VNC Server Not Optimized Due to Ommissions in 'config.txt'

[JeffHochberg]

The default VNC Server configuration is set to a very low resolution which is next to impossible to use.

There are two different VNC Server services for RealVNC. One is for headless devices (vncserver-virtuald.service), the other is for devices with a display connected (vncserver-x11-serviced.service).

HamPi is currently running vncserver-x11-serviced.service which expects an HDMI interface to be connected to the Pi. If one is not connected, then the GUI interface will fail to start, and vncserver-x11-serviced.service will fail to launch which will prevent people from connecting to it with VNC Viewer.

I still prefer using the X11 version of the VNC Server as it's a lot easier to manage than the headless version, but there are changes required in order to ensure that it runs optimally.

The default /boot/config.txt file should be modified in several ways to account for this:

Allow X11 to start without an HDMI interface connected by enabling:

hdmi_force_hotplug=1

2. Provide several pre-defined options in /boot/config.txt so users can SSH into the Pi, or use an existing VNC session to modify the file to comment/uncomment the desired/undesired resolutions. I have the config.txt file configured as follows:

uncomment to force a specific HDMI mode (this will force VGA)

hdmi_group=2

#1920x1080
hdmi_mode=82

#1280x720
#hdmi_mode=85

#1360x768 - 60 Hz
#hdmi_mode=39

#1360x760 - 120 Hz
#hdmi_mode=40

The hdmi_group=2 should be enabled in all cases. The hdmi_mode values can be modified based on the desired resolution for the VNC session.

When I want to run in 1920x1080 resolution, I simply uncomment hdmi_mode=82 and ensure any other resolutions are commented out. If I want to run in 1360x768 resolution, I comment out the other hdmi_mode and uncomment hdmi_mode=39. The hdmi_mode=40 is likely not needed as 120 Hz won't make a difference through a VNC session.

It's possible to create a menued interface for this, but given the timeframe to deliver the new image, that may or may not be possible. That's for you to determine.

My list of hdmi_mode values is a small selection based on the devices I use to connect to the VNC server. The complete list of HDMI modes is documented:

https://www.raspberrypi.org/documentation/configuration/config-txt/video.md

3. Lastly, the Raspberry Pi 4 comes with an option enabled by default that will also cause issues with RealVNC Server and should be commented out:

#dtoverlay=vc4-fkms-v3d