[wdmaudiodev] Re: usbaudio.sys and descriptors

  • From: Tim Roberts <timr@xxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Tue, 3 Nov 2015 09:49:41 -0800

Alan Davis wrote:

My goal is to use the built in generic audio drivers, the device has a
configuration of 2 microphone / line in inputs and 2 speakers / line
out outputs.

I've developed the descriptors as per the standard and I can get the
device to work fine with the generic drivers when it's only
microphones or speakers - audio can be recorded or played back OK.
When I try to enumerate with both microphone and speakers together in
the descriptor the device fails. In this dual mode they share the same
control end point.

What do you mean by that? Do you mean you are doing both of these with
one Audio Control interface? Why would you do that? As the spec says,
"each audio function has a single AudioControl interface and can have
several AudioStresming ... interfaces". Capture is a function, render
is a function. You should have one AC/AS interface pair for the
microphone side, and one AC/AS interface pair for the speaker side. It
won't make a shred of difference to your hardware -- the USB wire refers
to everything by endpoint, so you'll never see the interface numbers.
Interfaces are a software grouping convenience.

Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.


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