Public bug reported:
Binary package hint: pulseaudio
after updating from intrepid to jaunty pulseaudio does pretty weird stuff.
_sometimes_ when i start a playback (be it from audacious or a flash movie in
firefox) the pulseaudio process consumes all cpu time (of one core) and noise
and crackles get louder and louder. after about 30 seconds (i think thats
varying) everything gets back to normal.
the noise heard seems to come from a feedback loop of the input: when i stop
the input, the noise instantly stops too. if i restart the playback the noise
level drops and grows exponentially afterwards. i can repeat this... whenever i
hit play, which restarts the playback, i can notice the noise level drop and
the growth afterwards.
note that cpu load is independent of the input (control): it is triggered by
the start of the playback, but is not affected by stopping/replay etc. it just
ends after a while.
from my high level perspective this sounds like an unstable
oscillator/filter. as if there is a filter coded in pulseaudio that uses
its own output at some stage... and somehow the filter loop uses much
more samples (of previous output) because of a variable over or
underflow... but i have no idea whats really going on under the hood :)
the noise stops when i stop the input, not when i mute my main (=PCM)
control. maybe this is related to #272321.
sorry for the quite untechnical report, i have just a faint idea of how
the audio stack works.
ProblemType: Bug
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC0: ameno 5466 F.... mixer_applet2
Card0.Amixer.info:
Card hw:0 'Intel'/'HDA Intel at 0xd0620000 irq 22'
Mixer name : 'Intel G45 DEVELK'
Components : 'HDA:111d7676,80865002,00100202
HDA:80862803,80860101,00100000'
Controls : 51
Simple ctrls : 31
Card1.Amixer.info:
Card hw:1 'Bt878'/'Brooktree Bt878 at 0xd0701000, irq 21'
Mixer name : 'Bt87x'
Components : ''
Controls : 3
Simple ctrls : 5
DistroRelease: Ubuntu 9.04
Package: pulseaudio 1:0.9.14-0ubuntu20.1
SourcePackage: pulseaudio
Uname: Linux 2.6.29-02062902-generic x86_64
** Affects: pulseaudio (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug
--
virtual feedback loop with high cpu load
https://bugs.launchpad.net/bugs/375822
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