A screensaver is a useful tool but unfortunately it's annoying when there are active applicatoins like kaffeine or teamviewer and you have to move the mouse periodically just to deactivate the screensaver. Fortunately there exists a nice tool called caffeine. Just configure the applications you want to force to deactivate the screensaver and enjoy to view videose or to have remote sessions with shared screen without any screensaver interuption.
Unfortunatel it doesn't work any mor on Mint Maja with Mate. There fortunately exists a patch.