Lipreading using convolutional neural network

In recent automatic speech recognition studies, deep learning architecture applications for acoustic modeling have eclipsed conventional sound features such as Mel-frequency cepstral co- efficients. However, for visual speech recognition (VSR) stud- ies, handcrafted visual feature extraction mechanisms are still widely utilized. In this paper, we propose to apply a convo- lutional neural network (CNN) as a visual feature extraction mechanism for VSR. By training a CNN with images of a speaker's mouth area in combination with phoneme labels, the CNN acquires multiple convolutional filters, used to extract vi- sual features essential for recognizing phonemes. Further, by modeling the temporal dependencies of the generated phoneme label sequences, a hidden Markov model in our proposed sys- Tem recognizes multiple isolated words. Our proposed system is evaluated on an audio-visual speech dataset comprising 300 Japanese words with six different speakers. The evaluation re- sults of our isolated word recognition experiment demonstrate that the visual features acquired by the CNN significantly out- perform those acquired by conventional dimensionality com- pression approaches, including principal component analysis.