[alsa-devel] maestro3 & es1988: mic range too low

Takashi Iwai tiwai at suse.de
Mon Aug 18 14:42:42 CEST 2008

At Mon, 18 Aug 2008 15:28:00 +0300,
Ilkka Tengvall wrote:
> >> the reasoning for the original patch sounds reasonable. The
> >> mic volume is tunable, only at the very low range. I recall the laptop
> >> came with Win98, and there was no problem then with the sound -> not a
> >> HW problem. I have never got this laptop mic working with linux, so
> >> this is not anything that broke recently. I see there is
> >> check_volume_resolution function which tries to guess some of the
> >> register ranges, but maybe it get's it wrong with this HW.
> >
> > Maybe, maybe not.  You should check rather ac97 registers in
> > /proc/asound/card0/codec97#0/ac97#0-0+regs.  If build with
> > CONFIG_SND_DEBUG=y, you can write to the register directly, too.
> > See Documentaiton[/sound/alsa]/Procfile.txt.
> >
> I checked this file. It seems it gets the regs right for the mic
> (range 0x1f). The capture range is 0xf. I don't have the specs to
> compare it against, so I assume there is nothing to do more here.

Which registers, exactly?

> It seems mic value decreases while going up to full, where as capture
> increases.

I guess the former one is the mic loopback volume (attenuation), so no
wonder it behaves so.

> Another difference is maybe stereo / mono related, the
> capture changes both bytes whereas mic only the other one. Also one
> thing, should the mic level be around 0x40 - 0x5f, not 0x0 - 0x1f.

The bit 0x40 indicates the mic boost +20dB.


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