One thing that is almost always used in character animations is Lip Syncing. This is the process of syncing a character’s mouth up with their voice. Or simply making a character look like he is talking.
When you lip sync you don’t have to make the mouth “morph” into each position. You simply change out the image of the mouth in each frame of animation. I’m going to tell you how i do this in Flash.
Your first step is to draw the character’s mouth in different positions. I normally use 6 different mouth images. (you can use more or less depending on how smooth you want your animation) Start off with your normal character’s mouth. That would be how they would look in most scenes. Save this mouth as a symbol. I use this symbol and duplicate it as a template each time i make another mouth position. Then i start the other postions: the “O”, “AH”, “M, B, P”, “L, N, T, D”, and the “F, V” positions. Basically you make a mouth position for all of the basic sounds. Some people may use more, however when lip sycing the image will change so fast that sometimes it really isn’t necisary to draw more.
The “O” position is shaped as you would shape your mouth to say “too”. The mouth is basicallya circle. The “AH” position is the postion i use most of the time. It is simply an open mouth shape. You can show teeth and tounge if you wish. The “M, B, P” postions is the lips pressed together. Say “matt” and see how your lips look as you hum the “M” sound before your mouth opens. When i draw the “L, N, T, D” postion i always show the tounge. Say “the” and see how your tounge presses on your teeth. I sometimes make 2 symbols for this position. One with the tounge all the way up and one with it halfway down. But normally i just use one. The last position i make is the “F, V” position. Say “fat.” Notice your bottom lip starts off behind your top teeth. that’s how i draw this position. In the example below (these are Jay’s mouth from the Vegie-Tables.) I added a closed mouth because Jay’s normal mouth is an open smile. the closed mouth completes the syncs.
When designing each mouth position i base them off of the original mouth. In Flash i right click on the mouth and click on “Duplicate symbol”. I type in a proper name for the mouth position i’m about to make and then hit enter. It’s best to start the symbol out with the same words so that they will be next to each other in the symbol library. Now edit your new symbol. I usually go into the symbol and create a new layer. I then draw a new mouth over the existing mouth so that i can make sure the mouth is in the same location. Then i delete the layer with the old mouth. Repeat these steps for each position.
Now it’s time to sync your mouths. Make sure the audio is set to “Stream” in the properties box. This way you can find out exactly where each word and syllible starts and stops. Listen to the audio carefully. When you find the position of the first mouth change click in the mouth layer and create a new keyframe. Right click the mouth symbol and click “Swap Symbol” (this is why they should start with similar names). Then go to the appropriate mouth position and choose it. Continue this process each time another syllible is spoken. Add a keyframe with a “closed mouth” or “normal Mouth” position between each syllible. At first this process takes a bit of time, but with practice you can breeze through it.