shared across
elements slaved to a MediaController (as in 16615). For example two video
elements showing different video tracks from the same src (main video and sign
language, for example).

I'm not sure if the use of MediaController is the right test to enable/disable
sharing, though. Is it possible that two elements with the same src that are
not slaved to the same MediaController might share keys/licenses ?

It's common for all the resources associated with some presentation to share
the same keys, since this avoids the need for multiple or compound key/license
requests. I'm not sure we should rule this out for presentations where the
component resources are not synced with a MediaController, although I can't
think of any good examples of such presentations.

What's the disadvantage if we allow keys/licenses to be shared by all elements
on the page ?

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Received on Tuesday, 5 June 2012 19:58:01 UTC