func addNote() {
size := audio.SampleRate() / 60
notes := []float64{freqC, freqD, freqE, freqF, freqG, freqA * 2, freqB * 2}
defer func() {
scoreIndex++
scoreIndex %= len(score)
}()
l := make([]int16, size*30)
r := make([]int16, size*30)
note := score[scoreIndex]
for note == ' ' {
scoreIndex++
scoreIndex %= len(score)
note = score[scoreIndex]
}
freq := 0.0
switch {
case note == 'R':
freq = 0
case note <= 'B':
freq = notes[int(note)+len(notes)-int('C')]
default:
freq = notes[note-'C']
}
vol := 1.0 / 16.0
square(l, vol, freq, 0.25)
square(r, vol, freq, 0.25)
audio.Play(0, toBytes(l, r))
}
func init() {
s := float64(audio.SampleRate())
amp := []float64{1.0, 0.8, 0.6, 0.4, 0.2}
x := []float64{4.0, 2.0, 1.0, 0.5, 0.25}
for i := 0; i < len(pcm); i++ {
v := 0.0
twoPiF := 2.0 * math.Pi * baseFreq
for j := 0; j < len(amp); j++ {
a := amp[j] * math.Exp(-5*float64(i)/(x[j]*s))
v += a * math.Sin(float64(i)*twoPiF*float64(j+1)/s)
}
pcm[i] = v / 5.0
}
}
func square(out []int16, volume float64, freq float64, sequence float64) {
if freq == 0 {
for i := 0; i < len(out); i++ {
out[i] = 0
}
return
}
length := int(float64(audio.SampleRate()) / freq)
if length == 0 {
panic("invalid freq")
}
for i := 0; i < len(out); i++ {
a := int16(volume * math.MaxInt16)
if i%length < int(float64(length)*sequence) {
a = -a
}
out[i] = a
}
}
"image/color"
"log"
"math"
"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
"github.com/hajimehoshi/ebiten/example/common"
"github.com/hajimehoshi/ebiten/exp/audio"
)
const (
screenWidth = 320
screenHeight = 240
)
var pcm = make([]float64, 4*audio.SampleRate())
const baseFreq = 220
func init() {
s := float64(audio.SampleRate())
amp := []float64{1.0, 0.8, 0.6, 0.4, 0.2}
x := []float64{4.0, 2.0, 1.0, 0.5, 0.25}
for i := 0; i < len(pcm); i++ {
v := 0.0
twoPiF := 2.0 * math.Pi * baseFreq
for j := 0; j < len(amp); j++ {
a := amp[j] * math.Exp(-5*float64(i)/(x[j]*s))
v += a * math.Sin(float64(i)*twoPiF*float64(j+1)/s)
}
pcm[i] = v / 5.0