Video Comparer is an interesting commercial tool which can find similar videos by their content.
The key word here is "similar". The program doesn't just look for identical files. It can also match files when one has been cropped, rotated or resized. It's even able to identify videos where one clip exists within another (video A is a single scene extracted from video B).
Video Comparer works much like any other file comparison tools. Point it at the folder tree you'd like to examine, perhaps choose one or two options (there are several comparison modes, for example, from quick to full), and click Scan. The program crawls your folders, looking for videos (avi, mpg, mpeg, mkv, wmv, 3g2, 3gp, asf, asx, bsf, divx, f4v, flv, m2p, m2v, m4v, mov, mp4, ogv, rm, ts, vob and xvid files are supported).
We expected the comparison process to take an age, but in reality it was surprisingly speedy. The developer quotes 1 minute to compare 30 videos, 5 minutes for 100 or 40 minutes for 500 (the maximum this edition will compare), and we wouldn’t disagree.
Once Video Comparer has finished, it displays any likely duplicates. Synchronised timeline thumbnails show you the matching scenes, so you can see at a glance if the program is correct, and true duplicates may then be copied, moved or deleted with a click.
Perhaps unsurprisingly, the trial version has some major restrictions. It compares files, but won’t display their names, and doesn't allow you to delete or back up duplicates. It’s enough to see whether the comparison engine works for you, but doesn’t otherwise do very much.
From our initial tests, though, Video Comparer proved both accurate and speedy, and the Home Edition is certainly worth its 20 Euro/ $28 dollar price tag. Just keep in mind that it can only compare a maximum of 1,500 videos in a single scan; for unlimited scans you'll need the Pro Edition, which is a more questionable 100 Euro/ $140.