This tutorial is for PC only!
With a laptop (for example), you can decide to have the video signal on an external monitor. This can be useful if the video card is not supported by Recalbox or your internal monitor is not working anymore.
xrandr
This will give you the available video outputs, their resolutions and refresh rates. For example:
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
DVI-D-0 disconnected primary (normal left inverted right x axis y axis)
HDMI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm
2560x1440 59.95 + 69.93
1920x1080 60.00* 59.94 50.00 23.98 60.05 60.00 50.04
1680x1050 59.95
1440x900 59.89
1280x1024 75.02 60.02
1280x960 60.00
1280x800 59.81
1280x720 60.00 59.94 50.00
1152x864 75.00
1024x768 75.03 70.07 60.00
800x600 75.00 72.19 60.32 56.25
720x576 50.00
720x480 59.94
640x480 75.00 72.81 59.94 59.93
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)
DP-4 disconnected (normal left inverted right x axis y axis)
DP-5 connected (normal left inverted right x axis y axis)
2560x1440 59.95 +
1920x1080 59.94 50.00
1280x720 59.94 50.00
1024x768 60.00
800x600 60.32
720x576 50.00
720x480 59.94
640x480 59.94 59.93
recalbox.conf file:## Prefered external screen retrieved from ssh : xrandr
system.externalscreen.prefered=DP-5
## Force selected external screen to resolution ex : 1920x1080
system.externalscreen.forceresolution=1920x1080
## Force selected external screen to frequency ex: 60.00
system.externalscreen.forcefrequency=59.94
The ; sign will be in front of the 2 lines you are modifying by default. You will have to remove this character in front of each of the 2 lines to activate your modifications.