Abstract: Data obtained by dividing digital data into a low-frequency signal and a high-frequency signal and converting the low-frequency signal and a signal obtained by subjecting the high-frequency signal to a lossless compression coding process into a transmission format is transmitted. The lossless compression coding process is effected by dividing a digital data string input in the unit of sample constructed by a preset number of bits into block units constructed by a plurality of samples, removing a constant number of bits having a common value from each sample starting from the sign bit side thereof for all of the samples in each block to form a compressed block and attaching information indicating the number of removed bits to the compressed block.