c@225: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
c@225: /*
c@225:     QM DSP Library
c@225: 
c@225:     Centre for Digital Music, Queen Mary, University of London.
c@309:     This file 2005-2006 Christian Landone.
c@309: 
c@309:     This program is free software; you can redistribute it and/or
c@309:     modify it under the terms of the GNU General Public License as
c@309:     published by the Free Software Foundation; either version 2 of the
c@309:     License, or (at your option) any later version.  See the file
c@309:     COPYING included with this distribution for more information.
c@225: */
c@225: 
cannam@489: #ifndef QM_DSP_DECIMATOR_H
cannam@489: #define QM_DSP_DECIMATOR_H
c@225: 
c@375: /**
c@375:  * Decimator carries out a fast downsample by a power-of-two
c@375:  * factor. Only a limited number of factors are supported, from two to
c@375:  * whatever getHighestSupportedFactor() returns. This is much faster
c@375:  * than Resampler but has a worse signal-noise ratio.
c@375:  */
c@225: class Decimator  
c@225: {
c@225: public:
c@279:     /**
c@279:      * Construct a Decimator to operate on input blocks of length
c@279:      * inLength, with decimation factor decFactor.  inLength should be
c@279:      * a multiple of decFactor.  Output blocks will be of length
c@279:      * inLength / decFactor.
c@279:      *
c@279:      * decFactor must be a power of two.  The highest supported factor
c@279:      * is obtained through getHighestSupportedFactor(); for higher
c@279:      * factors, you will need to chain more than one decimator.
c@279:      */
cannam@499:     Decimator(int inLength, int decFactor);
c@225:     virtual ~Decimator();
c@225: 
c@388:     /**
c@388:      * Process inLength samples (as supplied to constructor) from src
c@388:      * and write inLength / decFactor samples to dst.  Note that src
c@388:      * and dst may be the same or overlap (an intermediate buffer is
c@388:      * used).
c@388:      */
c@388:     void process( const double* src, double* dst );
c@388: 
c@388:     /**
c@388:      * Process inLength samples (as supplied to constructor) from src
c@388:      * and write inLength / decFactor samples to dst.  Note that src
c@388:      * and dst may be the same or overlap (an intermediate buffer is
c@388:      * used).
c@388:      */
c@388:     void process( const float* src, float* dst );
c@388: 
c@247:     int getFactor() const { return m_decFactor; }
c@247:     static int getHighestSupportedFactor() { return 8; }
c@247: 
c@388:     void resetFilter();
c@388: 
c@225: private:
c@225:     void deInitialise();
cannam@499:     void initialise( int inLength, int decFactor );
cannam@499:     void doAntiAlias( const double* src, double* dst, int length );
cannam@499:     void doAntiAlias( const float* src, double* dst, int length );
c@225: 
cannam@499:     int m_inputLength;
cannam@499:     int m_outputLength;
cannam@499:     int m_decFactor;
c@225: 
c@225:     double Input;
c@225:     double Output ;
c@225: 
c@225:     double o1,o2,o3,o4,o5,o6,o7;
c@225: 
c@225:     double a[ 9 ];
c@225:     double b[ 9 ];
cannam@483:         
c@225:     double* decBuffer;
c@225: };
c@225: 
c@225: #endif //