LPC Formant_to_LPC (Formant me, double samplingPeriod) {
try {
autoLPC thee = LPC_create (my xmin, my xmax, my nx, my dx, my x1, 2 * my maxnFormants, samplingPeriod);
for (long i = 1; i <= my nx; i++) {
Formant_Frame f = & my d_frames[i];
LPC_Frame lpc = & thy d_frames[i];
long m = 2 * f -> nFormants;
LPC_Frame_init (lpc, m);
Formant_Frame_into_LPC_Frame (f, lpc, samplingPeriod);
}
return thee.transfer();
} catch (MelderError) {
Melder_throw (me, ": no LPC created.");
}
}
double LPC_Frame_getVTL_wakita (LPC_Frame me, double samplingPeriod, double refLength) {
struct structLPC_Frame lpc_struct;
LPC_Frame lpc = & lpc_struct;
struct structFormant_Frame f_struct;
Formant_Frame f = & f_struct;
struct structTube_Frame rc_struct, af_struct;
Tube_Frame rc = & rc_struct, af = & af_struct;
try {
long m = my nCoefficients;
double length, dlength = 0.001, wakita_length = NUMundefined;
double varMin = 1e308;
memset (& lpc_struct, 0, sizeof (lpc_struct));
memset (& f_struct, 0, sizeof (f_struct));
memset (& rc_struct, 0, sizeof (rc_struct));
memset (& af_struct, 0, sizeof (af_struct));
LPC_Frame_init (lpc, m);
Tube_Frame_init (rc, m, refLength);
Tube_Frame_init (af, m, refLength);
// Step 2
LPC_Frame_into_Formant_Frame (me, f, samplingPeriod, 0);
// LPC_Frame_into_Formant_Frame performs the Formant_Frame_init !!
if (f -> nFormants < 1) {
Melder_throw (U"Not enough formants.");
}
double *area = af -> c;
double lmin = length = 0.10;
double plength = refLength;
while (length <= 0.25) {
// Step 3
double fscale = plength / length;
for (long i = 1; i <= f -> nFormants; i++) {
f -> formant[i].frequency *= fscale;
f -> formant[i].bandwidth *= fscale;
}
/*
20000125: Bovenstaande schaling van f1/b1 kan ook gedaan worden door
MGfb_to_a (f, b, nf, samplingFrequency*length/refLength, a1)
De berekening is extreem gevoelig voor de samplefrequentie: een zelfde
stel f,b waardes geven andere lengtes afhankelijk van Fs. Ook het
weglaten van een hogere formant heeft consekwenties.
De refLength zou eigenlijk vast moeten liggen op
refLength=c*aantalFormanten/Fs waarbij c=340 m/s (geluidssnelheid).
Bij Fs=10000 zou aantalFormanten=5 zijn en refLength -> 0.17 m
*/
// step 4
Formant_Frame_into_LPC_Frame (f, lpc, samplingPeriod);
// step 5
rc -> length = length;
LPC_Frame_into_Tube_Frame_rc (lpc, rc);
// step 6.1
Tube_Frames_rc_into_area (rc, af);
// step 6.2 Log(areas)
double logSum = 0.0;
for (long i = 1; i <= af -> nSegments; i++) {
area[i] = log (area[i]);
logSum += area[i];
}
// step 6.3 and 7
double var = 0.0;
for (long i = 1; i <= af -> nSegments; i++) {
double delta = area[i] - logSum / af -> nSegments;
var += delta * delta;
}
if (var < varMin) {
lmin = length; varMin = var;
}
plength = length;
length += dlength;
}
wakita_length = lmin;
f -> destroy ();
lpc -> destroy ();
rc -> destroy ();
af -> destroy ();
return wakita_length;
} catch (MelderError) {
f -> destroy ();
lpc -> destroy ();
rc -> destroy ();
af -> destroy ();
return NUMundefined;
}
}
double LPC_Frame_getVTL_wakita (LPC_Frame me, double samplingPeriod, double refLength)
{
struct structLPC_Frame lpc_struct;
LPC_Frame lpc = & lpc_struct;
struct structFormant_Frame f_struct;
Formant_Frame f = & f_struct;
struct structTube_Frame rc_struct, af_struct;
Tube_Frame rc = & rc_struct, af = & af_struct;
long i, m = my nCoefficients;
double lmin, length, dlength = 0.001, plength, wakita_length = NUMundefined;
double *area, var, varMin = 1e38, logSum;
double fscale = 1;
memset(& lpc_struct, 0, sizeof(lpc_struct));
memset(& f_struct, 0, sizeof(f_struct));
memset(& rc_struct, 0, sizeof(rc_struct));
memset(& af_struct, 0, sizeof(af_struct));
if (! LPC_Frame_init (lpc, m) ||
! Tube_Frame_init (rc, m, refLength) ||
! Tube_Frame_init (af, m, refLength) ||
/*
Step 2
*/
! LPC_Frame_into_Formant_Frame (me, f, samplingPeriod, 0) ||
/*
LPC_Frame_into_Formant_Frame performs the Formant_Frame_init !!
*/
f -> nFormants < 1) goto end;
area = af -> c;
lmin = length = 0.10;
plength = refLength;
while (length <= 0.25)
{
/* Step 3 */
fscale = plength / length;
for (i = 1; i <= f -> nFormants; i++)
{
f -> formant[i].frequency *= fscale;
f -> formant[i].bandwidth *= fscale;
}
/*
20000125: Bovenstaande schaling van f1/b1 kan ook gedaan worden door
MGfb_to_a (f, b, nf, samplingFrequency*length/refLength, a1)
De berekening is extreem gevoelig voor de samplefrequentie: een zelfde
stel f,b waardes geven andere lengtes afhankelijk van Fs. Ook het
weglaten van een hogere formant heeft consekwenties.
De refLength zou eigenlijk vast moeten liggen op
refLength=c*aantalFormanten/Fs waarbij c=340 m/s (geluidssnelheid).
Bij Fs=10000 zou aantalFormanten=5 zijn en refLength -> 0.17 m
*/
/* step 4 */
if (! Formant_Frame_into_LPC_Frame (f, lpc, samplingPeriod)) goto end;
/* step 5 */
rc -> length = length;
if (! LPC_Frame_into_Tube_Frame_rc (lpc, rc)) goto end;
/* step 6.1 */
if (! Tube_Frames_rc_into_area (rc, af)) goto end;
/* step 6.2 Log(areas) */
for (logSum = 0, i = 1; i <= af -> nSegments; i++)
{
area[i] = log (area[i]);
logSum += area[i];
}
/* step 6.3 and 7*/
for (var = 0, i = 1; i <= af -> nSegments; i++)
{
double delta = area[i] - logSum / af -> nSegments;
var += delta * delta;
}
if (var < varMin)
{
lmin = length; varMin = var;
}
plength = length;
length += dlength;
}
wakita_length = lmin;
end:
Formant_Frame_destroy (f);
LPC_Frame_destroy (lpc);
Tube_Frame_destroy (rc);
Tube_Frame_destroy (af);
return wakita_length;
}
