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Diffstat (limited to 'src/loris/Filter.C')
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diff --git a/src/loris/Filter.C b/src/loris/Filter.C new file mode 100644 index 0000000..c60fddd --- /dev/null +++ b/src/loris/Filter.C @@ -0,0 +1,204 @@ +/* + * This is the Loris C++ Class Library, implementing analysis, + * manipulation, and synthesis of digitized sounds using the Reassigned + * Bandwidth-Enhanced Additive Sound Model. + * + * Loris is Copyright (c) 1999-2010 by Kelly Fitz and Lippold Haken + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY, without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + * + * + * Filter.C + * + * Implementation of class Loris::Filter, a generic digital filter of + * arbitrary order having both feed-forward and feedback coefficients. + * + * Kelly Fitz, 1 Sept 1999 + * revised 9 Oct 2009 + * loris@cerlsoundgroup.org + * + * http://www.cerlsoundgroup.org/Loris/ + * + */ + +#if HAVE_CONFIG_H + #include "config.h" +#endif + +#include "Filter.h" + +#include <algorithm> +#include <numeric> + +// begin namespace +namespace Loris { + +// --------------------------------------------------------------------------- +// default construction +// --------------------------------------------------------------------------- +//! Construct a filter with an all-pass unity gain response. +// +Filter::Filter( void ) : + m_ffwdcoefs( 1, 1.0 ), + m_fbackcoefs( 1, 1.0 ), + m_delayline( 1, 0 ), + m_gain( 1.0 ) +{ +} + +// --------------------------------------------------------------------------- +// copy construction +// --------------------------------------------------------------------------- +//! Make a copy of another digital filter. +//! Do not copy the filter state (delay line). +// +Filter::Filter( const Filter & other ) : + m_delayline( other.m_delayline.size(), 0. ), + m_ffwdcoefs( other.m_ffwdcoefs ), + m_fbackcoefs( other.m_fbackcoefs ), + m_gain( other.m_gain ) +{ + Assert( m_delayline.size() >= m_ffwdcoefs.size() - 1 ); + Assert( m_delayline.size() >= m_fbackcoefs.size() - 1 ); +} + +// --------------------------------------------------------------------------- +// assignment +// --------------------------------------------------------------------------- +//! Make a copy of another digital filter. +//! Do not copy the filter state (delay line). +// +Filter & +Filter::operator=( const Filter & rhs ) +{ + if ( &rhs != this ) + { + m_delayline.resize( rhs.m_delayline.size() ); + clear(); + + m_ffwdcoefs = rhs.m_ffwdcoefs; + m_fbackcoefs = rhs.m_fbackcoefs; + m_gain = rhs.m_gain; + + Assert( m_delayline.size() >= m_ffwdcoefs.size() - 1 ); + Assert( m_delayline.size() >= m_fbackcoefs.size() - 1 ); + } + return *this; +} + +// --------------------------------------------------------------------------- +// destructor +// --------------------------------------------------------------------------- +//! Destructor is virtual to enable subclassing. Subclasses may specialize +//! construction, and may add functionality, but for efficiency, the filtering +//! operation is non-virtual. +// +Filter::~Filter( void ) +{ +} + + +// --------------------------------------------------------------------------- +// apply +// --------------------------------------------------------------------------- +//! Compute a filtered sample from the next input sample. +//! +// +double +Filter::apply( double input ) +{ + // Implement the recurrence relation. m_ffwdcoefs holds the feed-forward + // coefficients, m_fbackcoefs holds the feedback coeffs. The coefficient + // vectors and delay lines are ordered by increasing age. + + double wn = - std::inner_product( m_fbackcoefs.begin()+1, m_fbackcoefs.end(), + m_delayline.begin(), -input ); + // negate input, then negate the inner product + + m_delayline.push_front( wn ); + + double output = std::inner_product( m_ffwdcoefs.begin(), m_ffwdcoefs.end(), + m_delayline.begin(), 0. ); + m_delayline.pop_back(); + + return output * m_gain; +} + +// --- access/mutation --- + +// --------------------------------------------------------------------------- +// numerator +// --------------------------------------------------------------------------- +//! Provide access to the numerator (feed-forward) coefficients +//! of this filter. The coefficients are stored in order of increasing +//! delay (lowest order coefficient first). + +std::vector< double > +Filter::numerator( void ) +{ + return m_ffwdcoefs; +} + +// --------------------------------------------------------------------------- +// numerator +// --------------------------------------------------------------------------- +//! Provide access to the numerator (feed-forward) coefficients +//! of this filter. The coefficients are stored in order of increasing +//! delay (lowest order coefficient first). + +const std::vector< double > +Filter::numerator( void ) const +{ + return m_ffwdcoefs; +} + +// --------------------------------------------------------------------------- +// denominator +// --------------------------------------------------------------------------- +//! Provide access to the denominator (feedback) coefficients +//! of this filter. The coefficients are stored in order of increasing +//! delay (lowest order coefficient first). + +std::vector< double > +Filter::denominator( void ) +{ + return m_fbackcoefs; +} + +// --------------------------------------------------------------------------- +// denominator +// --------------------------------------------------------------------------- +//! Provide access to the denominator (feedback) coefficients +//! of this filter. The coefficients are stored in order of increasing +//! delay (lowest order coefficient first). + +const std::vector< double > +Filter::denominator( void ) const +{ + return m_fbackcoefs; +} + +// --------------------------------------------------------------------------- +// clear +// --------------------------------------------------------------------------- +//! Clear the filter state. +// +void +Filter::clear( void ) +{ + std::fill( m_delayline.begin(), m_delayline.end(), 0 ); +} + +} // end of namespace Loris |