bool Butter::initializeInternal(const SignalBank &input)
{
switch(order_)
{
case 3:
{
aCoefs_.resize(4);
bCoefs_.resize(4);
Real T = 1.0/input.getFs();
Real wc = 2.0/T * tan(2*PI*fc_*T/2.0);
Real c1 = T*T*wc*wc;
Real c2 = c1*T*wc/8.0;
Real c3 = T*wc;
bCoefs_[0] = 1.0;
bCoefs_[1] = -3.0;
bCoefs_[2] = 3.0;
bCoefs_[3] = -1.0;
aCoefs_[0] = c2 + 0.5 * c1 + c3 + 1;
aCoefs_[1] = 3*c2 + 0.5 * c1 - c3 - 3;
aCoefs_[2] = 3*c2 - 0.5 * c1 - c3 + 3;
aCoefs_[3] = c2 - 0.5 * c1 + c3 - 1;
break;
}
default:
{
LOUDNESS_ERROR(name_ << ": Only third order low pass implemented.");
return 0;
}
}
//normalise by a[0]
normaliseCoefs();
//delay line
z_.assign(input.getNEars() * 2 * order_,0.0);
//output SignalBank
output_.initialize(input);
return 1;
}
bool Biquad::initializeInternal(const SignalBank &input)
{
if (type_ == "RLB")
{
RealVec bCoefs = {1.0, -2.0, 1.0};
RealVec aCoefs = {1.0, -1.99004745483398, 0.99007225036621};
setBCoefs (bCoefs);
setACoefs (aCoefs);
setCoefficientFs (48000);
}
else if (type_ == "prefilter")
{
RealVec bCoefs = {1.53512485958697,
-2.69169618940638,
1.19839281085285};
RealVec aCoefs = {1.0,
-1.69065929318241,
0.73248077421585};
setBCoefs (bCoefs);
setACoefs (aCoefs);
setCoefficientFs (48000);
}
LOUDNESS_ASSERT( bCoefs_.size() == 3 &&
aCoefs_.size() == 3,
"Filter coefficients do not satisfy filter order");
//normalise by a[0]
normaliseCoefs();
//Transform coefficients if sampling frequency is different from
//the one used in origin filter design
//See: Parameter Quantization in Direct-Form Recursive Audio Filters
//by Neunaber (2008)
if((coefficientFs_ != 0) && (coefficientFs_ != input.getFs()))
{
double fc = (coefficientFs_/PI) * atan( sqrt( (1+aCoefs_[1]+aCoefs_[2]) /
(1-aCoefs_[1]+aCoefs_[2])));
double Q = sqrt((aCoefs_[2]+1)*(aCoefs_[2]+1) - aCoefs_[1]*aCoefs_[1]) /
(2*fabs(1-aCoefs_[2]));
double Vl = (bCoefs_[0]+bCoefs_[1]+bCoefs_[2]) / (1+aCoefs_[1]+aCoefs_[2]);
double Vb = (bCoefs_[0] - bCoefs_[2]) / (1-aCoefs_[2]);
double Vh = (bCoefs_[0]-bCoefs_[1]+bCoefs_[2]) / (1-aCoefs_[1]+aCoefs_[2]);
double omega = tan(PI*fc/input.getFs());
double omegaSqrd = omega*omega;
double denom = omegaSqrd + omega/Q + 1;
aCoefs_[0] = 1.0;
aCoefs_[1] = 2*(omegaSqrd - 1) / denom;
aCoefs_[2] = (omegaSqrd - (omega/Q) + 1)/ denom;
bCoefs_[0] = (Vl * omegaSqrd + Vb * (omega/Q) + Vh) / denom;
bCoefs_[1] = 2*(Vl*omegaSqrd - Vh) / denom;
bCoefs_[2] = (Vl*omegaSqrd - (Vb*omega/Q) + Vh) / denom;
}
/*
std::cout << "A" << std::endl;
for (int i = 0; i < 3; ++i)
std::cout << aCoefs_[i] << std::endl;
std::cout << "B" << std::endl;
for (int i = 0; i < 3; ++i)
std::cout << bCoefs_[i] << std::endl;
*/
delayLine_.initialize(input.getNSources(),
input.getNEars(),
input.getNChannels(),
2,
input.getFs());
//output SignalBank
output_.initialize(input);
return 1;
}
