comparison dsp/transforms/DCT.h @ 191:857ca50ca25f

Add DCT

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