Principal component coding of mouth sequences

Facial features of a videophone image sequence are coded using the traditional technique of principal components (PCs). One of the main advantages of this method is that it makes use of a large a priori knowledge of the images and exploits the correlation between pixel values. The sequences are coded through a hybrid wire frame model in which the head and shoulder images are coded using a small number of bits. A box is placed around the mouth and eye regions which are coded at a higher bit rate using PCs. Since the image sequence is similar in its overall configuration, this scheme gives a very high compression ratio of around 500:1.