1974-09-13
1976-08-17
Claffy, Kathleen H.
G10L 100
Patent
active
039755878
ABSTRACT:
This invention relates to a digital vocoder where speech is translated to a digital version thereof. An adaptive filter in the form of an N stage Itakura type cascade derives from the speech a prediction residual and N spectral parameter in the form of weighting coefficients of the filter. The pitch period, derived from the prediction residual, the voiced/unvoiced decision derived from the first of the weighting coefficients and the peak amplitude of a pitch pulse, and a digital signal representing filter gain, derived from the last of the weighting coefficients are multiplexed with each other and the N spectral parameters for transmission to a receiver. The receiver employs an excitation generator responsive to the pitch period, the gain signal and the voiced/unvoiced decision to produce an excitation signal to excite an N/2 cascade connected stage receive filter. Each stage of the receive filter operates on a time shared basis on an adjacent pair of the N spectral parameters. The receive adaptive filter operation is the inverse of the transmit adaptive filter so that after digital to analog conversion the original speech is substantially reproduced.
REFERENCES:
patent: 3327058 (1967-06-01), Coker
patent: 3471648 (1969-10-01), Miller
patent: 3624302 (1971-11-01), Atal
patent: 3631520 (1971-12-01), Atal
patent: 3715512 (1973-02-01), Kelly
patent: 3746791 (1973-07-01), Wolf
patent: 3750024 (1973-07-01), Dunn
Itakura, Saito, "Digital Filtering . . . " Seventh Int'l Congress on Accoustics, Budapest, 1971.
Cowan John Richard
Dunn James Grant
Russo Anthony Joseph
Claffy Kathleen H.
Hill Alfred C.
International Telephone and Telegraph Corporation
Kemeny E. S.
O'Halloran John T.
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