mirror of
https://github.com/thestk/stk
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126 lines
3.4 KiB
C++
126 lines
3.4 KiB
C++
/***************************************************/
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/*! \class Iir
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\brief STK general infinite impulse response filter class.
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This class provides a generic digital filter structure that can be
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used to implement IIR filters. For filters containing only
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feedforward terms, the Fir class is slightly more efficient.
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In particular, this class implements the standard difference
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equation:
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a[0]*y[n] = b[0]*x[n] + ... + b[nb]*x[n-nb] -
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a[1]*y[n-1] - ... - a[na]*y[n-na]
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If a[0] is not equal to 1, the filter coeffcients are normalized
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by a[0].
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The \e gain parameter is applied at the filter input and does not
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affect the coefficient values. The default gain value is 1.0.
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This structure results in one extra multiply per computed sample,
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but allows easy control of the overall filter gain.
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by Perry R. Cook and Gary P. Scavone, 1995-2012.
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*/
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/***************************************************/
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#include "Iir.h"
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namespace stk {
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Iir :: Iir()
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{
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// The default constructor should setup for pass-through.
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b_.push_back( 1.0 );
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a_.push_back( 1.0 );
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inputs_.resize( 1, 1, 0.0 );
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outputs_.resize( 1, 1, 0.0 );
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}
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Iir :: Iir( std::vector<StkFloat> &bCoefficients, std::vector<StkFloat> &aCoefficients )
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{
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// Check the arguments.
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if ( bCoefficients.size() == 0 || aCoefficients.size() == 0 ) {
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oStream_ << "Iir: a and b coefficient vectors must both have size > 0!";
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handleError( StkError::FUNCTION_ARGUMENT );
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}
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if ( aCoefficients[0] == 0.0 ) {
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oStream_ << "Iir: a[0] coefficient cannot == 0!";
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handleError( StkError::FUNCTION_ARGUMENT );
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}
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gain_ = 1.0;
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b_ = bCoefficients;
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a_ = aCoefficients;
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inputs_.resize( b_.size(), 1, 0.0 );
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outputs_.resize( a_.size(), 1, 0.0 );
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this->clear();
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}
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Iir :: ~Iir()
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{
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}
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void Iir :: setCoefficients( std::vector<StkFloat> &bCoefficients, std::vector<StkFloat> &aCoefficients, bool clearState )
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{
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this->setNumerator( bCoefficients, false );
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this->setDenominator( aCoefficients, false );
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if ( clearState ) this->clear();
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}
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void Iir :: setNumerator( std::vector<StkFloat> &bCoefficients, bool clearState )
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{
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// Check the argument.
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if ( bCoefficients.size() == 0 ) {
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oStream_ << "Iir::setNumerator: coefficient vector must have size > 0!";
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handleError( StkError::FUNCTION_ARGUMENT );
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}
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if ( b_.size() != bCoefficients.size() ) {
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b_ = bCoefficients;
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inputs_.resize( b_.size(), 1, 0.0 );
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}
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else {
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for ( unsigned int i=0; i<b_.size(); i++ ) b_[i] = bCoefficients[i];
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}
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if ( clearState ) this->clear();
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}
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void Iir :: setDenominator( std::vector<StkFloat> &aCoefficients, bool clearState )
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{
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// Check the argument.
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if ( aCoefficients.size() == 0 ) {
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oStream_ << "Iir::setDenominator: coefficient vector must have size > 0!";
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handleError( StkError::FUNCTION_ARGUMENT );
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}
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if ( aCoefficients[0] == 0.0 ) {
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oStream_ << "Iir::setDenominator: a[0] coefficient cannot == 0!";
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handleError( StkError::FUNCTION_ARGUMENT );
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}
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if ( a_.size() != aCoefficients.size() ) {
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a_ = aCoefficients;
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outputs_.resize( a_.size(), 1, 0.0 );
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}
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else {
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for ( unsigned int i=0; i<a_.size(); i++ ) a_[i] = aCoefficients[i];
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}
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if ( clearState ) this->clear();
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// Scale coefficients by a[0] if necessary
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if ( a_[0] != 1.0 ) {
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unsigned int i;
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for ( i=0; i<b_.size(); i++ ) b_[i] /= a_[0];
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for ( i=1; i<a_.size(); i++ ) a_[i] /= a_[0];
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}
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}
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} // stk namespace
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