Video compression/expansion system

Abstract

An improved apparatus for rapidly compressing, expanding, and displaying broad band information which is transmitted over a narrow band communications channel. In the preferred embodiment, a video image is cyclically assembled in low resolution and high resolution phases from digitized data representing gray level intensity for individual pixels which have been grouped into pixel. During the initial cycle of the low resolution phase, a representative sample of cell intensity values is transmitted by a sending station to a receiving station according to a video compression routine. The receiving station then uses a video expansion routine to calculate an intensity value for those pixels whose intensity values were not transmitted and displays an initial image. This image is refined during subsequent low-resolution cycles by additional transmissions from the sending station which replace the calculated cell intensity values with an actual or better approximation value for that pixel. During the high resolution phase, an error determination routine or external input from a viewer selects those pixels containing the greatest deviation in intensity levels from the input video image. The error compression and expansion routines substitute a plurality of individual pixel intensity values for previously calculated intensity values. The present invention also discloses an apparatus for allowing color capable stations to send or receive color transmissions while retaining the capability to interact with noncolor stations. Color data is compressed and interleaved with black and white data by a color capable sending station and subsequently separated and expanded by a color capable receiving station.