is an irreversible mathematical operation. When you take 100 pixels and average them into 1 big pixel, you lose 99% of the data. There is no algorithm in the world that can retrieve the lost numbers.
An aplicacion para quitar censura de fotos that claims to "un-pixelate" a face is actually using . It is drawing a face that fits the blurry shape. It is scientifically impossible to recover the original fine details (like a unique scar or a specific eye color) from a heavy mosaic.
A: Video is even harder. Tools like Topaz Video AI can upscale and sharpen, but they cannot "remove" a mosaic. They can only smooth it, making it slightly less pixelated.