Lip feature extraction towards an automatic speechreading system

The use of color information can significantly improve the efficiency and robustness of lip feature extraction capability over purely grayscale-based methods. Edge information provides another useful tool in characterizing lip boundaries. We present a method of integrating both types of information to address the problem of lip feature extraction for the purpose of speechreading. We first examine various color models and view hue as an effective descriptor to characterize the lips due to its invariance to luminance and human skin color, and its discriminative properties. We use prominent red hue as an indicator to locate the position of the lips. Based on the identified lip area, we further refine the interior and exterior lip boundary using both color and spatial edge information, where those two are combined within a Markov random field (MRF) framework. Experimental results are presented to show the effectiveness of this method.