Lip-sync research - The basics

The four basic shapes the mouth makes are open/closed and wide/narrow.

That's it really. When lip-syncing a character with a plain circle for a mouth, the shapes in Figure 1.2 are all that’s needed to create the illusion of speech. This is the bare-bones of the method without all the detailed lip-curling for specific letter sounds such as 'F'.

"Animating lip sync is all illusion. What would really be happening isn’t nearly as relevant as the impression of what is happening. How about M? You may be thinking, “I need to roll my lips in together to say M, and I can’t do that with a wide-narrow-mouth-thing- amajig.” Sure you can, or at least you can give the impression in motion that the lips are rolled in—just close the mouth all the way—and that’s usually going to be good enough."  

Jason Osipa, Author of 'Stop Staring'

This is the issue I was having with my first tests of lip-syncing. I was recording myself in Photo Booth overpronunciating each word, then trying to animate in Maya. This made it look over the top and unrealistic. Here is an example below.