Date:	Thu, 12 Jun 2008 12:45:16 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	"Daniel J Blueman" <daniel.blueman@...il.com>
Cc:	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: ALC883 recording troubles...

At Wed, 11 Jun 2008 22:37:49 +0100,
Daniel J Blueman wrote:
> 
> On Wed, Jun 11, 2008 at 8:00 PM, Daniel J Blueman
> <daniel.blueman@...il.com> wrote:
> > On Tue, Jun 10, 2008 at 6:59 AM, Takashi Iwai <tiwai@...e.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.
> 
> Looking at the datasheet and ALSA report, changing the front mic node
> id also affects capturing from the (rear) mic input.

Depends on the hardware implementation.  But, usually, no, different
pin widgets are assigned for front and mic jacks.

> ftp://66.104.77.130/pc/audio/ALC883_DataSheet_1.3.pdf
> 
> We get the "hda_codec: Unknown model for ALC883, trying auto-probe
> from BIOS..." kernel message, so we may need to tweak
> pci/hda/patch_realtek.c.

Note that this is no error but information.  The driver has preset
models for known devices and use the static configuration table for
such devices.  For other devices, the driver just relies on BIOS
setup.

> Also, I can reproduce the problem the with HD
> and legacy front-panel audio settings in the BIOS. Do you know a way
> to dump eg the pin configuration in windows or other useful state, so
> I can compare with all the possible node ID configuration values?

Sorry, no, I've not booted Windows over years :)


Takashi
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