Akira Tsukihashi

Audio signal coding and decoding device

The present invention relates to an audio signal coding and decoding device for coding and decoding an audio signal using an adaptive differential coding system. The audio signal coding and decoding device according to the present invention comprises an adaptive differential pulse code modulation coding device for coding an audio signal, an adaptive differential pulse code modulation decoding device for decoding the audio signal coded, an integrator provided in the preceding stage of the coding device and for decreasing the variation between unit samples of the input audio signal of the coding device, and a differentiator provided in the succeeding stage of the decoding device and for processing the audio signal decoded by the decoding device so that the variation decreased by the integrator is restored to the original one. Since the integrator is provided in the preceding stage of the coding device, the variation between the unit samples of the input audio signal of the coding device is decreased. Therefore, a prediction error signal obtained by the coding device is decreased. As a result, quantizer step-size is decreased, resulting in a reduced quantization error.

The development of a circuit for the compression of digital audio

A circuit for the compression of digital audio has been developed which is very small in scale (less than 4000 gates) but exhibits nearly the same quality at 220.5 kb/s as the 705.6 kb/s 16 b PCM (pulse-code-modulated) sound. The proposed method improves the conventional ADPCM (adaptive differential pulse code modulation) coding method. This circuit was used to produce a low-cost and compact antishock compact disc player. >