Real-time foveated multiresolution system for low-bandwidth video communication

Foveated imaging exploits the fact that the spatial resolution of the human visual system decreases dramatically away from the point of gaze. Because of this fact, large bandwidth savings are obtained by matching the resolution of the transmitted image to the fall-off in resolution of the human visual system. We have developed a foveated multiresolution pyramid video coder/decoder which runs in real-time on a general purpose computer (i.e., a Pentium with the Windows 95/NT OS). The current system uses a foveated multiresolution pyramid to code each image into 5 or 6 regions of varying resolution. The user-controlled foveation point is obtained from a pointing device (e.g., a mouse or an eyetracker). Spatial edge artifacts between the regions created by the foveation are eliminated by raised- cosine blending across levels of the pyramid, and by `foveation point interpolation' within levels of the pyramid. Each level of the pyramid is then motion compensated, multiresolution pyramid coded, and thresholded/quantized based upon human contrast sensitivity as a function of spatial frequency and retinal eccentricity. The final lossless coding includes zero-tree coding. Optimal use of foveated imaging requires eye tracking; however, there are many useful applications which do not require eye tracking.