ADPCM encoding and decoding circuits

Details ADPCM encoding and decoding circuits ADPCM encoding and decoding circuits

1988-04-20

1989-08-22

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

341 51, 375 33, H03M 304

Patent

active

048603155

ABSTRACT:
In an ADPCM encoding and decoding system comprising an encoder having an adaptive predictor and an adaptive quantizer and a decoder having an adaptive predictor and an inverse adaptive quantizer, the adaptive predictors each comprise: an adaptive-zero predictor of an arbitrary order and an adaptive-pole predictor of an arbitrary order, for input signals with time-varying frequency components; a fixed-pole predictor of an arbitrary order, for input signals the frequency composition of which remains substantially invariant over time; and an offset predictor for rejecting an offset component of the input signals, these elements being connected in series. The adaptive-zero and adaptive-pole predictors generate estimates for voice signals with time-varying frequency components. The fixed-pole predictor generates estimates for voiceband data signals the frequency components of which remain substantially invariant over time. The adaptive predictors effectively operate for voice and voiceband data signals, providing a higher prediction gain. The quantizer provides a stably higher signal-to-quantization noise ratio for modem signals.

REFERENCES:
patent: 4075655 (1978-02-01), Iijima et al.
patent: 4617676 (1986-10-01), Jayant et al.
patent: 4654863 (1987-03-01), Belfield et al.
patent: 4743967 (1988-05-01), Takenaka et al.
"32 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM)" (Malaga-Torremolinos, 1984) Fascicle III.3-Rec. G721, pp. 125-158.

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