Biological Motion of Speech

The paper discusses the detailed analysis of visual speech. As with other forms of biological motion, humans are known to be very sensitive to the realism in the ways the lips move. In order to determine the elements that come to play in the perceptual analysis of visual speech, it is important to have control over the data. The paper discusses the capture of detailed 3D deformations of faces when talking. The data are detailed in both a temporal and spatial sense. The 3D positions of thousands of points on the face are determined at the temporal resolution of video. Such data have been decomposed into their basic modes, using ICA. It is noteworthy that this yielded better results than a mere PCA analysis, which results in modes that individually represent facial changes that anatomically inconsistent. The ICs better capture the underlying, anatomical changes that the face undergoes. Different visemes are all based on the underlying, joint action of the facial muscles. The IC modes do not reflect single muscles, but nevertheless decompose the speech related deformations into anatomically convincing modes, coined 'pseudo-muscles'.