Computer Vision And Image Compression
Broadcasting television signal, upon digitization, results in approximately 60 Mbits per second, while the capacity at the bottom level of the ISDN hierarchy is 64 Kbits per second. For many applications such as videophone and teleconferencing, one would like very much to squeeze the digitized video signal through the 64 Kbits/sec channel: A compression of about 1OOO:l is needed. Conventional compression techniques, such as the CCITT proposed standard, do not give good reconstructions when the amount of motion in the scene is even moderately high. To achieve good quality at 64 Kbits/sec or even lower rates, radical new approaches are called for. One potential direction is model-based compression. The basic idea is to have a static 3D model of the scene constructed at the receiving end. Then, the transmitting end will extract and transmit only the 3D motion information. The receiver takes this motion information and uses it to drive the 3D scene model; from the dynamic 3D model, computer graphics methods can be used to generate 2D image sequences for viewing. In this talk we shall estimate the bit rates achievable by this model-based approach, give some preliminary results, and discuss some of the difficult issues that need to be resolved in order for the approach to be feasible.