I have a bose USB audio 5.1 device, a generic USB audio device.
I noticed that the proper channels routing was missing from the default
generic
USB pcm, but dmix was used. And for the surround pcms I noticed it was the other way around!
I did modify the default pcm to include a routing plugin. I put 8
channels in
the routing plugin. I guess the proper way would be to detect the hw card number of channels and select a route plugin configuration with the
correct
count of channels (maybe their is a function to get that info?).
I linked the surround51 and surround71 pcms with the 'disable-able' dmix section from the default pcm.
I did not touch the surround40* pcms, surround pcms which are specific to
some
cards and the iec958 ones.
Post the output of your usb audio
lsusb -vvvv
Most likely your usb audio device does not support stereo
Post output of alsa-info.sh
Pulseaudio don't support if your volume control have more than two channels
http://cgit.freedesktop.org/pulseaudio/pulseaudio/commit/src/modules/alsa?id...