Artifacts in playback of rendered video on H.264

I edited together some time lapse video taken on a GoPro in 4K mode a frame every 5 seconds. It was placed on a car doing about 70 MPH. The problem occurs in the video taken at night. It might be an acid test for any encoder. Several places in the rendered video, there are compression artifacts on 1080 playback that look like this:

compression artifacts on playback

vlcsnap-2021-01-10-12h10m11s703.jpg (98.1 KiB) Viewed 1667 times

I checked and the source does not have any artifacts. I re-ran the render with the exact same parameters and the errors occur at the exact same place in the output.

Here is the rendered file posted as "unlisted" on Youtube:

Look at about 2:40 into the video and be sure set 1080P quality.

I tried to change the "Key Frames" parameter to "Every 4 frames". That moves the errors to other parts of the rendered output. I can provide the source files and project files if you want to investigate it.

If I switch to "Format" = Quicktime and Codec=MPEG, and all the problems are GONE.
I posted that to Youtube too:

DaVinci Resolve 17.0B build 18.
Windows 10 Version 10.0.19042 Build 19042
32 GB RAM
NVIDIA GeForce GTX 960 4 GB RAM driver ver. 460.89
Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz, 3401 Mhz, 4 Core(s), 8 Logical Processor(s)

Render settings: Format MP4, Codec H.264, Network optimization off, Resolution 1920x1080 HD,
frame rate 29.97, Quality Automatic "Best", Encoding profile "Auto", Keyframes Automatic
Frame reordering on.

Let me know if I left anything out.
- Reed

I've seen similar artifacts, but only when using H.264 as my source material.

I handle it by not filming in H.264.

Using any form of H.264 for shooting means you get three generations of compression: in camera, by yourself and finally by YT.

Try to improve at least your step by not using H.264! It's possible to upload short videos in a better codec, like DNxHR or ProRes.