void mdaTalkBox::lpc(float *buf, float *car, VstInt32 n, VstInt32 o)
{
float z[ORD_MAX], r[ORD_MAX], k[ORD_MAX], G, x;
VstInt32 i, j, nn=n;
for(j=0; j<=o; j++, nn--) //buf[] is already emphasized and windowed
{
z[j] = r[j] = 0.0f;
for(i=0; i<nn; i++) r[j] += buf[i] * buf[i+j]; //autocorrelation
}
r[0] *= 1.001f; //stability fix
float min = 0.00001f;
if(r[0] < min) { for(i=0; i<n; i++) buf[i] = 0.0f; return; }
lpc_durbin(r, o, k, &G); //calc reflection coeffs
for(i=0; i<=o; i++)
{
if(k[i] > 0.995f) k[i] = 0.995f; else if(k[i] < -0.995f) k[i] = -.995f;
}
for(i=0; i<n; i++)
{
x = G * car[i];
for(j=o; j>0; j--) //lattice filter
{
x -= k[j] * z[j-1];
z[j] = z[j-1] + k[j] * x;
}
buf[i] = z[0] = x; //output buf[] will be windowed elsewhere
}
}
static void lpc(float *buf, float *car, uint32_t n, uint32_t o)
{
SPFLOAT z[ORD_MAX], r[ORD_MAX], k[ORD_MAX], G, x;
uint32_t i, j, nn=n;
SPFLOAT min;
/* buf[] is already emphasized and windowed */
for(j=0; j<=o; j++, nn--) {
z[j] = r[j] = 0.0f;
for(i=0; i<nn; i++) r[j] += buf[i] * buf[i+j]; /* autocorrelation */
}
r[0] *= 1.001f; /* stability fix */
min = 0.00001f;
if(r[0] < min) { for(i=0; i<n; i++) buf[i] = 0.0f; return; }
lpc_durbin(r, o, k, &G); /* calc reflection coeffs */
for(i=1; i<=o; i++) {
if(k[i] > 0.995f) k[i] = 0.995f; else if(k[i] < -0.995f) k[i] = -.995f;
}
for(i=0; i<n; i++) {
x = G * car[i];
/* lattice filter */
for(j=o; j>0; j--) {
x -= k[j] * z[j-1];
z[j] = z[j-1] + k[j] * x;
}
buf[i] = z[0] = x; /* output buf[] will be windowed elsewhere */
}
}
