Code excited linear predictive vocoder using virtual searching

Details Code excited linear predictive vocoder using virtual searching Code excited linear predictive vocoder using virtual searching

1987-06-26

1990-03-20

Clark, David L.

Electrical audio signal processing systems and devices

One-way audio signal program distribution

Public address system

G10L 702

Patent

active

049107810

ABSTRACT:
Apparatus for encoding speech using a code excited linear predictive (CELP) encoder using a virtual searching technique during speech transitions such as from unvoiced to voiced regions of speech. The encoder compares candidate excitation vectors stored in a codebook with a target excitation vector representing a frame of speech to determine the candidate vector that best matches the target vector by repeating a first portion of each candidate vector into a second portion of each candidate vector. For increased performance, a stochastically excited linear predictive (SELP) encoder is used in series with the adaptive CELP encoder. The SELP encoder is responsive to the difference between the target vector and the best matched candidate vector to search its own overlapping codebook in a recursive manner to determine a candidate vector that provides the best match. Both of the best matched candidate vectors are used in speech synthesis.

REFERENCES:
patent: 4720861 (1988-01-01), Bertrand
Adoul et al., "Fast Celp Coding Based on Algebraic Codes", IEEE ICASSP, 81, pp. 1957-1960.
Crossman et al., "Multipulse Excited Channel Vocoder", IEEE ICASSP, 87, pp. 1926-1930.
Troncoso et al., "Efficient Procedures for Finding the Optimum Innovation in Stochastic coders", IEEE ICASSP, 86, pp. 2375-2378.
Schroeder et al, "Code-Excited Linear Prediction (HELP): High Quality Speech at Very Low Bit Rates", IEEE ICASSP, 85, pp. 937-940.
Singhal, S. and B. S. Atal, "Improving Performance of Multi-Pulse LPC Coders at Low Bit Rates", Proc. Int. Conf. Acoust., Speech and Sign. Process., San Diego, 1.3.1-1.3.4, 1984.
Atal, B. S. and M. R. Schroeder, "Stochastic Coding of Speech Signals at Very Low Bit Rates", Proc. of ICC, Amsterdam, 1610-1613, 1984.
Trancoso, I. M. and B. S. Atal, "Efficient Procedures for Finding the Optimum Innovation in Stochastic Coders", Proc. Int. Conf. Acoust., Speech and Sign. Process., Tokyo, 2379-2382, 1986.
Atal, B. S., "High-Quality Speech at Low Bit Rates: Multi-Pulse and Stochastically Excited Linear Predictive Coders", Proc. Int. Conf. Acoust., Speech and Sign. Process., Tokyo, 1681-1684, 1986.
Chen, J. H. and Gersho, A., "Real-Time Vector APC Speech Coding at 4800 bps with Adaptive Postfiltering", Proc. Int. Conf. Acoust., Speech and Sign. Process., Dallas, 2185-2188, 1987.

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