Calculate peak and dip envelope of a power spectrum. More...

Functions
void	spr_envelope_free (SprSspInfo *info)

int	spr_envelope_setup (SprSspInfo info, const char descript, void aux_info)

int	spr_envelope_process (SprSspInfo info, const void frame_in, void *frame_out)

Detailed Description

Calculate peak and dip envelope of a power spectrum.

Calculate the peak and dip envelope of a power spectrum with simple peak/dip tracker, and if requested, normalize the spectrum by this envelope.

[envelope]
`% info:`
Track the peak and/or dip values in a spectrogram. The input is assumed to be in the power doamin. Peak and dip tracking operates in the log-power domain.The module performs the following step (in the given order) and can output several intermediate results (in any order): 1.peak tracking (envelope) gain adjustment; calculate the gain factors that should be applied on the envelope so that the local average of the energy is about the same as in the input signal dip tracking spectral subtraction using the dip values as noise estimates on the input signal spectral subtraction using the dip values as noise estimates on the envelope (wait gain compensation if requested).
`alpha peak <nr>`
Maximal slope in the peak (log) spectrum (x[i+1]=(1.0-alpha)x[i]). The default value depends on the sample frequency and the number of fft bins.*
`alpha dip <nr>`
Maximal slope in the dip (log) spectrum. The default value depends on the sample frequency and the number of fft bins.
`nfr gain <nr>`
Look at a window of <nr> frames when calculating the local energy values for the gain compensation. The Default value is derived from <alpha_peak>.
`ssub [beta](1.0) [alpha](0.0)`
Use the dip values for spectral subtraction with an overestimation factor <beta> and a lower bound <alpha>: x=max(x<alpha>,x-<beta>dip).
`output [env/norm0/gain/env_gain/norm1/dip/ssub/norm2/ssub_env/norm3](env)`
Output: env: the envelope (before gain adjustment) norm0: the input signal divided by the envelope gain: the gain factors that should be applied on the envelope so that the local average energy is about the same as in the input signal env_gain: the envelope compensated with the gain factors norm1: the input signal divided by the envelope after the gain compensation (see offs_gain and offs_env_gain) dip: the dip values (single frame immediate noise estimate) ssub: the input signal with the dip values subtracted (spectral subtraction) norm2: the input signal after spectral subtraction divided by the envelope (with gain compensation if gain compensation was requested) ssub_env: the envelope signal (with gain compensation if gain compensation was requested) with the dip values subtracted (spectral subtraction) norm3: the signal after spectral subtraction divided by the envelope after the (optional) gain and dip compensation
`[do/no] [gain/ssub_env]`
Do or don't do gain compensation (step 2) and/or (don't) do spectral subtraction on the envelope (step 5). The steps that must be performed (1...5) can be derived from the requested output, except for steps 2 and 3 in some cases. This option turns these two step explicitly on or off.

Author: Kris Demuynck

Date: 23 february 1999

See Also: ssp_master.c

Functions

Detailed Description