How to adjust DMIC gain (or audio volume) ?

[jonathanh]

What’re the problems:
(1) The sound output volume is decent but not enough when the setting in system, sound, output is max out. Still searching solutions in how to further increase the volume (or DMIC gain) and how to use software to adjust the settings.

(2) The command ‘amixer -c tegrasndt186ref sset “DMIC3 Boost Gain” 25600’ would boost the gain and significantly increased audio record volume. But the also causes the stereo sound automatically converted to mono. Is there a command to boost the gain for stereo DMICs?

(3) “cset” the master volume control (MVC) with the commands as show in post#2 would instead fail the audio. No sound was produced by the commands. What’s the proper way to set the MVC?

(2) I think that there is a bug in the driver because ‘25600’ is too big and I seeing the following error in dmesg when this is set …

[ 314.961362] tegra210-dmic tegra210-dmic.2: Boost Gain overflow

The max value should be ‘25599’. This is not your problem, but FYI, this value is too big. We need to fix the driver so that it shows the correct limits and not …

Simple mixer control 'DMIC3 Boost Gain',0
  Capabilities: volume volume-joined
  Playback channels: Mono
  Capture channels: Mono
  Limits: 0 - 25600
  Mono: 0 [0%]

So I tried testing this and setting the gain to ‘400’ and I was able to verify that this worked and both channels were amplified. Setting the gain to 25599 also worked, but it was inaudible, basically noise, but again I did not have any issues with recording stereo. So at the moment, I am unable to reproduce this problem on my side. Can you try lower gain settings and see if you have the same problems?

(3) Your MVC settings look good to me and work for me. So per my other response check the Mux settings to make sure DMIC is not being routed to more than one device.

Regards,
Jon