Nippon Hoso' Kyokai

Kozo Kameda

Takeshi Kimura

Toshiyuki Takegahara

Hideki Suganami

Yoshiharu Hoshino

Satoru Koizumi

Yoshimichi Otsuka

As to a differential code (DPCM) transmission system for an input signal as such as an audio signal, in case higher frequency components thereof are dominant, every another samples of the input signal are alternately into two groups, in each of which differential coding effected, so as to maintain a dynamic range in higher frequency range; in case no frequency components exceeding one fourth of the sampling frequency are contained in the input signal, successive 3 MSB's having a pattern '1, 0, 1' or '0, 1, 0' are corrected into '1, 1, 1' or '0, 0, 0' respectively; and in case 2 symbols of a tertiary code converted from 3 bits of a binary code are transmitted and restored, peripheral bit arrangement of a matrix having rows consisting of the first symbols of the converted tertiary codes and columns consisting of the second symbols thereof are allotted such as Gray codes are obtained, while an inner 2.times.2 matrix of a 4.times.4 matrix formed by inserting a new threshold level between two threshold levels provided for detecting the tertiary code is allotted with bits relating to bits arranged at adjacent positions, so as to reduce the bit error rate of the restored binary code.

Differential code transmission system

A differential code (DPCM) transmission system for an audio signal, in case higher frequency components thereof are dominant, every another samples of the input signal are alternately into two groups, in each of which differential coding effected, so as to maintain a dynamic range in higher frequency range; when a near instantaneously compressed DPCM signal is transmitted, coding errors caused by the compression are corrected by varying the difference between samples in response to the comparison between a locally decoded signal and the original signal; when the frequency components exceeding one fourth of the sampling frequency are contained in the input signal, successive 3 MSB's having a pattern '1, 0, 1' or '0, 1, 0' are corrected into '1, 1, 1' or '0, 0, 0' respectively; and in case 2 symbols of a tertiary code converted from 3 bits of a binary code are transmitted and restored, peripheral bit arrangement of a matrix having rows consisting of the first symbols of the converted tertiary codes and columns consisting of the second symbols thereof are allotted such as Gray codes are obtained, while an inner 2.times.2 matrix of a 4.times. 4 matrix formed by inserting a new threshold level between two threshold levels provided for detecting the tertiary code is allocated with bits relating to bits arranged at adjacent positions, so as to reduce the bit error rate of the restored binary code.

Differential coding system

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Kozo Kameda