Preprocessing Filter for Image Compression in Teleconferencing System
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
Raw image data directly from an input device can be compressed from 8 bits per picture element (pel) to about 3 bits per pel, if an entropy preserving data compression scheme is used. It can be compressed to about 1.7 bits per pel, if an entropy non-preserving compression scheme is used. The compression can be further improved to about 0.68 bit per pel, if the raw input data is first prefiltered to eliminate the noise which randomizes the low differential amplitude of the signal. The following describes such a filter implemented with an analog circuit. It is compatible with the image input device and operated in real time, so that the filter is transparent to the digital system that follows for data compression.