Sound problems after updating KDE

After updating from openSUSE 11.1 to version 11.2 and the incorporated transition from KDE 3.5 to 4.3 on one PC the sound generated by KDE applications (including system notifications) only worked every once in a while: when logging in it was there or it was not until the end of the session, where this behaviour appeared to be arbitrary and non-reproducible. At the same time, non-KDE programs did not show such bugs, their sound happened to perform faultless.

Apparently, there was an initialization problem: something disturbed the KDE sound system during the session start and depending on whether KDE or the other system won, the symptoms described occured.

There was no contribution in KDE help for this problem. Various internet forums describe similar symptoms and offer approaches, I tried many of them without success, until I finally got the crucial point (unfortunately, I don't know the source anymore): KDE4 and PulseAudio—as of the current versions—do not get along with each other.

Indeed, on my system, PulseAudio was activated. This setting was taken over by the update from the former installation; when doing a new installation of openSUSE 11.2 from scratch, PulseAudio stays uninstalled by default (as it appeared to be at least on another PC), so that the problem in question does not arise in such a case.

Once addressed the cause of the problem, the solution is rather simple:

1. Deinstall pulseaudio along with the packages depending on it. By this opportunity, check if phonon and phonon-backend-xine are installed and all dependencies are resolved.
2. Unfortunately, now non-KDE sound is not working anymore. This is because the system sets two environment variables, SDL_AUDIODRIVER and ALSA_CONFIG_PATH, that still refer to the PulseAudio system. On openSUSE, this takes place in the file /etc/environment, where you should delete or comment out the corresponding entries:
   #ALSA_CONFIG_PATH=/etc/alsa-pulse.conf
   #SDL_AUDIODRIVER=pulse                
   After a relogin both KDE and non-KDE applications are expected to provide sound.
3. If it still happens to malfunctioning, you could try for instance one of the following: deinstall phonon-backend-gstreamer and arts, set the system variable PULSEAUDIO_ENABLE to "no" (in /etc/sysconfig/sound or by the item Hardware/Soundcard in sysconfig editor), add the user to the group audio.