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I'm attempting to use a TV as an external monitor for my laptop, connecting with a HDMI cable. When I plug the cable into HDMI 1 (on the TV, the laptop only has a single HDMI port) both the laptop and the TV recognize the connection and connect immediately.

My problem is that the TV will periodically blink / go blank. When I "Join" the displays, the TV displays properly, as long as there are no windows open on it, just the static desktop. Within a few seconds of moving a window onto the TV (from the laptop screen), horizontal blue lines start flickering at seemingly random locations on the screen, then the TV goes blank for a few seconds, then comes back on. Then the cycle repeats - a few seconds good, blue lines, blank. Once I move the window back over to the laptop screen, things settle down, and the TV displays the desktop, with blue lines flashing every 4-9 seconds, and only occasional blanking. The TV does not report a loss of signal an all in this mode.

When I set my displays as "Mirrored", the TV displays properly for a few seconds, and then goes blank or says that it has no signal. After a 5-20 seconds it will show up again, and then the cycle repeats.

I have a short video showing these behaviors at https://www.dropbox.com/s/l3ksukabm3lgeyg/20210127_200918.mp4?dl=0. (For anyone checking this question once it has been fixed, I might have removed the video.)

Hardware specs from "Settings|About": the laptop is a Dell Vostro 3560 (Intel i5-3210M CPU, 6GB RAM, AMD Turks/Intel HD Graphics 4000 [IVB GT2]) running Ubuntu 20.04 64 bit, Gnome version 3.36.8, using Wayland for the windowing system. The TV is a Samsung UN32M5300 smart TV (software version T-KTSAKUC-1290.3).

Things I have tried/checked:

  1. I swapped to a brand new HDMI cable (I don't know what version it is, but is connector has "High Speed" molded into it). No difference.
  2. I (ugh) booted over to Windows 10. The TV worked as an external monitor (in both mirrored and joined modes) flawlessly. Edit: I wanted to test changing the HDMI port on the TV under Windows (#5 below), so I booted back over. It's now exhibiting the same blanking behavior, but with no flashing.
  3. The refresh rate is set at 60.00 Hz, and I verified that that is the rate specified for the TV by Samsung. Just to check, I did try 59.94 Hz and 40.00 Hz, and there wasn't any change in the problem, so I went back to 60.00 Hz.
  4. I switched the windowing system from xorg to wayland after seeing it suggested on here (Ubuntu screen flickering). No change.
  5. I moved the cable to the second HDMI port on the TV [it's labeled "HDMI 2 (ARC)"]. This makes things worse. Even when the screens are "Joined", the TV will only display the desktop for a split second, then it goes blank for 20+ seconds, then reports no signal for a while, then blanks again, ad nauseam. When I moved the cable back to port 1, the original behavior resumed. I tried this a couple of times to verify that it wasn't a one off.

I think that the problem is somewhere in how the screen is refreshed, but I'm not sure, and don't know what to try next. Any suggestions?

Edit: To make things even more confusing, I noticed that when at the Ubuntu login screen, everything behaves properly. I waited ~20 minutes, and not one flicker, just a steady purple display.

Greg Shoults
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1 Answers1

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I was having the exact same problem, and the fix for me was turning off the "Auto Motion Plus" setting on the TV.

It was happening with Ubuntu 22.04, a fresh install of 24.04, and Windows 11 (although it was significantly less frequent and almost unnoticeable with Windows). And it was only happening with my new Lenovo Yoga laptop, but not with my older Dell Precision.

Laptop: Lenovo Yoga 7i, Intel Core i7-1355U, 16GB Memory, 512GB SSD, integrated Intel Iris Xe Graphics

TV: Samsung QN55

James
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