Bug 515212

Summary:	Panel sometimes appears on top of fullscreen MPV window with 23.98 FPS video and 164.80 Hz refresh rate screen
Product:	[Plasma] kwin	Reporter:	Sami <lappalainen.sami>
Component:	general	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	nate, niccolo.venerandi
Priority:	NOR
Version First Reported In:	6.5.5
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
See Also:	https://bugs.kde.org/show_bug.cgi?id=474488
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Sami 2026-01-28 17:05:39 UTC

SUMMARY

When playing a fullscreen video in mpv, the plasma panel sometimes appears on top of the video for a frame or 2. This only happens with 24 (23.98) fps video, when I have my monitor set to 165 (164.80) Hz. When using 144 Hz, the ratio of refresh rate to video framerate is a nice integer. With 165 Hz that is not the case. I've tried different video-sync and interpolation options in mpv, but they only make it worse. video-sync=display-resample is the best one, but it still happens with that one as well. Looking at the mpv stats overlay, mpv delays a frame every time the panel appears (or the panel appears every time mpv delays a frame, not sure which one causes which).

STEPS TO REPRODUCE
1. Set monitor refresh rate to 165 Hz
2. Play a 24fps video in mpv

OBSERVED RESULT
Panel keeps flickering on top of the video

EXPECTED RESULT
Panel does not do that

SOFTWARE/OS VERSIONS
Linux: Arch Linux 6.18.6-zen1-1-zen (64-bit)
KDE Plasma Version: 6.5.5
KDE Frameworks Version: 6.22.0
Qt Version: 6.10.1
Wayland
AMD

ADDITIONAL INFORMATION

The 2 workarounds I have found are setting your refresh rate to 144, or making a window rule for mpv to force it to stay on top of other windows.

This does not happen with 60fps video, even though the ratio of frames to refresh rate is not an integer in that case.

Not sure if adaptive sync affects this, but I tried with it off and the result is the same. Also tried allowing tearing in fullscreen windows.

This did not happen on an older version of Plasma but I'm not sure which one it was because I don't update my system as often as I probably should.

Not sure if this is an mpv bug or a KDE bug, but it feels like a KDE bug to me, considering it's only the panel that does that.

Visually very similar to, (if not the same as) this bug https://bugs.kde.org/show_bug.cgi?id=474488