[Regr: 5->6] Video QML different issues in timing and events

To play out video I am depending on the onStopped events of the QML Video element to start other elements. I have noticed since I ported my code into the 6.4 branch all kind of strange thing started to happen with the new video framework on various platforms.

On Alpine Linux (muslc) some of the more lower grade systems I most promently see the behavior where sometimes (or most of the time) the video never reaches the total duration of the video. As an example a video that is exactly 2.0s, plays up to 19.84s and does not trigger the stopped signal.

It feels so broken, that an issue must exists. I have just been unable to find it.

./myapp -platform eglfs
(myapp:2639): GLib-GObject-CRITICAL **: 16:30:31.851: g_object_unref: assertion 'G_IS_OBJECT (object)' failed

(myapp:2639): GLib-GObject-CRITICAL **: 16:30:31.866: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
qml: 1 170
qml: 1 671
qml: 1 1171
qml: 1 1671
qml: 1 1984
qml: 1 1984
qml: 1 1984

It is also not exclusively broken. Sometimes the first video plays, where the first nicely stops, but the second never triggers the onStopped.

qml: 1 194
qml: 1 695
qml: 1 1195
qml: 1 1695
qml: video second play
qml: 0 0
qml: 0 0
qml: 0 0
qml: 0 0
qml: 0 0

On more beefy systems running ArchLinux the videos were in fact played out, but onStopped sometimes mysterically triggers while playing in the middle of a video. In that case the video is already cut short after one second, rather than its full duration.

In the logging.txt I noticed there would be another backend possibility than gstreamer. When applying QT_MEDIA_BACKEND=ffmpeg at this moment I am positive on the behavior. Thus this might be a gstreamer related issue.