1 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
2
3 /*
4 QM DSP library
5 Centre for Digital Music, Queen Mary, University of London.
6 This file Copyright 2006 Chris Cannam.
7
8 This program is free software; you can redistribute it and/or
9 modify it under the terms of the GNU General Public License as
10 published by the Free Software Foundation; either version 2 of the
11 License, or (at your option) any later version. See the file
12 COPYING included with this distribution for more information.
13 */
14
15 #include "Pitch.h"
16
17 #include <math.h>
18
19 float
getFrequencyForPitch(int midiPitch,float centsOffset,float concertA)20 Pitch::getFrequencyForPitch(int midiPitch,
21 float centsOffset,
22 float concertA)
23 {
24 float p = float(midiPitch) + (centsOffset / 100);
25 return concertA * powf(2.0, (p - 69.0) / 12.0);
26 }
27
28 int
getPitchForFrequency(float frequency,float * centsOffsetReturn,float concertA)29 Pitch::getPitchForFrequency(float frequency,
30 float *centsOffsetReturn,
31 float concertA)
32 {
33 float p = 12.0 * (log(frequency / (concertA / 2.0)) / log(2.0)) + 57.0;
34
35 int midiPitch = int(p + 0.00001);
36 float centsOffset = (p - midiPitch) * 100.0;
37
38 if (centsOffset >= 50.0) {
39 midiPitch = midiPitch + 1;
40 centsOffset = -(100.0 - centsOffset);
41 }
42
43 if (centsOffsetReturn) *centsOffsetReturn = centsOffset;
44 return midiPitch;
45 }
46
47