Two channel audio output on multichannel audio interfaces

So, here’s the problem: when Vuo outputs a stereo signal with Send Live Audio to a multichannel audio interface, the audio signal is sent to all output channels.

I verified this on two audio interfaces today: a Metric Halo LIO-8 and a Yamaha CX-A5100. It happens with OS 10.10 and 10.11. Maybe it’s a Core Audio “feature”, but is there a way to circumvent this?

Funny thing: the Yamaha can be set to two-channel output and then it does behave as expected, i.e. audio is sent only to channel 1 and 2.

Metric Halo

Yamaha, eight-channel output

Yamaha, two-channel output

If the Send Live Audio node’s Send Channels list has fewer channels than the system audio device, it duplicates the last item in the list. (I don’t see this in the node description. I’ll make sure it gets documented.)

This behavior is to streamline the common case where the composition produces mono audio and you want to send it to both stereo channels.

To send only to certain channels on your audio device, you can expand the Send Channels drawer to as many channels as you have, and only connect cables to the list items corresponding to the channels you want to send.

Oh, I thought I tried that, but obviously I didn’t try hard enough…


That is such a great thing to know @jstrecker! Thanks for adding to the node description! :-)