sspmod_freq_warp.c File Reference

Transformation of a kid FFT power spectrum by including more formants. More...

Functions
int	spr_freq_warp_setup (SprSspInfo *Info, const char **descript, void *aux_info)
int	spr_freq_warp_process (SprSspInfo *Info, const void *frame_in, void *frame_out)
void	spr_freq_warp_free (SprSspInfo *Info)

Detailed Description

Transformation of a kid FFT power spectrum by including more formants.

This programs transforms a kid FFT power spectrum into a 'normal' one. First the spectrum is expanded with its DC-value. After a forward and reverse filtering, the expanded spectrum is linearly warped to its original length. Note that the use of this program enables the calculation of a fixed-length FFT power spectrum.

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[freq_warp]
fac [number](1.16)
Expanding factor of the FFT spectrum. Default 1.16.
facme [number](0.4)
Only the last <FACME>% fraction of the original spectrum is used to calculate the DC-value. Default 0.4.
numerator <coeff> ...
Numerator of the forward and reverse filter, starting with the coeff. for input(t), then for input(t-1) ...
denominator <coeff> ...
Denominator of the forward and reverse filter, starting with the coeff. for output(t), then for output(t-1) ...

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Author

Ioannis Dologlou (algorithm)

Kris Hermus (conversion to routines)

Date

3 November 1997, 12 March 1998