US5351338A
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Time variable spectral analysis based on interpolation for speech coding
Assignee: Telefonaktiebolaget LM Ericsson AB
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Filing: 1992-07-06
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Granted: 1994-09-27
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Expires: 2012-07-06
Abstract
Abstract A time variable spectral analysis for speech coding based upon interpolation between speech frames. A speech signal is modeled by a linear filter which is obtained by a time variable linear predictive coding analysis algorithm. Interpolation between adjacent speech frames is used in order to express a time variation of the speech signal. In addition, interpolation between adjacent frames secures a continuous track of filter parameters across different speech frames.
Inventors
- 👤 Torbjorn K. Wigren
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 15:11
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/02; G10L19/04; G10L19/06
Claims Analysis
Total Claims: 74
Claim 1
Independent Claim
176 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames using time variable spectral models, the method comprising the steps of: sampling a signal to obtain a series of discrete samples and constructing therefrom a series of frames; modeling the spectrum of said signal using a filter model utilizing interpolation of parameter signals between a previous, present and next frame for forming estimated parameters; calculating regressor signals from said estimated parameters; smoothing the spectrum by combining the regressor signals with a smoothing parameter to obtain smoothed regressor signals; combining said smoothed regressor signals with weighting factors to produce a first set of signals; combining parameter signals from the previous frame with said smoothed regressor signals, a signal sample and a weighting factor to produce a second set of signals; calculating parameter signals for the present frame and the next frame from the first and second set of signals; determining whether the filter model is stable after each frame; and stabilizing the filter model if the filter model is determined to be unstable.
Claim 2
Independent Claim
176 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames using time variable spectral models, the method comprising the steps of: sampling a signal to obtain a series of discrete samples and constructing therefrom a series of frames; modeling the spectrum of said signal using a filter model utilizing interpolation of parameter signals between a previous, present and next frame for forming estimated parameters; calculating regressor signals from said estimated parameters; smoothing the spectrum by combining the regressor signals with a smoothing parameter to obtain smoothed regressor signals; combining said smoothed regressor signals with weighting factors to produce a first set of signals; combining parameter signals from the previous frame with said smoothed regressor signals, a signal sample and a weighting factor to produce a second set of signals; calculating parameter signals for the present frame and the next frame from the first and second set of signals; determining whether the filter model is stable after each frame; and stabilizing the filter model if the filter model is determined to be unstable.
Claim 3
Dependent Claim
28 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said filter model is a linear, time-varying all-pole filter.
Claim 4
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said filter model includes a numerator.
Claim 5
Dependent Claim
24 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said interpolation is piecewise constant.
Claim 6
Dependent Claim
24 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said interpolation is piecewise linear.
Claim 7
Dependent Claim
32 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said interpolation extends over more frames than said previous, present and next frames.
Claim 8
Dependent Claim
23 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said interpolation is nonlinear.
Claim 9
Dependent Claim
29 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein spectral smoothing is obtained by prewindowing of the estimated parameters.
Claim 10
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein spectral smoothing is obtained by correlation weighting.
Claim 11
Dependent Claim
31 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein a Schur-Cohn-Jury test is used to determine if said model is stable.
Claim 12
Dependent Claim
36 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein the stability of said model is determined by calculating reflection coefficients and examining the reflection coefficients sizes.
Claim 13
Dependent Claim
30 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein the stability of said model is determined by calculation of poles.
Claim 14
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said model is stabilized by pole-mirroring.
Claim 15
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said model is stabilized by bandwidth expansion.
Claim 16
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said signal frame is a speech frame.
Claim 17
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, said signal frame is a radar signal frame.
Claim 18
Dependent Claim
35 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals for the present frame and the next frame are calculated using Gaussian elimination.
Claim 19
Dependent Claim
37 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals for the present frame and the next frame are calculated using Gaussian elimination with LU-decomposition.
Claim 20
Dependent Claim
34 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals for the present frame and the next frame are calculated using QR-factorization.
Claim 21
Dependent Claim
34 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals for the present frame and the next frame are calculated using U-D-factorization.
Claim 22
Dependent Claim
34 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals for the present frame and the next frame are calculated using Cholesky-factorization.
Claim 23
Dependent Claim
36 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals for the present frame and the next frame are calculated using a Levenberg-Marquardt method.
Claim 24
Dependent Claim
36 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals for the present frame and the next frame are calculated using a recursive formulation.
Claim 25
Dependent Claim
24 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are a-parameters.
Claim 26
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are reflection coefficients.
Claim 27
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are area coefficients.
Claim 28
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are log-area parameters.
Claim 29
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are log-area ratio parameters.
Claim 30
Dependent Claim
28 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are formant frequencies and corresponding bandwidths.
Claim 31
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolating of uninterpolated input signal frames according to claim 1, wherein said parameter signals are arcsine parameters.
Claim 32
Dependent Claim
24 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are autocorrelation-parameters.
Claim 33
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said parameter signals are line spectral frequencies.
Claim 34
Dependent Claim
30 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein an additional known input signal to said spectral model is utilized.
Claim 35
Dependent Claim
28 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 1, wherein said filter model is non-linear in the parameter signals.
Claim 36
Independent Claim
168 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames using time variable spectral models, the method comprising: sampling a signal to obtain a series of discrete samples and constructing therefrom a series of frames; modeling the spectrum of said signal using a filter model utilizing interpolation of parameters between a previous, present and next frame for forming estimated parameters; calculating regressor signals from said estimated parameters; smoothing the spectrum by combining the regressor signals with a smoothing parameter to obtain smoothed regressor signals; combining said smoothed regressor signals with a weighting factor to produce a first set of signals; combining parameter signals from the previous frame with said smoothed regressor signals, a signal sample and a weighting factor to produce a second set of signals; calculating parameter signals for the present frame from the first and second set of signals; determining whether the filter model is stable after each frame; stabilizing the filter model if the filter model is determined to be unstable.
Claim 37
Independent Claim
168 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames using time variable spectral models, the method comprising: sampling a signal to obtain a series of discrete samples and constructing therefrom a series of frames; modeling the spectrum of said signal using a filter model utilizing interpolation of parameters between a previous, present and next frame for forming estimated parameters; calculating regressor signals from said estimated parameters; smoothing the spectrum by combining the regressor signals with a smoothing parameter to obtain smoothed regressor signals; combining said smoothed regressor signals with a weighting factor to produce a first set of signals; combining parameter signals from the previous frame with said smoothed regressor signals, a signal sample and a weighting factor to produce a second set of signals; calculating parameter signals for the present frame from the first and second set of signals; determining whether the filter model is stable after each frame; stabilizing the filter model if the filter model is determined to be unstable.
Claim 38
Dependent Claim
28 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said filter model is a linear, time-varying all-pole filter.
Claim 39
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said filter model includes a numerator.
Claim 40
Dependent Claim
24 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said interpolation is piecewise constant.
Claim 41
Dependent Claim
24 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said interpolation is piecewise linear.
Claim 42
Dependent Claim
32 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said interpolation extends over more frames than said previous, present and next frames.
Claim 43
Dependent Claim
23 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said interpolation is nonlinear.
Claim 44
Dependent Claim
29 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein spectral smoothing is obtained by prewindowing of the estimated parameters.
Claim 45
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein spectral smoothing is obtained by correlation weighting.
Claim 46
Dependent Claim
31 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein a Schur-Cohn-Jury test is used to determine if said model is stable.
Claim 47
Dependent Claim
36 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein the stability of said model is determined by calculating reflection coefficients and examining the reflection coefficients sizes.
Claim 48
Dependent Claim
30 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein the stability of said model is determined by calculation of poles.
Claim 49
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said model is stabilized by pole-mirroring.
Claim 50
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said model is stabilized by bandwidth expansion.
Claim 51
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said signal frame is a speech frame.
Claim 52
Dependent Claim
27 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said signal frame is a radar signal frame.
Claim 53
Dependent Claim
32 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter vector signal for the present frame is calculated using Gaussian elimination.
Claim 54
Dependent Claim
33 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal for the present frame is calculated using Gaussian elimination with LU-decomposition.
Claim 55
Dependent Claim
30 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal for the present frame is calculated using QR-factorization.
Claim 56
Dependent Claim
30 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal for the present frame is calculated using U-D-factorization.
Claim 57
Dependent Claim
30 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal for the present frame is calculated using Cholesky-factorization.
Claim 58
Dependent Claim
32 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal for the present frame is calculated using a Levenberg-Marquardt method.
Claim 59
Dependent Claim
32 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal for the present frame is calculated using a recursive formulation.
Claim 60
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is an a-parameter.
Claim 61
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is a reflection coefficient.
Claim 62
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is an area coefficient.
Claim 63
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is a log-area parameter.
Claim 64
Dependent Claim
27 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is a log-area ratio parameter.
Claim 65
Dependent Claim
30 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is a formant frequency and a corresponding bandwidth.
Claim 66
Dependent Claim
26 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is an arcsine parameter.
Claim 67
Dependent Claim
25 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is an autocorrelation-parameter.
Claim 68
Dependent Claim
27 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said parameter signal is a line spectral frequency.
Claim 69
Dependent Claim
31 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein an additional known input signal to said spectral filter model is utilized.
Claim 70
Dependent Claim
28 words
A method of linear predictive coding analysis and interpolation of uninterpolated input signal frames according to claim 35, wherein said filter model is non-linear in the parameter signals.
Claim 71
Independent Claim
70 words
A method of signal coding, the method comprising: determining a first spectral analysis of signal frames using time variable spectral models and utilizing interpolation of spectral parameters between frames; determining a second spectral analysis using time invariant spectral models; comparing the first analysis to the second spectral analyses to determine which spectral analysis has the highest quality; and selecting the spectral analysis with the highest quality to code the signal.
Claim 72
Independent Claim
70 words
A method of signal coding, the method comprising: determining a first spectral analysis of signal frames using time variable spectral models and utilizing interpolation of spectral parameters between frames; determining a second spectral analysis using time invariant spectral models; comparing the first analysis to the second spectral analyses to determine which spectral analysis has the highest quality; and selecting the spectral analysis with the highest quality to code the signal.
Claim 73
Dependent Claim
45 words
A method of signal coding according to claim 69, wherein said spectral analyses are compared by measuring the signal energy reduction after synthesis filtering with said time variable and time invariant spectral models, and choosing the spectral analysis that gives the highest signal energy reduction.
Claim 74
Dependent Claim
60 words
A method of signal coding according to claim 70, further comprising the step of: determining is said first spectral analysis gives a stable model, wherein said spectral analysis is selected as said first spectral analysis if said first spectral analysis gives a stable model, and said second spectral analysis is selected if said first spectral analysis given an unstable model.
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