Artifacts (dots, coloured spots) when rendering

Hi,

Looking for some guidance on what to troubleshoot next to solve this.

Background: I receive coloured timelines as DRPs from a colleague, and load them on this machine to render them. Their own machine renders the footage fine with no artifacts at all.

Issue:
- At times, when rendering a timeline, artifacts will appear on the rendered image.
- Coloured dots, black spotches, sometimes vertical lines.
- Almost always toward the top edge of frame.
- Never the same frame twice, occurs at different random moments throughout the timeline.
- Occurs always in the rendered out image, but infrequently in the Colour panel in Resolve itself.

20200815_seb_sample_1_braw_severe.jpg (58.17 KiB) Viewed 2865 times

See attached images. In my testing I ranked them as "severe", "slight" or no artifacts.

Source media: BRAW from UMP 4.6K, @ 4.6K 8:1; AND Sony Venice XOCN LT 4K UHD
Source media location: Samsung 860 EVO 2TB NVME
Rendering format: 1920 x 1080, DPX 10-bit
CPU: Intel i9-9900K @ Stock 3.6 GHz
RAM: 32 GB DDR4
GPU: Nvidia RTX 2070 8GB VRAM
GPU Driver: Studio 451.77
OS: Windows 10 Home 64bit (Version 2004, OS Build 19041.388)
DaVinci Resolve Studio (16.2.4.016)

Enabling or disabling any of the below makes no difference, and will still result in a defective image:
- Use GPU for BRAW decoding
- Performance Mode
- GPU Processing Mode, Auto, Manual, OpenCL or CUDA
- Use display GPU for compute
- Nodes with Grain

Disabling the below will result in a clean rendered image:
- Nodes with Noise Reduction
- All grade nodes (but of course defeating my use case)

Noise Reduction is so far, the only variable that when bypassed on a per-clip basis, makes the artifacting disappear completely and the image renders fine.

Does anyone have any ideas? Is the GPU bust?

Final comments:
- I've had the issue on this machine since early January, where I was rendering BRAW media to DNxHD 36 proxies, and had identical artifacting.
- Interestingly, however, I did not use any NR nodes at that time, just a 3D LUT Film to Extended Video V4.
- The issue has occurred before and after system restarts, and an OS reinstall.

that looks a lot like GPU artifacting, can you try to render something just on CPU?

Can you run a game/test suite and see if it happens in there as well?

try this: https://benchmark.unigine.com/heaven

Looks like NR is the consistent culprit here. I would expect the 2070 to handle it fine, so maybe a bad unit?

Thanks for the suggestions.

Looks like you both were on the right track, the graphics card appears to be faulty.

The Unigine Heaven benchmark shows plenty of flashing spots.

I ran screen capturing during the benchmark and marked moments where it occurs. Interesting that it seems to always occur in the top-left quarter of the frame.

I'll contact the place of purchase and see what can be done there, bought the unit in December 2018. Might have luck because Australia.

I'd still love to be able to render out this timeline with NR & grain on CPU-only, even if it was to render at an extremely slow pace.

20200816_benchmark_still_2.jpg (172.19 KiB) Viewed 2827 times

All the work done on the Color page runs exclusively on the GPU. There is no option to run it from the CPU.

You may need the new card to get this job done. (Which, if you think about it, is a really good excuse to upgrade hardware. )

Yes the GPU is faulty, looks like it's the memory. Have had this issue many times in the past so it looked eerily familiar.

I hope you can file an RMA and get it replaced/repaired.

As a temporary fix you could use MSI Afterburner and clock the memory of the GPU down like 100MHZ and see if that fixes the issue.

As a temporary fix you could use MSI Afterburner and clock the memory of the GPU down like 100MHZ and see if that fixes the issue.

Thanks so much for this suggestion. I used MSI Afterburner and knocked down the memory clock by -102 MHz, and a render at regular settings with NR enabled now came out with no artifacts at all, nil. Render speed was also not impacted.

In the Unigine Heaven benchmark, -102 MHz was not enough to stop artifacting, needed to go down to about -329 MHz, and the artifacting stopped.

This fixes the problem for me, especially since it made no impact on render times (for the small sections of my test anyway).

But I still don't like the idea of having faulty hardware, so I might still go ahead with the RMA sooner rather than later, albeit the turnaround time could take weeks.

As a temporary fix you could use MSI Afterburner and clock the memory of the GPU down like 100MHZ and see if that fixes the issue.

Thanks so much for this suggestion. I used MSI Afterburner and knocked down the memory clock by -102 MHz, and a render at regular settings with NR enabled now came out with no artifacts at all, nil. Render speed was also not impacted.

In the Unigine Heaven benchmark, -102 MHz was not enough to stop artifacting, needed to go down to about -329 MHz, and the artifacting stopped.

This fixes the problem for me, especially since it made no impact on render times (for the small sections of my test anyway).

But I still don't like the idea of having faulty hardware, so I might still go ahead with the RMA sooner rather than later, albeit the turnaround time could take weeks.

Glad it solved your render, there is a know issue with the 2070 where the memory is too highly clocked from the factory. I saw many reports on this.

I had the same issue with my GTX 1080 TI. This seems to finally have solved it!
Thank you very much for posting the solution

I had the same issue with my GTX 1080 TI. This seems to finally have solved it!
Thank you very much for posting the solution

I'm glad!

I should mention that some weeks after I resolved the issue by underclocking the memory, I had the graphics card stop working entirely and just output black video.

I started an RMA with Gigabyte through the dealer I bought it with and Gigabyte repaired it. The artifacts issue did not return either.

I hope for your sake that your graphics card is not on the fritz.

Now I'm worried again
Did your card die because of underclocking the memory?

Well, as there's no warranty on this card for quite a while now - if the card should fail completely, it's time for an upgrade I guess...

Now I'm worried again
Did your card die because of underclocking the memory?

Actually I'm not sure why I made the comparison, your card is a GTX 1080 Ti and mine is an RTX 2070.

I don't think it was because of the underclocking, but I guess I will never know the reason why.

Well, the artifacts on my renders disappeared, as soon as I underclocked my card to about -350 MHz (just to be sure). So it seems to be a similar if not the same issue.
If my card should die in the upcoming days/weeks I'll post it here. Then it should be pretty evident that underclocking a card is just a temporary fix.

Underclocking GPUs doesn't cause any damage.