I have been producing a music video using glsl and external video footage, typically the workflow is to record the video using movie file out and the animation codec at 60fps. Then I then edit in Premiere and export. However, YouTube and Vimeo encodes the video in a really awful way.
Too bad because it looks great when I export a H264 from Premiere even at 30fps or a 4444 or a 422 LT. I have tried different bit rates. Everything looks good when I play the file on my computer. Even uploading to instagram looks fine. YT and Vimeo seem to be problematic.
It’s an age old issue, those (free) platforms will re-encode all your uploads to bitrates as low as possible to save bandwidth.
You can also check previous discussion here: