View Independent Computer Lip-Reading

Computer lip-reading systems are usually designed to work using a full-frontal view of the face. However, many human experts tend to prefer to lip-read using an angled view. In this paper we consider issues related to the best viewing angle for an automated lip-reading system. In particular, we seek answers to the following questions: (1) Do computers lip-read better using a frontal or a non-frontal view of the face? (2) What is the best viewing angle for a computer lip-reading system? (3) How can a computer lip-reading system be made to work independently of viewing angle? We investigate these issues using a purpose built audio-visual dataset that contains simultaneous recordings of a speaker reciting continuous speech at five angles. We find that the system performs best on a non-frontal view, perhaps because lip gestures, such as lip-protrusion and lip-rounding, are more pronounced when viewing from an angle. We also describe a simple linear mapping that allows us to map any view of the face to the view that we find to be optimal. Hence we present a view-independent lip-reading system.