You may need to use something like this in your /.asoundrc to make Alsa output sound to all channels.
pcm.!default {
type route
slave.pcm surround51
slave.channels 6
ttable.0.0 1
ttable.1.1 1
ttable.0.2 1
ttable.1.3 1
ttable.0.4 0.5
ttable.1.4 0.5
ttable.0.5 0.5
ttable.1.5 0.5
}
One page links to Alsa5.1Notes:
lib/main.php:944: Notice: PageInfo: Cannot find action page