https://bugs.kde.org/show_bug.cgi?id=527858
Bug ID: 527858
Summary: Night Light causes heavy dropped frames in video
playback on Wayland, especially in fullscreen (AMD RX
6600, 4K)
Classification: Plasma
Product: kwin
Version First unspecified
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: night color
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
With Night Light enabled, video playback on Plasma Wayland drops a large number
of frames, much more in fullscreen than in a window. With Night Light disabled,
dropped frames stay in the single digits (in Brave/YouTube). No driver errors
are logged and GPU load is low.
ENVIRONMENT
- Operating System: CachyOS Linux
- KDE Plasma 6.8.1, KDE Frameworks 6.31.0, Qt 6.12.0
- Graphics platform: Wayland (KWin)
- Kernel: 7.3.0-4-cachyos (also reproduced with 6.18.55-2-cachyos-lts)
- Mesa 26.2.5, radeonsi / RADV
- GPU: AMD Radeon RX 6600 (Navi 23)
- CPU: Intel Core i7-9700F, 32 GiB RAM
- Display: 3840x2160@60 via DisplayPort, scale 1.75, VRR: Never, HDR disabled
- Night Light mode: Sunrise and sunset
STEPS TO REPRODUCE
1. Enable Night Light in System Settings (mode: Sunrise and sunset).
2. Play a 4K60 video in mpv with:
mpv --vo=gpu-next --gpu-api=vulkan --gpu-context=waylandvk --hwdec=vaapi
<video>
(YouTube in Brave also shows it.)
3. Press Shift+I to show the stats. Note the "output" dropped frames in the
window, then press F for fullscreen.
ACTUAL RESULT
- Night Light enabled: mpv dropped 47 frames in the window and 1115 in
fullscreen. YouTube in Brave shows a steep rise in dropped frames after
entering fullscreen, and YouTube lowers the resolution.
- Night Light disabled: dropped frames in Brave/YouTube stay in the single
digits, in the window and in fullscreen.
EXPECTED RESULT
Night Light should not influence the frame rate of video playback.
ADDITIONAL OBSERVATIONS
- GPU load stays below 35 % during playback. The journal shows no amdgpu
errors, resets or timeouts.
- Not related to: kernel version, Brave vs. Firefox vs. mpv, hardware decoding
(decoder drops 0 frames), Adaptive Sync/VRR, resolution (1080p behaves the
same), scaling (100 % behaves the same), or KWin direct scanout
(KWIN_DRM_NO_DIRECT_SCANOUT=1).
- mpv with --vo=dmabuf-wayland (no GPU rendering) drops almost no frames (2 /
4).
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