audio: Bug fix: Multi source (or nodes) should be used to play multi sounds

example/piano/main.go

@@ -43,7 +43,7 @@ func init() {
 			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
+		pcm[i] = v / 5.0
 	}
 }
 
@@ -112,7 +112,7 @@ func update(screen *ebiten.Image) error {
 		if keyStates[key] != 1 {
 			continue
 		}
-		addNote(220*math.Exp2(float64(i)/12.0), 1.0/8.0)
+		addNote(220*math.Exp2(float64(i)/12.0), 1.0)
 	}
 	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f", ebiten.CurrentFPS()))
 	return nil

internal/audio/audio.go

@@ -23,12 +23,12 @@ var audioEnabled = false
 const bufferSize = 1024
 const SampleRate = 44100
 
-var nextInsertionPosition = 0
 var currentPosition = 0
 
 type channel struct {
-	l []int16
-	r []int16
+	l                     []int16
+	r                     []int16
+	nextInsertionPosition int
 }
 
 var MaxChannel = 32
@@ -55,7 +55,7 @@ func Start() {
 
 func isPlaying(channel int) bool {
 	ch := channels[channel]
-	return nextInsertionPosition < len(ch.l)
+	return ch.nextInsertionPosition < len(ch.l)
 }
 
 func channelAt(i int) *channel {
@@ -88,8 +88,8 @@ func Play(channel int, l []int16, r []int16) bool {
 	if ch == nil {
 		return false
 	}
-	ch.l = append(ch.l, make([]int16, nextInsertionPosition-len(ch.l))...)
-	ch.r = append(ch.r, make([]int16, nextInsertionPosition-len(ch.r))...)
+	ch.l = append(ch.l, make([]int16, ch.nextInsertionPosition-len(ch.l))...)
+	ch.r = append(ch.r, make([]int16, ch.nextInsertionPosition-len(ch.r))...)
 	ch.l = append(ch.l, l...)
 	ch.r = append(ch.r, r...)
 	return true
@@ -112,7 +112,9 @@ func Queue(channel int, l []int16, r []int16) {
 }
 
 func Update() {
-	nextInsertionPosition += SampleRate / 60
+	for _, ch := range channels {
+		ch.nextInsertionPosition += SampleRate / 60
+	}
 }
 
 func min(a, b int) int {
@@ -138,7 +140,31 @@ func isChannelsEmpty() bool {
 	return true
 }
 
-func loadChannelBuffers() (l, r []int16) {
+func loadChannelBuffer(channel int) (l, r []int16) {
+	channelsLock.Lock()
+	defer channelsLock.Unlock()
+
+	if !audioEnabled {
+		return nil, nil
+	}
+
+	ch := channels[channel]
+	inputL := make([]int16, bufferSize)
+	inputR := make([]int16, bufferSize)
+	length := min(len(ch.l), bufferSize)
+	for i := 0; i < length; i++ {
+		inputL[i] = ch.l[i]
+		inputR[i] = ch.r[i]
+	}
+	usedLen := min(bufferSize, len(ch.l))
+	ch.l = ch.l[usedLen:]
+	ch.r = ch.r[usedLen:]
+
+	ch.nextInsertionPosition -= min(bufferSize, ch.nextInsertionPosition)
+	return inputL, inputR
+}
+
+/*func loadChannelBuffers() (l, r []int16) {
 	channelsLock.Lock()
 	defer channelsLock.Unlock()
 
@@ -162,7 +188,7 @@ func loadChannelBuffers() (l, r []int16) {
 		ch.r = ch.r[usedLen:]
 	}
 	return inputL, inputR
-}
+}*/
 
 func IsPlaying(channel int) bool {
 	channelsLock.Lock()

internal/audio/audio_js.go

@@ -21,23 +21,18 @@ import (
 )
 
 // Keep this so as not to be destroyed by GC.
-var node js.Object
+var nodes = []js.Object{}
 var context js.Object
 
-func initialize() {
-	context = js.Global.Get("AudioContext").New()
-	// TODO: ScriptProcessorNode will be replaced with Audio WebWorker.
-	// https://developer.mozilla.org/ja/docs/Web/API/ScriptProcessorNode
-	node = context.Call("createScriptProcessor", bufferSize, 0, 2)
-	node.Call("addEventListener", "audioprocess", func(e js.Object) {
+func audioProcess(channel int) func(e js.Object) {
+	return func(e js.Object) {
 		defer func() {
 			currentPosition += bufferSize
 		}()
 
 		l := e.Get("outputBuffer").Call("getChannelData", 0)
 		r := e.Get("outputBuffer").Call("getChannelData", 1)
-		inputL, inputR := loadChannelBuffers()
-		nextInsertionPosition -= min(bufferSize, nextInsertionPosition)
+		inputL, inputR := loadChannelBuffer(channel)
 		const max = 1 << 15
 		for i := 0; i < bufferSize; i++ {
 			// TODO: Use copyFromChannel?
@@ -49,11 +44,24 @@ func initialize() {
 			l.SetIndex(i, float64(inputL[i])/max)
 			r.SetIndex(i, float64(inputR[i])/max)
 		}
-	})
+	}
+}
+
+func initialize() {
+	context = js.Global.Get("AudioContext").New()
+	// TODO: ScriptProcessorNode will be replaced with Audio WebWorker.
+	// https://developer.mozilla.org/ja/docs/Web/API/ScriptProcessorNode
+	for i := 0; i < MaxChannel; i++ {
+		node := context.Call("createScriptProcessor", bufferSize, 0, 2)
+		node.Call("addEventListener", "audioprocess", audioProcess(i))
+		nodes = append(nodes, node)
+	}
 	audioEnabled = true
 }
 
 func start() {
 	// TODO: For iOS, node should be connected with a buffer node.
-	node.Call("connect", context.Get("destination"))
+	for _, node := range nodes {
+		node.Call("connect", context.Get("destination"))
+	}
 }

internal/audio/audio_openal.go

@@ -60,39 +60,46 @@ func initialize() {
 		}
 
 		audioEnabled = true
-		source := openal.NewSource()
+		sources := openal.NewSources(MaxChannel)
 		close(ch)
 
 		emptyBytes := make([]byte, 4*bufferSize)
 
-		const bufferNum = 16
-		buffers := openal.NewBuffers(bufferNum)
-		for _, buffer := range buffers {
-			buffer.SetData(openal.FormatStereo16, emptyBytes, SampleRate)
-			source.QueueBuffer(buffer)
-		}
-		source.Play()
-		if alErr := openal.GetError(); alErr != 0 {
-			panic(fmt.Sprintf("OpenAL error: %d", alErr))
+		for _, source := range sources {
+			const bufferNum = 16
+			buffers := openal.NewBuffers(bufferNum)
+			for _, buffer := range buffers {
+				buffer.SetData(openal.FormatStereo16, emptyBytes, SampleRate)
+				source.QueueBuffer(buffer)
+			}
+			source.Play()
+			if alErr := openal.GetError(); alErr != 0 {
+				panic(fmt.Sprintf("OpenAL error: %d", alErr))
+			}
 		}
 
 		for {
-			if source.State() != openal.Playing {
-				panic(fmt.Sprintf("invalid source state: %d (0x%[1]x)", source.State()))
+			oneProcessed := false
+			for channel, source := range sources {
+				if source.State() != openal.Playing {
+					panic(fmt.Sprintf("invalid source state: %d (0x%[1]x)", source.State()))
+				}
+				processed := source.BuffersProcessed()
+				if processed == 0 {
+					continue
+				}
+				oneProcessed = true
+				buffers := make([]openal.Buffer, processed)
+				source.UnqueueBuffers(buffers)
+				for _, buffer := range buffers {
+					l, r := loadChannelBuffer(channel)
+					b := toBytes(l, r)
+					buffer.SetData(openal.FormatStereo16, b, SampleRate)
+					source.QueueBuffer(buffer)
+				}
 			}
-			processed := source.BuffersProcessed()
-			if processed == 0 {
+			if !oneProcessed {
 				time.Sleep(1)
-				continue
-			}
-			buffers := make([]openal.Buffer, processed)
-			source.UnqueueBuffers(buffers)
-			for _, buffer := range buffers {
-				l, r := loadChannelBuffers()
-				b := toBytes(l, r)
-				buffer.SetData(openal.FormatStereo16, b, SampleRate)
-				source.QueueBuffer(buffer)
-				nextInsertionPosition -= min(bufferSize, nextInsertionPosition)
 			}
 		}
 	}()