Window recording in Linux and Mac

This will grab the image from desktop, starting with the upper-left corner at x=100, y=200 with a width and height of 1024⨉768.

advanced = { video_size: '1024x768' }
ScreenRecorder::Desktop.new(input: ':0.0+100,200' output: 'recording.mp4' )

Source: https://trac.ffmpeg.org/wiki/Capture/Desktop