I know that i have to turn off hardware acceleration in order to take screenshots of my videos but is there a software that can take only the part of the video i'm playing and automatically saves it in a place so i can take large amounts?

I am planning on making a screenshot gallery and i need a easy and fast way to take screens of videos. Since i'm gonna be taking about 100 images, it's really hard to take screens through hypersnap or printScreenSysRq.

So basically, a software that takes ONLY the region of the video and saves it automatically so i can just press a hotkey and the screen saves itself in a designated folder.