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Merge pull request #121 from navin-neu/biquad-filter-types

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add support for different filter types in biquad
This commit is contained in:
garyscavone
2022-05-15 10:02:17 -04:00
committed by GitHub
parent 16918b0914 79334d2c8d
commit 70835eccb4
2 changed files with 154 additions and 2 deletions
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81
src/BiQuad.cpp
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@@ -24,6 +24,10 @@ BiQuad :: BiQuad() : Filter()
inputs_.resize( 3, 1, 0.0 );
outputs_.resize( 3, 1, 0.0 );
K_ = 0.0;
kSqr_ = 0.0;
denom_ = 1.0;
Stk::addSampleRateAlert( this );
}
@@ -73,6 +77,11 @@ void BiQuad :: setResonance( StkFloat frequency, StkFloat radius, bool normalize
b_[1] = 0.0;
b_[2] = -b_[0];
}
else {
b_[0] = 1.0;
b_[1] = 0.0;
b_[2] = 0.0;
}
}
void BiQuad :: setNotch( StkFloat frequency, StkFloat radius )
@@ -89,8 +98,57 @@ void BiQuad :: setNotch( StkFloat frequency, StkFloat radius )
#endif
// This method does not attempt to normalize the filter gain.
b_[2] = radius * radius;
b_[0] = 1.0;
b_[1] = (StkFloat) -2.0 * radius * cos( TWO_PI * (double) frequency / Stk::sampleRate() );
b_[2] = radius * radius;
a_[1] = 0.0;
a_[2] = 0.0;
}
void BiQuad :: setLowPass( StkFloat fc, StkFloat Q )
{
setCommonFilterValues(fc, Q);
b_[0] = kSqr_ * Q * denom_;
b_[1] = 2 * b_[0];
b_[2] = b_[0];
}
void BiQuad :: setHighPass( StkFloat fc, StkFloat Q )
{
setCommonFilterValues(fc, Q);
b_[0] = Q * denom_;
b_[1] = -2 * b_[0];
b_[2] = b_[0];
}
void BiQuad :: setBandPass( StkFloat fc, StkFloat Q )
{
setCommonFilterValues(fc, Q);
b_[0] = K_ * denom_;
b_[1] = 0.0;
b_[2] = -b_[0];
}
void BiQuad :: setBandReject( StkFloat fc, StkFloat Q )
{
setCommonFilterValues(fc, Q);
b_[0] = Q * (kSqr_ + 1) * denom_;
b_[1] = 2 * Q * (kSqr_ - 1) * denom_;
b_[2] = b_[0];
}
void BiQuad :: setAllPass( StkFloat fc, StkFloat Q )
{
setCommonFilterValues(fc, Q);
b_[0] = a_[2];
b_[1] = a_[1];
b_[2] = 1;
}
void BiQuad :: setEqualGainZeroes( void )
@@ -100,4 +158,25 @@ void BiQuad :: setEqualGainZeroes( void )
b_[2] = -1.0;
}
void BiQuad :: setCommonFilterValues( StkFloat fc, StkFloat Q)
{
#if defined(_STK_DEBUG_)
if ( fc < 0.0 ) {
oStream_ << "BiQuad::updateKValues: fc argument (" << fc << ") is negative!";
handleError( StkError::WARNING ); return;
}
if ( Q < 0.0 ) {
oStream_ << "BiQuad::updateKValues: Q argument (" << Q << ") is negative!";
handleError( StkError::WARNING ); return;
}
#endif
K_ = tan(PI * fc / Stk::sampleRate());
kSqr_ = K_ * K_;
denom_ = 1 / (kSqr_ * Q + K_ + Q);
a_[1] = 2 * Q * (kSqr_ - 1) * denom_;
a_[2] = (kSqr_ * Q - K_ + Q) * denom_;
}
} // stk namespace