Why are these flickering lines appearing during a fade to black in my Premiere render? I am working on documentation of a performance/musical instrument design project I completed in the springtime. The footage I received from my cameraman was shot on a GH5, and it's technical specs are 23.976 fps, 1920x1080, and H.264 10 bit 4:2:2. 

I have completed my edit in Premiere and used a couple of "Dip to Black" effects as transitions between different moments of my performance. Everything looked great and I rendered the project out. After watching the render, I noticed that on every fade to black transition, a bunch of flickering lines would appear on the white wall behind me. 

Here is an example of the problem: https://vimeo.com/346004760 (the password is "help")

Does anyone have any clue as to why these flickering lines are appearing during fade to black transitions? How could I get rid of them?

I've spent the past two days trying to find a solution, to no avail: the problem continues to appear. Aside from countless hours of Googling, here is a list of things I have tried:


Switching from GPU to Software renderer
Removing all effects except dip to black i.e just Dip to Black on pure raw footage
Using opacity keyframes from 100 > 0 > 100 instead of dip to black
Rendering the project in every imaginable way i.e .avi, very high bitrates, CBR, playing with every encoding settings
Cleaning media cache
Installing an older version of Premiere, downgrading the project, and rendering out of the older version 
Rendering the same footage on a Macbook (I usually work on a PC) 


I did learn that I can replicate the issue just by setting In and Out points on the timeline and rendering inside Premiere i.e by going to Sequence > Render In to Out. The flickering lines then appear when I preview the timeline. They do not appear if I haven't pressed "Render In to Out". This cut my troubleshooting time down considerably, as I didn't have to keep exporting footage.
I believe what you reference is called "artifacts".

Those phenomenons are a result of compression. Vimeo does not use the raw file you upload as playback. Instead, the file is converted and compressed for storage-purposes mainly. This might be one reason as of why this is appearing.

The second possibility is that your footage was not recorded at a deep-enough bitrate, and so it seems from the information you gave. h.264 is always a lossy codec, which means that you're gonna throw away a chunk of data when writing a file in h.264. I know that the gh5 is able to record in avchd, which would be a far better choice in terms of image quality compared to mov h264 or mp4 h264. Try recording in that format.

Lastly, using a flat profile could safe you some extra-information in those parts that get compressed could help you. The gh5 has a vlog-L profile as well as a Cinelike D one. These are so called "flat profiles" which will lower the contrast and saturation at first, but give you the ability to adjust contrast and brightness afterwards. Recording in a flat profile captures more information in very bright or very dark areas, which would otherwise get lost. Trying this might also improve your results.

However, Vimeo, youtube, Clipfish, hell what ever Streaming-Service you use - compression will take place, which means that your video will look worse there than in the original file. Depending on what you're planning on the long run (for example sending a video to a client) it might be a better idea to straight up upload the prores4444 or DNxHR or similar near-lossless codec and send the link to the client (for example via ftp-server) so he/she/it can download it directly without the use of 3rd-party streaming-services.

Hope my answer was helpful, happy filming!