Fast frequency-domain pitch estimation

Apparatus for estimating a pitch frequency of a speech signal, comprising an audio processor, which is adapted to compute a first transform of the speech signal to a frequency domain over a first time interval and a second transform of the speech signal to a frequency domain over a second time interval, which contains the first time interval, and to estimate the pitch frequency of the speech signal responsive to the first and second frequency transforms,

• wherein the first and second transforms comprise Short Time Fourier Transforms.

Apparatus for estimating a pitch frequency of a speech signal, comprising an audio processor, which is adapted to compute a first transform of the speech signal to a frequency domain over a first time interval and a second transform of the speech signal to a frequency domain over a second time interval, which contains the first time interval, and to estimate the pitch frequency of the speech signal responsive to the first and second frequency transforms,

• wherein the first time interval comprises a current frame of the speech signal, and the second time interval comprises the current frame and a preceding frame, and wherein the processor is adapted to compute the second transform by combining the first transform with a transform computed over the preceding frame, and
• wherein the transforms generate respective spectral coefficients, and wherein the processor is adapted to apply a phase shift to the coefficients generated by the transform computed over the preceding frame and to add the phase-shifted coefficients to the coefficients generated by the transform computed over the first time interval.

Apparatus for estimating a pitch frequency of a speech signal, comprising an audio processor, which is adapted to compute a first transform of the speech signal to a frequency domain over a first time interval and a second transform of the speech signal to a frequency domain over a second time interval, which contains the first time interval, and to estimate the pitch frequency of the speech signal responsive to the first and second frequency transforms,

• wherein the processor is adapted to derive first and second line spectra of the signal from the first and second transforms, respectively, and to determine the pitch frequency based on the line spectra.

Apparatus for estimating a pitch frequency of a speech signal, comprising an audio processor, which is adapted to find a line spectrum of the speech signal, the spectrum comprising spectral lines having respective line amplitudes and line frequencies, to compute a utility function, which is indicative, for each candidate pitch frequency in a given pitch frequency range, of a compatibility of the spectrum with the candidate pitch frequency, the utility function comprising at least one influence function that is periodic in a ratio of the frequency of one of the spectral lines to the candidate pitch frequency, and to estimate the pitch frequency of the speech signal responsive to the periodic function.

Apparatus for estimating a pitch frequency of a speech signal, comprising an audio processor, which is adapted to find a line spectrum of the speech signal, the spectrum comprising spectral lines having respective line amplitudes and line frequencies, to compute a utility function that is periodic in the frequencies of the lines in the spectrum, which function is indicative, for each candidate pitch frequency in a given pitch frequency range, of a compatibility of the spectrum with the candidate pitch frequency, and to estimate the pitch frequency of the speech signal responsive to the periodic function,

• wherein the utility function comprises at least one influence function that is periodic in a ratio of the frequency of one of the spectral lines to the candidate pitch frequency, and
• wherein the at least one influence function comprises a function of the ratio having maxima at integer values of the ratio and minima therebetween, and
• wherein the at least one influence function comprises a piecewise linear function c(f), having a maximum value in a first interval surrounding f=0, a minimum value in a second interval surrounding f=1/2, and a value that varies linearly in a transition interval between the first and second intervals.

A computer software product, comprising a computer-readable storage medium in which program instructions are stored, which instructions, when read by a computer receiving a speech signal, cause the computer to compute a first transform of the speech signal to a frequency domain over a first time interval and a second transform of the speech signal over a second time interval to the frequency domain, which contains the first time interval, and to estimate the pitch frequency of the speech signal responsive to the first and second transforms,

• wherein the first and second transforms comprise Short Time Fourier Transforms.

A computer software product, comprising a computer-readable storage medium in which program instructions are stored, which instructions, when read by a computer receiving a speech signal, cause the computer to find a line spectrum of the speech signal, the spectrum comprising spectral lines having respective line amplitudes and line frequencies, to compute a utility function, which is indicative, for each candidate pitch frequency in a given pitch frequency range, of a compatibility of the spectrum with the candidate pitch frequency, the utility function comprising at least one influence function that is periodic in a ratio of the frequency of one of the spectral lines to the candidate pitch frequency, and to estimate the pitch frequency of the speech signal responsive to the periodic function.