c@380: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
c@380: /*
c@380:     QM DSP Library
c@380: 
c@380:     Centre for Digital Music, Queen Mary, University of London.
c@380: 
c@380:     This program is free software; you can redistribute it and/or
c@380:     modify it under the terms of the GNU General Public License as
c@380:     published by the Free Software Foundation; either version 2 of the
c@380:     License, or (at your option) any later version.  See the file
c@380:     COPYING included with this distribution for more information.
c@380: */
c@380: 
c@380: #ifndef DECIMATORB_H
c@380: #define DECIMATORB_H
c@380: 
c@380: #include <vector>
c@380: 
c@380: /**
c@380:  * DecimatorB carries out a fast downsample by a power-of-two
c@380:  * factor. It only knows how to decimate by a factor of 2, and will
c@380:  * use repeated decimation for higher factors. A Butterworth filter of
c@380:  * order 6 is used for the lowpass filter.
c@380:  */
c@380: class DecimatorB
c@380: {
c@380: public:
c@380:     void process( const double* src, double* dst );
c@380:     void process( const float* src, float* dst );
c@380: 
c@380:     /**
c@380:      * Construct a DecimatorB to operate on input blocks of length
c@380:      * inLength, with decimation factor decFactor.  inLength should be
c@380:      * a multiple of decFactor.  Output blocks will be of length
c@380:      * inLength / decFactor.
c@380:      *
c@380:      * decFactor must be a power of two.
c@380:      */
c@380:     DecimatorB(int inLength, int decFactor);
c@380:     virtual ~DecimatorB();
c@380: 
c@380:     int getFactor() const { return m_decFactor; }
c@380: 
c@380: private:
c@380:     void deInitialise();
c@380:     void initialise(int inLength, int decFactor);
c@380:     void doAntiAlias(const double* src, double* dst, int length, int filteridx);
c@380:     void doProcess();
c@380: 
c@380:     int m_inputLength;
c@380:     int m_outputLength;
c@380:     int m_decFactor;
c@380: 
c@380:     std::vector<std::vector<double> > m_o;
c@380: 
c@380:     double m_a[7];
c@380:     double m_b[7];
cannam@483:         
c@380:     double *m_aaBuffer;
c@380:     double *m_tmpBuffer;
c@380: };
c@380: 
c@380: #endif
c@380: