Re: 13->14 microphone routing/mixing issues

G. Paul Ziemba wrote:
> Hi,
> 
> I upgraded from 13-stable to 14-stable last week, which seems to have
> changed some aspects of the audio system.
> 
> My microphone is now being played out the speaker, resulting in
> feedback if the microphone gain is above zero. I read the mixer(8)
> man page but I don't understand what is wrong.
> 
> Although setting the microphone gain to zero quells the feedback,
> doing so also means there is no microphone signal toward, e.g.,
> teleconference software in the web browser.
> 
> How can I make the microphone usable again without feeding into the
> speaker?
> 
> Speakers and microphone are attached to the "rear analog" ports.
> 
> % mixer -a
> pcm0:mixer: <Realtek ALC888 (Rear Analog 5.1/2.0)> on hdaa0 (play/rec) (default)
>     vol       = 0.86:0.86     pbk
>     pcm       = 1.00:1.00     pbk
>     speaker   = 0.74:0.74     rec
>     line      = 0.01:0.01     rec
>     mic       = 0.00:0.00     rec src
>     mix       = 0.74:0.74     rec
>     rec       = 0.35:0.35     pbk
>     igain     = 0.50:0.50     pbk
>     ogain     = 1.00:1.00     pbk
> pcm1:mixer: <Realtek ALC888 (Front Analog)> on hdaa0 (play/rec)
>     vol       = 0.84:0.84     pbk
>     pcm       = 1.00:1.00     pbk
>     speaker   = 0.00:0.00     rec
>     rec       = 0.35:0.35     pbk
>     igain     = 0.00:0.00     pbk
>     ogain     = 1.00:1.00     pbk
>     monitor   = 0.67:0.67     rec src
> pcm2:mixer: <Realtek ALC888 (Rear Digital)> on hdaa0 (play)
>     vol       = 1.00:1.00     pbk
>     pcm       = 1.00:1.00     pbk
> pcm3:mixer: <Intel Kaby Lake (HDMI/DP 8ch)> on hdaa1 (play)
>     vol       = 1.00:1.00     pbk
>     pcm       = 1.00:1.00     pbk
> 
> Thanks for your insights.

After a quick search I do not see any change to ALC888 between 13 and
14. However I see your "igain" (input monitoring gain/level) is set to
0.50. What happens if you set it to 0?

$ mixer igain.volume=0

Christos