Harmonic speech coding arrangement where a set of parameters for a continuous magnitude spectrum is determined by a speech analyzer and the parameters are used by a synthesizer to determine a spectrum which is used to determine senusoids for synthesis

• US 5,179,626 A
• Filed: 04/08/1988
• Issued: 01/12/1993
• Est. Priority Date: 04/08/1988
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.), Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: AT&T, Inc.
• Inventors: Thomson, David L.
• Primary Examiner(s): Fleming, Michael R.
• Assistant Examiner(s): Doerrler, Michelle
• Application Number:
  US07/179,170
• Time in Patent Office: 1,740 Days
• Field of Search: 381/29-40, 381/51, 364/513.5
• US Class Current: 704/200
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders

Abstract

A harmonic coding arrangement where the magnitude spectrum of the input speech is modeled at the analyzer by a relatively small set of parameters and, significantly, as a continuous rather than only a line magnitude spectrum. The synthesizer, rather than the analyzer, determines the magnitude, frequency, and phase of a large number of sinusoids which are summed to generate synthetic speech. Rather than receiving information explicitly defining the sinusoids from the analyzer, the synthesizer receives the small set of parameters and uses those parameters to determine a spectrum, which, in turn, is used by the synthesizer to determine the sinusoids for synthesis.

Claims

1. In a harmonic speech coding arrangement, a method of processing speech signals, said speech signals comprising frames of speech, said method comprising

determining from a present one of said frames a magnitude spectrum having a plurality of spectrum points, the frequency of each of said spectrum points being independent of said speech signals,

calculating a set of parameters for a continuous magnitude spectrum that models said determined magnitude spectrum at each of said spectrum points, the number of parameters of said set being less than the number of said spectrum points, said continuous magnitude spectrum comprising a sum of a plurality of functions, one of said functions being a magnitude spectrum for a previous one of said frames,

encoding said set of parameters as a set of parameter signals representing said speech signals,

communicating said set of parameter signals representing said speech signals for use in speech synthesis, and

synthesizing speech based on said communicated set of parameter signals.

2. A method in accordance with claim 1 wherein at least one of said functions is a magnitude spectrum of a periodic pulse train.

3. A method in accordance with claim 1 wherein one of said functions is a magnitude spectrum of a first periodic pulse train and another one of said functions is a magnitude spectrum of a second periodic pulse train.

4. A method in accordance with claim 1 wherein one of said functions is a vector chosen from a codebook.

5. A method in accordance with claim 1 further comprising

determining a phase spectrum from a present one of said frames,

calculating a second set of parameters modeling said determined phase spectrum by prediction of a phase spectrum for said present frame from a phase spectrum for a previous one of said frames,

encoding said second set of parameters as a second set of parameter signals representing said speech signals, and

communicating said second set of parameter signals representing said speech signals for use in speech synthesis.

6. A method in accordance with claim 1 wherein said determining comprises

determining one magnitude spectrum from a present one of said frames, and

determining another magnitude spectrum from a previous one of said frames, and wherein said method further comprises

determining one plurality of sinusoids from said one magnitude spectrum,

determining another plurality of sinusoids from said another magnitude spectrum,

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency,

determining a phase spectrum from said present frame,

calculating a second set of parameters modeling said determined phase spectrum by prediction of a phase spectrum for said present frame from a phase spectrum for a previous one of said frames based on said matched ones of said one and said another pluralities of sinusoids,

encoding said second set of parameters as a second set of parameter signals representing said speech signals, and

communicating said second set of parameter signals representing said speech signals for use in speech synthesis.

7. A method in accordance with claim 1 wherein said determining comprises

determining one magnitude spectrum from a present one of said frames, and

determining another magnitude spectrum from a previous one of said frames, and wherein said method further comprises

determining one plurality of sinusoids from said one magnitude spectrum,

determining another plurality of sinusoids from said another magnitude spectrum,

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency and amplitude,

determining a phase spectrum from said present frame,

calculating a second set of parameters modeling said determined phase spectrum by prediction of a phase spectrum for said present frame from a phase spectrum for a previous one of said frames based on said matched ones of said one and said another pluralities of sinusoids,

encoding said second set of parameters as a second set of parameter signals representing said speech signals, and

communicating said second set of parameter signals representing said speech signals for use in speech synthesis.

8. A method in accordance with claim 1 wherein said determining comprises

determining one magnitude spectrum from a present one of said frames, and

determining another magnitude spectrum from a previous one of said frames, and wherein said method further comprises

determining one plurality of sinusoids from said one magnitude spectrum,

determining another plurality of sinusoids from said another magnitude spectrum,

determining a pitch of said present frame,

determining a pitch of said frame other than said present frame,

determining a ratio of said pitch of said present frame and said pitch of said frame other than said present frame,

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency and said determined ratio,

determining a phase spectrum from said present frame,

calculating a second set of parameters modeling said determined phase spectrum by prediction of a phase spectrum for said present frame from a phase spectrum for a previous one of said frames based on said matched ones of said one and said another pluralities of sinusoids,

encoding said second set of parameters as a second set of parameter signals representing said speech signals, and

communicating said second set of parameter signals representing said speech signals for use in speech synthesis.

9. A method in accordance with claim 1 wherein said determining comprises

determining one magnitude spectrum from a present one of said frames, and

determining another magnitude spectrum from a previous one of said frames other than said present frame, and wherein said method further comprises

determining one plurality of sinusoids from said one magnitude spectrum,

determining another plurality of sinusoids from said another magnitude spectrum,

determining a pitch of said present frame,

determining a pitch of said frame other than said present frame,

determining a ratio of said pitch of said present frame and said pitch of said frame other than said present frame,

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency and amplitude and said determined ratio,

determining a phase spectrum from said present frame,

calculating a second set of parameters modeling said determined phase spectrum by prediction of a phase spectrum for said present frame from a phase spectrum for a previous one of said frames based on said matched ones of said one and said another pluralities of sinusoids,

encoding said second set of parameters as a second set of parameter signals representing said speech signals, and

communicating said second set of parameter signals representing said speech signals for use in speech synthesis.

10. A method in accordance with claim 1 said method further comprising

determining a phase spectrum from a present one of said frames,

obtaining a first phase estimate by parametric analysis of said present frame,

obtaining a second phase estimate by prediction of a phase spectrum for said present frame from a phase spectrum for a previous one of said frames,

selecting one of said first and second phase estimates,

determining a second set of parameters, said second parameter set being associated with said selected phase estimate and said second parameter set modeling said determined phase spectrum,

encoding said second set of parameters as a second set of parameter signals representing said speech signals, and

communicating said second set of parameter signals representing said speech signals for use in speech synthesis.

11. A method in accordance with claim 1 said method further comprising

determining a plurality of sinusoids from said determined magnitude spectrum,

determining a phase spectrum from a present one of said frames,

obtaining a first phase estimate by parametric analysis of said present frame,

obtaining a second phase estimate by prediction of a phase spectrum for said present frame from a phase spectrum for a previous one of said frames,

selecting one of said first and second phase estimates in accordance with an error criterion at the frequencies of said determined sinusoids,

determining a second set of parameters, said second parameter set being associated with said selected phase estimate and said second parameter set modeling said determined phase spectrum,

encoding said second set of parameters as a second set of parameter signals representing said speech signals, and

communicating said second set of parameter signals representing said speech signals for use in speech synthesis.

12. In a harmonic speech coding arrangement, a method of processing speech signals comprising

determining from said speech signals a magnitude spectrum having a plurality of spectrum points, the frequency of each of said spectrum points being independent of said speech signals,

calculating a set of parameters for a continuous magnitude spectrum that models said determined magnitude spectrum at each of said spectrum points, the number of parameters of said set being less than the number of said spectrum points,

encoding said set of parameters as a set of parameter signals representing said speech signals,

communicating said set of parameter signals representing said speech signals for use in speech synthesis, and

synthesizing speech based on said communicated set of parameter signals;

wherein said calculating comprises

calculating said parameter set to fit said continuous magnitude spectrum to said determined magnitude spectrum in accordance with a minimum mean squared error criterion.

13. In a harmonic speech coding arrangement, a method of processing speech signals comprising

determining from said speech signals a magnitude spectrum having a plurality of spectrum points, the frequency of each of said spectrum points being independent of said speech signals,

calculating a set of parameters for a continuous magnitude spectrum that models said determined magnitude spectrum at each of said spectrum points, the number of parameters of said set being less than the number of said spectrum points,

encoding said set of parameters as a set of parameter signals representing said speech signals,

communicating said set of parameter signals representing said speech signals for use in speech synthesis,

determining a phase spectrum from said speech signals,

calculating a second set of parameters modeling said determined phase spectrum,

encoding said second set of parameters as a second set of parameter signals representing said speech signals,

communicating said second set of parameter signals representing said speech signals for use in speech synthesis, and

synthesizing speech based on said communicated sets of parameter signals.

14. A method in accordance with claim 13 wherein said calculating a second set of parameters comprises

calculating said second parameter set modeling said determined phase spectrum as a sum of a plurality of functions.

15. A method in accordance with claim 14 wherein one of said functions is a vector chosen from a codebook.

16. A method in accordance with claim 13 wherein said calculating a second set of parameters comprises

calculating said second parameter set using pole-zero analysis to model said determined phase spectrum.

17. A method in accordance with claim 13 wherein said calculating a second set of parameters comprises

calculating said second parameter set using all pole analysis to model said determined phase spectrum.

18. A method in accordance with claim 13 wherein said calculating a second set of parameters comprises

using pole-zero analysis to model said determined phase spectrum,

using all pole analysis to model said determined phase spectrum,

selecting one of said pole-zero analysis and said all pole analysis, and

determining said second parameter set based on said selected analysis.

19. In a harmonic speech coding arrangement, a method of processing speech signals comprising

determining from said speech signals a magnitude spectrum having a plurality of spectrum points, the frequency of each of said spectrum points being independent of said speech signals,

calculating a set of parameters for a continuous magnitude spectrum that models said determined magnitude spectrum at each of said spectrum points, the number of parameters of said set being less than the number of said spectrum points,

encoding said set of parameters as a set of parameter signals representing said speech signals,

communicating said set of parameter signals representing said speech signals for use in speech synthesis,

determining a plurality of sinusoids from said determined magnitude spectrum,

determining a phase spectrum from said speech signals,

calculating a second set of parameters modeling said determined phase spectrum at the frequencies of said determined sinusoids, and

encoding said second set of parameters as a second set of parameter signals representing said speech signals,

communicating said second set of parameter signals representing said speech signals for use in speech synthesis, and

synthesizing speech based on said communicated sets of parameter signals.

20. In a harmonic speech coding arrangement, a method of synthesizing speech comprising

receiving a set of parameters corresponding to input speech comprising frames of input speech,

determining a spectrum from said parameter set, said spectrum having amplitude values for a range of frequencies, said determining a spectrum comprising

determining an estimated magnitude spectrum for a present one of said frames as a sum of a plurality of functions, one of said functions being an estimated magnitude spectrum for a previous one of said frames, said method further comprising

determining a plurality of sinusoids from said spectrum, the sinusoidal frequency of at least one of said sinusoids being determined based on amplitude values of said spectrum, and

synthesizing speech as a sum of said sinusoids.

21. A method in accordance with claim 20 wherein at least one of said functions is a magnitude spectrum of a periodic pulse train, the frequency of said pulse train being defined by said received parameter set.

22. A method in accordance with claim 20 wherein one of said functions is a magnitude spectrum of a first periodic pulse train and another one of said functions is a magnitude spectrum of a second periodic pulse train, the frequencies of said first and second pulse trains being defined by said received parameter set.

23. A method in accordance with claim 20 wherein said determining a spectrum comprises

determining an estimated phase spectrum using an all pole model and said received parameter set.

24. A method in accordance with claim 20 wherein said receiving step comprises

receiving said parameter set for said present frame of speech, and wherein said determining a spectrum comprises

in response to a first value of one parameter of said parameter set, determining an estimated phase spectrum for said present frame using a parametric model and said parameter set, and

in response to a second value of said one parameter, determining an estimated phase spectrum for said present frame using a prediction model based on a previous frame of speech.

25. A method in accordance with claim 20 wherein said receiving comprises

receiving one set of parameters for one of said frames of input speech and another set of parameters for another of said frames of input speech after said one frame, wherein said determining a spectrum comprises

determining one spectrum from said one parameter set and another spectrum from said another parameter set, wherein said determining a plurality of sinusoids comprises

determining one plurality of sinusoids from said one spectrum and another plurality of sinusoids from said another spectrum, wherein said method further comprises

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency, and wherein said synthesizing comprises

interpolating between matches ones of said one and said another pluralities of sinusoids.

26. A method in accordance with claim 20 wherein said receiving comprises

receiving one set of parameters for one of said frames of input speech and another set of parameters for another of said frames of input speech after said one frame, wherein said determining a spectrum comprises

determining one spectrum from said one parameter set and another spectrum from said another parameter set, wherein said determining a plurality of sinusoids comprises

determining one plurality of sinusoids from said one spectrum and another plurality of sinusoids from said another spectrum, wherein said method further comprises

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency and amplitude, and wherein said synthesizing comprises

interpolating between matched ones of said one and said another pluralities of sinusoids.

27. A method in accordance with claim 20 wherein said receiving comprises

receiving one set of parameters for one of said frames of input speech and another set of parameters for another of said frames of input speech after said one frame, wherein said determining a spectrum comprises

determining one spectrum from said one parameter set and another spectrum from said another parameter set, wherein said determining a plurality of sinusoids comprises

determining one plurality of sinusoids from said one spectrum and another plurality of sinusoids from said another spectrum, wherein said method further comprises

determining a pitch of said present frame,

determining a pitch of said frame other than said present frame,

determining a ratio of said pitch of said one frame and said pitch of said another frame, and

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency and said determined ratio, and wherein said synthesizing comprises

interpolating between matched ones of said one and said another pluralities of sinusoids.

28. A method in accordance with claim 20 wherein said receiving comprises

receiving one set of parameters for one of said frames of input speech and another set of parameters for another of said frames of input speech after said one frame, wherein said determining a spectrum comprises

determining one spectrum from said one parameter set and another spectrum from said another parameter set, wherein said determining a plurality of sinusoids comprises

determining one plurality of sinusoids from said one spectrum and another plurality of sinusoids from said another spectrum, wherein said method further comprises

determining a pitch of said present frame,

determining a pitch of said frame other than said present frame,

determining a ratio of said pitch of said one frame and said pitch of said another frame, and

matching ones of said one plurality of sinusoids with ones of said another plurality of sinusoids based on sinusoidal frequency and amplitude and said determined ratio, and wherein said synthesizing comprises

interpolating between matched ones of said one and said another pluralities of sinusoids.

29. In a harmonic speech coding arrangement, a method of synthesizing speech comprising

receiving a set of parameters,

determining a spectrum having amplitude values for a range of frequencies from said parameter set by estimating a magnitude spectrum as a sum of a plurality of functions, wherein one of said functions is a vector from a codebook, said vector being identified by an index defined by said received parameter set,

determining a plurality of sinusoids from said spectrum, the sinusoidal frequency of at least one of said sinusoids being determined based on amplitude values of said spectrum, and

synthesizing speech as a sum of said sinusoids.

30. In a harmonic speech coding arrangement, a method of synthesizing speech comprising

receiving a set of parameters,

determining a spectrum from said parameter set, said spectrum having amplitude values for a range of frequencies,

determining a plurality of sinusoids from said spectrum, the sinusoidal frequency of at least one of said sinusoids being determined based on amplitude values of said spectrum, and

synthesizing speech as a sum of said sinusoids;

wherein said determining a spectrum comprises

determining an estimated phase spectrum as a sum of a plurality of functions.

31. A method in accordance with claim 30 wherein one of said functions is a vector from a codebook, said vector being identified by an index defined by said received parameter set.

32. In a harmonic speech coding arrangement, a method of synthesizing speech comprising

receiving a set of parameters,

determining a spectrum from said parameter set, said spectrum having amplitude values for a range of frequencies,

determining a plurality of sinusoids from said spectrum, the sinusoidal frequency of at least one of said sinusoids being determined based on amplitude values of said spectrum, and

synthesizing speech as a sum of said sinusoids;

wherein said determining a spectrum comprises

determining an estimated phase spectrum using a pole-zero model and said received parameter set.

33. In a harmonic speech coding arrangement, a method of synthesizing speech comprising

receiving a set of parameters,

determining a spectrum from said parameter set, said spectrum having amplitude values for a range of frequencies,

determining a plurality of sinusoids from said spectrum, the sinusoidal frequency of at least one of said sinusoids being determined based on amplitude values of said spectrum, and

synthesizing speech as a sum of said sinusiods;

wherein said determining a spectrum comprises

determining an estimated magnitude spectrum, wherein said determining a plurality of sinusoids comprises

finding a peak in said estimated magnitude spectrum,

subtracting from said estimated magnitude spectrum a spectral component for a sinusoid with the frequency and amplitude of said peak, and

repeating said finding and said subtracting until the estimated magnitude spectrum is below a threshold for all frequencies.

34. A method in accordance with claim 33 wherein said spectral component comprises a wide magnitude spectrum window.

35. In a harmonic speech coding arrangement, a method of synthesizing speech comprising

receiving a set of parameters,

determining a spectrum from said parameter set, said spectrum having amplitude values for a range of frequencies,

determining a plurality of sinusoids from said spectrum, the sinusoidal frequency of at least one of said sinusoids being determined based on amplitude values of said spectrum, and

synthesizing speech as a sum of said sinusoids;

wherein said determining a spectrum comprises

determining an estimated magnitude spectrum, and

determining an estimated phase spectrum, wherein said determining a plurality of sinusoids comprises

determining sinusoidal amplitude and frequency for each of said sinusoids based on said estimated magnitude spectrum, and

determining sinusoidal phase for each of said sinusoids based on said estimated phase spectrum.

36. In a harmonic speech coding arrangement, a method of processing speech, said speech comprising frames of speech, said method comprising

determining from said speech a magnitude spectrum having a plurality of spectrum points, the frequency of each of said spectrum points being independent of said speech, said magnitude of spectrum having a plurality of points being determined from a present one of said frames,

calculating a set of parameters for a continuous magnitude spectrum that models said determined magnitude spectrum at each of said spectrum points, the number of parameters of said set being less than the number of said spectrum points, said continuous magnitude spectrum comprising a sum of a plurality of functions, one of said functions being a magnitude spectrum for a previous one of said frames,

communicating said parameter set,

receiving said communicated parameter set,

determining a spectrum from said received parameter set,

determining a plurality of sinusoids from said spectrum determined from said received parameter set, and

synthesizing speech as a sum of said sinusoids.

37. In a harmonic speech coding arrangement, apparatus comprising

means responsive to speech signals for determining a magnitude spectrum having a plurality of spectrum points, said speech signals comprising frames of speech, said determining means determining said magnitude spectrum having a plurality of spectrum points from a present one of said frames,

means responsive to said determining means for calculating a set of parameters for a continuous magnitude spectrum that models said determined magnitude spectrum at each of said spectrum points, the number of parameters of said set being less than the number of said spectrum points, said continuous magnitude spectrum comprising a sum of a plurality of functions, one of said functions being a magnitude spectrum for a previous one of said frames,

means for encoding said set of parameters as a set of parameter signals representing said speech signals,

means for communicating said set of parameter signals representing said speech signals for use in speech synthesis, and

means for synthesizing speech based on said set of parameter signals communicated by said communicating means.

38. In a harmonic speech coding arrangement, a speech synthesizer comprising

means responsive to receipt of a set of parameters corresponding to input speech comprising frames of input speech for determining a spectrum, said spectrum having amplitude values for a range of frequencies, said determining means including means for developing an estimated magnitude spectrum for a present one of said frames as a sum of a plurality of functions, one of said functions being an estimated magnitude spectrum for a previous one of said frames,

means for determining a plurality of sinusoids from said spectrum, the sinusoidal frequency of at least one said sinusoids being determined based on amplitude values of said spectrum, and

means for synthesizing speech as a sum of said sinusoids.