Monitor resolution problem when using a VGA to HDMI adaptor

JCx227 · 03-31-2022, 09:55 AM

Hello and thanks for taking the time to read my problem.

Specifics

I am using a Optix G241VC curved monitor. I am running 2 computers through a KMV switch which has only HDMI inputs and outputs. For PC 1 this is no problem as it is my gaming rig and quite up to date. PC 2 is older and the machine I do non gaming things. It has only VGA graphics capability but no problem, I thought, and used a VGA to HDMI adapter and it does work.... sort of.

The monitor has both HDMI and VGA inputs but they cant be used simultaiosuly as I tried this as a work around.

I am using tailsOS

The Problem

When all set up using the VGA to HDMI adaptor the resolution is stuck on 1024 x 768 4:3 with no options to change it in the display settings. It also states it is an "unknown display". Under the colour tab the colour profile is VGA-1 Monitor

When I pull the adaptor out and reconect the VGA cable directly to the monitor as I have now I am able to enjoy 1920 x 1080 at 19:6. It is recognised as Microstep 24" and under the colour tab it is recognised as Optix G241VC Monitor

I would be very greatful for your assitance. Thanks

business_kid · 03-31-2022, 12:04 PM

Hello, JCx227 & welcome to LQ.

1st things 1st: Tails is not really an OS. It's something you carry in your pocket if you don't want to leave a trail, and better viewed as a tool.

On the video: HDMI sockets can be interrogated by the pc to an extent, but standards for vga plugs go wa…ay back. Have you tried a modeline? Youcan write a file (e.g. 20-video.conf) in /etc/X11/xorg.conf.d/ and give it these sections

ServerLayout
Monitor
Device
Screen

Get the information from 'man xorg.conf'

That's work, btw but if you've no other way out…

computersavvy · 03-31-2022, 08:30 PM

There are 2 different issues here.

First is the KVM switch. It may or may not properly transmit data between the monitor and PC for proper configuration. Some do and some don't.

Second is the cable used.
You said that when you connect VGA to VGA it works properly.
What about connecting VGA (PC) to HDMI (monitor) while bypassing the KVM switch. Does that work properly? If it does then something about the kvm switch may be the issue. If it does not then the cable is blocking proper communications and the PC cannot "see" the details of the monitor for proper config.

mrmazda · 03-31-2022, 11:23 PM

With a direct VGA to VGA connection, hwinfo --monitor should generate lines similar to these:

Code:

    Vert. Sync Range: 24-75 Hz
    Hor. Sync Range: 26-81 kHz

These can be used in a config file, e.g. /etc/X11/xorg.conf.d/50-monitor.conf, containing:

Code:

Section "Monitor"
	Identifier	"DefaultMonitor"
	VendorName	"MyBrand"
	ModelName	"MyModel"
	HorizSync	26-81
	VertRefresh	24-75
	Option	"PreferredMode"	"1920x1080"
EndSection

This, appropriately adjusted to include the numbers for the specific display, is all the information Xorg usually needs to emulate the EDID information that apparently doesn't get processed correctly when the KVM switch and cable converter are used. Others may suggest a modeline is needed, but independent modeline generators rarely do any better calculating than Xorg does automatically, if & when given the needed data as above suggested. I've been using HorizSync and VertRefresh with difficult environments for well over a decade, and never have needed a pre-configured modeline. When configured with HorizSync and VertRefresh, instead of with a modeline, very likely plugging in a different display at some future time won't result in unusable output that inhibits removing or editing the .conf file containing the modeline.

On TailsOS with Gnome, it may be necessary to tweak display settings, but hopefully HorizSync and VertRefresh are all you actually need to work around the KVM problem.

Arnulf · 04-01-2022, 07:41 AM

Quote:

Originally Posted by JCx227

Optix G241VC curved monitor
[…]

PC 2 is older and the machine I do non gaming things. It has only VGA graphics capability but no problem, I thought

VGA output to flatpanel monitor is generally a problem! It's absolutely senseless to convert digital graphics data to analog signals on graphics adapter, sending these susceptible to interference analog signals via a cable to flatpanel monitor and than convert it to digital signals. This senseless procedure may result in annoying blur, ghosting, …

Check if you can replace graphics adapter in PC 2 with a (non nvidia) graphics adapter which provides DVI oder HDMI output.

computersavvy · 04-01-2022, 08:08 PM

Quote:

Originally Posted by Arnulf

VGA output to flatpanel monitor is generally a problem! It's absolutely senseless to convert digital graphics data to analog signals on graphics adapter, sending these susceptible to interference analog signals via a cable to flatpanel monitor and than convert it to digital signals. This senseless procedure may result in annoying blur, ghosting, …

Check if you can replace graphics adapter in PC 2 with a (non nvidia) graphics adapter which provides DVI oder HDMI output.

His monitor has a vga imput, so it is designed for that signal. The fix suggested by mrmazda is very likely to fix the issues he sees without the need for spending money on a new graphics card.

enigma9o7 · 04-01-2022, 09:45 PM

Quote:

Originally Posted by JCx227

The monitor has both HDMI and VGA inputs but they cant be used simultaiosuly as I tried this as a work around.

What happens when you try it this way? If both PCs are hooked up to the monitor, you should be able to just switch inputs with buttons on the monitor itself....