Low bit-rate facial motion picture coding using image warping

A method of low bit-rate facial image coding specifically designed for the use in video telephone is presented. The basic principle for this facial image coding is to exploit the capabilities of 2D image warping techniques to generate the replica of sender's facial expression merely by deforming a master face image, which is sent once at the beginning of telephone call. Several parameters that describe facial expressions are monitored at the transmitter at the video frame rate of 30 frames/s, then transmitted to the receiver using the in-band data channel. Since transmission of actual image data happens once or when another image is required, the bit-rate is much lower than that required by ordinary video image transmission. A fast bilinear mapping method for warped images, a grid mesh set over the facial image, various warping algorithms to realize head movement and facial motions with respect to eyes and mouth are discussed. This paper also compares the presented low bit-rate facial image coding to its competing methods such as MPEG and the method using a 3D facial model.