support surround sound (aka 5.1 / aka 3D sound / aka multi-channels)

Issue #113 new
Pierrick Koch created an issue

I found 2 source mentioning surround sound:

but the mixer's doc says :

//The channels argument is used to specify whether to use mono or stereo. 1 for mono and 2 for stereo. No other values are supported (negative values are treated as 1, values greater than 2 as 2).//

I'm using: