Speech coding apparatus
First Claim
1. A speech coding apparatus comprising:
- a linear predictive analysis unit which receives an input signal of digitalized speech, performs linear prediction, and extracts a linear prediction parameter;
a code book which stores codes comprised of white noise series;
a prediction filter unit, operatively connected to said linear predictive analysis unit and to said code book, which uses the linear prediction parameter and the codes for filter calculations to produce a reproduced signal;
a comparator, operatively connected to said prediction filter unit and receiving as input the reproduced signal and the input signal, and comparing the reproduced signal to the input signal to produce an error signal;
an error evaluation unit, operatively connected to said comparator and said code book, and calculating an optimum code giving a minimum error signal; and
an output unit, operatively connected to said linear predictive analysis unit and said code book, and receiving the optimum code and the linear prediction parameter, outputting a coded output signal;
wherein the said code book comprises a reduced code book only storing reduced codes formed by thinning said code book to 1/M (M being an integer of two or more) of the sampling values inherently possessed by the code bookwherein said reduced codes are formed by thinning the codes at predetermined intervals to produce thinned codes in said code book.
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Abstract
A speech coding apparatus which selects an optimum code from a code book, the optimum code giving the minimum magnitude of error signal between the input signal and the reproduced signal obtained by a filter calculation using a linear prediction parameter from a linear predictive analysis unit with respect to the codes of the code book, wherein the code book is formed by thinning to 1/M (M being an integer of two or more) the plurality of sampling values constituting the codes. To compensate for the deterioration of the quality of the reproduced signal caused by thinning the sampling values in this way, an additional linear predictive analysis unit is further introduced and use made of an amended linear prediction parameter instead of the linear prediction parameter from the originally provided linear predictive analysis unit.
46 Citations
13 Claims
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1. A speech coding apparatus comprising:
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a linear predictive analysis unit which receives an input signal of digitalized speech, performs linear prediction, and extracts a linear prediction parameter; a code book which stores codes comprised of white noise series; a prediction filter unit, operatively connected to said linear predictive analysis unit and to said code book, which uses the linear prediction parameter and the codes for filter calculations to produce a reproduced signal; a comparator, operatively connected to said prediction filter unit and receiving as input the reproduced signal and the input signal, and comparing the reproduced signal to the input signal to produce an error signal; an error evaluation unit, operatively connected to said comparator and said code book, and calculating an optimum code giving a minimum error signal; and an output unit, operatively connected to said linear predictive analysis unit and said code book, and receiving the optimum code and the linear prediction parameter, outputting a coded output signal; wherein the said code book comprises a reduced code book only storing reduced codes formed by thinning said code book to 1/M (M being an integer of two or more) of the sampling values inherently possessed by the code book wherein said reduced codes are formed by thinning the codes at predetermined intervals to produce thinned codes in said code book. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A speech coding apparatus comprising:
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a linear predictive analysis unit which receives an input signal of digitalized speech, performs linear prediction, and extracts a linear prediction parameter; a code book which stores codes comprised of white noise series; a prediction filter unit, operatively connected to said linear predictive analysis unit and to said code book, which uses the linear prediction parameter and the codes for filter calculations to produce a reproduced signal; a comparator, operatively connected to said prediction filter unit and receiving as input the reproduced signal and the input signal, and comparing the reproduced signal to the input signal to produce an error signal; an error evaluation unit, operatively connected to said comparator and said code book, and calculating an optimum code giving a minimum error signal; an output unit, operatively connected to said linear predictive analysis unit and said code book, and receiving the optimum code and the linear prediction parameter, outputting a coded output signal; and
wherein the said code book comprises a reduced code book only storing reduced codes formed by thinning said code book to 1/M (M being an integer of two or more) of the sampling values inherently possessed by the code book;further comprising means for compensating for a deterioration of quality of the reproduced signal caused by thinning the codes; and wherein said compensating means comprises an additional linear predictive analysis unit, operatively connected to said code book and to said output unit, and receiving as input the input signal and the optimum code, said additional linear prediction analysis unit calculating an amended linear prediction parameter output to said output unit. - View Dependent Claims (10, 11)
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12. A speech coding apparatus for coding a speech signal, comprising:
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a code book having codes; a first linear predictive analysis unit, receiving as input the speech signal and producing a first linear prediction parameter; a prediction filter unit, operatively connected to said code book and said first linear predictive analysis unit, receiving as input the codes and the first linear prediction parameter and producing a reproduced signal; a comparator, operatively connected to said prediction filter unit, receiving as input the speech signal and the reproduced signal, and producing an error signal; an error evaluation unit, operatively connected to said comparator and said code book, receiving as input the codes and the error signal and calculating an optimum code that produces a minimum error signal; a second linear predictive analysis unit, operatively connected to said code book, and receiving as input the speech signal and the optimum code, producing a residual signal, and calculating a second linear prediction parameter; and an output unit, operatively connected to said code book and said second linear predictive analysis unit, receiving as input the optimum code and the second linear prediction parameter, and producing as output a coded output signal. - View Dependent Claims (13)
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Specification