fscale.c File Reference

frequency transformations (perceptual) More...

Typedefs
typedef float(*	SprSspFScaleCvt )(float freq)

Enumerations
enum	{   SPR_FREQSCALE_MEL, SPR_FREQSCALE_BARK, SPR_FREQSCALE_ERB, SPR_FREQSCALE_PLP,   SPR_FREQSCALE_MELDM, SPR_FREQSCALE_MELHTK, SPR_FREQSCALE_ERBGM, SPR_FREQSCALE_LINEAR,   SPR_FREQSCALE_NFREQSCALE }
	auditory frequency scales More...

Functions
float	spr_fscale_melhtk2hz (float mel)
float	spr_fscale_hz2melhtk (float hz)
float	spr_fscale_meldm2hz (float mel)
float	spr_fscale_hz2meldm (float hz)
float	spr_fscale_mel2hz (float mel)
	Frequency scale conversion from Mel to Hz. More...
float	spr_fscale_hz2mel (float hz)
	Frequency scale conversion from Hz to Mel. More...
float	spr_fscale_barkplp2hz (float bark)
	Frequency scale conversion from Bark (PLP) to Hz. More...
float	spr_fscale_hz2barkplp (float hz)
	Frequency scale conversion from Hz to Bark (PLP). More...
float	spr_fscale_bark2hz (float bark)
	Frequency scale conversion from Bark to Hz. More...
float	spr_fscale_hz2bark (float hz)
	Frequency scale conversion from Hz to Bark. More...
float	spr_fscale_erb2hz (float erb)
	Frequency scale conversion from Erb to Hz. More...
float	spr_fscale_hz2erb (float hz)
	Frequency scale conversion from Hz to Erb. More...
float	spr_fscale_erbgm2hz (float erb)
	Frequency scale conversion from Erb (Glasberg & Moore) to Hz. More...
float	spr_fscale_hz2erbgm (float hz)
	Frequency scale conversion from Hz to Erb (Glasberg & Moore). More...
float	spr_fscale_lin2hz (float hz)
	Frequency scale conversion from Hz to Erb. More...
float	spr_fscale_hz2lin (float hz)
	Frequency scale conversion from Hz to Erb. More...

Variables
const char *const	spr_ssp_str_scaletype [SPR_FREQSCALE_NFREQSCALE+1]
SprSspFScaleCvt	spr_ssp_fscale_to_hz []
SprSspFScaleCvt	spr_ssp_fscale_from_hz []

Detailed Description

frequency transformations (perceptual)

This module contains different functions for frequency transformations from the linear frequency scale to a critical band number. The scales are close to linear below 1 kHz and close to logarithmic above. 6 different frequency-scales are implemented:

mel2hz(), hz2mel()

mel-scale

meldm2hz(), hz2meldm()

approximation of mel-scale from Davis & Mermelstein

bark2hz(), hz2bark()

bark-scale

barkplp2hz(), hz2barkplp()

plp-bark-scale from Schroeder (cf. plp)

erb2hz(), hz2erb()

erb-scale

erbgm2hz(), hz2erbgm()

erb-scale according to Glasberg and Moore

lin2hz(), hz2lin()

a linear scale

In addition, hz2spc and spc2hz convert Hz value in spectrum points and vice versa.

Date

7 Feb 1994

Author

Tom Claes

See Also

sspmod_filter_bank.c