Here are some lovely examples of what can be achieved with a combination of technological prowess and human patience. Denis Shiryaev takes old, noisy, shaky black and white videos, and adds stabilisation, resolution enhancement, facial feature enhancement and some light colourisation. Then he adds sound. This is far from a fully-automatic process: he takes weeks over each one, but without the help of neural networks, it would take months or years if it were even possible.
Here’s a collection of old Lumière Brothers’ films that have had his treatment. Even though, by modern YouTube standards, almost nothing happens in them, I found them surprisingly compelling, yet also calming.
Oh, and this, though less convincing, is also fun: