This has been reported by numerous users of KStars. Audio notifications playing in KStars are leaking file descriptors, often leading to the App failure to save or generate any new files. The only warning in the logs we get is this: 2020-09-27T02:15:20.064 CEST DEBG ][ default] - WARNING: Phonon::createPath: Cannot connect Phonon::MediaObject ( no objectName ) to Phonon::AudioOutput ( no objectName ). This was reported mostly on Raspberry PI buster, but also on Ubuntu 20.04. When on Plasma (KDE Neon), there is no issue in playing the sound or the leaky file descriptor. Is it possible that failure to play sounds does not clean up a file descriptor that was prepared to play the sound but then failed?
We keep getting more reports from users where KStars using Phonon notifications is breaking their system: https://indilib.org/forum/ekos/10705-kstars-ekos-freezing-on-large-image-sequences-astroberry.html#77529 Is this some packaging issue? Phonon issue? upstream? downstream?
Which phonon backend is installed/used?
Whatever phonon backend available for Raspberry PI OS (Buster), so I guess this: https://packages.debian.org/buster/phonon-backend-vlc Running ldd /usr/bin/kstars yields this: libphonon4qt5.so.4 => /usr/lib/arm-linux-gnueabihf/libphonon4qt5.so.4 (0xb2ca4000) which points to this: libphonon4qt5.so.4.10.2
Hm. I see the forum thread mentions gstreamer though. Perplexing. The Warning you posted doesn't really say anything. Just that the media graph cannot be built (supposedly because the backend encountered some error). Somewhat relatedly: is there a reason you don't use knotifications instead of phonon directly? Specifically knotifications would preferably build with libcanberra rather than phonon.
It could have been gstreamer, I'm not sure. We don't use phonon directly, this error is triggered by this: KNotification::event(name, message); If the event had sound enabled (which is by default by many events), then we get the Phonon error and it starts leaking file descriptors. Eventually, the situation goes out of hand and KStars crashes due to this.
You should talk to the distro then. On Linux in particular we expect knotifications to be built with canberra, not phonon.
Reported in Debian/Raspian as https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1000549
The respective Debian bug has been closed on Feb-11th, see above. So slowly this should trickle now through the different distributions (experimental -> testing -> stable)