Combine/Concatenate video clips that overlaps recording.

As I see it, the Excel is "good enough", you just copy the column "I" to a batch file and execute it, making a more elaborate batch would only "move" the calculation to it and put the ffmpeg commands into a FOR loop, it would be much more "elegant" but it won't shave anything from computing time, i.e. nothing more "efficient" as the number of ffmpeg commands will be anyway the same.

Elaborating on calimelo's idea ) , you could maybe "intentionally" leave only 1 second of overlap and then extract the frames for this 1 second only (twice, 1 second from the "tail" of the "before" file and 1 second from the "head" of the "after" file).
This way the amount of frames to extract and hash will be minimal.

jaclaz