[BlindWanderer]

mkvSynth for VFR the only real way of doing it would be a) undo the VFR or b) add timebased editing to the scripting engine or c) associate timecodes with each frame.

b & c are good options (and basicly the same), probably would be good to have both of them. Having time based would let you cut video half way through a frames time.

Having not taken the time to read and understand the AviSynth core but i think it would require a major rewrite. Maybe this would be good to beg the Devs, into adding to AviSynth 3.


for MKVSource looks like the only way is to undo VFR by adding frames. Here is a list of funtions that would be good to have in a MKVSource plugin.
MKVSource(filename, audiotrack, videotrack, forcedframerate)
MKVVFR(clip)
MKVInfo(filename)
if forcedframerate is not set i think it should auto-detect what this is by reading the timecodes. Also MKVInfo should return the auto-detected framerate along with available streams in the mkv.