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

Wilck, Martin martin.wilck at ts.fujitsu.com
Tue Apr 28 01:33:55 PDT 2015

On Di, 2015-04-28 at 12:10 +0800, Raymond Yau wrote:
> 2015-04-27 19:08 GMT+08:00 Wilck, Martin
> <martin.wilck at ts.fujitsu.com>:
>         On Fr, 2015-04-24 at 13:53 +0800, Raymond Yau wrote:
>         However the driver seems to hide this complexity. For
>         simplicity, we
>         should focus the discussion on the jack mics and leave
>         "Internal Mic"
>         aside. I can only say that from user land, volume control of
>         "Internal
>         Mic" apparently behaved the same as the other two Mics.
> But the mic jack can also be used as line in according to lifeboof
> e744 datasheet, The output jack can be used as line out or headphone
> User need to know the real 0dB at the pulseaudio volume scale when
> using line in 
> http://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/Developer/Clients/WritingVolumeControlUIs/

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.

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.

>         Coming back to the original point, wouldn't you agree that the
>         way these
>         volume controls behave by default is erratic & confusing?
> There are 118 unique dB level out of 256 combination when volume has
> 64 steps and boost has 4 steps.
> Pulseaudio just use ( 64 + 4 ) or ( 4 + 64 ) hardware setting with
> pulseaudio software volume when changing the order of using volume and
> boost 

4 + 64 is working well and uses (almost) all of the 118 steps. 64 + 4
does not. That's one of the points I have been trying to make. 

My other point is that "64" alone, with a fixed Boost setting, would
work best, at least for my hardware, which is a standard Intel C220 HD
audio controller that should be present on many laptops these days.



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