Binary package hint: linux-image-2.6.32-22-generic
Sometimes during audio playback, a kernel thread named "[hd-audio0]" will consume excessive amounts of CPU and cause audio crackling. It seems to be more easily triggered when displaying video in fullscreen (or Rhythmbox visualizations) or dragging windows around while playing music, somehow relating it graphics operations (running default radeon driver with KMS and Compiz).
This all started after moving from Ubuntu Karmic to Lucid (never had this problem before).
Setting package to kernel, since it's probably alsa snd_hda_intel kernel module which is to blame.
Ubuntu 10.04 x86, Intel Core Duo 2GHz, 3GB RAM, ATI X1400 Radeon Mobility graphics.
Audio chip: Analog Devices AD1981 [HDA]
WORKAROUND: Disabling radeon KMS makes all the audio crackling go away.
Attaching:
* Screenshot of top running over Rhythmbox w/fullscreen visualizations, showing [hd-audio0] consuming more CPU than everything else at the time (audio crackles).
* Output of "lspci -vvnn"
* Output of "dmesg"
* Contents of /proc/interrupts
* ALSA info, as provided by the alsa-info.sh script.
Related to this: https://bugzilla.kernel.org/show_bug.cgi?id=14935 ???
Currently testing if "position_fix=1" option to module snd-hda-intel will help.