The role of dynamics in visual speech biometrics

This paper begins by introducing biometrics and their underlying performance factors. Biometrics are sometimes classed as either behavioural or physiological. Difficulties with these classes are discussed in terms of the importance of dynamics, highlighting the key point that definitions are clarified if the biometric information-bearing signal itself is considered. Emphasis is then given to visual speech in the form of lip profiles The case is made that these are a special case in that they provide a vehicle for a twin biometric: both behavioural and physiological It is argued that lips might well be unique in providing a practical twin biometric. Illustration is presented in the form of practical experiments based around visual speech and lip profiles. Experimental results using short, test and training segments from video recordings give recognition error rates as: physiological lip-profiles 2% and behavioural lip-profiles 15%.