If you've ever wondered how adaptive interlacing works, here's a slo-mo demo of it for the old Panasonic Plasma TVs that manage to do pretty good deinterlacing with zero added lag.
https://www.youtube.com/watch?v=b8hLAWf3USo
or if you need a bit more explaining and not just visuals:
https://www.youtube.com/watch?v=dzxugg2jFkw
of course there's many methods, this is just one. But I found it interesting to actually see what's happening, and it gives you a good general ideal of the method.