How can I use an audio device's other channel for input to iChat and Skype?

Question

I have an external microphone setup that I like to use for audio and video chats. My audio interface has four input channels, and my primary inputs to this interface happen to be its channels 3-4. When I view System Preferences -> Sound -> Input and select the interface, I see levels as would be expected, but doing the same in iChat or Skype preferences show no level.

When setting up GarageBand to use this interface, I notice that it provides two stereo channels: 1-2 and 3-4. I am thus led to believe that System Preferences shows a total of all levels on all channels, while iChat and Skype simply default to the 1-2 inputs and ignore the rest.

Is there some way to send channels 3-4 of my external audio interface (it's a ProSonus Inspire1394) to iChat and Skype? I couldn't find anything in Audio MIDI Setup to help out, but maybe someone knows specifics.

Answer 1

Well, seems like I just had to think about it a little bit more. My workaround is not possible using only system utilities. I used Soundflower and LineIn from Rogue Amoeba software.

Using LineIn, I could select channels 3-4 specifically from the PreSonus device and route those to the two-channel Soundflower device. Then, I simply selected the Soundflower device as my input in iChat.

Answer 2

In general, Soundflower is the app of choice when discussing /any/ of these "how do I route audio from application X to application Y" type questions.