Hibiki/panako/units.go

package panako

import "math"

type Hertz float64

// Cent Twelve-tone equal temperament divides the Octave into 12 semitones of 100 Cent each.
type Cent int64

// Octave The interval between one musical pitch and another with double its frequency
type Octave int

const CentsPerOctave = 1200

func (h Hertz) DifferenceInCent(b Hertz) Cent {
	return Cent(CentsPerOctave * math.Log2(float64(b/h)))
}

func (h Hertz) DifferenceInHertz(b Hertz) Hertz {
	return b - h
}

func (h Hertz) Octaves(octaves Octave) Hertz {
	return h * Hertz(math.Pow(2, float64(octaves)))
}

func (h Hertz) Cents(cents Cent) Hertz {
	return h * Hertz(math.Pow(2, float64(cents)/CentsPerOctave))
}