/**
* Converts a Hertz value to relative cents. E.g. 440Hz is converted to 900 if the reference is a
* C.
*
* @param hertzValue A value in hertz.
* @return A value in relative cents.
*/
public static double hertzToRelativeCent(final double hertzValue) {
double absoluteCentValue = PitchUnit.hertzToAbsoluteCent(hertzValue);
// make absoluteCentValue positive. E.g. -2410 => 1210
if (absoluteCentValue < 0) {
absoluteCentValue = Math.abs(1200 + absoluteCentValue);
}
// so it can be folded to one octave. E.g. 1210 => 10
return absoluteCentValue % 1200.0;
}
/**
* Calculates the frequency (Hz) for a MIDI key.
*
* @param midiKey The MIDI key. A MIDI key is an integer between 0 and 127, inclusive.
* @return A frequency in Hz corresponding to the MIDI key.
* @exception IllegalArgumentException If midiKey is not in the valid range between 0 and 127,
* inclusive.
*/
public static double midiKeyToHertz(final int midiKey) {
if (midiKey < 0 || midiKey > 127) {
LOG.warning(
"MIDI keys are defined between 0 and 127 or from "
+ midiKeyToHertz(0)
+ "Hz to "
+ midiKeyToHertz(127)
+ "Hz, MIDI KEY "
+ midiKey
+ " is out of this range.");
}
return PitchUnit.midiCentToHertz(midiKey);
}
/**
* A MIDI key is an integer between 0 and 127, inclusive. Within a certain range every pitch is
* mapped to a MIDI key. If a value outside the range is given an IllegalArugmentException is
* thrown.
*
* @param hertzValue The pitch in Hertz.
* @return An integer representing the closest midi key.
* @exception IllegalArgumentException if the hertzValue does not fall within the range of valid
* MIDI key frequencies.
*/
public static int hertzToMidiKey(final Double hertzValue) {
final int midiKey = (int) Math.round(PitchUnit.hertzToMidiCent(hertzValue));
if (midiKey < 0 || midiKey > 127) {
LOG.warning(
"MIDI keys are defined between 0 and 127 or from "
+ midiKeyToHertz(0)
+ "Hz to "
+ midiKeyToHertz(127)
+ "Hz, "
+ hertzValue
+ "does not map directly to a MIDI key.");
}
return midiKey;
}
/**
* Converts a Hertz value to pitch in this unit.
*
* @param hertzValue The value in Hertz.
* @return The pitch in this unit.
*/
private double convertHertz(final double hertzValue) {
final double convertedPitch;
switch (this) {
case ABSOLUTE_CENTS:
convertedPitch = PitchUnit.hertzToAbsoluteCent(hertzValue);
break;
case HERTZ:
convertedPitch = hertzValue;
break;
case MIDI_CENT:
convertedPitch = PitchUnit.hertzToMidiCent(hertzValue);
break;
case MIDI_KEY:
convertedPitch = PitchUnit.hertzToMidiKey(hertzValue);
break;
case RELATIVE_CENTS:
convertedPitch = PitchUnit.hertzToRelativeCent(hertzValue);
break;
default:
throw new AssertionError("Unknown pitch unit: " + getHumanName());
}
return convertedPitch;
}
private double convertToHertz(final double value, final PitchUnit valueUnit) {
final double hertzValue;
switch (valueUnit) {
case ABSOLUTE_CENTS:
hertzValue = PitchUnit.absoluteCentToHertz(value);
break;
case HERTZ:
hertzValue = value;
break;
case MIDI_CENT:
hertzValue = PitchUnit.midiCentToHertz(value);
break;
case MIDI_KEY:
hertzValue = PitchUnit.midiKeyToHertz((int) value);
break;
case RELATIVE_CENTS:
hertzValue = PitchUnit.relativeCentToHertz(value);
break;
default:
throw new AssertionError("Unknown pitch unit: " + getHumanName());
}
return hertzValue;
}
