Vector quantization in a harmonic speech coding arrangement

• US 5,023,910 A
• Filed: 04/08/1989
• Issued: 06/11/1991
• 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): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/321,119
• Time in Patent Office: 794 Days
• Field of Search: 381/29-41, 364/513.5
• US Class Current: 704/206
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/038 Vector quantisation, e.g. TwinVQ audio

Abstract

A harmonic speech coding arrangement where vector quantization is used to improve speech quality. Parameters are determined at the analyzer of an illustrative coding arrangement to model the magnitude and phase spectra of the input speech. A first codebook of vectors is searched for a vector that closely approximates the difference between the true and estimated magnitude spectra. A second codebook of vectors is searched for a vector that closely approximates the difference between the true and the estimated phase spectra. Indices and scaling factors for the vectors are communicated to the synthesizer such that scaled vectors can be added into the magnitude and phase spectra for use at the synthesizer in generating speech as a sum of sinusoids.

Claims

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

determining a spectrum comprising a Fourier transform of said speech,

calculating, based on said determined spectrum, a set of parameters modeling said speech, at least one parameter of said parameter set comprising an index to a codebook of vectors,

communicating said calculated parameter set including said index,

receiving said communicated parameter set including said index,

processing said received parameter set including said index to determine a plurality of sinusoids corresponding to harmonics of said speech, and

synthesizing speech as a sum of said sinusoids.

2. A method in accordance with claim 1 wherein said determined spectrum comprises a magnitude spectrum.

3. A method in accordance with claim 2 wherein said codebook of vectors comprises vectors constructed from a transform of a plurality of sinusoids with random frequencies and amplitudes.

4. A method in accordance with claim 2 wherein said calculating comprises

finding peaks in said magnitude spectrum, and

determining a plurality of sinusoids corresponding to said peaks.

5. A method in accordance with claim 2 wherein said processing comprises

determining a magnitude spectrum from said received parameter set including said index, and

determining a sinusoidal amplitude and a sinusoidal frequency for each of said sinusoids from said magnitude spectrum determined from said received parameter set.

6. A method in accordance with claim 5 wherein said determining a sinusoidal amplitude and a sinusoidal frequency comprises

finding peaks in said magnitude spectrum determined from said received parameter set, and

determining said sinusoidal amplitude and said sinusoidal frequency for each of said sinusoids from said peaks in said magnitude spectrum.

7. A method in accordance with claim 1 wherein said determined spectrum comprises a phase spectrum.

8. A method in accordance with claim 7 wherein said codebook of vectors comprises vectors constructed from white Gaussian noise sequences.

9. A method in accordance with claim 7 wherein said processing comprises

determining a phase spectrum from said received parameter set including said index, and

determining a sinusoidal phase for each of said sinusoids from said phase spectrum determined from said received parameter set.

10. A method in accordance with claim 1 wherein said determined spectrum comprises a Fast Fourier Transform of said speech.

11. A method in accordance with claim 1 wherein said determined spectrum comprises an interpolated spectrum.

12. A method in accordance with claim 1 wherein said calculating comprises

determining a plurality of sinusoids from said determined spectrum, and

selecting said index to minimize error in accordance with an error criterion at the frequencies of said sinusoids.

13. A method in accordance with claim 1 wherein said processing comprises

determining a sinusoidal amplitude for each of said sinusoids based in part on a vector defined by said received index.

14. A method in accordance with claim 1 wherein said processing comprises

determining a sinusoidal frequency for each of said sinusoids based in part on a vector defined by said received index.

15. A method in accordance with claim 1 wherein said processing comprises

determining a sinusoidal phase for each of said sinusoids based in part on a vector defined by said received index.

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

determining a spectrum from said speech,

calculating, based on said determined spectrum, a set of parameters modeling said speech and

communicating said parameter set, wherein at least one parameter of said parameter set comprises an index to a codebook of vectors, and

wherein said determining comprises determining a magnitude spectrum and a phase spectrum, and wherein said calculating comprises

calculating said parameter set comprising first parameters modeling said determined magnitude spectrum and second parameters modeling said determined phase spectrum, at least one of said first parameters comprising an index to a first codebook of vectors, and at least one of said second parameters comprising an index to a second codebook of vectors.

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

determining a spectrum from said speech,

calculating, based on said determined spectrum, a set of parameters modeling said speech and

communicating said parameter set, wherein at least one parameter of said parameter set comprises an index to a codebook of vectors, and

wherein said calculating comprises

determining a plurality of sinusoids from said determined spectrum, including determining sinusoidal amplitude of each of said plurality of sinusoids,

estimating, based on said speech, sinusoidal amplitude of each of said plurality of sinusoids,

determining errors between said determined sinusoidal amplitudes and said estimated sinusoidal amplitudes, and

vector quantizing said determined errors to determine said index.

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

determining a spectrum from said speech,

calculating, based on said determined spectrum, a set of parameters modeling said speech and

communicating said parameter set, wherein at least one parameter of said parameter set comprises an index to a codebook of vectors, and

wherein said calculating comprises

determining a plurality of sinusoids from said determined spectrum, including determining sinusoidal frequency of each of said plurality of sinusoids,

estimating, based on said speech, sinusoidal frequency of each of said plurality of sinusoids,

determining errors between said determined sinusoidal frequencies and said estimated sinusoidal frequencies, and

vector quantizing said determined errors to determine said index.

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

determining a spectrum from said speech,

calculating, based on said determined spectrum, a set of parameters modeling said speech and

communicating said parameter set, wherein at least one parameter of said parameter set comprises an index to a codebook of vectors, and

wherein said calculating comprises

determining a plurality of sinusoids from said determined spectrum, including determining sinusoidal phase of each of said plurality of sinusoids,

estimating, based on said speech, sinusoidal phase of each of said sinusoids,

determining errors between said determined sinusoidal phases and said estimated sinusoidal phases, and

vector quantizing said determined errors to determine said index.

20. A harmonic coding arrangement for processing speech comprising

means responsive to said speech for determining a spectrum comprising a Fourier transform of said speech,

means responsive to said determining means for calculating, based on said determined spectrum, a set of parameters modeling said speech, at least one parameter of said parameter set comprising an index to a codebook of vectors,

means for communicating said calculated parameter set including said index,

means for receiving said communicated parameter set including said index,

means for processing said received parameter set including said index to determine a plurality of sinusoids corresponding to harmonics of said speech, and

means for synthesizing speech as a sum of said sinusoids.