Screen resolution

Hi there!

Seems a little pretty machine that Jetson nano.
I am familiar with ubuntu, but, I do have some questions…

If I run xrandr without gdm3 it sais can’t export display?

And If I do I get the following resolutions:
Screen 0: minimum 8 x 8, current 5120 x 800, maximum 16384 x 16384
HDMI-0 connected 3840x800+1280+0 (normal left inverted right x axis y axis) 0mm x 0mm
3840x800 59.81*+
3072x768 60.01
1600x1200 60.01
1280x1024 75.03 60.00
1024x768 75.03 60.01
800x600 75.00 60.32
640x480 75.00 59.94
DP-0 connected primary 1360x768+0+32 (normal left inverted right x axis y axis) 410mm x 230mm
1360x768 60.02*+
1280x768 59.87
1024x768 75.03 60.01
832x624 75.05
800x600 75.00 60.32
720x400 70.04
640x480 75.00 59.94

Why does it state that current resolution is 5120x8000 while the actual supported resolution is 3840x800 (made them bold) Is that the pixel count of both screens?

Also, whitout graphical target, I te text login screen is at the hdmi port,
would it be possible to place that on the display port?

Thanks!
Cheers, Vincent

If you run any program from within the GUI, then the “DISPLAY” environment variable is inherited. If you’ve run xrandr from outside of the GUI, then you absolutely must set this yourself. From in the GUI you can find out which DISPLAY it is with:
echo $DISPLAY

Then from some program which is not running through the GUI, so long as you are running as the same user as the GUI, then you can do this prior to using commands such as xrandr (I am assuming you are using a DISPLAY of “:0”, but it might be something else, e.g., it might be “:1”):
export DISPLAY=":0"

If you don’t want to export for all commands, then you can prefix this to your current command with the “export”. For example:
DISPLAY=":0" xrandr

If you are using ssh with a port forwarding via either the “-X” or “-Y” options, or if you are logging in as a different user, then you will not be able to get this to work. If there is no GUI running, then all commands which require a GUI (including xrandr) are guaranteed to fail (which is the case when running without graphical.target unless you’ve manually started an X session).

There are some graphical programs which can run without X, but most cannot. I’ve never used this, there might be some gstreamer sinks which can do this.

I couldn’t answer the part about pixel counts, but I am guessing you are correct that it is combining the pixel counts of the two screens.

In text mode I’ve only seen the screens mirror each other. I’ve thought too that it would be useful in a dual monitor setup to have two separate text displays, but how would you tell the system which one the keyboard goes to? Normally if you are in text mode, then ALT-F1 through ALT-F6 act as key bindings to switch to the different getty/agetty (the text mode terminal) instances 1 through 6. The normal case is that although there would be 6 getty/agetty listening, that only one is actually active at a time. You would need a way to bind some ALT-F# to the “left” screen, and some to the “right” screen. This would be quite useful, but I’ve never seen it done before, and is probably not particularly easy.

Hi,

Thanks for the fast reply. I will test the export DISPLAY=":0"setting.

About the login console:
It is only displayed on the hdmi connector. The DP is a different screen, also whithout graphical target.

I indeed am going to use the setup in combination with-node red an gstreamer, to run a video installation.

Right now the nano can feed a matrox triple head with a resolution of 3840x800 (that is translated to 3x projector of 1280x800)

Probably the workaround will be to fetch a good dp to dvi dual link adapter. So the matrox will be the 2nd monitor.

Thanks

Vincent

Text mode resolution is a completely different set of software. In the case of the HDMI cable, if an application needs X running, then it won’t matter which display if that display is not running X…it simply would not work. Specialty “sinks” in gstreamer (which I do not use and cannot give details for) can work with video displays which do not run X. In the case of not running with X, then the DISPLAY would not matter and would be irrelevant.