157 lines
4.0 KiB
C++
157 lines
4.0 KiB
C++
/**********************************************************************
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Audacity: A Digital Audio Editor
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PitchName.cpp
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Copyright 2005-9, Vaughan Johnson and Dominic Mazzoni.
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All rights reserved.
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*******************************************************************//*!
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\file PitchName.cpp
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\brief Utilities for converting from frequency to pitch
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and from pitch to absolute (e.g., C4 for middle C)
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or nominal (A through G#) pitch name.
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*//*******************************************************************/
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#include <math.h>
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#include <stdio.h>
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#include "PitchName.h"
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// FreqToMIDInoteNumber takes a frequency in Hz (exponential scale relative to
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// alphabetic pitch names) and returns a pitch ID number (linear
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// scale), such that A440 (A4) is 69, middle C (C4) is 60, etc.
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// Each register starts with C (e.g., for middle C and A440,
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// it's register 4).
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double FreqToMIDInoteNumber(double freq)
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{
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// Make the calculation relative to A440 (A4), note number 69.
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return double (69.0 + (12.0 * (log(freq / 440.0) / log(2.0))));
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}
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// PitchIndex returns the [0,11] index for a double pitchNum,
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// as per result from FreqToMIDInoteNumber, corresponding to modulo 12
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// of the integer part of (pitchNum + 0.5), so 0=C, 1=C#, etc.
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unsigned int PitchIndex(double pitchNum)
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{
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return ((int)(pitchNum + 0.5) % 12);
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}
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wxChar gPitchName[10];
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wxChar * pPitchName;
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// PitchName takes pitchNum (as per result from
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// FreqToMIDInoteNumber) and returns a standard pitch/note name [C, C#, etc.).
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// Sharps are the default, unless, bWantFlats is true.
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wxChar * PitchName(double pitchNum, bool bWantFlats /* = false */)
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{
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pPitchName = gPitchName;
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switch (PitchIndex(pitchNum)) {
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case 0:
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*pPitchName++ = wxT('C');
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break;
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case 1:
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if (bWantFlats) {
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*pPitchName++ = wxT('D');
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*pPitchName++ = wxT('b');
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} else {
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*pPitchName++ = wxT('C');
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*pPitchName++ = wxT('#');
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}
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break;
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case 2:
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*pPitchName++ = wxT('D');
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break;
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case 3:
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if (bWantFlats) {
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*pPitchName++ = wxT('E');
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*pPitchName++ = wxT('b');
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} else {
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*pPitchName++ = wxT('D');
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*pPitchName++ = wxT('#');
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}
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break;
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case 4:
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*pPitchName++ = wxT('E');
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break;
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case 5:
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*pPitchName++ = wxT('F');
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break;
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case 6:
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if (bWantFlats) {
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*pPitchName++ = wxT('G');
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*pPitchName++ = wxT('b');
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} else {
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*pPitchName++ = wxT('F');
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*pPitchName++ = wxT('#');
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}
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break;
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case 7:
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*pPitchName++ = wxT('G');
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break;
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case 8:
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if (bWantFlats) {
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*pPitchName++ = wxT('A');
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*pPitchName++ = wxT('b');
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} else {
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*pPitchName++ = wxT('G');
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*pPitchName++ = wxT('#');
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}
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break;
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case 9:
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*pPitchName++ = wxT('A');
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break;
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case 10:
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if (bWantFlats) {
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*pPitchName++ = wxT('B');
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*pPitchName++ = wxT('b');
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} else {
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*pPitchName++ = wxT('A');
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*pPitchName++ = wxT('#');
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}
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break;
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case 11:
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*pPitchName++ = wxT('B');
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break;
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}
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*pPitchName = wxT('\0');
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return gPitchName;
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}
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// PitchName_Absolute does the same thing as PitchName, but appends
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// the register number, e.g., instead of "C" it will return "C4"
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// if the pitchNum corresonds to middle C.
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// Sharps are the default, unless, bWantFlats is true.
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wxChar * PitchName_Absolute(double pitchNum, bool bWantFlats /* = false */)
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{
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PitchName(pitchNum, bWantFlats);
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// PitchName sets pPitchName to the next available char in gPitchName,
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// so it's ready to append the register number.
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wxSnprintf(pPitchName, 8, wxT("%d"), (((int)(pitchNum + 0.5) / 12) - 1));
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return gPitchName;
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}
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// Indentation settings for Vim and Emacs and unique identifier for Arch, a
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// version control system. Please do not modify past this point.
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//
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// Local Variables:
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// c-basic-offset: 3
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// indent-tabs-mode: nil
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// End:
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//
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// vim: et sts=3 sw=3
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// arch-tag: 71a57231-e6fd-4e65-8839-08451f7b4dff
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