Code excited linear prediction speech coding system
First Claim
1. A method of encoding and transmitting an input speech signal by code excited linear prediction type encoding to provide a decodable signal, said method comprising the steps of:
- (a) providing a residual signal vector from a white noise code book, based on an error signal so as to reduce the error signal,(b) applying linear prediction to the white noise residual signal vector to obtain a code vector and a first coefficient,(c) applying linear prediction to a residual signal of a previous speech signal delayed by a pitch frequency to obtain a pitch prediction vector and a second coefficient,(d) providing an impulse residual signal vector having a predetermined relationship with the residual signal vector from the white noise code book,(e) applying linear prediction to the impulse residual signal vector provided in step (d) to obtain an impulse vector and a third coefficient,(f) applying variable gains to at least the code vector obtained by said step (b) and the impulse vector obtained by said step (e),(g) adding the code, pitch prediction and impulse vectors after applying the variable gains in step (f) to form a reproduced signal,(h) evaluating a difference between the reproduced signal formed by said step (g) and the input speech signal to provide the error signal for said step (a), and(i) transmitting a decodable signal based on at least the first, second and third coefficients.
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Abstract
A code excited linear prediction (CELP) type speech signal coding system is provided, a code vector obtained by applying linear prediction to a vector of a residual speech signal of white noise is stored in a code book. A pitch prediction vector obtained by applying linear prediction to a residual signal of a preceding frame is given a delay corresponding to a pitch frequency and added to the code vector. Use is made of an impulse vector obtained by applying linear prediction to a residual signal vector of impulses having a predetermined relationship with the vectors of the white noise code book. Variable gains are given to at least the above code vector and impulse vector, a reproduced signal is produced, and this reproduced signal is used for identification of the input speech signal. Thus, a pulse series corresponding to the sound source of voiced speech sounds is created.
122 Citations
36 Claims
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1. A method of encoding and transmitting an input speech signal by code excited linear prediction type encoding to provide a decodable signal, said method comprising the steps of:
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(a) providing a residual signal vector from a white noise code book, based on an error signal so as to reduce the error signal, (b) applying linear prediction to the white noise residual signal vector to obtain a code vector and a first coefficient, (c) applying linear prediction to a residual signal of a previous speech signal delayed by a pitch frequency to obtain a pitch prediction vector and a second coefficient, (d) providing an impulse residual signal vector having a predetermined relationship with the residual signal vector from the white noise code book, (e) applying linear prediction to the impulse residual signal vector provided in step (d) to obtain an impulse vector and a third coefficient, (f) applying variable gains to at least the code vector obtained by said step (b) and the impulse vector obtained by said step (e), (g) adding the code, pitch prediction and impulse vectors after applying the variable gains in step (f) to form a reproduced signal, (h) evaluating a difference between the reproduced signal formed by said step (g) and the input speech signal to provide the error signal for said step (a), and (i) transmitting a decodable signal based on at least the first, second and third coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for encoding and transmitting an input speech signal, comprising:
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a pitch frequency delay circuit to delay a residual signal of a previous speech signal by a pitch frequency, a code book to store a plurality of white noise residual signal vectors, an impulse generating circuit to generate an impulse having a predetermined relationship with the white noise residual signal vectors stored in said code book, a linear prediction circuit operatively connected to said pitch frequency delay circuit, said code book, and said impulse generating circuit to output vectors and a coefficient, a variable gain circuit operatively connected to said linear prediction circuit to apply a variable gain to at least one of the output vectors of said linear prediction circuit, a first addition circuit operatively connected to said variable gain circuit to produce a reproduced composite vector, a second addition circuit operatively connected to said first addition circuit to add the reproduced composite vector and a vector of the input speech signal to output an error signal, an evaluating circuit operatively connected to said second addition circuit and said code book to identify a white noise residual signal vector stored in said code book in response to the error signal, and an output transmitter operatively connected to at least said linear prediction circuit to transmit a decodable signal based on at least the coefficient. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. An apparatus for encoding and transmitting an input speech signal to provide a decodable signal, comprising:
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first code book means for storing first data and generating a white noise signal based on the stored first data and an index; second code book means for storing second data and generating an impulse signal based on the stored second data and the index; linear prediction means for applying linear prediction to the white noise and impulse signals and generating a coefficient; processing means for comparing the white noise and impulse signals with the input speech signal to provide an error signal; evaluating means for generating the index based on the error signal; and transmitting means for transmitting a decodable signal based on at least the coefficient. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. An apparatus for encoding an input speech signal, comprising:
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code book means for storing white noise data and generating a white noise signal based on the stored white noise data and an index; impulse means for generating an impulse signal having a predetermined relationship with the white noise data stored in said code book means based on the index; linear prediction means for applying linear prediction to the white noise and impulse signals and generating a coefficient; processing means for comparing the white noise and impulse signals with the input speech signal to provide an error signal; evaluating means for generating the index based on the error signal; and transmitting means for transmitting a decodable signal based on at least the coefficient. - View Dependent Claims (30, 31)
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32. A method of encoding and transmitting an input speech signal to provide a decodable signal, comprising the steps of:
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(a) generating a first signal based on stored first data and an index; (b) generating a second signal based on stored second data and the index; (c) applying linear prediction to the first and second signals and generating third and fourth signals and a coefficient; (d) adding the third and fourth signals to generate a fifth signal; (e) comparing the fifth signal with the input speech signal to generate an error signal; (f) generating the index based on the error signal; and (g) transmitting a decodable signal based on at least the coefficient. - View Dependent Claims (33, 34)
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35. An apparatus for receiving and decoding a decodable signal to reproduce a speech signal, comprising:
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receiving means for receiving and demultiplexing the decodable signal to generate at least an index signal and a coefficient; first code book means for storing first data and generating a white noise signal based on the stored first data and the index signal from the receiving means; second code book means for storing second data and generating an impulse signal based on the stored second data and the index signal from the receiving means; linear prediction means for applying linear prediction to the white noise and impulse signals based on the coefficient from said receiving means to reproduce the speech signal.
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36. An apparatus for receiving and decoding a decodable signal to reproduce a speech signal, comprising:
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receiving means for receiving and demultiplexing the decodable signal to generate at least an index signal, a coefficient and a phase signal; code book means for storing a plurality of white noise residual signal vectors and outputting a white noise residual signal vector based on the index signal from said receiving means; impulse generating means for generating an impulse signal having a predetermined relationship with the white noise residual signal vectors stored in said code book based on the phase signal from said receiving means; and linear prediction means for applying linear prediction to the white noise residual signal vectors and the impulse signal based on the coefficient from the receiving means to reproduce the speech signal.
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Specification