Pixelation is basically an average of the real image at that location. Still images or moving images can have this feature/problem.

To remove pixelation, there's not really much you can do. It's the same with focus and out of focus images. You can easily go from high image quality to lower image quality just by doing the math for averaging. But, once the average is all you have to work with, you CAN'T get the high image quality back. For pixelation, all you can do is increase the resolution and average the pixel edges of the low resolution to smooth out the sharp image changes. Smoothing out pixelation will look like it's just very blurry with no jagged edges.

It's not a problem that can be programmed out. It's a lack of data.

There IS some software that's being developed that uses a generative adversarial network (GAN) which can "guesstimate" what the original image WAS. It's kind of like seeing a pencil drawing of an apple and the computer figures out that it's supposed to be an apple and shows you one that matches the approximate shape. (Not a good explanation, actually, but it gives you an idea why it's not mathematically exact.)