Following up: I’ve tried that pipeline on all of the previously bugged systems after installing gstreamer1.0-libav.
Tested with local files, SoundCloud, TuneIn, SomaFM and Spotify.
It works well with all the types except Spotify tracks. When I try to play any Spotify track I encounter the same symptoms I experienced with GStreamer 1.14 without libav (playback stuck at 0:00), plus the Audio buffer stats requests, but no listener traces during the failed playback.
I’m not sure if it’s an issue with any additional encoding performed by libspotify, but it sounds to me like the GStreamer pipelines that involve encoding have become quite brittle/unstable after 1.14 (could it be related to the changes to the async logic?) and it’s probably worth a bit more investigation from the devs.