Method of and apparatus for coding speech signal

• US 5,884,252 A
• Filed: 05/31/1996
• Issued: 03/16/1999
• Est. Priority Date: 05/31/1995
• Status: Expired due to Term

• Current Assignee: Rakuten, Inc. (Rakuten Group, Inc.)
• Original Assignee: NEC Corporation
• Inventors: Ozawa, Kazunori
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): Opsasnick, Michael N.
• Application Number:
  US08/657,660
• Time in Patent Office: 1,019 Days
• Field of Search: 704/219, 704/220, 704/221, 704/222, 704/226, 704/229, 704/230
• US Class Current: 704/220
• CPC Class Codes: G10L 19/125 Pitch excitation, e.g. pitch synchronous innovation CELP [PSI-CELP]

Abstract

In a speech coding apparatus, a spectral parameter calculator determines spectral parameters from an inputted speech signal, quantizes the spectral parameters, and outputs a plurality of quantization candidates. An adaptive code book determines delays with respect to each of the quantization candidates outputted from the spectral parameter calculator, generates a pitch predictive signal based on a past excitation signal for each of the delays and associating quantization candidates, and outputs a quantization candidate and a delay that provide a minimum distortion between the speech signal and the pitch predictive signal. An excitation quantizer quantizes and outputs the excitation signal of the speech signal. A gain quantizer quantizes and outputs a gain of at least one of the adaptive code book and the quantized excitation signal.

Claims

1. An apparatus for coding a speech signal, comprising:

a spectral parameter calculator for determining spectral parameters from an inputted speech signal, quantizing the spectral parameters, and outputting a plurality of quantization candidates;

an adaptive code book for determining delays with respect to each of said quantization candidates outputted from said spectral parameter calculator, generating a pitch predictive signal based on a past excitation signal for each of the delays and associating quantization candidates, and outputting a quantization candidate and a delay which provide a minimum distortion between the speech signal and said pitch predictive signal;

a excitation quantizer for quantizing and outputting the excitation signal of said speech signal; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

17. The apparatus according to claim 1, further comprising:

an impulse response calculator for receiving the quantized spectral parameters and for calculating and outputting an impulse response of a weighting filter based on the quantized spectral parameters;

a weighting signal calculator for weighting the quantized gain output by said gain quantizer and for outputting a weighted signal as a result thereof;

a response signal quantizer for receiving the quantization candidates from said spectral parameter calculator for each of a plurality of subframes, and for calculating and outputting, using a stored value of a filter memory, a response signal for one subframe;

an audio weighting circuit for receiving the inputted speech signal divided into subframes and for receiving the plurality of quantization candidates from said spectral parameter calculator, for calculating an audio weighting on the speech signal in each of the subframes, and for outputting an audio-weighted speech signal as a result thereof; and

a subtractor for subtracting the audio-weighted speech signal from the response signal to produce a subtracted signal as a result;

wherein said adaptive code book comprises;

a delay searching and distortion calculating circuit which receives the past excitation signal on a first input terminal, the subtracted signal on a second input terminal, and the impulse response on a third input terminal, and for determining the delay as a result;

a decision circuit for receiving a plurality of distortions and corresponding delays from the delay searching and distortion calculating circuit, and for determining the delay which provides the minimum distortion between the speech signal and said pitch predictive signal; and

a residual calculator connected to receive the delay which provides the minimum distortion from said decision circuit and for effecting pitch prediction to determine a corresponding pitch predictive signal that is output to said excitation quantizer.

2. An apparatus for coding a speech signal, comprising:

a spectral parameter calculator for determining spectral parameters from an inputted speech signal, quantizing the spectral parameters, and outputting a plurality of quantization candidates;

an adaptive code book for determing delay, generating delay candidates existing within predetermined delay range, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for a delay candidate and quantization candidate, for each of all combinations between each of said delay candidates and each of quantization candidates, and outputting an optimal combination between a quantization candidate and a delay which provides a minimum distortion between the inputted speech signal and said quantized excitation signal; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

18. The apparatus according to claim 2, further comprising:

an impulse response calculator for receiving the quantized spectral parameters and for calculating and outputting an impulse response of a weighting filter based on the quantized spectral parameters;

a weighting signal calculator for weighting the quantized gain output by said gain quantizer and for outputting a weighted signal as a result thereof;

a response signal quantizer for receiving the quantization candidates from said spectral parameter calculator for each of a plurality of subframes, and for calculating and outputting, using a stored value of a filter memory, a response signal for one subframe;

an audio weighting circuit for receiving the inputted speech signal divided into subframes and for receiving the plurality of quantization candidates from said spectral parameter calculator, for calculating an audio weighting on the speech signal in each of the subframes, and for outputting an audio-weighted speech signal as a result thereof; and

a subtractor for subtracting the audio-weighted speech signal from the response signal to produce a subtracted signal as a result;

wherein said adaptive code book comprises;

a search range setting circuit for presetting a search range for a plurality of delay and for outputting the predetermined delay range as a result;

a delay searching and distortion calculating circuit which receives the past excitation signal on a first input terminal, the subtracted signal on a second input terminal, and the impulse response on a third input terminal, and the predetermined delay range on a fourth input terminal, and for determining the delay as a result;

a decision circuit for receiving a plurality of distortions and corresponding delays from the delay searching and distortion calculating circuit, and for determining the delay which provides the minimum distortion between the speech signal and said pitch predictive signal; and

a residual calculator connected to receive the delay which provides the minimum distortion from said decision circuit and for effecting pitch prediction to determine and output a corresponding pitch predictive signal for the delay which provides the minimum distortion.

3. An apparatus for coding a speech signal, comprising:

a spectral parameter and delay calculator for calculating spectral parameters and a first delay from a signal extracted from a past excitation signal for a delay and an inputted speech signal;

a spectral parameter quantizer for quantizing the spectral parameters and outputting at least one quantization candidate;

an adaptive code book for determining a second delay based on said first delay, calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates;

an excitation quantizer for quantizing and outputting the excitation signal of said speech signal; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

19. The apparatus according to claim 3, further comprising:

an impulse response calculator for receiving the quantized spectral parameters and for calculating and outputting an impulse response of a weighting filter based on the quantized spectral parameters;

a weighting signal calculator for weighting the quantized gain output by said gain quantizer and for outputting a weighted signal as a result thereof;

a response signal quantizer for receiving the quantization candidates from said spectral parameter calculator for each of a plurality of subframes, and for calculating and outputting, using a stored value of a filter memory, a response signal for one subframe;

an audio weighting circuit for receiving the inputted speech signal divided into subframes and for receiving the plurality of quantization candidates from said spectral parameter calculator, for calculating an audio weighting on the speech signal in each of the subframes, and for outputting an audio-weighted speech signal as a result thereof; and

a subtractor for subtracting the audio-weighted speech signal from the response signal to produce a subtracted signal as a result;

wherein said adaptive code book comprises;

a search range setting circuit for receiving the first delays and for determining and outputting a search range based on the second delay candidates neighboring said first delay;

a delay searching and distortion calculating circuit which receives the past excitation signal on a first input terminal, the subtracted signal on a second input terminal, and the impulse response on a third input terminal, and the search range on a fourth input terminal, and for determining the delay as a result;

a decision circuit for receiving a plurality of distortions and corresponding delays from the delay searching and distortion calculating circuit, and for determining the delay which provides the minimum distortion between the speech signal and said pitch predictive signal; and

a residual calculator connected to receive the delay which provides the minimum distortion from said decision circuit and for effecting pitch prediction to determine a corresponding pitch predictive signal that is output to said excitation quantizer.

4. An apparatus for coding a speech signal, comprising:

a spectral parameter and delay calculator for being supplied with an inputted speech signal, jointly calculating spectral parameters and a first delay from a signal scissored from a past drive signal for a delay and the inputted speech signal;

a drive signal calculator for calculating a drive signal from said spectral parameters and said speech signal;

a spectral parameter quantizer for quantizing the spectral parameters and outputting at least one quantization candidate;

an adaptive code book for determing second delay based on said first delay, calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates,

a excitation quantizer for quantizing and outputting the excitation signal of said speech signal; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

5. An apparatus for coding a speech signal, comprising:

a mode decision unit for deciding a mode of an inputted speech signal and outputting mode decision information;

a spectral parameter calculator for determining spectral parameters from the speech signal, quantizing the spectral parameters, and outputting a plurality of quantization candidates;

an adaptive code book for determining delay with respect to each of said quantization candidates, respectively, outputted from said spectral parameter quantizer, generating a pitch predective signal based on a past excitation signal for each of the delays and associating quantization candidates, and outputting a quantization candidate and a delay which provide a minimum distortion between the speech signal and said pitch predective signal, if the mode decision information outputted from said mode decision unit represents a predetermined mode;

a excitation quantizer for quantizing and outputting the excitation signal of said speech signal; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

6. An apparatus for coding a speech signal, comprising:

a mode decision unit for deciding a mode of an inputted speech signal and outputting mode decision information;

a spectral parameter calculator for determining spectral parameters from the speech signal, quantizing the spectral parameters, and outputting a plurality of quantization candidates;

an adaptive code book for determining `delay, generating delay candidates existing within predetermined delay range, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for a delay candidate and quantization candidate, for each of all combinations between each of said delay candidates and each of quantization candidates, and outputting an optimal combination between a quantization candidate and a delay which provides a minimum distortion between the inputted speech signal and said pitch predective signal, if the mode decision information outputted from said mode decision unit represents a predetermined mode; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

7. An apparatus for coding a speech signal, comprising:

a mode decision unit for decoding a mode of an inputted speech signal and outputting mode decision information;

a spectral parameter calculator for determining spectral parameters from the speech signal, quantizing the spectral parameters, and outputting a plurality of quantization candidates;

a spectral parameter and delay calculator for calculating spectral parameters and a first delay from a signal extracted from a past excitation signal for a delay and an inputted speech signal;

a spectral parameter quantizer for quantizing the spectral parameters and outputting at least one quantization candidate;

an adaptive codebook code book for determining a second delay based on said first delay, calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates, if the mode decision information outputted from said mode decision unit represents a predetermined mode;

an excitation quantizer for quantizing and outputting the excitation signal of said speech signal; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

8. An apparatus for coding a speech signal, comprising:

a mode decision unit for deciding a mode of an inputted speech signal and outputting mode decision information;

a spectral parameter calculator and delay calculator for being supplied with an inputted speech signal, jointly calculating spectral parameters and a first delay from a signal extracted from a past drive signal for a delay and the inputted speech signal;

a drive signal calculator for calculating a drive signal from said spectral parameters and said speech signal;

a spectral parameter quantizer for quantizing the spectral parameters and outputting at least one quantization candidate;

an adaptive codebook code book for determining a second delay based on said first delay, calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates, if the mode decision information outputted from said mode decision unit represents a predetermined mode;

an excitation quantizer for quantizing and outputting the excitation signal of said speech signal; and

a gain quantizer for quantizing and outputting a gain of at least one of said adaptive code book and said quantized excitation signal.

9. A method of coding a speech signal, comprising the steps of:

determining spectral parameters from an inputted speech signal, quantizing the spectral parameters, and outputting a plurality of quantization candidates; and

determining delays with respect to said quantization candidates, generating a pitch predictive signal based on a past excitation signal for each of the delays and each of the quantization candidates, and determining a quantization candidate and a delay which provide a minimum distortion between the inputted speech signal and said pitch predictive signal.

10. A method of coding a speech signal, comprising the steps of:

determining spectral parameters from an inputted speech signal, quantizing the spectral parameters, and outputting a plurality of quantization candidates;

determining delay, generating delay candidates existing within predetermined delay range, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for a delay candidate and quantization candidate, for each of all combinations between each of said delay candidates and each of quantization candidates, and outputting an optimal combination between a quantization candidate and a delay which provides a minimum distortion between the inputted speech signal and said quantized excitation signal.

11. A method of coding a speech signal, comprising the steps of:

calculating spectral parameters and a first delay from a signal extracted from a past excitation signal for a delay and an inputted speech signal;

determining at least one quantization candidate for said spectral parameters; and

calculating at least one second delay based on said first delay, calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates.

12. A method of coding a speech signal, comprising the steps of:

inputting a speech signal, calculating spectral parameters and a first delay from a signal extracted from a past drive signal for a delay and the inputted speech signal;

calculating a drive signal from said spectral parameters and said speech signal;

determining at least one quantization candidate for said spectral parameters;

calculating at least one second delay based on said first delay, calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates.

13. A method of coding a speech signal, comprising the steps of:

deciding a mode of an inputted speech signal;

determining spectral parameters from the speech signal, quantizing the spectral parameters, and determining a plurality of quantization candidates; and

determining a delay with respect to each of said quantization candidates, respectively, outputted from said spectral parameter quantizer, generating a pitch predective signal based on a past excitation signal for each of the delays and associating quantization candidates, and outputting a quantization candidate and a delay which provide a minimum distortion between the speech signal and said pitch predictive signal, if the mode decision information outputted from said mode decision unit represents a predetermined mode.

14. A method of coding a speech signal, comprising the steps of:

deciding a mode of an inputted speech signal;

determining spectral parameters from the speech signal, quantizing the spectral parameters, and determining a plurality of quantization candidates; and

determining delay, generating delay candidates existing within predetermined delay range, generating a pitch predictive signal calculated using a signal extracted from past excitation signal for a delay candidate and quantization candidate, for each of all combinations between each of said delay candidates and each of quantization candidates, and outputting an optimal combination between a quantization candidate and a delay which provides a minimum distortion between the inputted speech signal and said pitch predective signal, if the mode decision information outputted from said mode decision unit represents a predetermined mode.

15. A method of coding a speech signal, comprising the steps of:

deciding a mode of an inputted speech signal;

determining spectral parameters from the speech signal, quantizing the spectral parameters, and determining a plurality of quantization candidates;

calculating spectral parameters and a first delay from a signal extracted from a past excitation signal for a delay and the inputted speech signal;

quantizing the spectral parameters and determining at least one quantization candidate; and

calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from a past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates, if the mode decision information outputted from said mode decision unit represents a predetermined mode.

16. A method of coding a speech signal, comprising the steps of:

deciding a mode of an inputted speech signal;

calculating spectral parameters and a first delay from a signal extracted from a past drive signal for a delay and the inputted speech signal;

calculating a drive signal from said spectral parameters and said speech signal;

quantizing said spectral parameters and determining at least one quantization candidate; and

calculating at least one second delay candidate neighboring said first delay, generating a pitch predictive signal calculated using a signal extracted from past excitation signal for said second delay candidate and quantization candidate, for all of the combinations between each of second delay candidates and each of quantization candidates, if the mode decision information outputted from said mode decision unit represents a predetermined mode.