Data compression system using frequency band translation and intermediate sample extrapolation

Claim 1

An improved bit saving system for use in a data communications system which transfers digital representations of an information signal of a given frequency spectrum from a transmitter to a receiver wherein the transmitter and receiver includes means to generate corresponding data series representing the information signal based upon periodic real data samples thereof, intermediate extrapolated values thereof, and correction values, wherein the transmitter includes: i. sampling means (414) for periodically sampling said information signal thereby to generate real data samples, ii. transmission means (415) for enabling the transmission of selected ones of said real data samples, and iii. correction means (420) for generating and enabling the transmission of said correction values, said correction values representing the difference between extrapolated and real data samples, and wherein the receiver includes: iv. correction means (420') responsive to transmitted correction values for correcting intermediate extrapolated data samples produced thereat in order to generate said corresponding data series, the improvement wherein the transmitter and receiver each include: A. frequency band translation means (422) comprising: i. means for subdividing the frequency spectrum of the information signal represented by the data series into plural sub-bands, and ii. means for frequency-translating selected ones of said sub-bands above a predetermined lower frequency band to sub-bands of said predetermined lower frequency thereby to enable extrapolation using discrete samples thereof without aliasing, and B. extrapolation means (426) for producing said extrapolated values from said plural sub-bands, said extrapolation means comprising: i. derivative computation means for determining plural order derivatives of each of said low-frequency sub-bands, ii. zero order derivative determination means for computing the value of the low-frequency signal of each said sub-bands based upon the respective computed plural order derivatives from said computation means, and C. reconstruction means (432) for combining said low-frequency sub-bands from said determination means in order to reconstruct a composite representing said extrapolated sample thereby to enable the transmitter to determine the correction value and the receiver to correct the extrapolated value.