MBE synthesizer for very low bit rate voice messaging systems

• US 5,684,926 A
• Filed: 01/26/1996
• Issued: 11/04/1997
• Est. Priority Date: 01/26/1996
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Li, Xiaojun, Huang, Jian-Cheng, Simpson, Floyd
• Primary Examiner(s): Tung, Kee M.
• Application Number:
  US08/592,252
• Time in Patent Office: 648 Days
• Field of Search: 395/2.67, 395/2.71, 395/2.73, 395/2.77, 395/2.16, 395/2.14, 395/2.17, 395/2.74, 395/2.09
• US Class Current: 704/268
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 19/10 the excitation function being a multipulse excitation
• CPC Class Codes: G10L 19/16 Vocoder architecture

Abstract

An MBE synthesizer (116) for generating a segment of speech from compressed speech data received by a receiver (2004). The compressed speech data includes one or more indexes (2240, 2242) and pitch data (2248). The MBE synthesizer (116) includes the following: an excitation generator (2222) utilizing a transform function for generating transformed excitation components responsive to the pitch data (2248). A memory (3006) for storing a table of predetermined spectral vectors (2205) and associated predetermined voicing vectors (2203). A harmonic amplitude estimator (2209) that is responsive to the one or more predetermined spectra/vectors identified by the indexes (2240, 2242) received, that generates harmonic amplitude control signals. The harmonic amplitude estimator (2209) which includes a peak detector (2503), a peak enhancer (2505), a valley detector (2507), a valley enhancer (2509). A multi-band voicing controller (2214), responsive to the predetermined voicing vectors which are associated with the one or more predetermined spectral vectors identified, for controlling a selection of the excitation components.

Claims

1. An MBE synthesizer for generating a segment of speech from compressed speech data which is received by a receiver coupled thereto, the compressed speech data which is received includes one or more indexes, the MBE synthesizer comprising:

an excitation generator for generating voiced excitation components and unvoiced excitation components;

a memory for storing a table of predetermined spectral vectors identified by indexes, at least a portion of the table of the predetermined spectral vectors having associated therewith predetermined voicing vectors;

a harmonic amplitude estimator, responsive to one or more predetermined spectral vectors identified by indexes corresponding to the one or more indexes received, and for generating therefrom harmonic amplitude control signals;

a multi-band voicing controller, responsive to the predetermined voicing vectors which are associated with the one or more predetermined spectral vectors identified, for controlling a selection of the excitation components; and

a multiplier, for multiplying the harmonic amplitude control signals and the excitation components selected, for generating spectral components representing the segment of speech.

2. The MBE synthesizer according to claim 1, further comprising an input buffer, coupled to the receiver, for storing the compressed speech data including the one or more indexes received.

3. The MBE synthesizer according to claim 1, wherein the predetermined voicing vectors comprise a plurality of voicing parameters, each of the plurality of voicing parameters associated with a band of excitation components.

4. The MBE synthesizer according to claim 3, wherein the plurality of voicing parameters define a likelihood of the band of excitation components as being voiced and unvoiced.

5. The MBE synthesizer according to claim 1, wherein the excitation components which are voiced comprise discrete Fourier voiced amplitude components and discrete Fourier voiced phase components, and wherein the excitation components which are unvoiced comprise discrete Fourier unvoiced amplitude components and discrete Fourier unvoiced phase components.

6. The MBE synthesizer according to claim 5 wherein

said multi-band voicing controller controls a selection of phase excitation components from the discrete Fourier voiced phase components and from the discrete Fourier unvoiced phase components, the phase excitation components selected representing spectral phase components, and

further controls a selection of amplitude excitation components from the discrete Fourier voiced amplitude components and from the discrete Fourier unvoiced amplitude components, and wherein the MBE synthesizer further comprises

a multiplier, for multiplying the harmonic amplitude control signals and the amplitude excitation components selected, for generating spectral amplitude components, and

wherein said MBE synthesizer further comprises an inverse transform generator for transforming the spectral phase components and the spectral amplitude components into digitized samples representing the segment of speech.

7. The MBE synthesizer according to claim 1, wherein the compressed speech data further includes frame voicing data identifying that the segment of speech is unvoiced, and wherein said multi-band voicing controller is further responsive to the frame voicing data for controlling the selection of the unvoiced excitation components during the segment of speech.

8. The MBE synthesizer according to claim 1 wherein the table of predetermined spectral vectors having associated therewith predetermined voicing vectors represents a first code book, and wherein said memory further includes a table of predetermined residue vectors representing a second code book.

9. An MBE synthesizer for generating a segment of speech from compressed speech data which is received by a receiver coupled thereto, the compressed speech data which is received including one or more indexes and pitch data, the MBE synthesizer comprising:

an excitation generator utilizing a transform function for generating excitation components which are transformed voiced excitation components and transformed unvoiced excitation components, wherein the generation of the transformed voiced excitation components being responsive to the pitch data;

a memory for storing one or more tables of predetermined spectral vectors identified by indexes;

a harmonic amplitude estimator, responsive to one or more predetermined spectral vectors identified by indexes corresponding to the one or more indexes received, and for generating therefrom harmonic amplitude control signals;

a multi-band voicing controller for controlling a selection of the transformed voiced excitation components and transformed unvoiced excitation components; and

a multiplier, for multiplying the harmonic amplitude control signals and the transformed voiced excitation components and transformed unvoiced excitation components selected, for generating spectral components representing the segment of speech.

10. The MBE synthesizer according to claim 9 further comprising an input buffer, coupled to the receiver, for storing the compressed speech data which is received including pitch data.

11. The MBE synthesizer according to claim 9, wherein said excitation generator comprises:

a pitch wave generator for generating a sequence of repetitive digital pitch wave samples in response to the pitch data;

a framer for deriving windowed pitch wave samples by selecting a portion of the sequence of repetitive digital pitch wave samples generated during a window of predetermined duration; and

a transform generator for generating transformed voiced excitation components from the windowed pitch wave samples, the transformed voiced excitation components comprising a voiced phase excitation components and a voiced amplitude excitation components.

12. The MBE synthesizer according to claim 11, wherein the sequence of repetitive digital pitch wave samples is defined by a predetermined sequence of data stored with a memory.

13. The MBE synthesizer according to claim 11 further comprising a normalizer, responsive to the voiced amplitude excitation components for maintaining a total energy for the transformed voiced excitation components at a predetermined energy level.

14. The MBE synthesizer according to claim 11, wherein said transform generator generates the voiced excitation components utilizing a discrete Fourier transform of the windowed pitch wave samples, wherein the transformed voiced excitation components represent discrete Fourier voiced amplitude components and discrete Fourier voiced phase components.

15. The MBE synthesizer according to claim 11, further comprising:

a random phase generator and a constant amplitude generator for generating unvoiced excitation components, wherein the unvoiced excitation components generated by said random phase generator represent discrete Fourier unvoiced phase components, and wherein the unvoiced excitation components generated by said constant amplitude generator represent discrete Fourier unvoiced amplitude components.

16. The MBE synthesizer according to claim 9 wherein the table of predetermined spectral vectors has associated therewith predetermined voicing vectors, and wherein

said multi-band voicing controller is responsive to the predetermined voicing vectors associated with the one or more predetermined spectral vectors identified, for controlling a selection of the transformed voiced excitation components and transformed unvoiced excitation components.

17. The MBE synthesizer according to claim 9, further comprising an inverse transform generator for transforming the spectral components representing a segment of speech into digitized samples representing the segment of speech.

18. The MBE synthesizer according to claim 9, wherein the compressed speech data further includes frame voicing data identifying that the segment of speech is unvoiced, and wherein said multi-band voicing controller is further responsive to the frame voicing data for controlling the selection of the transformed unvoiced excitation components during the segment of speech.

19. An MBE synthesizer for generating a segment of speech from compressed speech data which is received by a receiver coupled thereto, the compressed speech data which is received including one or more indexes and pitch data, the MBE synthesizer comprising:

an excitation generator for generating transformed voiced excitation components and transformed unvoiced excitation components, wherein the generation of the voiced excitation components being responsive to the pitch data;

a memory for storing one or more tables of predetermined spectral vectors identified by indexes;

a harmonic amplitude estimator, responsive to one or more predetermined spectral vectors identified by indexes corresponding to the one or more indexes received, and for generating therefrom harmonic amplitude control signals which are further associated with harmonics defined by the pitch data which is received, and wherein said harmonic amplitude estimator further comprises

a peak detector having a peak magnitude threshold for detecting harmonic amplitude control signals having a magnitude greater than the peak magnitude threshold,

a peak enhancer for generating peak enhanced harmonic amplitude control signals by enhancing magnitudes of harmonic amplitude control signals having magnitudes greater then the peak magnitude threshold,

a valley detector having a minimum magnitude threshold for detecting peak enhanced harmonic amplitude control signals having a magnitude less than the minimum magnitude threshold, and

a valley enhancer for generating enhanced harmonic amplitude control signals by decreasing the magnitudes of the peak enhanced harmonic amplitude control signals having magnitudes less than the minimum magnitude threshold;

a multi-band voicing controller for controlling a selection of the transformed voiced excitation components and transformed unvoiced excitation components; and

a multiplier, for multiplying the harmonic amplitude control signals and the transformed voiced excitation components and transformed unvoiced excitation components selected, for generating spectral components representing the segment of speech.

20. The MBE synthesizer according to claim 19, wherein the peak magnitude threshold is a predetermined proportion of a magnitude of a harmonic amplitude control signal having a maximum amplitude within the harmonic amplitude control signals derived from compressed speech data representing a segment of speech.

21. The MBE synthesizer according to claim 19, wherein the peak enhancer generates the peak enhanced harmonic amplitude control signals by multiplying the magnitude of the harmonic amplitude control signals having magnitudes greater than the peak magnitude threshold by a predetermined number.

22. The MBE synthesizer according to claim 19, wherein the minimum magnitude threshold is a lesser of a first predetermined proportion of a first adjacent peak enhanced harmonic amplitude control signal and a second predetermined proportion of a second adjacent peak enhanced harmonic amplitude control signals.

23. The MBE synthesizer according to claim 19, wherein the valley enhancer generates enhanced harmonic amplitude control signals by multiplying the magnitudes of the peak enhanced harmonic amplitude control signals having a magnitude less than the minimum magnitude threshold by a predetermined number.

24. The MBE synthesizer according to claim 23, wherein harmonic magnitudes are the magnitudes of the peak enhanced harmonic amplitude control signals having the magnitudes less than the minimum magnitude threshold and wherein said harmonic amplitude estimator further comprises:

a magnitude comparator for comparing the harmonic magnitudes with a calculated threshold; and

a magnitude calculator for generating the enhanced harmonic amplitude control signals by calculating the harmonic magnitudes with a first predetermined formula when the harmonic magnitudes that are greater than the calculated threshold and calculating the harmonic magnitudes with a second predetermined formula when the harmonic magnitudes are greater than the calculated threshold.

25. The MBE synthesizer according to claim 19, wherein said harmonic amplitude estimator is further coupled to an input buffer which is coupled to the receiver, for storing the compressed speech data including the one or more indexes received.

26. An MBE synthesizer for generating a segment of speech from compressed speech data which is received by a receiver coupled thereto, the compressed speech data which is received including one or more indexes, the MBE synthesizer comprising:

a memory for storing a table of predetermined spectral vectors identified by indexes, at least a portion of the table of the predetermined spectral vectors having associated therewith predetermined voicing vectors, wherein the predetermined voicing vectors comprise a plurality of voicing parameters associated with a plurality of bands of spectral information, a voicing parameter identifying a likelihood of a band of the plurality of bands being voiced or unvoiced;

a harmonic amplitude estimator, responsive to the one or more indexes for identifying one or more predetermined spectral vectors, and for generating therefrom harmonic amplitudes coefficients;

multi-band voicing controller, being responsive to the predetermined voicing vector and to the harmonic amplitudes coefficients, for controlling voiced/unvoiced characteristics of each of the plurality of bands of spectral information;

multi-band excitation generator for generating excitation components, the excitation components being divided into a plurality of bands of spectral information; and

a multiplier, coupled to the harmonic amplitude estimator and to the multi-band voicing controller, for controlling amplitudes of the excitation components by multiplying the harmonic amplitude coefficients and the excitation components to generate a spectral components representing a segment of speech.

27. The MBE synthesizer according to claim 26, further comprising an input buffer, coupled to the receiver, for storing the compressed speech data including the one or more indexes received.

28. The MBE synthesizer according to claim 26, wherein the voiced excitation components are discrete Fourier voiced amplitude components and discrete Fourier voiced phase components, and wherein the unvoiced excitation components are discrete Fourier unvoiced amplitude components and discrete Fourier unvoiced phase components.

29. The MBE synthesizer according to claim 28 wherein

said multi-band voicing controller controls a selection of phase excitation components from the discrete Fourier voiced phase components and from the discrete Fourier unvoiced phase components, the phase excitation components selected representing spectral phase components, and said multi-band voicing controller further controls the selection of amplitude excitation components from the discrete Fourier voiced amplitude components and from the discrete Fourier unvoiced amplitude components;

and

a multiplier, for multiplying the harmonic amplitude control signals and the amplitude excitation components selected, for generating spectral amplitude components, and

wherein said MBE synthesizer further comprises an inverse transform generator for transforming the spectral phase components and the spectral amplitude components into digitized samples representing the segment of speech.

30. The MBE synthesizer according to claim 26, wherein the compressed speech data further includes frame voicing data identifying that the segment of speech is unvoiced, and wherein said multi-band voicing controller is further responsive to the frame voicing data for controlling the selection of the unvoiced excitation components during the segment the segment of speech.