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Alsa
asound.conf
By default sound is processed through dmix plugin which handles rate and channels conversion.
Plugin: hw
This plugin communicates directly with the ALSA kernel driver. It is a raw communication without any conversions.
To override “default” pcm device and route outputdirectly into hardware:
pcm.!default { type hw card 0 format S16_LE }
With settings above, there is no possiblity to play mono sound (channel=1), when there is stereo audio device.
Plguin: plug
Is a plugin responsible for rate and format conversion.
pcm.!default { type plug slave { pcm "hw:0,0" format S16_LE } }
There might be problems with some programs though. Some applications always try to open a control device with the same name as the pcm device they are given, so you may also need to create a dummy control device with the same name:
ctl.!default { type hw card 0 }