libsidplayfp  1.0.3
TwoPassSincResampler.h
00001 /*
00002  * This file is part of libsidplayfp, a SID player engine.
00003  *
00004  * Copyright 2011-2013 Leandro Nini <drfiemost@users.sourceforge.net>
00005  * Copyright 2007-2010 Antti Lankila
00006  *
00007  * This program is free software; you can redistribute it and/or modify
00008  * it under the terms of the GNU General Public License as published by
00009  * the Free Software Foundation; either version 2 of the License, or
00010  * (at your option) any later version.
00011  *
00012  * This program is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU General Public License
00018  * along with this program; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
00020  */
00021 
00022 #ifndef TWOPASSSINCRESAMPLER_H
00023 #define TWOPASSSINCRESAMPLER_H
00024 
00025 #include <math.h>
00026 
00027 #include "Resampler.h"
00028 #include "SincResampler.h"
00029 
00030 namespace reSIDfp
00031 {
00032 
00038 class TwoPassSincResampler : public Resampler
00039 {
00040 private:
00041     SincResampler* s1;
00042     SincResampler* s2;
00043 
00044 public:
00045     TwoPassSincResampler(double clockFrequency, double samplingFrequency,
00046                          double highestAccurateFrequency)
00047     {
00048         /* Calculation according to Laurent Ganier. It evaluates to about 120 kHz at typical settings.
00049          * Some testing around the chosen value seems to confirm that this does work. */
00050         const double intermediateFrequency = 2. * highestAccurateFrequency
00051                                              + sqrt(2. * highestAccurateFrequency * clockFrequency
00052                                                      * (samplingFrequency - 2. * highestAccurateFrequency) / samplingFrequency);
00053         s1 = new SincResampler(clockFrequency, intermediateFrequency, highestAccurateFrequency);
00054         s2 = new SincResampler(intermediateFrequency, samplingFrequency, highestAccurateFrequency);
00055     }
00056 
00057     ~TwoPassSincResampler()
00058     {
00059         delete s1;
00060         delete s2;
00061     }
00062 
00063     bool input(int sample)
00064     {
00065         return s1->input(sample) && s2->input(s1->output());
00066     }
00067 
00068     int output() const
00069     {
00070         return s2->output();
00071     }
00072 
00073     void reset()
00074     {
00075         s1->reset();
00076         s2->reset();
00077     }
00078 };
00079 
00080 } // namespace reSIDfp
00081 
00082 #endif