Computationally efficient sine wave synthesis for acoustic waveform processing
First Claim
1. A method of processing an acoustic waveform, the method comprising:
- sampling a waveform to obtain a series of discrete samples and constructing therefrom a series of frames, each frame spanning a plurality of samples;
analyzing each frame of samples to extract a set of variable frequency components having individual amplitudes;
tracking said components from one frame to a next frame, said tracking including matching a component from the one frame with a component in the next frame having a similar value regardless of shifts in frequency and spectral energy; and
interpolating the values of the components from the one frame to the next frame by performing an overlap-and-add function utilizing Fourier analysis to generate a reconstruction of said waveforms.
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Abstract
Methods and apparatus for reducing discontinuities between frames of sinusoidally modeled acoustic waveforms, such as speech, which occur when sampling at low frame rates. A Fast Fourier Transform-based overlap-add technique is applied to amplitude, frequency and phase components of sinusoidal waves after frame-to-frame sine wave matching has been performed. Matched sine wave amplitudes and frequencies are linearly interpolated and mid-point phase is estimated such that the mid-frame sine wave is best fit to the most recent half-frame segments of the lagging and leading sine waves. Synthetic mid-frame sine waves are generated using the interpolated amplitude and frequency and estimated phase values. Synthesized acoustic waveforms of high quality from original source waveforms can be produced in sinusoidal analysis/synthesis operations at coding frame rates of 50 Hz and lower. The methods and devices disclosed herein are particularly useful for computationally efficient coding and synthesis of speech waveforms.
78 Citations
26 Claims
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1. A method of processing an acoustic waveform, the method comprising:
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sampling a waveform to obtain a series of discrete samples and constructing therefrom a series of frames, each frame spanning a plurality of samples; analyzing each frame of samples to extract a set of variable frequency components having individual amplitudes; tracking said components from one frame to a next frame, said tracking including matching a component from the one frame with a component in the next frame having a similar value regardless of shifts in frequency and spectral energy; and interpolating the values of the components from the one frame to the next frame by performing an overlap-and-add function utilizing Fourier analysis to generate a reconstruction of said waveforms. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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6. The method of claim 1 wherein the method further includes suppressing tonal noise values.
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7. The method of claim 6 wherein the method further includes estimating a noise envelope and using said noise envelope estimate to drive a noise suppression filter.
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8. The method of claim 6 wherein the method further includes generating broadband noise to replace said suppressed noise values.
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9. A method for suppressing tonal noise artifacts during the reconstruction of an acoustic waveform from a sinusoidal parametric representation of the waveform, the method comprising;
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estimating a noise envelope from a set of variable frequency components having individual amplitudes which comprise a parametric representation of the waveform; reconstructing an acoustic waveform from said parametric representation; and filtering said reconstructed waveform using said noise envelope estimates to suppress tonal noise estimates.
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10. A method of deriving phase values for frequency components during reconstruction of an acoustic waveform from a sinusoidal representation of the waveform, the method comprising:
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determining a phase of the fundamental frequency by integration of a pitch frequency obtained by linear interpolation of matched fundamental frequencies between successive frames; determining a pitch onset time by locating the time at which the phase function crosses the nearest multiple of the phase synchrony point; and allocating phase values to the frequency components, such that all of the frequency components come into phase every pitch onset time.
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11. A system for processing an acoustic waveform, the system comprising
sampling means for sampling a waveform to obtain a series of discrete samples and constructing therefrom a series of frames, each frame spanning a plurality of samples, analyzing means for analyzing each frame of samples to extract a set of variable frequency components having individual amplitudes, tracking means for tracking said components from one frame to a next frame, said tracking means including matching means for matching a component from the one frame with a component in the next frame having a similar value regardless of shifts in frequency and special energy, interpolating means for interpolating the values of the components from the one frame to the next frame, including means for performing an overlap-and-add function utilizing Fourier analysis to generate a reconstruction of said waveform.
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19. A receiver for receiving a coded parametric representation of an acoustic waveform in which the representation comprises as set of variable frequency components having individual amplitudes defining sine waves which can be summed to recreate the waveform at a particular frame of time, the receiver comprising:
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decoding means for extracting a set of frequency components having individual amplitudes from each frame of a coded representation of an acoustic waveform; tracking means for tracking said components from one frame to a next frame, said tracking means, including matching means for matching a component from the one frame with a component in the next frame having a similar value regardless of shifts in frequency and spectral energy; and interpolation means for interpolating the values of the components from the one frame to the next frame, including means for performing an overlap-and-add function utilizing Fourier analysis, to generate a reconstruction of said waveform. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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Specification