c@225: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
c@225: 
c@225: /*
c@225:     QM DSP library
c@225:     Centre for Digital Music, Queen Mary, University of London.
c@225:     This file Copyright 2006 Chris Cannam.
c@309: 
c@309:     This program is free software; you can redistribute it and/or
c@309:     modify it under the terms of the GNU General Public License as
c@309:     published by the Free Software Foundation; either version 2 of the
c@309:     License, or (at your option) any later version.  See the file
c@309:     COPYING included with this distribution for more information.
c@225: */
c@225: 
c@225: #include "Pitch.h"
c@225: 
c@304: #include <math.h>
c@225: 
c@225: float
c@225: Pitch::getFrequencyForPitch(int midiPitch,
cannam@483:                             float centsOffset,
cannam@483:                             float concertA)
c@225: {
c@225:     float p = float(midiPitch) + (centsOffset / 100);
c@225:     return concertA * powf(2.0, (p - 69.0) / 12.0);
c@225: }
c@225: 
c@225: int
c@225: Pitch::getPitchForFrequency(float frequency,
cannam@483:                             float *centsOffsetReturn,
cannam@483:                             float concertA)
c@225: {
c@225:     float p = 12.0 * (log(frequency / (concertA / 2.0)) / log(2.0)) + 57.0;
c@225: 
c@225:     int midiPitch = int(p + 0.00001);
c@225:     float centsOffset = (p - midiPitch) * 100.0;
c@225: 
c@225:     if (centsOffset >= 50.0) {
cannam@483:         midiPitch = midiPitch + 1;
cannam@483:         centsOffset = -(100.0 - centsOffset);
c@225:     }
c@225:     
c@225:     if (centsOffsetReturn) *centsOffsetReturn = centsOffset;
c@225:     return midiPitch;
c@225: }
c@225: