Multirate digital voice communication processor
First Claim
1. A multirate digital voice communication processor for generating and utilizing a high data-rate digital signal with a low data-rate subset therein to permit the direct processing of this signal at both wideband and narrowband processors without analog tandeming comprising:
- a speech input;
a linear predictive coding processor for decomposing an input speech signal into filter coefficient components and a prediction residual component;
a narrowband excitation parameter extractor for representing said prediction residual component by a low data-rate digital signal;
a wideband excitation signal encoder for representing said prediction residual component by a high data-rate digital signal;
means for multiplexing into a data stream and transmitting said filter coefficient components, said narrowband low data-rate digital signal, and said wideband high data-rate digital signal;
means for receiving a transmitted encoded signal and demultiplexing said filter coefficient components and said low and high data-rate digital signals therefrom; and
means for decoding said demultiplexed encoded signals and reconstructing an approximation of the original speech prior to encoding.
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Abstract
To provide alternative operation at 2.4 or 9.6 Kb/s bit rates, a multirateigital processor generates a data frame of 216 bits representing sync and voice encoded at both rates, with the 2.4 Kb/s embedded as a subset within the frame. Rate conversion is made by inserting or deleting 162 bits per frame. Speech signal is transformed by linear prediction into coefficients and residual signals. The coefficients are transmitted similarly at both 2.4 and 9.6 Kb/s rates. However, the residual is processed into a simple pitch/hiss excitation signal for 2.4 Kb/s, but is processed into a Fourier transform of its baseband (250-1500 Hz) for 9.6 Kb/s excitation signal transmission.
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Citations
15 Claims
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1. A multirate digital voice communication processor for generating and utilizing a high data-rate digital signal with a low data-rate subset therein to permit the direct processing of this signal at both wideband and narrowband processors without analog tandeming comprising:
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a speech input; a linear predictive coding processor for decomposing an input speech signal into filter coefficient components and a prediction residual component; a narrowband excitation parameter extractor for representing said prediction residual component by a low data-rate digital signal; a wideband excitation signal encoder for representing said prediction residual component by a high data-rate digital signal; means for multiplexing into a data stream and transmitting said filter coefficient components, said narrowband low data-rate digital signal, and said wideband high data-rate digital signal; means for receiving a transmitted encoded signal and demultiplexing said filter coefficient components and said low and high data-rate digital signals therefrom; and means for decoding said demultiplexed encoded signals and reconstructing an approximation of the original speech prior to encoding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification