Commit 14bccef8 authored by Jean-Marc Valin's avatar Jean-Marc Valin
Browse files

Comments on the spreading function

parent 991410be
......@@ -32,8 +32,12 @@
#include "psy.h"
#include <math.h>
/* The Vorbis freq<->Bark mapping */
#define toBARK(n) (13.1f*atan(.00074f*(n))+2.24f*atan((n)*(n)*1.85e-8f)+1e-4f*(n))
#define fromBARK(z) (102.f*(z)-2.f*pow(z,2.f)+.4f*pow(z,3.f)+pow(1.46f,z)-1.f)
/* Psychoacoustic spreading function. The idea here is compute a first order
recursive smoothing. The filter coefficient is frequency dependent and
recursive filter. The filter coefficient is frequency dependent and
chosen such that we have a -10dB/Bark slope on the right side and a -25dB/Bark
slope on the left side. */
static void spreading_func(float *psd, float *mask, int len, int Fs)
......@@ -47,10 +51,15 @@ static void spreading_func(float *psd, float *mask, int len, int Fs)
{
float f;
float deriv;
/* Real frequency (in Hz) */
f = Fs*i*(1/(2.f*len));
/* This is the derivative of the Vorbis freq->Bark function (see above) */
deriv = (8.288e-8 * f)/(3.4225e-16 *f*f*f*f + 1) + .009694/(5.476e-7 *f*f + 1) + 1e-4;
/* Back to FFT bin units */
deriv *= Fs*(1/(2.f*len));
/* decay corresponding to -10dB/Bark */
decayR[i] = pow(.1f, deriv);
/* decay corresponding to -25dB/Bark */
decayL[i] = pow(0.0031623f, deriv);
}
/* Compute right slope (-10 dB/Bark) */
......@@ -68,6 +77,29 @@ static void spreading_func(float *psd, float *mask, int len, int Fs)
mem = mask[i];
}
//for (i=0;i<len;i++) printf ("%f ", mask[i]); printf ("\n");
#if 0 /* Prints signal and mask energy per critical band */
for (i=0;i<25;i++)
{
int start,end;
int j;
float Esig=0, Emask=0;
start = (int)floor(fromBARK((float)i)*(2*len)/Fs);
if (start<0)
start = 0;
end = (int)ceil(fromBARK((float)(i+1))*(2*len)/Fs);
if (end<=start)
end = start+1;
if (end>len-1)
end = len-1;
for (j=start;j<end;j++)
{
Esig += psd[j];
Emask += mask[j];
}
printf ("%f %f ", Esig, Emask);
}
printf ("\n");
#endif
}
/* Compute a marking threshold from the spectrum X. */
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment