Question / Help How to only capture window changes

[laucomm]

I would like to capture the contents of a window that changes very little and only occasionally over time and I want to capture it with the best quality but as small as possible.

So I am wondering if it is possible to capture a frame only if it the window content has changed since the last captured frame? That would give me one frame per change instead of x frames per second, which is exactly what I want. Is that possible and if so, how can I achieve this?

 

[EBrito]

You can crop and capture only the part you want.

 

[laucomm]

That is not what I am asking for. Let's assume there is a windows which content is entirely black except a small white circle somewhere in the window.
I want to capture the whole window content, so the whole black content and the white circle, but I want to drop all duplicate frames. So for example, if the white circle has move since the last saved frame, I want to save the current frame as well. If it has not, I want to drop the frame.

 

[laucomm]

Alright, I found a way to do it directly with ffmpeg using gdigrab and mpdecimate.