reference
http://www.cse.ohio-state.edu/~bondhugu/surround-pulse.shtml
http://nemonein.egloos.com/4164489
1. vi /etc/pulse/daemon.conf
uncomment default-sample-channels line
and
default-sample-channels = [the number of channels]
(6 for 5.1 ch, 8 for 7.1 ch)
2. alsamixer -c 0
control the volumes and save
alsactl store
3. restart
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