This is a small tutorial on how I do the lipsync. We will need an audio recorder (eg Audacity), the program Papagayo, a video editor (like Avidemux), a text editor (like gedit) and of course Synfig.
I advise to look at the pictures of Preston Blair. http://www.animationarchive.org/2006/05/media-preston-blairs-animation-1st.html
We have done our draw (in this case in front view).
1. Record with Audacity the text you want to use.
2. Then fix it (if necessary) and export it to WAV format. We'll name it "Texto.wav".
3. Open the file Texto.wav with Papagayo.
4. Fixed the text according to Papagayo instructions and save as "Texto.pgo".
5. Once settled choose "voice Export ..." We will save it as "Texto.dat".
6. Open "Texto.dat" with gedit. We'll note the position of the corresponding phonemes, so 1 corresponds to 1f, 24 corresponds to 1s, 25 corresponds to 1s 1f, 50 corresponds to 2s 2f, etc.
Now we know the exact position of each phoneme. We still to decide how many different poses we want. (We can use the outline given by Preston Blair, or use your own).
Come to our animation. Let's make the mouth move, without heads.
1. We export the mouth (if we follow the Preston Blair draws, we'll export the head).
2. Change Interpolation to constant.
3. Now, on the exported canvas, we will draw each pose in the appropriate frame, doubling the keyframe when necessary. If the text speed is very fast, then it's not necessary to draw all the phonemes.
Also, we can draw all the phonemes we need in the first second and start the animation from frame 1s, so we will double the corresponding keyframe at any time. In this case we must start to render from 1s.
Another thing we can do is create a library of phonemes, taking advantage of the "paste canvas layer" as in this tutorial. http://vimeo.com/10318012 .
Then we'll use the video editor (Avidemux) to add audio to video.
I hope it can help you.