qm-dsp
1.8
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00001 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */ 00002 00003 /* 00004 QM DSP library 00005 Centre for Digital Music, Queen Mary, University of London. 00006 This file Copyright 2006 Chris Cannam. 00007 00008 This program is free software; you can redistribute it and/or 00009 modify it under the terms of the GNU General Public License as 00010 published by the Free Software Foundation; either version 2 of the 00011 License, or (at your option) any later version. See the file 00012 COPYING included with this distribution for more information. 00013 */ 00014 00015 #include "Pitch.h" 00016 00017 #include <math.h> 00018 00019 float 00020 Pitch::getFrequencyForPitch(int midiPitch, 00021 float centsOffset, 00022 float concertA) 00023 { 00024 float p = float(midiPitch) + (centsOffset / 100); 00025 return concertA * powf(2.0, (p - 69.0) / 12.0); 00026 } 00027 00028 int 00029 Pitch::getPitchForFrequency(float frequency, 00030 float *centsOffsetReturn, 00031 float concertA) 00032 { 00033 float p = 12.0 * (log(frequency / (concertA / 2.0)) / log(2.0)) + 57.0; 00034 00035 int midiPitch = int(p + 0.00001); 00036 float centsOffset = (p - midiPitch) * 100.0; 00037 00038 if (centsOffset >= 50.0) { 00039 midiPitch = midiPitch + 1; 00040 centsOffset = -(100.0 - centsOffset); 00041 } 00042 00043 if (centsOffsetReturn) *centsOffsetReturn = centsOffset; 00044 return midiPitch; 00045 } 00046