Key points based segmentation of lips

Lip segmentation is an essential stage in many multimedia systems such as videoconferencing, lip reading, or low bit rate coding communication systems. We propose an accurate and robust lip segmentation algorithm. First, characteristic points are found by using "hybrid edges" (which combine color 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 model that is flexible enough to reproduce the specificity of very different lip shapes. Compared to existing models, it brings a significant accuracy improvement. Moreover, it ensures a robust convergence towards the edges.