previously you also mentioned browser activities.
So it could be your browser, possibly trying to access your hardware directly.
try to test that theory, to make the problem reproducible.

Hi all,

I have performed the testing for about 8 hrs. Before testing I have thoroughly cleaned the PC, including the cooling fan of AMD CPU. I have not cleaned it ever since its building about 2 and half years ago.

Settings:-
Resolution:
3840x2160 (16:9)
2560x1440 (16:9)
.....

Refresh Rate:
60Hz
59.94Hz
50Hz
30Hz
...

The values are preset. I can select any of them but am not allowed changing their value.

Test Results
1)
3840x2160@50Hz

No flickering on browsing online video
No flickering reading documents either online or local documents
No flickering on clicking links of documents

2)
3840x2160@59.94Hz
No flickering on browsing online video
No flickering reading documents either online or local documents
No flickering on clicking links of documents

3)
3840x2160@60Hz
Flickering occasionally on browsing online video
No flickering reading documents either online or local documents
Occasional flickering on clicking links of documents

Remark:
Playing time of video - 1 hour
Video quality - 4K and old video

Old video - on full screen leaving large empty space, about 4~5", on both sides
Occasional flickering found on all above settings.

Regards

Define it in terms of software used, not tasks performed.

I think that is up to the user to check each type of software used. In general the resolution and refresh rate that work fine for my needs may not work for you because you use different software -- desktop, apps, etc. My office style work is less taxing than your extreme game playing, etc.

^ I was asking OP which software causes flickering.

Wireless mouse?

Are there external devices whose operation might correlate with the occasions where the screen blanking takes place?

For example, I have a desk lamp with a three-way LED bulb that's located next to my Asus monitor and it often blanks the screen for a couple of seconds when I switch the lamp off. (Curiously, this does not always happen. Don't ya just love intermittent glitches?)

Just a thought...

The HDMI cable is protected from electrostatic induction. The HDMI cable is covered with metal woven mesh and with ferrite beads at both ends. See attached photo

Regards

Attached Thumbnails

 

OS - Ubuntu 20.04 desktop (now)
Browsers - Firebox and Chrome
Documents - Text Editor

Regards

No gaming here

Regards

I'm coming at this late. I gather from previous posts that 60Hz is good enough, but your box can't pump out 4k @ 60hz. If you run 'xrandr' in a terminal it might confirm that. 60Hz will be good enough for most folks but if you skip lines, you'll notice that as flickering.

I see 2 possibilities:

• Go to an interlaced mode if you can
• Speed up the box if you can.

An interlaced mode is where you write every 2nd line each time. So the box writes lines 1,3,5,7,… followed by another frame of line 2,4,6,8… I actually have my eye on your 30Hz mode. In many parts of Europe, we used a PAL system for analogue tv.That used an interlaced 25Hz signal, and did funny things to cancel out the effect of ghosting. So there was no red/blue control, it just worked naturally. But interlacing made the 25 HZ look like 50 HZ which was good enough. You could interlace your 30 HZ to look like 60HZ.

As for speeding up the box, if you have a spare partition, or can make 20G room, try an install of Linux Mint. It's just Ubuntu, with a single Mint repo. But the single repo handles stuff noticeably faster in X, which may help. It also supplies proprietary drivers without any qualms. Have you got proprietary drivers installed? If Mint solves it, you may want to change distro. It's a 1st cousin of debian anyhow, with good support.

I was giving examples of non-stress vs extreme stress types of use that definitely could influence video behavior.

$ xrandrIt seems that it can.

I can do it on live USB, burning Linux Mint on it.

Just read following article;
How to Fix the YouTube Screen Flickering in Mozilla Firefox
https://news.softpedia.com/news/how-...x-525866.shtml
I'll test it on live USB running Ubuntu 20.04 desktop

Edit
====
Linux Mint 20 comes with 3 desktops, Cinnamon, MATE and Xfce desktops. Which edition shall I use?

Regards

Hi,

No gaming here. All video tested before were movie

Regards

I use primarily XFCE. Cinnamon is ok, I don't think I've run Mate much. They're all fairly lightweight.

Hi,

Download linuxmint-20-xfce-64bit.iso and burnt it on an USB stick.

Started up linuxmint-20-xfce and performed following tests

Settings:
Resolution: 3840x2160
Refresh Rate: 60Hz
Browser: Firefox
Playing online video: still flickering occasionally
Text Editor: Reading documents - if scrolling the document too fast, flickering may occur.

However I couldn't reproduce the flickering.

New discovery;-
Ubuntu 20.04 desktop

Screen Resolution - 3840x2160
Refresh Rate - 60Hz

I found that the possible cause of flickering of the Dell 32" 4K display may come from the MS wireless mouse. Previously, I connected the receiver of the wireless mouse and keyboard to a USB port at the back of the display.

Later I changed a Logitech wireless mouse and keyboard and have their receiver connected to an USB extension cable. The cable was then hanging on the top of the desktop PC. I have tested this setting last night and this morning and the frequency of flickering greatly reduced. I'll continue to observe it for another 2 days before marking this thread solved.

Regards