Strange graphical error, possible gpu fault?


Well-known Member
I was watching Netflix on my pc for the first time in a while last night and I noticed that the image looked pretty bad. This was particularly evident on parts of the screen that contained blocks of colour, particularly on darker objects. They look like they're being rendered at some absurdly low bit rate whilst other parts of the image can look perfectly fine. Here's a screenshot from a Youtube video to show what's happening. There's the blocky bands of colour at the bottom of the sky and around the bright tail lights of the plane.

Blocky Image 2.jpg

Most games seem to be ok, although pubg looked fairly poor, and this problem occurs on all videos (at 1080p) even downloaded episodes from Netflix. It's been driving me nuts and here are the things I've tried so far to identify the problem.

Different monitor and lead (DP & hdmi)
Different browser (Edge and Chrome)
Different display and monitor drivers
Set Neflix playback options to high quality (HD subscription)

GPU is an RX 5700. Internet is 100mbps wired connection, speed tested to be fine. Any ideas into what the problem might be would be much appreciated. I've tried so many things at this stage I'm thinking it could be a gpu fault. I also repaired one bent pin on my Ryzen 5 2600 last week that solved some issues I had with memory timings. This issue seems strangely specific for it to be cpu related though.


Distinguished Member
Cant see anything in that photo.

From your description it sounds like macroblocking which is typical of video compression, in some circumstances these can be overly noticeable depending upon the display.

Try dialing down the contrast on your monitor, make sure the gamma is 2.2 If the monitor has support for 10-bit output try that too, you will need to be on DP.

If none of those do anything try disabling GPU video acceleration making it CPU only and see if that makes any difference.

1) Download MPC-BE
2) Go to view->options
3) Select internal filters->video decoders
4) Deselect all DXVA2 entries
5) Click on video decoder configuration and select disable DXVA for SD H.264

Now try playing one of the affected videos in MPC-BE, it should be decoding the video only on the CPU. If the problem persists then its not the GPU hardware video decoding.


Well-known Member
Excellent, thanks for the informative post. Yes I did come across the term macroblocking when Googling the problem but couldn't find any solutions. I will give what you suggested a try now.

EDIT: Just tried an affected video using the settings on MPC-BE and the problem very much still persists. Would you say this indicates a problem with the cpu then or is there anything else I can try at driver level such as bios updates etc? Thanks
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Well-known Member
If you can see macroblocks and banding on the static image you posted, I'm inclined to think you might need to get your monitor recalibrated or fiddle with the colour/gamma curve in your GPU settings.


Well-known Member
Thanks, I'll have a play with the settings now. I did notice that every time I updated my graphics drivers the monitor driver reset to generic rather than the specific model.

EDIT: I've loaded a profile for the monitor, dialed in some recommended settings and completed the Windows colour management setup. The problem is less visible on blacks but is still very noticable on greys and other colours.

I also just tried a couple of dvd's and they look awful, like 720p or worse. I can also see the effect on still images as well. Something clearly not right on a hardware or driver level by the looks of it.
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Distinguished Member
Sounds like its the monitor to me.

One other thing to try and is get this tool and use it on linux mint (mimics windows) or ubuntu .iso image and boot from a USB flash drive with that into the OS, if the visual problems persist it cant be windows/drivers.

Get VLC from the OS app stores to play video.


Well-known Member
I'm starting to think that too although I could see the same issues running the pc through the tv. Had the cpu out earlier to check it was ok and just updated the chipset drivers. I have a couple of older monitors in the loft so will get one of those out later.

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