关键词: 唇读, 特征提取, 离散余弦变换（DCT）, 线性判别分析（LDA）

Abstract: To solve the key problem of extracting visual speech feature in lipreading，a method based on DCT and LDA is proposed.To extract most discriminative visual feature among different mouth classes，first，DCT is performed on the visual speech region；and then based on LDA the most discriminative feature vector is extracted from DCT coefficients.The experiments on speaker-dependent，speaker-independent database and in real-time lipreading environment show that this method is more effective than traditional manual DCT coefficients extraction method and PCA feature extraction method.

Key words: lipreading, feature extraction, Discrete Cosine Transformation（DCT）, Linear Discriminative Analysis（LDA）