What could be causing these strange flickering pixels in some images?
October 16, 2014 11:56 AM   Subscribe

Recently, I noticed some pixels flickering on one of my monitors. At first I assumed it was a problem with the monitor until I noticed the flickering pixels scrolled when the image scrolled (i.e., it's always the same pixel in the image regardless where the image is on the screen). So then I thought it was an animated image, but if I drag the window over to the other monitor, the flickering goes away.

This image from a current FPP post illustrates what I see. On the left side, I've added two pixels exactly where they flicker on my monitor. The right side is the unmodified version for comparison.

Additional notes:

How the image is viewed makes no difference. Photoshop, Chrome, Windows Media Player, etc. If I take a screenshot, the screenshot behaves exactly the same-- flickering in the same spot in the image, only on the one monitor. Even the screenshot I uploaded to imgur has the flickering pixels on the right side image.

Multiple instances of the same image on screen will usually have the pixels in the same part of the image.

The flickering isn't at a regular interval and nor is it synchronized between pixels. The best description I can give is that each flicker pixel has a consistent probability of being on. It might be 99%, it might be 50% it might be 20%.

It's not simply the monitor having problems with a specific color, a pixel of identical RGB value in another part of the image may not flicker.

Changing part of the image near the flickering pixel can cause it to stop.

System is Windows 7, AMD Radeon HD 6700 series video card. Offending monitor is an Acer V223w and is set as "secondary display" in Windows.
posted by justkevin to Computers & Internet (9 answers total)
 
Check to see that the cable isn't loose. Check to see that the cable isn't faulty. Try connecting another computer to the same monitor using the same cable. Try connecting another computer to the same monitor using a different cable.
posted by oceanjesse at 12:12 PM on October 16, 2014 [1 favorite]


What happens if you swap the cables on the two monitors? Are both monitors identical and/or are they being fed by different ports on the video card? For example, I have two identical model monitors and one is on HDMI, one on DVI with an adapter, just because that's the best two ports I've got. I only have one of each.

That test (provided the two monitors are similar, at least to the extent of each having the same ports as the other for swapping purposes) would seem to isolate whether it's a port on the video card.

I like oceanjesse's loose cable idea too.
posted by randomkeystrike at 12:12 PM on October 16, 2014


It's possible that your monitor has a dead pixel or two, but you can't say that for sure until you try the other stuff.
posted by oceanjesse at 12:13 PM on October 16, 2014


This sounds like a slightly buggy display driver, worth trying to see if an updated version is available.
posted by Lanark at 12:13 PM on October 16, 2014 [3 favorites]


ive seen video overlay do that in the past when it screws up, where it tags a certain pixel value as belonging to an overlay so you get a few pixels showing 'through' to another image/video underneath. I don't think that should happen with modern os/gfx/drivers though. If you can make a large solid image with the pixel value of the offending pixels you might be able to tell if thats the case.
posted by TheAdamist at 12:26 PM on October 16, 2014 [1 favorite]


Do both monitors have the same native resolution (or post the model numbers for both)? Are both monitors connected using the same interface -- HDMI, DVI, or analog?

When you have an image with bad pixels, try swapping cables while the monitors are live and see if the bad pixels swap to the other monitor.
posted by JackFlash at 1:16 PM on October 16, 2014


This could also be caused by a faulty video card driving the second monitor. If it's got some bad RAM, then the pixel associated with that slot of memory will be displayed incorrectly.
posted by Hatashran at 2:55 PM on October 16, 2014


If the problem pixels don't stay fixed in a single position on the monitor (e.g. you can move the image around on the monitor and the problem pixels move with it), then it's extremely unlikely that it's a monitor or cabling problem, and I'd pretty much dismiss those out of hand. That would leave a video card driver problem (most likely) or a hardware problem with the video card (also possible, though I'd consider it less likely). I'd start with upgrading (or downgrading, if you've updated them recently) your video card drivers, and if that doesn't do anything, see if you can find a spare video card that you can test with.

Keep in mind that modern OSes and programs use hardware acceleration significantly, so buggy drivers can cause artifacts in plenty of places you wouldn't ordinarily expect.
posted by Aleyn at 3:04 PM on October 16, 2014


I had something like this happen once, and it turned out that there was something wrong with the monitor's controller board. Certain colors would always render in a weird flickering way. If this is happening to you, you should be able to isolate particular color(s) that flicker, regardless of what image or program you're viewing them in. Try playing around with the color palette tools in photoshop or gimp. You might also try a digital input source if you're using analog right now, in case the problem is in the analog-to-digital converter.

In my case, I was able to get Dell to replace the monitor even though it was out of warranty.
posted by qxntpqbbbqxl at 11:17 PM on October 16, 2014


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