[wdmaudiodev] USB Audio I/F Loop Back
- From: "Jim Leiterman" <jim@xxxxxxxxxxxxxxxxxx>
- To: <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Mon, 16 May 2005 07:19:37 -0700
Digital Audio Loop Back deivce/driverI have a utility that is a sine wave
generator that generates DirectX output stereo waves @44.1kHz. This works fine
monitoring it on various USB based Audio I/F devices. I use the DirectX output
and a head phone monitor on the device.
This tool also works fine for capturing incoming stereo snippets at 44.1kHz and
displaying these captured waves using the multimedia capture. I use the USB
enumerate to detect the device is plugged in, then I enumerate the list of
multimedia input capture devices and look for an ASCII match.
The problem comes on at least one USB Audio I/F device where it seems that it
can not output and capture at the same time. I use a patch cable to loop back
the signal and will get moments of clarity but most of the time what sounds
like an extra loop back or the wave pointer for the device gets lost so irratic
sound, etc. but will momentary correct or repeat itself. The painted capture
data during these times is garbage. De-activating the generator and
re-activating starts the process over. Turning off the capture seems to fix the
problem. Using a second computer to generate the wave as an external source and
the primary computer to use the USB Audio I/F to capture works fine.
Is there any reason why it seems to work on one device and not another? Does
windows sometimes leak the input signal back out the output? I have noticed
that if I go into volume control properties for this USB Audio I/F device there
are no input properties only outuput.
Any thoughts?
Other related posts:
- » [wdmaudiodev] USB Audio I/F Loop Back
