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    SubjectRe: ALC883 recording troubles...
    On Thu, Jun 12, 2008 at 11:49 AM, Takashi Iwai <tiwai@suse.de> wrote:
    > At Wed, 11 Jun 2008 20:00:17 +0100,
    > Daniel J Blueman wrote:
    >>
    >> 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.
    >
    > You can try to adjust VREF value of mic pins.
    > For example, the node 0x18 and 0x19 correspond to the rear and front
    > mics, respectively. Then run the following as root:
    >
    > # ./hda-verb /dev/snd/hwC0D0 0x18 SET_PIN_WID 0x21
    >
    > which will change the widget 0x18 (rear mic) to input-VREF 50%
    > (0x21). The original value is input-VREF 80% (0x24).

    Yes, I had tried this and it does not help, perhaps only changing the
    magnitude of the sampled mic input.

    Another smoking gun, is when changing certain mixer settings (both on
    gnome-mixer and alsamixer), eg playback->front mic amplitude, moving
    the slider up and down, the L/R linking seems to be almost randomly
    unlinked and the other L/R channel jumps to a different value. When
    re-linking the L/R channels, often, it'll unlink again and change both
    value after reading back the change; mute can be erratic too.
    Confirmed with 2.6.26-r5.

    Is there a good way to debug this also?

    > Takashi
    --
    Daniel J Blueman


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