Comment # 7 on bug 961143 from Wolfgang Rosenauer

Hmm, the touch points between Mozilla and GStreamer I commented above. For
pulseaudio vs. Mozilla I never heard of generic issues but what you also can
make sure is to wipe ~/.cache/gstreamer-1.0 once because I've seen media output
fail because of a broken cache.

Mozilla does not maintain any sound output cache like thing. So if it's really
about a copy of a file which now causes the sound to break I have no idea what
this could be Mozilla specific. Also when you removed .mozilla and it still
fails I don't see Firefox really involved here. The difference to Konqueror
and/or Chromium is likely mainly just the difference of the integration of the
different frameworks (here GStreamer and pulseaudio/alsa) and their
configuration in the user profile.

Is Firefox able to provide _any_ sound output? Think about WebM, OGG, WAV so
it's entirely clear if it's GStreamer or "just" the output?