Comment 71 for bug 886449

@Julian, thanks for testing. I just verified that the package in quantal indeed have a four-channel-input section:

(Copy-pasted from /usr/share/pulseaudio/alsa-mixer/profile-sets/default.conf )

[Mapping analog-4-channel-input]
# Alsa doesn't currently provide any better device name than "hw" for 4-channel
# input. If this causes trouble at some point, then we will need to get a new
# device name standardized in alsa.
device-strings = hw:%f
channel-map = aux0,aux1,aux2,aux3
priority = 1
direction = input

Can you verify that your file also has this section, that you're running Ubuntu 12.10 (not 12.04), that PulseAudio is version 2.1 (pulseaudio --version), and if all this is true, also send a PulseAudio verbose log ( https://wiki.ubuntu.com/PulseAudio/Log ) for further analysis?
Thanks!