comparison base/Pitch.cpp @ 225:49844bc8a895

* Queen Mary C++ DSP library

+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    QM DSP library
+    Centre for Digital Music, Queen Mary, University of London.
+    This file Copyright 2006 Chris Cannam.
+    All rights reserved.
+*/
+
+#include "Pitch.h"
+
+#include <cmath>
+
+float
+Pitch::getFrequencyForPitch(int midiPitch,
+			    float centsOffset,
+			    float concertA)
+{
+    float p = float(midiPitch) + (centsOffset / 100);
+    return concertA * powf(2.0, (p - 69.0) / 12.0);
+}
+
+int
+Pitch::getPitchForFrequency(float frequency,
+			    float *centsOffsetReturn,
+			    float concertA)
+{
+    float p = 12.0 * (log(frequency / (concertA / 2.0)) / log(2.0)) + 57.0;
+
+    int midiPitch = int(p + 0.00001);
+    float centsOffset = (p - midiPitch) * 100.0;
+
+    if (centsOffset >= 50.0) {
+	midiPitch = midiPitch + 1;
+	centsOffset = -(100.0 - centsOffset);
+    }
+    
+    if (centsOffsetReturn) *centsOffsetReturn = centsOffset;
+    return midiPitch;
+}
+