no 5.1 audio support

5.1 audio (6 channels) is not supported by QAudioDeviceInfo.

Reading qaudiodeviceinfo_win32_p.cpp / qaudiodeviceinfo_alsa_p.cpp I can see :

QAudioDeviceInfoInternal::updateLists()
{
...
channelz.append(1);
channelz.append(2);
...
}

which explains why audio is forced to mono/stereo only.
I'm building a desktop cross-platform surround audio application, so that's a blocker feature...