/*
Analog formant filter response :
H(f) = i f B / (f1^2 - f^2 + i f B)
*/
static int Sound_into_FormantFilter_frame (Sound me, FormantFilter thee, long frame, double bw) {
Melder_assert (bw > 0);
autoMatrix pv = Sound_to_spectralpower (me);
double z1 = pv -> x1;
double dz = pv -> dx;
long nf = pv -> nx;
for (long i = 1; i <= thy ny; i++) {
double p = 0;
double fc = thy y1 + (i - 1) * thy dy;
double *pow = pv -> z[1];
for (long j = 1; j <= nf; j++) {
// H(f) = ifB / (fc^2 - f^2 + ifB)
// H(f)| = fB / sqrt ((fc^2 - f^2)^2 + f^2B^2)
//|H(f)|^2 = f^2B^2 / ((fc^2 - f^2)^2 + f^2B^2)
// = 1 / (((fc^2 - f^2) /fB)^2 + 1)
double f = z1 + (j - 1) * dz;
double a = NUMformantfilter_amplitude (fc, bw, f);
p += a * pow[j];
}
thy z[i][frame] = p;
}
return 1;
}
void FormantFilter_drawFilterFunctions (FormantFilter me, Graphics g, double bandwidth,
int toFreqScale, int fromFilter, int toFilter, double zmin, double zmax,
int dbScale, double ymin, double ymax, int garnish) {
if (! checkLimits (me, FilterBank_HERTZ, toFreqScale, & fromFilter, & toFilter,
& zmin, & zmax, dbScale, & ymin, & ymax)) {
return;
}
if (bandwidth <= 0) {
Melder_warning (U"Bandwidth must be greater than zero.");
}
long n = 1000;
autoNUMvector<double>a (1, n);
Graphics_setInner (g);
Graphics_setWindow (g, zmin, zmax, ymin, ymax);
for (long j = fromFilter; j <= toFilter; j++) {
double df = (zmax - zmin) / (n - 1);
double fc = my y1 + (j - 1) * my dy;
long ibegin, iend;
for (long i = 1; i <= n; i++) {
double f = zmin + (i - 1) * df;
double z = scaleFrequency (f, toFreqScale, FilterBank_HERTZ);
if (z == NUMundefined) {
a[i] = NUMundefined;
} else {
a[i] = NUMformantfilter_amplitude (fc, bandwidth, z);
if (dbScale) {
a[i] = to_dB (a[i], 10, ymin);
}
}
}
setDrawingLimits (a.peek(), n, ymin, ymax, &ibegin, &iend);
if (ibegin <= iend) {
double fmin = zmin + (ibegin - 1) * df;
double fmax = zmax - (n - iend) * df;
Graphics_function (g, a.peek(), ibegin, iend, fmin, fmax);
}
}
Graphics_unsetInner (g);
if (garnish) {
double distance = dbScale ? 10 : 1;
char32 const *ytext = dbScale ? U"Amplitude (dB)" : U"Amplitude";
Graphics_drawInnerBox (g);
Graphics_marksBottom (g, 2, 1, 1, 0);
Graphics_marksLeftEvery (g, 1, distance, 1, 1, 0);
Graphics_textLeft (g, 1, ytext);
Graphics_textBottom (g, 1, GetFreqScaleText (toFreqScale));
}
}
/*
Analog formant filter response :
H(f) = i f B / (f1^2 - f^2 + i f B)
*/
static int Sound_into_Spectrogram_frame (Sound me, Spectrogram thee, long frame, double bw) {
Melder_assert (bw > 0);
autoSpectrum him = Sound_to_Spectrum_power (me);
for (long ifilter = 1; ifilter <= thy ny; ifilter ++) {
double p = 0;
double fc = thy y1 + (ifilter - 1) * thy dy;
double *pow = his z [1];
for (long ifreq = 1; ifreq <= his nx; ifreq ++) {
// H(f) = ifB / (fc^2 - f^2 + ifB)
// H(f)| = fB / sqrt ((fc^2 - f^2)^2 + f^2B^2)
//|H(f)|^2 = f^2B^2 / ((fc^2 - f^2)^2 + f^2B^2)
// = 1 / (((fc^2 - f^2) /fB)^2 + 1)
double f = his x1 + (ifreq - 1) * his dx;
double a = NUMformantfilter_amplitude (fc, bw, f);
p += a * pow[ifreq];
}
thy z[ifilter][frame] = p;
}
return 1;
}
