audio: Introduce channels

audio.go

@@ -18,10 +18,15 @@ import (
 	"github.com/hajimehoshi/ebiten/internal/audio"
 )
 
-func AppendToAudioBuffer(l []float32, r []float32) {
-	audio.Append(l, r)
+func AudioSampleRate() int {
+	return audio.SampleRate
 }
 
-func AddToAudioBuffer(l []float32, r []float32) {
-	audio.Add(l, r)
+func AppendToAudioBuffer(channel int, l []float32, r []float32) bool {
+	return audio.Append(channel, l, r)
+}
+
+// TODO: better name
+func CurrentAudioTime() int {
+	return audio.CurrentBytes()
 }

example/audio/main.go

@@ -43,15 +43,12 @@ const (
 	freqGS = 830.6
 )
 
-// TODO: Need API to get sample rate?
-const sampleRate = 44100
-
 const score = `CCGGAAGR FFEEDDCR GGFFEEDR GGFFEEDR CCGGAAGR FFEEDDCR`
 
 var scoreIndex = 0
 
 func square(out []float32, volume float64, freq float64, sequence float64) {
-	length := int(sampleRate / freq)
+	length := int(float64(ebiten.AudioSampleRate()) / freq)
 	if length == 0 {
 		panic("invalid freq")
 	}
@@ -65,15 +62,15 @@ func square(out []float32, volume float64, freq float64, sequence float64) {
 }
 
 func addNote() {
-	const size = sampleRate / 60
+	size := ebiten.AudioSampleRate() / 60
 	notes := []float64{freqC, freqD, freqE, freqF, freqG, freqA * 2, freqB * 2}
 
 	defer func() {
 		scoreIndex++
 		scoreIndex %= len(score)
 	}()
-	l := make([]float32, size*30)
-	r := make([]float32, size*30)
+	l := make([]float32, size*30*2)
+	r := make([]float32, size*30*2)
 	note := score[scoreIndex]
 	for note == ' ' {
 		scoreIndex++
@@ -92,7 +89,7 @@ func addNote() {
 	vol := 1.0 / 32.0
 	square(l, vol, freq, 0.5)
 	square(r, vol, freq, 0.5)
-	ebiten.AddToAudioBuffer(l, r)
+	ebiten.AppendToAudioBuffer(-1, l, r)
 }
 
 func update(screen *ebiten.Image) error {

internal/audio/audio.go

@@ -16,6 +16,8 @@
 
 package audio
 
+const SampleRate = 44100
+
 func Init() {
 	// TODO: Implement
 }
@@ -24,10 +26,12 @@ func Start() {
 	// TODO: Implement
 }
 
-func Append(l []float32, r []float32) {
+func Append(channel int, l []float32, r []float32) bool {
 	// TODO: Implement
+	return false
 }
 
-func Add(l []float32, r []float32) {
+func CurrentBytes() int {
 	// TODO: Implement
+	return 0
 }

internal/audio/audio_js.go

@@ -25,11 +25,23 @@ var node js.Object
 var context js.Object
 
 const bufferSize = 1024
+const SampleRate = 44100
 
-var (
-	bufferL = make([]float32, 0)
-	bufferR = make([]float32, 0)
-)
+type channel struct {
+	l []float32
+	r []float32
+}
+
+var channels = make([]*channel, 16)
+
+func init() {
+	for i, _ := range channels {
+		channels[i] = &channel{
+			l: []float32{},
+			r: []float32{},
+		}
+	}
+}
 
 func min(a, b int) int {
 	if a < b {
@@ -38,29 +50,50 @@ func min(a, b int) int {
 	return b
 }
 
+var currentBytes = 0
+
+func CurrentBytes() int {
+	return currentBytes
+}
+
 func Init() {
 	context = js.Global.Get("AudioContext").New()
-	// TODO: ScriptProcessorNode will be replaced Audio WebWorker.
+	// TODO: ScriptProcessorNode will be replaced with Audio WebWorker.
 	// https://developer.mozilla.org/ja/docs/Web/API/ScriptProcessorNode
-	const bufLen = 1024
-	node = context.Call("createScriptProcessor", bufLen, 0, 2)
+	node = context.Call("createScriptProcessor", bufferSize, 0, 2)
 	node.Call("addEventListener", "audioprocess", func(e js.Object) {
+		defer func() {
+			currentBytes += bufferSize
+		}()
+
 		l := e.Get("outputBuffer").Call("getChannelData", 0)
 		r := e.Get("outputBuffer").Call("getChannelData", 1)
-		for i := 0; i < bufLen; i++ {
+		inputL := make([]float32, bufferSize)
+		inputR := make([]float32, bufferSize)
+		for _, ch := range channels {
+			if len(ch.l) == 0 {
+				continue
+			}
+			l := min(len(ch.l), bufferSize)
+			for i := 0; i < l; i++ {
+				inputL[i] += ch.l[i]
+				inputR[i] += ch.r[i]
+			}
 			// TODO: Use copyFromChannel?
-			if len(bufferL) <= i {
+			usedLen := min(bufferSize, len(ch.l))
+			ch.l = ch.l[usedLen:]
+			ch.r = ch.r[usedLen:]
+		}
+		for i := 0; i < bufferSize; i++ {
+			// TODO: Use copyFromChannel?
+			if len(inputL) <= i {
 				l.SetIndex(i, 0)
 				r.SetIndex(i, 0)
 				continue
 			}
-			l.SetIndex(i, bufferL[i])
-			r.SetIndex(i, bufferR[i])
+			l.SetIndex(i, inputL[i])
+			r.SetIndex(i, inputR[i])
 		}
-		// TODO: Will the array heads be released properly on GopherJS?
-		usedLen := min(bufLen, len(bufferL))
-		bufferL = bufferL[usedLen:]
-		bufferR = bufferR[usedLen:]
 	})
 }
 
@@ -69,26 +102,34 @@ func Start() {
 	node.Call("connect", context.Get("destination"))
 }
 
-func Append(l []float32, r []float32) {
-	if len(l) != len(r) {
-		panic("len(l) must equal to len(r)")
+func channelAt(i int) *channel {
+	if i == -1 {
+		for _, ch := range channels {
+			if 0 < len(ch.l) {
+				continue
+			}
+			return ch
+		}
+		return nil
 	}
-	bufferL = append(bufferL, l...)
-	bufferR = append(bufferR, r...)
+	ch := channels[i]
+	// TODO: Can we append even though all data is not consumed? Need game timer?
+	if 0 < len(ch.l) {
+		return nil
+	}
+	return ch
 }
 
-func Add(l []float32, r []float32) {
-	// TODO: Adjust timing for frame?
+func Append(i int, l []float32, r []float32) bool {
+	// TODO: Mutex (especially for OpenAL)
 	if len(l) != len(r) {
 		panic("len(l) must equal to len(r)")
 	}
-	m := min(len(l), len(bufferL))
-	for i := 0; i < m; i++ {
-		bufferL[i] += l[i]
-		bufferR[i] += r[i]
-	}
-	if m < len(l) {
-		bufferL = append(bufferL, l[m:]...)
-		bufferR = append(bufferR, r[m:]...)
+	ch := channelAt(i)
+	if ch == nil {
+		return false
 	}
+	ch.l = append(ch.l, l...)
+	ch.r = append(ch.r, r...)
+	return true
 }