Harmonicity estimation, audio classification, pitch determination and noise estimation
First Claim
1. A method of processing an audio signal in a voice communication device, comprising:
- calculating, in a first spectrum generator circuit of the device, a log amplitude spectrum (LX) of the audio signal;
deriving, in a second spectrum generator circuit, a first spectrum (LSS) by calculating each component of the first spectrum as a sum of components of the log amplitude spectrum on frequencies which, in linear frequency scale, are odd multiples of the component'"'"'s frequency of the first spectrum;
further deriving, in the second spectrum generator circuit coupled to the first spectrum generator circuit, a second spectrum (LSH) by calculating each component of the second spectrum as a sum of components of the log amplitude spectrum on frequencies which, in linear frequency scale, are even multiples of the component'"'"'s frequency of the second spectrum;
yet further deriving, in the second spectrum generator a harmonic-to subharmonic ratio (HSR) spectrum in a linear amplitude domain by subtracting the LSS spectrum from the LSH spectrum (HSR=LSH−
LSS);
generating, in a harmonicity estimator circuit, a measure of harmonicity (H) as a monotonically increasing function of a maximum component of the HSR spectrum within a predetermined frequency range, wherein the maximum component has the most dominant harmonics; and
using the harmonicity estimator circuit to generate at least two measures of harmonicity of the audio signal based on different frequency ranges defined by different expected maximum frequencies;
providing an output of the harmonicity estimator circuit to a feature calculator to classify the audio signal into at least one of several defined audio types based on at least one of a difference and ratio between harmonicity measures obtained by the harmonicity estimator circuit based on the different frequency ranges as a portion of features extracted from the audio signal, to determine a bandwidth requirement of the voice communication device; and
transmitting the determined bandwidth requirement to a backend process through a communication link to manage at least one of the bandwidth requirement and an application utilized by the voice communication device.
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Abstract
Embodiments are described for harmonicity estimation, audio classification, pitch determination and noise estimation. Measuring harmonicity of an audio signal includes calculation a log amplitude spectrum of audio signal. A first spectrum is derived by calculating each component of the first spectrum as a sum of components of the log amplitude spectrum on frequencies. In linear frequency scale, the frequencies are odd multiples of the component'"'"'s frequency of the first spectrum. A second spectrum is derived by calculating each component of the second spectrum as a sum of components of the log amplitude spectrum on frequencies. In linear frequency scale, the frequencies are even multiples of the component'"'"'s frequency of the second spectrum. A difference spectrum is derived subtracting the first spectrum from the second spectrum. A measure of harmonicity is generated as a monotonically increasing function of the maximum component of the difference spectrum within predetermined frequency range.
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Citations
8 Claims
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1. A method of processing an audio signal in a voice communication device, comprising:
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calculating, in a first spectrum generator circuit of the device, a log amplitude spectrum (LX) of the audio signal; deriving, in a second spectrum generator circuit, a first spectrum (LSS) by calculating each component of the first spectrum as a sum of components of the log amplitude spectrum on frequencies which, in linear frequency scale, are odd multiples of the component'"'"'s frequency of the first spectrum; further deriving, in the second spectrum generator circuit coupled to the first spectrum generator circuit, a second spectrum (LSH) by calculating each component of the second spectrum as a sum of components of the log amplitude spectrum on frequencies which, in linear frequency scale, are even multiples of the component'"'"'s frequency of the second spectrum; yet further deriving, in the second spectrum generator a harmonic-to subharmonic ratio (HSR) spectrum in a linear amplitude domain by subtracting the LSS spectrum from the LSH spectrum (HSR=LSH−
LSS);generating, in a harmonicity estimator circuit, a measure of harmonicity (H) as a monotonically increasing function of a maximum component of the HSR spectrum within a predetermined frequency range, wherein the maximum component has the most dominant harmonics; and using the harmonicity estimator circuit to generate at least two measures of harmonicity of the audio signal based on different frequency ranges defined by different expected maximum frequencies; providing an output of the harmonicity estimator circuit to a feature calculator to classify the audio signal into at least one of several defined audio types based on at least one of a difference and ratio between harmonicity measures obtained by the harmonicity estimator circuit based on the different frequency ranges as a portion of features extracted from the audio signal, to determine a bandwidth requirement of the voice communication device; and transmitting the determined bandwidth requirement to a backend process through a communication link to manage at least one of the bandwidth requirement and an application utilized by the voice communication device. - View Dependent Claims (2, 3, 4)
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5. An apparatus for processing an audio signal in a voice communication device, comprising:
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a first spectrum generator circuit of the device configured to calculate a log amplitude spectrum (LX) of the audio signal; a second spectrum generator circuit coupled to the first spectrum generator circuit to derive a first spectrum (LSS) by calculating each component of the first spectrum as a sum of components of the log amplitude spectrum on frequencies which, in linear frequency scale, are odd multiples of the component'"'"'s frequency of the first spectrum; and
to further derive a second spectrum (LSH) by calculating each component of the second spectrum as a sum of components of the log amplitude spectrum on frequencies which, in linear frequency scale, are even multiples of the component'"'"'s frequency of the second spectrum; and
yet to further derive a harmonic-to-subharmonic ratio (HSR) spectrum in a linear amplitude domain by subtracting the LSS spectrum from the LSH spectrum (HSR=LSH−
LSS); and
a harmonicity estimator circuit configured to determine a measure of harmonicity (H) as a monotonically increasing function of a maximum component of the HSR spectrum within a predetermined frequency range, wherein the maximum component has the most dominant harmonics;
the harmonicity estimator circuit further generating at least two measures of harmonicity of the audio signal based on different frequency ranges defined by different expected maximum frequencies;a transmission link providing an output of the harmonicity estimator circuit to a feature calculator to classify the audio signal into at least one of several defined audio types based on at least one of a difference and ratio between harmonicity measures obtained by the harmonicity estimator circuit based on the different frequency ranges as a portion of features extracted from the audio signal, to determine a bandwidth requirement of the voice communication device; and a communication link transmitting the determined bandwidth requirement to a backend process to manage at least one of the bandwidth requirement and an application utilized by the voice communication device. - View Dependent Claims (6, 7, 8)
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Specification