Adaptive prediction

Details Adaptive prediction Adaptive prediction

1982-04-14

1984-10-02

Kemeny, E. S. Matt

Electrical audio signal processing systems and devices

One-way audio signal program distribution

Public address system

340347DD, 375 27, G10L 100, H03K 1301

Patent

active

044752270

ABSTRACT:
An improved Adaptive Predictor Circuit for use in an Adaptive Differential PCM Coding system (ADPCM) uses tap coefficient values to determine adaptation rate. The stability margin of a fourth order adaptive predictor is improved by dynamically changing the adaptation speed of the tap coefficients (a.sub.i) depending upon the location of the poles with respect to the unit circle in the Z domain. The predictor comprises a 4-tap adaptive transversal filter (31) and a coefficient update circuit (32) for the same. The output of the coefficient update a.sub.i (where i=1,2,3,4) is also delivered to a logic circuit (34) which calculates a predetermined function of the tap coefficients. If the calculated function is greater than a given threshold, an input speech or voiceband data signal is concluded and a normal speed of adaptation is permitted. However, if the calculated function is less than the threshold, a narrowband signal is indicated and the adaptation speed is substantially reduced.

REFERENCES:
patent: 3973081 (1976-08-01), Hutchins
patent: 4140876 (1979-02-01), Gagnon
patent: 4437087 (1984-03-01), Petr
CCITT Study Group, XVIII Contribution No. FR 3, Apr. 1981, "32 kbits/s ADPCM Codecs", Question 7/XVIII, pp. 1-15.
IEEE Trans. on Communications, May-Jun. 1982, "A 60 Channel PCM-ADPCM Converter", J. M. Raulin, G. Bonnerot, J. L. Jeandot and R. Lacroix.
IEEE Proceedings, vol. 68, No. 4, "Adaptive Prediction in Speech Differential Encoding Systems", by J. D. Gibson, pp. 488-525, Apr. 1980.
ICASSP Conf. Proc., Mar.-Apr. 1981, "Performance of a 32 kbits/s ADPCM CODER for Digital Long-Haul Telephone Transmission", Bonnerot et al., pp. 848-851.
Internat'l Conf. on Communications, Jun. 1981, "Digital PCM-ADPCM Converter for Digital Tandem Connections", Bonnerot et al., pp. 62.4.1 through 62.4.5.

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