* for the asymmetric output volume -60/18dB, make sure that normalized 50 means 0dB
* slider is centered
* return value if value for volume was changed
For AFV itself, a low latency device is required (which on Windows most likely will pick WASAPI).
For notifications and effects, the most compatible device is required (which on Windows will most likely fall back to QWindowsAudio).
QAudioDeviceInfo is a low level technical class, which shouldn't be used in higher level code. Remove it from all APIs
where possible and just create it in order to interface with QAudio
Different QAudioDevice plugins have different default buffer sizes. In
order to cope with bigger buffer sizes than the expected 20 ms,
let the buffer be filled and push from it every 20 ms via timer.
