[alsa-devel] Strange findings about the microphone in SigmaTel STAC9221 A1

Takashi Iwai tiwai at suse.de
Tue May 15 14:26:30 CEST 2007

At Fri, 11 May 2007 10:48:44 +0100,
Ivan N. Zlatev wrote:
> My hda-intel card is with the following codec:
> Codec: SigmaTel STAC9221 A1
> Address: 0
> Vendor Id: 0x83847680
> Subsystem Id: 0x106b1700
> Revision Id: 0x103401
> I am using alsa 1.0.14rc4. I have a built-in microphone, which doesn't
> work, but today I found out something interesting. If I set the
> capture to minimum and place Mux at specific positions (Works with
> middle-ish and top, not bottom-ish) suddenly the mic started
> recording, but the quality is extremly bad. I have attached amixer and
> co. Does anyone have a clue what the issue is and how could possibly
> this little bit of random foundings to be used to possibly fix the
> mic?

If this is 100% reproducible, you'll see likely a difference in
/proc/asound/card0/codec#* file between working and non-working
states.  Could you attach codec files in both states?

The quality problem is perhaps because of the wrong pin setting.
It's set in Hi-Z without vref.  But it's a bit strange because
stac92xx_get_vref() should return the proper vref value.  Could you
check whether this really gets called and which value is returned,
e.g. by adding printk() there?


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