[wdmaudiodev] Re: newbie questions about filter drivers
- From: Tim Roberts <timr@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Thu, 14 Oct 2004 13:00:38 -0700
dprado@xxxxxxxxxxxxxx wrote:
First of all thank you for the reply. I´ll explain what I need , a little
better. I have a third party application ( that cannot be changed ) , and this
application aallows me to configure two different audio output devices, that it
uses simultaneously, writing different PCM data to each of them. I have a USB
audio hardware that has obviously left and write channels. I want to configure
this application to use two "different" audio devices that actually are virtual
sound devices, one of them writes only to left channel of the real usb audio
hardware and the other to the right channel of the real usb audio hardware.
That way since I do not need stereo sound, I can use ONE hardware and the
application believes it is writing to two differente devices.
I know this would be much easier to do in user mode. But the application is
already written and I have no control over it.
from what I understand a lower filter will not work, how can the lower
filter
know which "virtual device" the user application used?
Because above you, there will be two driver stacks: two copies of
usbaudio.sys, two copies of sysaudio.sys, two copies of wdmaud.sys, two
devices exposed to user mode. I don't know whether it has to be a lower
filter to usbaudio.sys or an upper filter to usbd.sys, but I believe
that's the spot where you need to branch off your second device. Each
request will come to you from a different FDO. You'll merge them and
forward it on.
If this is just a hobby task for you, to avoid buying another set of
speakers, you should probably forget it. You're probably talking about
five weeks of development and debugging work.
--
- Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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