Lip sync scared me for a long time but this was due to my lack of experience more than the actual job of animating lips and expressions to the audio.
For a while, I thought doing lip sync meant to choose a sequence of premade phonems and blend them more or less successfully as led to think by the Preston Blair animation book. To be fair, this is pretty much what you are supposed to do in most TV series but the result will always look very approximative and of low quality which is fine when your audience is preschool.
A good lip sync for feature animation should instead be done by focusing on other elements like the following:
1- open and close of the jaw
2- narrowing and widening of the mouth corners
3- asymmetry of the mouth (Mouth Left/Right, Rotation should blend shapes can help greatly for that)
4- lips roll
5- mouth Up/Down attribute to anticipate plosive sounds and create more contrast
6- lips translation, mainly drag for plosive phonemes such as Bb/Mm/Pp
7- appealing mouth corner arcs
8- good interaction of the tongue with the teeth and jaw
9- drag, overlap, rotation and translation of the jaw
A good rig such as the freely available Norman or Morpheus, despite the collapsing geometry for specific closed mouth shapes, should allow you to handle those criteria.
To illustrate this, here is a video I extracted from the Toy Story3 trailer and animated by Victor Navone. I added on-screen notes and a graphical representation of the audio waveform so you can compare the timing of the audio to the mouth shapes. (thanks Chris Cantero for the animation credits).
To read all the notes, save the video on your hard drive and play it frame by frame. Microsoft Windows users should play the video with KMPlayer to get the audio feedback while step framing.
I think one or two frames are missing for the bottom lip roll overlap but this should make it a very good start to your lip sync learning.
As a side note, the final shot has been slightly altered in the theatrical release with Buzz holding Jessee’s left hand rather than her right, I would be interested to know what the reasoning was behind that decision. They are obviously going for a tighter shot so we can focus on Jessee’s reaction but I don’t like her new pose much as her arm gets in the way and is buried in her silhouette. Here is a screenshot from Victor’s Toy Story 3 showreel.
I hope you like it, I have a James Baxter pencil test coming up next.