I am running a Debian stable with Cinnamon graphical interface 3.6.7 and my computer is connected to a multimedia projector. I havea an Intel Graphic card.
The projected image is too big and I can't change neither the place of my multimedia projector nor the place of my wall to reduce the size of the projected image.
Thus I would like to find a command line so that the resolution of the projected image is the same but such that a black band is at the border of my screen (see Figures below). I expect then that the projected image will have a smaller size.
Solution (@Ipor Sircer)
xrandr --output HDMI1 --fb 1620x880