[openal] 5.1 and 7.1 speaker setups

[Ian Reed]

Hi Chris,

Thanks for your help in the other thread.

I have a new question.
Can you explain how the support for 5.1 and 7.1 speaker systems works?

I don't see anywhere to tell OpenAL Soft that the user has a 5.1 or 7.1 
speaker setup.
I do see that I could supply 6 or 8 channels when creating the buffer, 
and set the format to be Multi51Chn16Ext or Multi71Chn16Ext (OpenTK enum 
names).
Does OpenAL Soft then use the virtual speakers to place the 6 or 8 
channels, and then mix that down to a single wave form the sound card uses?
Or is it able to detect 5.1 or 7.1 through the selected device and send 
the extra channels to the OS/soundcard?

Do all sound libraries use virtual speakers to mix down to a single wave 
form when it goes to the sound card, or do sound APIs ever tell the 
sound card directly that they have 5.1/7.1 sound channels?

Thanks for your help, and patience.