How bout this, modified from another function (there are plenty of dupe frames detectors out there).
EDIT: SCript removed, see here for better alternative:-
https://forum.doom9.org/showthread.php?t=175357
Client
Code:
Avisource(".\N.AVI")
WriteDupeFrames(0.5,Ranges=False)
I'll do a FrameSel mod (MakeReDupCmd with ranges) within a couple of days.