static double vsa = (1.0 / 4294967295.0); //(Denormal Fix)
public static void init_3band_state(ref EQSTATE es, int lowfreq, int highfreq, int mixfreq)
{
//// Clear state
//memset(es, 0, sizeof(EQSTATE));
es.lg = 1.0;
es.mg = 1.0;
es.hg = 1.0;
// filter cutoff frequencies
es.lf = 2 * Math.Sin(Math.PI * ((double)lowfreq / (double)mixfreq));
es.hf = 2 * Math.Sin(Math.PI * ((double)highfreq / (double)mixfreq));
}
public static double do_3band(ref EQSTATE es, double sample)
{
double l, m, h;
// (lowpass)
es.f1p0 += (es.lf * (sample - es.f1p0)) + vsa;
es.f1p1 += (es.lf * (es.f1p0 - es.f1p1));
es.f1p2 += (es.lf * (es.f1p1 - es.f1p2));
es.f1p3 += (es.lf * (es.f1p2 - es.f1p3));
l = es.f1p3;
// (highpass)
es.f2p0 += (es.hf * (sample - es.f2p0)) + vsa;
es.f2p1 += (es.hf * (es.f2p0 - es.f2p1));
es.f2p2 += (es.hf * (es.f2p1 - es.f2p2));
es.f2p3 += (es.hf * (es.f2p2 - es.f2p3));
h = es.sdm3 - es.f2p3;
// midrange (signal - (low + high))
m = es.sdm3 - (h + l);
// Scale, Combine and store
l *= es.lg;
m *= es.mg;
h *= es.hg;
// Shuffle history buffer
es.sdm3 = es.sdm2;
es.sdm2 = es.sdm1;
es.sdm1 = sample;
// Return result
return(l + h + m);
}
public static extern double do_3band([MarshalAs(UnmanagedType.Struct)] ref EQSTATE es, double sample);
public static extern void init_3band_state([MarshalAs(UnmanagedType.Struct)] ref EQSTATE es, int lowfreq, int highfreq, int mixfreq);
