Frame skipping when playing 720p 50/60fps video on a 1080p60 monitor using vo=gpu-next with gpu-api=opengl.

Important Information

Provide following Information:

• mpv 0.38.0_181_g467c1e860a-1
• Arch Linux with KDE Plasma Desktop (Wayland session)
• AUR (mpv-git)
• I don't known which version of mpv introduced the problem
• KWin 6.0.4 (without using scaling)
• Intel Graphics HD 4600 / libva-intel-driver 4.2.1

My configuration:

vo=gpu-next
hwdec=vaapi
gpu-api=opengl
vf=vavpp:deint=motion-compensated:interlaced-only=yes (put in a separate profile for "video-frame-info/interlaced" == true).

I sometimes watch various sports broadcasts. Often it's 1080i50 and I don't notice any issues with frame drops or jerks. Everything looks fine when I turn on a 720p50 broadcast and watch in a window. But I immediately see a slideshow when I expand the window to full screen mode. I can also see frame skipping in the log. It is logical to assume that the problem is related to scaling. I specified explicitly scale=bilinear and the frame skipping almost stopped. But with all other better scaling options everything works terribly. When using vo=gpu with default scaling there is also frame drops but not as bad.

I installed the Vulkan driver today and specified gpu-api=vulkan. With these parameters everything works as expected. Maybe the problem is related to OpenGL in Wayland or specifically KDE.

gpu-next-opengl.log

Start by reviewing gpu-next-opengl.log and reproducing the stated 720p50/60 fullscreen case on KDE Wayland with gpu-api=opengl, comparing bilinear scaling and Vulkan behavior. The issue is resolved when fullscreen playback no longer shows the reported frame skipping with the affected scaling options.