Convert to 60fps

[frozensolid]

Hmm,.. there are the following options:

• Filtering->Avisynth->Frame->FPS adjust (+ Avisynth Preview), or
  
• Filtering->Vapoursynth->Other->Frame Interpolation ( + Vapoursynth Preview), or
  
• Filtering->Speed Change->Speed Settings->Interpolate frame rate (in this case the preview will just play double speed and not show the effect, since MPlayer doesn't support interpolating frames)
  

Assuming you used either Avisynth or Vapoursynth for the frame interpolation, Avisynth/Vapoursynth Preview should work fine.
If it doesn't, create a debug output level 9 (read sticky) and I can look into it.

Cu Selur

[*]

here is the debug https://www.mediafire.com/file/y3egjnapj...t.txt/file
here is the video on what happen exactly https://www.mediafire.com/file/66e2ny2ut...1.mkv/file