Towards a practical lipreading system
A practical lipreading system can be considered either as subject dependent (SD) or subject-independent (SI). An SD system is user-specific, i.e., customized for some particular user while an SI system has to cope with a large number of users. These two types of systems pose variant challenges and have to be treated differently. In this paper, we propose a simple deterministic model to tackle the problem. The model first seeks a low-dimensional manifold where visual features extracted from the frames of a video can be projected onto a continuous deterministic curve embedded in a path graph. Moreover, it can map arbitrary points on the curve back into the image space, making it suitable for temporal interpolation. Based on the model, we develop two separate strategies for SD and SI lipreading. The former is turned into a simple curve-matching problem while for the latter, we propose a video-normalization scheme to improve the system developed by Zhao et al. We evaluated our system on the OuluVS database and achieved recognition rates more than 20% higher than the ones reported by Zhao et al. in both SD and SI testing scenarios.