You're welcome here
Sorry for the rushed reply but it's 2am and i'm from my phone
www.pasteall.org/60924/python
Banding when using a denoising script is caused by processing thr image at a bitdepth too low, i modified the paste so that it use a 16bit pipeline [hoping that FT3dfilter support it].
I've also lowered the number of reference for motion estimation cause i've find degrain3 to strong.
Thsad of 400 is pretty high, try to use a lower value, something like 200,
Also i think you save your original blender render in jpg, don't do that, save it in png, even better if on png48, i've never used blender so i can't help you here.
Last tip, if the video you save is a temporary one to be reprocessed you can use a 10bit build of x264 on lossless mode [crf=0] and outputting a 4:4:4 video [--output-csp i444], or save it in png48 using imwri.write()
If it is the final render then let me know and wait utc 12:00 and i'll expand my explaination
Let me know if you have questions