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Filtering of enumerateDevices() results

From: Joe Berkovitz <joe@noteflight.com>
Date: Mon, 18 May 2015 16:48:02 -0400
Message-ID: <CA+ojG-bVzO-9w-ws8+De2fxjHhZnRq6AaHNnA9iVMJE=zuSXow@mail.gmail.com>
To: public-media-capture@w3.org, Stefan HÃ¥kansson <stefan.lk.hakansson@ericsson.com>, Harald Tveit Alvestrand <harald@alvestrand.no>
Cc: Audio Working Group <public-audio@w3.org>
Hi Media Capture folks,

I am trying to confirm the intent of the MC spec with respect to the
filtering of device information in the result from enumerateDevices(). This
is a prelude to the AudioWG getting back to you with a more carefully
thought out set of requests, as Harald requested. We want to ask for things
that will be easy for you to add and generate the minimum of discussion and

It appears that the result is "censored" to remove user-readable device
names unless there is permission granted to access at least one local
device. I presume this has an anti-fingerprinting purpose.

It also seems that the only way to get such permission granted is to call
getUserMedia() and get permission to access some device matching some
constraints -- which might not be the one the user actually wants to use --
in order to obtain a list of alternatives.

Now, the user might decline that permission request, but perhaps might have
allowed access to one of the alternative devices -- if only the app could
have presented a choice. However, it couldn't, because enumerateDevices()
wasn't allowed to offer that information yet.  This seems like a Catch-22
type of situation.

Is my understanding of the spec correct, and can you provide any guidance
to the situation in which an app would like to present choices before
asking for permission on a specific device? Is there some way that the UA
can ask the user for permission to share the names of devices with the
application, to avoid this chicken-and-egg situation?

.            .       .    .  . ...Joe

*Joe Berkovitz*

*Noteflight LLC*
49R Day Street / Somerville, MA 02144 / USA
phone: +1 978 314 6271
"Your music, everywhere"
Received on Monday, 18 May 2015 20:48:30 UTC

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