The Navy has developed a Multirate Processor (MRP) which generates digitized speech at 2.4, 9.6, and 16 kb/s by the linear predictive coding principle. This multirate capability is achieved by embedding the 2.4 kb/s data in the 9.6 kb/s data stream and the 9.6 kb/s data in the 16 kb/s data stream. Conversion between the rates is accomplished by truncating a certain portion of the bits from the higher-data rate signal or appending extra bits to the lower-data rate signal. The MRP mediumband (9.6 kb/s or 16 kb/s) mode is a baseband residual excited LPC in which the baseband residual is transmitted in terms of Fourier spectral components. Under various operational conditions, the Diagnostic Rhyme Test (DRT) scores for the 9.6 kb/s rate of the MRP compare favorably to the DRT scores of an existing 16 kb/s rate Continuously Variable Slope Delta (CVSD) encoder.
[1]
V. Viswanathan,et al.
Design of a Robust Baseband LPC Coder for Speech Transmission Over 9.6 Kbit/s Noisy Channels
,
1982,
IEEE Trans. Commun..
[2]
David Y. Wong,et al.
Development of a 4.8-9.6 kbps RELP vocoder
,
1979,
ICASSP.
[3]
A. J. Goldberg.
2400/16, 000 Bps Multirate voice processor
,
1978,
ICASSP.
[4]
John Makhoul,et al.
Baseband LPC coders for speech transmission over 9.6 kb/s noisy channels
,
1980,
ICASSP.
[5]
Harold E. Watkins.
Description of a hybrid 7.2 kbps vocoder
,
1979,
ICASSP.
[6]
J. Makhoul,et al.
An embedded-code multirate speech transform coder
,
1980,
ICASSP.
[7]
T. Bially,et al.
Voice Communication in Integrated Digital Voice and Data Networks
,
1980,
IEEE Trans. Commun..