Christian!
Did you try ALSA only. It looks like an alsa problem. So tests with aplay or
something might be helpful. You know, that aplay can be launched with a
verbosity switch? I believe you can put -vv (or VV, not sure) there to get
even more output.
With aplay you should playback a file with enough channels, so ALSA doesn't
get confused with channel-counts in audiofile and PCM device.
That might only be a first pointer, but hopefully of some help.
Kindest regards
Julien
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