[Bug 26207] Provide a way to check system capabilities required for UHD playback

https://www.w3.org/Bugs/Public/show_bug.cgi?id=26207

--- Comment #3 from David Dorwin <ddorwin@google.com> ---
(In reply to Jerry Smith from comment #1)
UHD might be a use case, but I don't think this feature request is more general
and the summary should reflect this.

My initial thoughts:

#1 is simple and perhaps the short-term solution (it's already defined) while
the other options are explored.

#2 may be the best way to provide answers to robustness questions. The
server/application knows what types of licenses it supports, so why not let it
ask the CDM directly. Anything else requires the application and UA to
translate robustness requirements to text and text to robustness capabilities,
respectively. This model is also consistent with getUsableKeyIds().

However, this may not always be sufficient since licenses don't normally
specify the types of media (audio vs. video) or codec(s) to be used with each
key. Without such information, applications might get false positives or
negatives.

Also, it's unclear how this would work since licenses are usually issued after
a license request and the license may depend on information from the device,
which is not possible with such a simple query. There may be room for
improvement here, but it's something to keep in mind.

#3 - There is a general lack of powerful capability detection for
HTMLMediaElement, most of which is unrelated to robustness. I think that should
be solved in general outside of EME. I believe this needs to be solved for
unprotected content and there are a lot of stakeholders and interested parties
that may not be participating in the EME specification.

Such a discussion will either solve the robustness problem or provide a model
EME can build on. While such a querying API might be easily extensible, the
robustness-media type mapping seems like something that may not fit well on a
generic solution. Also, output protection might be the only capability for
which detection may require a noticeable delay on subsequent calls. Such a
delay could make the querying capability less useful since the goal is to start
fetching the right media streams as quickly as possible.

I do not think standardizing labels for proprietary robustness mechanisms makes
sense, at least without corresponding standardization of related aspects of the
license. It seems difficult to come up with a consistent vocabulary that will
work across key systems without excluding some valid scenarios. Content
providers define their needs in the license, which is what makes #2 attractive.

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Received on Friday, 11 July 2014 18:59:18 UTC