c@415: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
c@415: 
c@415: /*
c@415:     QM DSP Library
c@415: 
c@415:     Centre for Digital Music, Queen Mary, University of London.
c@415:     This file by Chris Cannam.
c@415: 
c@415:     This program is free software; you can redistribute it and/or
c@415:     modify it under the terms of the GNU General Public License as
c@415:     published by the Free Software Foundation; either version 2 of the
c@415:     License, or (at your option) any later version.  See the file
c@415:     COPYING included with this distribution for more information.
c@415: */
c@415: 
cannam@489: #ifndef QM_DSP_DCT_H
cannam@489: #define QM_DSP_DCT_H
c@415: 
c@415: #include "FFT.h"
c@415: 
c@415: #include <vector>
c@415: 
c@415: class DCT
c@415: {
c@415: public:
c@415:     /**
c@415:      * Construct a DCT object to calculate the Discrete Cosine
c@415:      * Transform given input of size n samples. The transform is
c@415:      * implemented using an FFT of size 4n, for simplicity.
c@415:      */
c@415:     DCT(int n);
c@415: 
c@415:     ~DCT();
c@415: 
c@415:     /**
c@415:      * Carry out a type-II DCT of size n, where n is the value
c@415:      * provided to the constructor above.
c@415:      *
c@415:      * The in and out pointers must point to (enough space for) n
c@415:      * values.
c@415:      */
c@415:     void forward(const double *in, double *out);
c@415: 
c@415:     /**
c@415:      * Carry out a type-II unitary DCT of size n, where n is the value
c@415:      * provided to the constructor above. This is a scaled version of
c@415:      * the type-II DCT corresponding to a transform with an orthogonal
c@415:      * matrix. This is the transform implemented by the dct() function
c@415:      * in MATLAB.
c@415:      *
c@415:      * The in and out pointers must point to (enough space for) n
c@415:      * values.
c@415:      */
c@415:     void forwardUnitary(const double *in, double *out);
c@415: 
c@415:     /**
c@415:      * Carry out a type-III (inverse) DCT of size n, where n is the
c@415:      * value provided to the constructor above.
c@415:      *
c@415:      * The in and out pointers must point to (enough space for) n
c@415:      * values.
c@415:      */
c@415:     void inverse(const double *in, double *out);
c@415: 
c@415:     /**
c@415:      * Carry out a type-III (inverse) unitary DCT of size n, where n
c@415:      * is the value provided to the constructor above. This is the
c@415:      * inverse of forwardUnitary().
c@415:      *
c@415:      * The in and out pointers must point to (enough space for) n
c@415:      * values.
c@415:      */
c@415:     void inverseUnitary(const double *in, double *out);
c@415: 
c@415: private:
c@415:     int m_n;
c@415:     double m_scale;
c@415:     std::vector<double> m_scaled;
c@415:     std::vector<double> m_time2;
c@415:     std::vector<double> m_freq2r;
c@415:     std::vector<double> m_freq2i;
c@415:     FFTReal m_fft;
c@415: };
c@415: 
c@415: #endif