I have a ASUS N53S laptop, it has a 1920*1080 resolution build in screen. If it matters: GPU is Nvidia GeForce GT 550M. It has a VGA port which I don't/rarely use and a HDMI port.

In my HDMI port I plug in an external Samsung monitor OR TV, both are same HD resolution as my internal screen (1920*1080). Or nothing when I'm 'on the road with my laptop'.

Now what I want is that my screen is duplicated/mirrored if I plug in one of my other screens in the HDMI port.

The problem however: when I check the mirror screen checkbox, the maximum resolution is set to 1024*768. There is also an 'unknown screen' in the screen options window, every time I try to change any screen settings, I have to set that unkown screen of because it will make my cursos flicker. So I disable the unkown screen, then mirror my main screen but then the resolution option is limited.

I'm not sure what to do.

PS: My Ubuntu version is in Dutch, so I might not have translated everything correctly.