c@349: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
c@349: 
c@349: /*
c@349:     QM DSP library
c@349:     Centre for Digital Music, Queen Mary, University of London.
c@349:  
c@349:     This program is free software; you can redistribute it and/or
c@349:     modify it under the terms of the GNU General Public License as
c@349:     published by the Free Software Foundation; either version 2 of the
c@349:     License, or (at your option) any later version.  See the file
c@349:     COPYING included with this distribution for more information.
c@349: */
c@349: 
c@349: #ifndef KAISER_WINDOW_H
c@349: #define KAISER_WINDOW_H
c@349: 
c@349: #include <vector>
c@349: #include <cmath>
c@349: 
c@377: /**
c@377:  * Kaiser window: A windower whose bandwidth and sidelobe height
c@377:  * (signal-noise ratio) can be specified. These parameters are traded
c@377:  * off against the window length.
c@377:  */
c@349: class KaiserWindow
c@349: {
c@349: public:
c@349:     struct Parameters {
cannam@483:         int length;
cannam@483:         double beta;
c@349:     };
c@349: 
c@349:     /**
c@349:      * Construct a Kaiser windower with the given length and beta
c@349:      * parameter.
c@349:      */
c@349:     KaiserWindow(Parameters p) : m_length(p.length), m_beta(p.beta) { init(); }
c@349: 
c@349:     /**
c@349:      * Construct a Kaiser windower with the given attenuation in dB
c@349:      * and transition width in samples.
c@349:      */
c@349:     static KaiserWindow byTransitionWidth(double attenuation,
cannam@483:                                           double transition) {
cannam@483:         return KaiserWindow
cannam@483:             (parametersForTransitionWidth(attenuation, transition));
c@349:     }
c@349: 
c@349:     /**
c@349:      * Construct a Kaiser windower with the given attenuation in dB
c@349:      * and transition bandwidth in Hz for the given samplerate.
c@349:      */
c@349:     static KaiserWindow byBandwidth(double attenuation,
cannam@483:                                     double bandwidth,
cannam@483:                                     double samplerate) {
cannam@483:         return KaiserWindow
cannam@483:             (parametersForBandwidth(attenuation, bandwidth, samplerate));
c@349:     }
c@349: 
c@349:     /**
c@349:      * Obtain the parameters necessary for a Kaiser window of the
c@349:      * given attenuation in dB and transition width in samples.
c@349:      */
c@349:     static Parameters parametersForTransitionWidth(double attenuation,
cannam@483:                                                    double transition);
c@349: 
c@349:     /**
c@349:      * Obtain the parameters necessary for a Kaiser window of the
c@349:      * given attenuation in dB and transition bandwidth in Hz for the
c@349:      * given samplerate.
c@349:      */
c@349:     static Parameters parametersForBandwidth(double attenuation,
cannam@483:                                              double bandwidth,
cannam@483:                                              double samplerate) {
cannam@483:         return parametersForTransitionWidth
cannam@483:             (attenuation, (bandwidth * 2 * M_PI) / samplerate);
c@349:     } 
c@349: 
c@349:     int getLength() const {
cannam@483:         return m_length;
c@349:     }
c@349: 
c@349:     const double *getWindow() const { 
cannam@483:         return m_window.data();
c@349:     }
c@349: 
c@349:     void cut(double *src) const { 
cannam@483:         cut(src, src); 
c@349:     }
c@349: 
c@349:     void cut(const double *src, double *dst) const {
cannam@483:         for (int i = 0; i < m_length; ++i) {
cannam@483:             dst[i] = src[i] * m_window[i];
cannam@483:         }
c@349:     }
c@349: 
c@349: private:
c@349:     int m_length;
c@349:     double m_beta;
c@349:     std::vector<double> m_window;
c@349: 
c@349:     void init();
c@349: };
c@349: 
c@349: #endif