forcing two channel output

Alexander Motin mav at
Fri Aug 28 17:38:07 UTC 2009

Andriy Gapon wrote:
> Please see verbose dmesg here:
> I get 4 pcm devices and I understand their functions as following:
> 0. digital hdmi
> 1. analog rear
> 2. analog front
> 3. digital
> It seems that when I use dsp1 sound goes to 4 jacks at the rear.

Indeed. Your Codec is configured for 7.1 output, but snd_hda at this 
moment does not support more then two channels. So for historical reason 
it duplicates stereo output to every channel pair. I am going to look at 
this again after 8.0 release.

> But I have only a simple stereo system connected to only one output.
> Should I do anything?

You can, if you want/need it.

> Can I tell sound driver and hardware to not bother and route sound to only one output?
> Should I simply disable the unused jacks (with as=0) or maybe split them off to
> separate pcms that I won't use?

You can do whatever you like: disable them with as=0 or turn into many 
separate devices with as=15, or even turn them into many additional inputs.

Alexander Motin

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