song.go

package beepster

import (
	"github.com/octotep/go-mxl"
	"math"
)

type Song struct {
	NumTracks uint8
	Track     []chan Note
	Reps      int
}

func CreateSong(numTracks uint8, numRepetitions int) *Song {
	// Create the song and fill out all the information we know about it
	mysong := new(Song)
	mysong.NumTracks = numTracks
	mysong.Reps = numRepetitions
	mysong.Track = make([]chan Note, mysong.NumTracks)
	for i := range mysong.Track {
		mysong.Track[i] = make(chan Note, 14)
	}
	return mysong
}

func (song *Song) CreateFiller(trackId uint8, cleanup func(), tracks ...*[]Note) func() {
	return func() {
		defer cleanup()
		for i := 0; i < song.Reps; i++ {
			// Loop through all arrays given
			for _, val := range tracks {
				// Loop through all notes in one of the arrays
				for _, note := range *val {
					song.Track[trackId] <- note
				}
			}
		}
		close(song.Track[trackId])
	}
}

func CreateSongFromXML(mxlDoc mxl.MXLDoc, numRepetitions int) *Song {
	mysong := new(Song)
	mysong.NumTracks = uint8(len(mxlDoc.Parts))
	mysong.Reps = numRepetitions
	mysong.Track = make([]chan Note, mysong.NumTracks)
	for i := range mysong.Track {
		mysong.Track[i] = make(chan Note, 14)
	}
	return mysong
}

func (song *Song) CreateFillerFromXml(trackId uint8, bpm uint, cleanup func(), track mxl.Part) func() {
	return func() {
		defer cleanup()
		for i := 0; i < song.Reps; i++ {
			// Loop through all arrays given
			currentDiv := 1
			for _, measure := range track.Measures {
				// Check for new division
				if measure.Atters.Divisions != 0 {
					currentDiv = measure.Atters.Divisions
				}

				// Loop through all notes in one of the arrays
				for _, note := range measure.Notes {
					// Only process the note if it is not part of a chord
					if note.Chord.Local == "" {
						var freq float32
						if note.Pitch.Step == "" {
							// It's a rest
							freq = 0.0
						} else {
							// Calc the correct pitch from the frequency
							freq = PitchToFreq(note.Pitch)
						}
						// How long one quarter note is in seconds
						lengthOfQuarter := 60.0 / float32(bpm)
						// The length of the current note in seconds
						totalTime := float32(note.Duration) / float32(currentDiv) * lengthOfQuarter
						// Delay before the next note in ms
						delay := 5
						// Convert totalTime to ms and subtract delay at the end of the note
						length := int(totalTime*1000) - delay
						song.Track[trackId] <- Note{freq, uint32(length), uint32(delay)}
					}
				}
			}
		}
		close(song.Track[trackId])
	}
}

func PitchToFreq(pitch mxl.Pitch) float32 {
	var letter int
	if pitch.Step == "C" {
		letter = 0
	} else if pitch.Step == "D" {
		letter = 2
	} else if pitch.Step == "E" {
		letter = 4
	} else if pitch.Step == "F" {
		letter = 5
	} else if pitch.Step == "G" {
		letter = 7
	} else if pitch.Step == "A" {
		letter = 9
	} else if pitch.Step == "B" {
		letter = 11
	}
	absoluteHalfSteps := 12*(pitch.Octave-1) + letter + int(pitch.Accidental)
	a440 := 45
	relativeHalfSteps := absoluteHalfSteps - a440

	var freq float32
	// 2^(n/12) * 440
	freq = float32(math.Pow(2, float64(float64(relativeHalfSteps)/12.0))) * 440.0
	return freq
}