Audio pre-processing methods and apparatus
First Claim
1. A method of pre-processing an acoustic waveform prior to transmission to reduce the peak-to-RMS ratio of the waveform, the method comprising:
- a. sampling the waveform to obtain a series of discrete samples and constructing therefrom a series of frames, each frame spanning a plurality of samples;
b. analyzing each frame of samples to extract a set of variable frequency components having individual amplitudes and phases;
c. removing the natural phase dispersion from said variable frequency components and substituting therefor a desired phase dispersion;
d. tracking said components from one frame to a next frame; and
e. interpolating the values of the components from the one frame to the next frame to obtain a parametric representation of the waveform whereby a synthetic waveform having a flattened time-domain envelope can be constructed by generating a set of sine waves corresponding to the interpolated values of the parametric representation.
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Abstract
A lower threshold for dynamic range compression and clipping is allowed by sinusoidal estimation and phase adjustment of the original speech signal to obtain a lower Peak to RMS ratio. A sinusoidal speech representation system is applied to the problem of speech dispersion by pre-processing the waveform prior to transmission to reduce the peak-to-RMS ratio of the waveform. The sinusoidal system first estimates and then removes the natural phase dispersion in the frequency components of the speech signal. Artificial dispersion based on pulse compression techniques is then introduced with little change in speech quality. The new phase dispersion allocation serves to preprocess the waveform prior to dynamic range compression and clipping, allowing considerably deeper thresholding than can be tolerated on the original waveform.
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Citations
20 Claims
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1. A method of pre-processing an acoustic waveform prior to transmission to reduce the peak-to-RMS ratio of the waveform, the method comprising:
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a. sampling the waveform to obtain a series of discrete samples and constructing therefrom a series of frames, each frame spanning a plurality of samples; b. analyzing each frame of samples to extract a set of variable frequency components having individual amplitudes and phases; c. removing the natural phase dispersion from said variable frequency components and substituting therefor a desired phase dispersion; d. tracking said components from one frame to a next frame; and e. interpolating the values of the components from the one frame to the next frame to obtain a parametric representation of the waveform whereby a synthetic waveform having a flattened time-domain envelope can be constructed by generating a set of sine waves corresponding to the interpolated values of the parametric representation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13)
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11. A device for pre-processing an acoustic waveform prior to transmission to reduce the peak-to-RMS ratio of the waveform, the device comprising:
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a. sampling means for sampling the waveform to obtain a series of discrete samples and constructing therefrom a series of frames, each frame spanning a plurality of samples; b. analyzing means for analyzing each frame of samples to extract a set of variable frequency components having individual amplitudes and phrases; c. phase substitution means for removing the natural phase dispersion from said variable frequency components and for substituting therefor a desired phase dispersion d. tracking means for tracking said variable frequency components from one frame to a next frame; and e. interpolating means for interpolating the values of the components from the one frame to the next frame to obtain a parametric representation of the waveform whereby a synthetic waveform having a flattened time-domain envelope can be constructed by generating a set of sine waves corresponding to the interpolated values of the parametric representation. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification