/* LadderFilterProcess *************************************************/
Error_t
LadderFilterProcess(LadderFilter *filter, float *outBuffer, float *inBuffer, unsigned n_samples)
{
// Pre-calculate Scalars
float TWO_VT_INV = 1.0 / (2 * filter->Vt);
float TWO_VT_G = 2 * filter->Vt * (1 - exp(-TWO_PI * filter->cutoff / filter->sample_rate));
// Filter audio
for (unsigned i = 0; i < n_samples; ++i)
{
// Stage 1 output
filter->y[0] = filter->y[0] + TWO_VT_G * (f_tanh(inBuffer[i] - 4 * \
f_tanh(2 * filter->resonance * filter->y[3]) * \
TWO_VT_INV) - filter->w[0]);
filter->w[0] = f_tanh(filter->y[0] * TWO_VT_INV);
// Stage 2 output
filter->y[1] = filter->y[1] + TWO_VT_G * (filter->w[0]- filter->w[1]);
filter->w[1] = f_tanh(filter->y[1] * TWO_VT_INV);
// Stage 3 output
filter->y[2] = filter->y[2] + TWO_VT_G * (filter->w[1]- filter->w[2]);
filter->w[2] = f_tanh(filter->y[2] * TWO_VT_INV);
// Stage 4 output
filter->y[3] = filter->y[3] + TWO_VT_G * (filter->w[2]- filter->w[3]);
filter->w[3] = f_tanh(filter->y[3] * TWO_VT_INV);
// Write output
outBuffer[i] = filter->y[3];
}
return NOERR;
}
bool TestExtMath::test_tanh() {
VC(f_tanh(1.23), 0.84257932565893);
return Count(true);
}