First Idea
1.First Pause Video
2. Then press Ctrl+PrtScSysRq button (now you have snap shoot of screen)
3. Then Open paint and Press Ctrl+v (Here is your image, save this file)
4. then Open this image with Picture Manager and crop the unnecessary part of image.

Second Idea
1. In window run command type snipping tool, this with this tool you can capture image.
Thanks