[pulseaudio-discuss] Mic Boost on AC97 audio causes bad behavior of mic volume control

Raymond Yau superquad.vortex2 at gmail.com
Wed Apr 29 19:48:02 PDT 2015


> >
> As I already wrote, the way it is today, if I set 100%/0dB either with
> the GNOME volume control, "alsamixer -D pulse", or "pactl
> set-source-volume 2 100%", the result is 30dB Capture + 24dB Boost,
> which is *not* maximum level. So the user is currently not correctly
> informed about the "real 0dB", even if you factor in the boost.


pulseaudio documentation/wiki on volume only mention sink

> However, for line in, the jumpy behavior of the current input control
> would be even worse than for the Mic. My guess would be that for line
> in, Boost had better be set to 0dB all the time, and "real 0dB" would be
> "30dB Capture + 0dB Boost". You just gave another argument for not
> merging "Mic Boost" into the overall volume.

How did you add Line in support ?

1) use hint add_jack_modes = 1

2) retask mic in jack to line in jack by early patching


- add_jack_modes (bool): add "xxx Jack Mode" enum controls to each
  I/O jack for allowing to change the headphone amp and mic bias VREF

- line_in_auto_switch (bool): enable/disable the line-in auto-switch
  feature; default false

For line in recording, user expect pavucontrol provide a point at the
volume slider which set  Capture Volume and Line Boost at 0dB and no
pulseaudio software volume similar to spdif passthrough to prevent clipping


HDA driver have quirks about limiting the internal mic boost,

The base volume of pulseaudio source is not constant any more

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