| 摘要 |
PURPOSE:To improve the SN ratio and the distortion rate to compress and transmit signals of high quality by providing the first and the second variance calculating circuits which calculates variances of an input signal and a difference signal respective ly and an output selecting circuit which compares these variances with each other to transmit a signal obtained by compressing the signal having the smaller variance. CONSTITUTION:A forecasted value of a compressed signal which is the output of the first compressor 2a is calculated, and the difference between this value and the next input signal is operated by a subtractor 1. The compressed signal which is the output of the first compressor 2a and a compressed signal which is the output of the second compressor 7 are held in the first memory 8 and the second memory 9 respectively until data of N-number of samples are stored. The first variance calculat ing circuit 4 calculates the variance in accordance with data of N-number of samples of the input signal, and the second variance calculating circuit 5 calculates the variance in accordance with data of N-number of samples of the difference signal, and values of variances obtained by the first and the second variance calculating circuits 4 and 5 are compared with each other by a variance comparing circuit 6, and an output selecting circuit 10 takes out N-number of data having the smaller variance from the first memory 8 or the second memory 9 as an output signal.
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