Hi Mahmood,

I don't think FFT is needed for doing what you want to do. Adjust brightness/contrast to end up with a black & white image, and xor bitmaps to determine image changes (hits). Calculate center of hits (I would expect a hit to be multiple pixels wide) and use bitmap x-y to map to target position and score.

I'm surprised it's such a sort range (50M). For rifle I would expect some 100M+. This of course does expand the possible area of hits...the further out there, the more variation not just because of the shooter but also because of ammunition, wind, etc.

I have been using OSD chips to put text on top of video. We are using ST's STV5730A, it's a nice chip, easy to work with. The data sheet is pretty lame though. ST was going to drop production of the chip, but there was enough demand for it that they are keeping it in production, and raising the price instead.

I have also used Mitsubishi M35062. It is similar, but has some different capabilities. It also has the *worst* excuse for a datasheet I've ever seen.

If you end up using either of these chips and need help figuring out how they really work, let me know.

Good luck,

Dennis