Bell Telephone Laboratories

Lucent Technologies Inc.

At&t Bell Laboratories

Ronald E Crochiere

Richard Vandervoort Cox

Vasu Iyengar

Michael F Tompsett

Carlo Heinrich Sequin

Jose M Tribolet

An echo canceller includes receive and send paths each having an input and output port, a first non-adaptive filter with first filter coefficients for generating a first replica signal in response to a receive input signal, a second adaptive filter with second filter coefficients for generating a second replica signal in response to the receive input signal, a first subtracter for generating a send output signal representing a difference between a send input signal and the first replica signal, a second subtracter for generating an error signal representing a difference between the send output signal and the second replica signal, and a controller for replacing the first filter coefficients by the sum of the first and second filter coefficients and for resetting the second filter coefficients in response to a calculation that includes a first quantity associated with the send output signal and a second quantity associated with the error signal.

Echo canceller with adaptive and non-adaptive filters

Continuous stream processing of an input signal to find the autocorrelation function and pitch period is simplied. The input speech signal is sampled at 8 khz, from which the autocorrelation function is formed by multiplying each sample by a stored-delay reduced sequence of up to 30 past samples. The reduced sequence is formed by every fourth sample of input signal gated to storage. Autocorrelation values are sequentially compared by a peak-peaker for maxima, thus further minimizing storage requirements to find the pitch period.

Real time pitch detection by stream processing

A charge transfer device includes two channels and a common input structure. The input structure is operated in a manner to divide a charge packet of signal-independent size into two complementary packets for movement along the two channels. A single-channel embodiment employs a similar input structure.

Linear differential charge splitting input for charge coupled devices

To improve the speech quality at lower bit rates within a digital communication system in which the coefficients of a frequency transform (e.g. discrete cosine transform) are adaptively encoded with adaptive quantization and adaptive bit-assignment, the adaptation is controlled by a short-term spectral estimate signal formed by combining the formant spectrum and the pitch excitation spectrum of the coefficient signals.

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Berkeley Heights, NJ, United States of America

Ronald E Crochiere