KFR_SINTRIN expression_pointer<T> make_kfilter(int samplerate)
{
const biquad_params<T> bq[] = {
biquad_highshelf(T(1681.81 / samplerate), T(+4.0)),
biquad_highpass(T(38.1106678246655 / samplerate), T(0.5)).normalized_all()
};
return to_pointer(biquad(bq, placeholder<T>()));
}
/**
* Given a sample rate, a buffer of 3 samples, the cutoff frequency, and the quality
* of the filter, will return a single sample
***/
float filtLowPass(float sampRate, filtStream_t* stream, double cutoff, float q )
{
double w0 = 2 * M_PI * (cutoff / sampRate);
double sinw0 = sin(w0);
double cosw0 = cos(w0);
double alpha = sinw0 / (2 * q);
filter_t LPF;
LPF.b0 = (1 - cosw0)/2;
LPF.b1 = 1 - cosw0;
LPF.b2 = (1 - cosw0)/2;
LPF.a0 = 1 + alpha;
LPF.a1 = -2 * cosw0;
LPF.a2 = 1 - alpha;
double y = biquad(&LPF, stream);
return y;
}
