Although its already being mentioned on other thread , i preferred creating new thread because i believe i have good examples to reproduce the problem easily.
Playback is just fine when subtitles are off (talking about text one , simple srt file)
But when subtitles are on , it seems there is frame skip(s) every time subtitle is shown (not while it displayed).
I have some test judder videos which i created a dummy subtitles for them (they are audio-less so audio output problem is out of the equation)
They are downloadable from https://drive.google.com/drive/folders/1ewxril7331dlillggkfnlkcg8qwrtxc1 (also uploaded 1 zip of single frame rate movie here)
There is a file for each frame rate (23.976-59.940) , the srt files have the same content just different filename.
When playing back the file you can notice :
1.First time subtitles is show (text is "line 1") there is a frame skip (i think this problem also happened on previous libreelec/rpi)
2.When "line 1" is removed , no problem.
3.Now , when "line 2" is shown there is again a frame skip , but since "line 3" and "line 4" are shown with a 1 second wait , it seems there is no frame skip.
4."line 5" comes after a longer break , so again a frame skip and so does "line 7".
In my setup , the skips are most noticeable on the 59.940 file (highest frame rate) but can be noticed also on the lower ones (30.0 and 25.0 seems to be harder to spot).
Please note that in order to check the files properly you need
1.Enable change refresh rate on playback start (so 24fps file will be used under 24p resolution)
2.Disable any motion interpolation/compensation on your TV/monitor if you have any enabled (Generally i don't recommend using it )
Hope this help in fixing this issue.
Please let me know if anything else is needed.