>
> On Tue, Jun 10, 2008 at 6:59 AM, Takashi Iwai <tiwai@suse.de> wrote:
> > At Mon, 9 Jun 2008 20:59:00 +0100,
> > Daniel J Blueman wrote:
> >>
> >> Hi Takashi-san,
> >>
> >> I'm experiencing DC offset with the microphone on 2.6.24 (Ubuntu 8.04
> >> LTS x86-64). I can see on Audacity that the DC offset that varies with
> >> the recording capture level.
> >
> > Could you elaborate? The mic bias level could be changed via the pin
> > control value. Usually, it's set as VREF 80%.
>
> When the recording->capture level is set to 0, the mic has no DC
> offset as expected. Maxing the recording->capture level, the mic input
> is saturated, in between, we see a linear connection.
>
> >> Plus, the mixer playback->mic-boost
> >> muting enables/disables mic-boost in recording.
> >
> > This is a known bug in alsa-lib mixer abstraction. No kernel issue.
>
> >> It feels like the ALC883 pins aren't configured quite right. The mobo
> >> is an Asus P5E-VM with current BIOS [1]
> >>
> >> What's the routine to debug this? Would it help to install windows,
> >> dump the register space and compare?
> >
> > You can find *.INI file that contains the default pin configuration
> > in Windows. This might be useful in the case BIOS is broken but
> > Windows does a black magic.
>
> That'll be these defaults stashed in the INF file [2]. Let me know if
> it's not what you expected and I'll publish the complete INF file.
>
> > Anyway, please run alsa-info.sh with --no-upload option and show the
> > generated file here. It contains the codec information and mixer
> > setup.
> >
http://hg.alsa-project.org/alsa/raw-file/tip/alsa-info.sh
>
> See [3].
>
> > Also, you can adjust the pin setting on the fly via hda-verb utility
> > below:
> >
http://ftp.suse.com/pub/people/tiwai/misc/hda-verb-0.2.tar.bz2
> >
> > Don't forget to build snd-hda-intel module with
> > CONFIG_SND_HDA_HWDEP=y to use this command.
>
> I'll give this a shot if I get time.
