Chris@191: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
Chris@191: 
Chris@191: /*
Chris@191:     QM DSP Library
Chris@191: 
Chris@191:     Centre for Digital Music, Queen Mary, University of London.
Chris@191:     This file by Chris Cannam.
Chris@191: 
Chris@191:     This program is free software; you can redistribute it and/or
Chris@191:     modify it under the terms of the GNU General Public License as
Chris@191:     published by the Free Software Foundation; either version 2 of the
Chris@191:     License, or (at your option) any later version.  See the file
Chris@191:     COPYING included with this distribution for more information.
Chris@191: */
Chris@191: 
Chris@191: #ifndef DCT_H
Chris@191: #define DCT_H
Chris@191: 
Chris@191: #include "FFT.h"
Chris@191: 
Chris@191: #include <vector>
Chris@191: 
Chris@191: class DCT
Chris@191: {
Chris@191: public:
Chris@191:     /**
Chris@191:      * Construct a DCT object to calculate the Discrete Cosine
Chris@191:      * Transform given input of size n samples. The transform is
Chris@191:      * implemented using an FFT of size 4n, for simplicity.
Chris@191:      */
Chris@191:     DCT(int n);
Chris@191: 
Chris@191:     ~DCT();
Chris@191: 
Chris@191:     /**
Chris@191:      * Carry out a type-II DCT of size n, where n is the value
Chris@191:      * provided to the constructor above.
Chris@191:      *
Chris@191:      * The in and out pointers must point to (enough space for) n
Chris@191:      * values.
Chris@191:      */
Chris@191:     void forward(const double *in, double *out);
Chris@191: 
Chris@191:     /**
Chris@191:      * Carry out a type-II unitary DCT of size n, where n is the value
Chris@191:      * provided to the constructor above. This is a scaled version of
Chris@191:      * the type-II DCT corresponding to a transform with an orthogonal
Chris@191:      * matrix. This is the transform implemented by the dct() function
Chris@191:      * in MATLAB.
Chris@191:      *
Chris@191:      * The in and out pointers must point to (enough space for) n
Chris@191:      * values.
Chris@191:      */
Chris@191:     void forwardUnitary(const double *in, double *out);
Chris@191: 
Chris@191:     /**
Chris@191:      * Carry out a type-III (inverse) DCT of size n, where n is the
Chris@191:      * value provided to the constructor above.
Chris@191:      *
Chris@191:      * The in and out pointers must point to (enough space for) n
Chris@191:      * values.
Chris@191:      */
Chris@191:     void inverse(const double *in, double *out);
Chris@191: 
Chris@191:     /**
Chris@191:      * Carry out a type-III (inverse) unitary DCT of size n, where n
Chris@191:      * is the value provided to the constructor above. This is the
Chris@191:      * inverse of forwardUnitary().
Chris@191:      *
Chris@191:      * The in and out pointers must point to (enough space for) n
Chris@191:      * values.
Chris@191:      */
Chris@191:     void inverseUnitary(const double *in, double *out);
Chris@191: 
Chris@191: private:
Chris@191:     int m_n;
Chris@191:     double m_scale;
Chris@191:     std::vector<double> m_scaled;
Chris@191:     std::vector<double> m_time2;
Chris@191:     std::vector<double> m_freq2r;
Chris@191:     std::vector<double> m_freq2i;
Chris@191:     FFTReal m_fft;
Chris@191: };
Chris@191: 
Chris@191: #endif