A parametric model for realistic lip segmentation

Lip segmentation is an essential stage in many multimedia systems such as videoconferencing, lip reading, or low bit rate coding communication systems. In this paper, we propose an accurate and robust lip segmentation algorithm. First, the mouth region and several characteristic points are detected by using "hybrid edges" (which combine colour and intensity information) and a priori knowledge about the lip morphology. Corners position, which is crucial, is provided by a coarse-to-fine process. Then, a parametric model is fitted on the lips. We consider that the lip boundary is composed of several independent cubic polynomial curves. It gives a low complexity global model that is flexible enough to reproduce the specificity of very different lip shapes. Compared to existing models, it brings a significant accuracy and realism improvement. Moreover, it ensures a robust convergence towards the edges because the different parts of the model are independent.