DATA COMPRESSION SYSTEM USING FREQUENCY BAND TRANSLATION AND INTERMEDIATE SAMPLE EXTRAPOLATION

A digital data transmission system for transmitting selected periodic ones of real data samples and intermediate extrapolated data samples. The transmitting end of the communication system includes means for sampling periodic ones of an information signal, an extrapolator for estimating intermediate samples between the selected periodic real samples, correction means for generating a correction value based upon the difference between extrapolated data and real data samples, and transmitting means that transmit periodic ones of real data samples and intermediate correction values. The receiving end includes means for receiving selected real digital data samples and the correction values, and a second extrapolator for estimating intermediate samples between the transmitted real data samples. The receiving end also includes correction means for reconstructing representations of the intermediate data samples computed at the transmitting end based upon the transmitted periodic real data sample and the transmitted correction value. Accordingly, the invention attains bit savings in the communication system. At the both the transmitting and receiving ends, intermediate extrapolated data samples are formed on plural frequency-translated subbands of the lower portion of the voice spectrum. Each low-frequency subband is used for producing the extrapolated value of the respective low-frequency subband. A composite extrapolated signal is formed by combining the results from each subband thereby to reconstruct the intermediate extrapolated sample. Tracking errors between the transmitting extrapolator and the receiving extrapolator are aligned by use of the correction values.