For my Avisynth/MEncoder setting I have this setup for watching old 4:3 content on 16:9 tvs
# AviSynth script is now fully customisable
# The following variables are available:
# <movie>: The complete DirectShowSource instruction, e.g. DirectShowSource(filename, convertfps)
# <sub>: The complete subtitle instruction if there's any detected (SRT/SUB/IDX/ASS/SSA)
# <moviefilename>: The video filename for if you want to do all this by yourself
It works great, but for variable framerate videos I'm having issues with Avisynth/MEncoder. However with AviSynth/FFmpeg the audio and video seem to remain in sync on variable frame rate videos, but my filters aren't being used. Under AviSynth/FFmpeg settings it appears that the only setting that are available are for ffmpeg and I can't use any avs script. Is there anyway to get around this?