annotate base/Pitch.h @ 537:3cc4b7cd2aa5

* Merge from one-fftdataserver-per-fftmodel branch.  This bit of
reworking (which is not described very accurately by the title of
the branch) turns the MatrixFile object into something that either
reads or writes, but not both, and separates the FFT file cache
reader and writer implementations separately.  This allows the
FFT data server to have a single thread owning writers and one reader
per "customer" thread, and for all locking to be vastly simplified
and concentrated in the data server alone (because none of the
classes it makes use of is used in more than one thread at a time).
The result is faster and more trustworthy code.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam.
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _PITCH_H_
#define _PITCH_H_

#include <QString>

class Pitch
{
public:
    /**
     * Return the frequency at the given MIDI pitch plus centsOffset
     * cents (1/100ths of a semitone).  centsOffset does not have to
     * be in any particular range or sign.
     *
     * If concertA is non-zero, use that as the reference frequency
     * for the A at MIDI pitch 69; otherwise use the tuning frequency
     * specified in the application preferences (default 440Hz).
     */
    static float getFrequencyForPitch(int midiPitch,
				      float centsOffset = 0,
				      float concertA = 0.0);

    /**
     * Return the nearest MIDI pitch to the given frequency.
     *
     * If centsOffsetReturn is non-NULL, return in *centsOffsetReturn
     * the number of cents (1/100ths of a semitone) difference between
     * the given frequency and that of the returned MIDI pitch.  The
     * cents offset will be in the range [-50,50).
     * 
     * If concertA is non-zero, use that as the reference frequency
     * for the A at MIDI pitch 69; otherwise use the tuning frequency
     * specified in the application preferences (default 440Hz).
     */
    static int getPitchForFrequency(float frequency,
				    float *centsOffsetReturn = 0,
				    float concertA = 0.0);

    /**
     * Return the nearest MIDI pitch range to the given frequency
     * range, that is, the difference in MIDI pitch values between the
     * higher and lower frequencies.
     *
     * If centsOffsetReturn is non-NULL, return in *centsOffsetReturn
     * the number of cents (1/100ths of a semitone) difference between
     * the given frequency difference and the returned MIDI pitch
     * range.  The cents offset will be in the range [-50,50).
     * 
     * If concertA is non-zero, use that as the reference frequency
     * for the A at MIDI pitch 69; otherwise use the tuning frequency
     * specified in the application preferences (default 440Hz).
     */
    static int getPitchForFrequencyDifference(float frequencyA,
                                              float frequencyB,
                                              float *centsOffsetReturn = 0,
                                              float concertA = 0.0);

    /**
     * Return a string describing the given MIDI pitch, with optional
     * cents offset.  This consists of the note name, octave number
     * (with MIDI pitch 0 having octave number -2), and optional
     * cents.
     *
     * For example, "A#3" (A# in octave 3) or "C2-12c" (C in octave 2,
     * minus 12 cents).
     *
     * If useFlats is true, spell notes with flats instead of sharps,
     * e.g. Bb3 instead of A#3.
     */
    static QString getPitchLabel(int midiPitch,
				 float centsOffset = 0,
				 bool useFlats = false);

    /**
     * Return a string describing the nearest MIDI pitch to the given
     * frequency, with cents offset.
     *
     * If concertA is non-zero, use that as the reference frequency
     * for the A at MIDI pitch 69; otherwise use the tuning frequency
     * specified in the application preferences (default 440Hz).
     *
     * If useFlats is true, spell notes with flats instead of sharps,
     * e.g. Bb3 instead of A#3.
     */
    static QString getPitchLabelForFrequency(float frequency,
					     float concertA = 0.0,
					     bool useFlats = false);

    /**
     * Return a string describing the given pitch range in octaves,
     * semitones and cents.  This is in the form e.g. "1'2+4c".
     */
    static QString getLabelForPitchRange(int semis, float cents = 0);

    /**
     * Return true if the given frequency falls within the range of
     * MIDI note pitches, plus or minus half a semitone.  This is
     * equivalent to testing whether getPitchForFrequency returns a
     * pitch in the MIDI range (0 to 127 inclusive) with any cents
     * offset.
     *
     * If concertA is non-zero, use that as the reference frequency
     * for the A at MIDI pitch 69; otherwise use the tuning frequency
     * specified in the application preferences (default 440Hz).
     */
    static bool isFrequencyInMidiRange(float frequency,
                                       float concertA = 0.0);
};


#endif