how to trace lip movement from a video ?

how can I trace a person's lip movement from a video to decode what he/she speak?

Answer 1

[Image Analyst]

Search for algorithms here http://www.visionbib.com/bibliography/contentspeople.html#Face%20Recognition,%20Detection,%20Tracking,%20Gesture%20Recognition,%20Fingerprints,%20Biometrics

21.3.4 Lipreading, Lip Reading, Lip Tracking
    21.3.4.1 Combined Audio Visual Recognition and Analysis
    21.3.4.2 Mouth Location, Lip Location, Detection

The Computer Vision System Toolbox may be useful in carrying out algorithms.