Constant rate transmission digital word image compression, for transmission from satellite, using transform coding and controlling quantization steps according to data rate of previous block

摘要

The compression method produces digital word blocks transformed by an orthogonal transformer (12) and quantizes (14) the coefficients. An entropy code (20) of the coefficients is produced, and the coded words are temporarily held in a memory (18). The quantization steps are controlled so that the number of bits in the coded blocks is approximately equal to the number of bits removed from the memory, taking account (54) of the measured data rate of the previous block. An Independent claim is included for the application of the method of the invention to the transmission of images of the earth's surface from a satellite.