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

[Raymond Yau]

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/


> > > Here is how PA, Capture, and Boost volume, in dB, correlate in the
> > error
> > > case (i.e. if "Capture" is listed before the relevant "Mic Boost" in
> > the
> > > path conf file, the current PA default). PA volumes are obtained
> > using
> > > "pactl list sources", Capture/Boost values using "amixer -c1 get
> > > <scontrol>":
> > >
> > > PA(%)   PA(dB)  Captu   Boost   Capture+Boost-66dB
> > > 121%    5.00    30.00   36.00   0.000000
> > > 100%    0.00    30.00   24.00   -12.000000
> >
> >
> >
> > >
> > > In contrast, if I list "Mic Boost" before "Capture" in the path conf
> > > file, it looks like this:
> > > PA(%)   PA(dB)  Captu   Boost   Capture+Boost-dB
> > > 121%    5.00    30.00   36.00   0.000000
> > > 100%    0.00    29.25   36.00   -0.750000
> >
> > If base volume is -66dB , why maximum volume and boost is 121%?
>
> > Seem total hardware gain exceed pulseaudio limit on maximum gain
>
> Sorry for causing confusion. I had observed that setting "0dB" or "100%"
> in PA didn't actually set full HW volume (actual volume was -12dB or
> -0.75 dB, see above). So I let my test script move beyond 100%, and
> because my it made 5dB steps, this has set +5dB/121%. I might as well
> just set 100.01% in PA. I seems to be necessary to go slightly beyond
> 100% in PA in order to reach the actual maximum (+30dB Capture and +36dB
> Boost). That may be a rounding problem. It's not relevant to my point
> here (well, some may argue that getting -12dB when you set 100% volume
> is unexpected, but that's a minor issue for me).
>
> 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
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