[Realtek ALC268] Recording problem on Acer Aspire One (ZG5)

This is a report for Ubuntu 10.10 (Maverick Meerkat). After some investigation, my intuition is that it is the result of an interaction between PulseAudio and ALSA.

State #1
     Fresh install
     sudo apt-get update && sudo apt-get upgrade
Symptoms:
     Recording from the built-in microphone works from the Sound Recorder but not from Google Talk, Skype, etc.

State #2
     sudo apt-get install pavucontrol
     set the left and right inputs to different levels, as suggested on various forum posts
Symptoms:
     Recording from the built-in microphone works in Google Talk for a short time (< 2s), but then dies.

State #3
     sudo apt-get install linux-alsa-driver-modules-$(uname -r)
     sudo reboot
Symptoms:
     No change

State #4
     sudo apt-get purge libcanberra-pulse pulseaudio pulseaudio-esound-compat pulseaudio-module-bluetooth pulseaudio-module-gconf pulseaudio-module-udev pulseaudio-module-x11 gstreamer0.10-pulseaudio pulseaudio-utils pavucontrol
     sudo reboot
Symptoms:
     No change

State #5
     sudo echo "options snd-hda-intel model=acer-aspire" > /etc/modprobe.d/alsa-base.conf
     sudo reboot
Symptoms:
     Recording is now working in Google Talk, Skype, etc, but the result is extremely noisy. There is a loud hum/buzz in the background. Changing the input volume/gains in alsamixer causes the recording to go silent.

Hope that gives you some leads!
~br

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: alsa-base 1.0.23+dfsg-1ubuntu4
ProcVersionSignature: Ubuntu 2.6.35-23.41-generic 2.6.35.7
Uname: Linux 2.6.35-23-generic i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC268 Analog [ALC268 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC268 Analog [ALC268 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: br 2300 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0x58540000 irq 45'
   Mixer name : 'Realtek ALC268'
   Components : 'HDA:10ec0268,1025015b,00100101'
   Controls : 9
   Simple ctrls : 6
Date: Sun Dec 19 19:49:07 2010
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SelectedCard: 0 Intel HDA-Intel - HDA Intel
SourcePackage: alsa-driver
Symptom: audio
Title: [Realtek ALC268] Recording problem
dmi.bios.date: 05/09/2008
dmi.bios.vendor: Acer
dmi.bios.version: v0.3114
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.vendor: Acer
dmi.board.version: Base Board Version
dmi.chassis.type: 1
dmi.chassis.vendor: Chassis Manufacturer
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAcer:bvrv0.3114:bd05/09/2008:svnAcer:pnAOA150:pvr1:rvnAcer:rn:rvrBaseBoardVersion:cvnChassisManufacturer:ct1:cvrChassisVersion:
dmi.product.name: AOA150
dmi.product.version: 1
dmi.sys.vendor: Acer