severe playback stutter (looks like dropped frames) with ‘Plex HTPC’ running at 23.976Hz (either through enabled RefreshRate switching or when set manually)
skipping forwards or backwards a couple of times FIXES the issue and the playback gets smooth
skip again (or pause/unpause) and it stutters again
when refresh rate switching is disabled, and ‘Plex HTPC’ runs at 2160p60, then there is no severe stutter - only expected minor hiccups due to the 24FPS->60Hz mismatch
Kodi does not show that behaviour with refresh rate switching enabled or when RR is set to 23.976Hz
MediaPortal does not show that behaviour with refresh rate switching enabled or when RR is set to 23.976Hz
mpv does not show that behaviour when RR is set to 23.976Hz (edit: the standalone build I download came with an mpv.conf and custom settings, this is why it did not show the issue, plain mpv has the stutter issue too)
MPC-HC with MadVR does not show that behaviour with refresh rate switching enabled or when RR is set to 23.976Hz
on my AppleTV 4k movie playback in the Plex App is smooth with refresh rate switching enabled
when I forcefully disable v-sync for Plex HTPC inside NVCPL then this fixes the stutter, but obviously leads to tearing (v-sync might be connected to this stutter though)
My conclusion based on that data: something is wrong with the Plex HTPC application when the refresh rate is set to a matching 23.97Hz
Is this be caused by Plex HTPC not running the player in exclusive fullscreen mode?
Went through the hassle of testing this on a 2nd PC, with the exact same outcome.
No one else using the Plex HTPC application with refresh rate switching / 23.976Hz?
I noticed something similar, also with the same workaround to disable v-sync… However, I could also see that same behavior in mpv. I used Gravity at minute 8 or so (earth panning shot) to verify “perfect” or “broken” playback. I tried it with d3d11 and vulkan backends and it seems only the d3d11 backend is broken.
On my end, this happened after updating to the newest nvidia driver (RTX 3050)… Reinstalling one specific version fixed it for me. Version 512.96 Studio to be precise. Restarting from scratch by reinstalling windows or reinstalling a newer version with an earlier DDU uninstall did not fix this. I also filled out the nvidia driver bug form but no response there (yet).
Maybe you can also try using the Vulkan backend and/or the mentioned driver (DDU first)?
(Vulkan backend => mpv.conf in the Appdata/PlexHTPC dir with the following line gpu-context=winvk added)
Only issue with the above settings is that the system does not switch HDR off once you stop the playback.
only when you play a SDR video or close PLEX HTPC it will turn off HDR.
great find! installing that driver has indeed fixed the issue!
FWIW, these two values (I elided the one that I’m not speaking to) will be set by an option in the GUI in a future version which allows HDR metadata passthrough to the display. Do note that this is experimental so expect that it may have some issues.
So finally had time to test this and wow! Indeed adding swapchain-depth=1 to the mpv.conf file with a new driver (i tested 522.30, still affected but not as immense as versions before) has fixed the stuttering on my setup, also without introducing more dropped frames. Awesome! Thanks for the tip!
Glad to hear that this works for you too! @gbooker02 is this worth to be considered to be added to the default config? or could that option cause problems?
For us it fixed the severe stutter.
I was waiting to see what the results here were before considering it. The question is what does it do on non-NVIDIA systems? Is it detrimental to Intel or AMD setups for instance?
I don’t know where to add swapchain-depth=1 (found the file, don’t know exactly where to add it.) I installed 512.96 driver and fixed the stuttering. I read that in future updates adding the line will be gone so I will stay with this one that works.
If I had to guess, you didn’t find the file but instead found the mpv.conf.md file because the actual file doesn’t exist until you create it. You just create the file, add this one line to it, and that’s all. If you want to confirm that it works, it will show up in the application logs as it reads your mpv.conf.
Yes it’s md, I thought as notepad opened it that is a system file that would change with an update. So I just create a txt file with this line in the folder?
As promised I now had some time to test the swapchain-depth setting on my AMD RX580 system as well. It works fine with the setting set inside the mpv.conf. I have not seen any weird behavior, playback was smooth as expected.
Unfortunately the setting is good for the 23,97 movies but not for the others. I had to reinstall the old nvidia driver as above to play everything smoothly. Forgot to remove the setting with the old driver and stuttering was more than obvious. I think plex was experimenting with this driver and the changes after that killed it. Now I play everything with the old driver without the swapchain-depth setting and play perfect.
