If you set aside the mosaic issue and focus on the rest of the video, you can achieve dramatic improvements:
If you are looking for a guide to or removing pixelation , you might explore tools like: ds ssni987rm reducing mosaic i spent my s extra quality
Example ffmpeg command for extra quality without mosaic removal: If you set aside the mosaic issue and
: Download Topaz Video AI (trial), load SSNI-987, select the "Proteus" model, push "Deblock" to 70, "Sharpen" to 40, and upscale to 200%. Then spend your "S" on a large external hard drive to store the result. That is the only "extra quality" worth paying for. select the "Proteus" model