audio: Implement for desktops with OpenAL (#104)

example/audio/main.go

@@ -111,7 +111,7 @@ func update(screen *ebiten.Image) error {
 }
 
 func main() {
-	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Rotate (Ebiten Demo)"); err != nil {
+	if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Audio (Ebiten Demo)"); err != nil {
 		log.Fatal(err)
 	}
 }

internal/audio/audio.go

@@ -14,6 +14,10 @@
 
 package audio
 
+import (
+	"sync"
+)
+
 const bufferSize = 1024
 const SampleRate = 44100
 
@@ -28,6 +32,7 @@ type channel struct {
 var MaxChannel = 32
 
 var channels = make([]*channel, MaxChannel)
+var channelsLock sync.Mutex
 
 func init() {
 	for i, _ := range channels {
@@ -46,8 +51,30 @@ func Start() {
 	start()
 }
 
+func isPlaying(channel int) bool {
+	ch := channels[channel]
+	return nextInsertionPosition < len(ch.l)
+}
+
+func channelAt(i int) *channel {
+	if i == -1 {
+		for i, _ := range channels {
+			if !isPlaying(i) {
+				return channels[i]
+			}
+		}
+		return nil
+	}
+	if !isPlaying(i) {
+		return channels[i]
+	}
+	return nil
+}
+
 func Play(channel int, l []float32, r []float32) bool {
-	// TODO: Mutex (especially for OpenAL)
+	channelsLock.Lock()
+	defer channelsLock.Unlock()
+
 	if len(l) != len(r) {
 		panic("len(l) must equal to len(r)")
 	}
@@ -63,7 +90,9 @@ func Play(channel int, l []float32, r []float32) bool {
 }
 
 func Queue(channel int, l []float32, r []float32) {
-	// TODO: Mutex (especially for OpenAL)
+	channelsLock.Lock()
+	defer channelsLock.Unlock()
+
 	if len(l) != len(r) {
 		panic("len(l) must equal to len(r)")
 	}
@@ -76,21 +105,6 @@ func Update() {
 	nextInsertionPosition += SampleRate / 60
 }
 
-func channelAt(i int) *channel {
-	if i == -1 {
-		for i, _ := range channels {
-			if !IsPlaying(i) {
-				return channels[i]
-			}
-		}
-		return nil
-	}
-	if !IsPlaying(i) {
-		return channels[i]
-	}
-	return nil
-}
-
 func min(a, b int) int {
 	if a < b {
 		return a
@@ -98,7 +112,22 @@ func min(a, b int) int {
 	return b
 }
 
+func isChannelsEmpty() bool {
+	channelsLock.Lock()
+	defer channelsLock.Unlock()
+
+	for _, ch := range channels {
+		if 0 < len(ch.l) {
+			return false
+		}
+	}
+	return true
+}
+
 func loadChannelBuffers() (l, r []float32) {
+	channelsLock.Lock()
+	defer channelsLock.Unlock()
+
 	inputL := make([]float32, bufferSize)
 	inputR := make([]float32, bufferSize)
 	for _, ch := range channels {
@@ -118,6 +147,8 @@ func loadChannelBuffers() (l, r []float32) {
 }
 
 func IsPlaying(channel int) bool {
-	ch := channels[channel]
-	return nextInsertionPosition < len(ch.l)
+	channelsLock.Lock()
+	defer channelsLock.Unlock()
+
+	return isPlaying(channel)
 }

internal/audio/audio_openal.go

@@ -17,10 +17,35 @@
 package audio
 
 import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
 	"github.com/timshannon/go-openal/openal"
+	"math"
 	"runtime"
+	"time"
 )
 
+func toBytes(l, r []float32) []byte {
+	if len(l) != len(r) {
+		panic("len(l) must equal to len(r)")
+	}
+	b := &bytes.Buffer{}
+	for i, _ := range l {
+		l := int16(l[i] * math.MaxInt16)
+		r := int16(r[i] * math.MaxInt16)
+		if err := binary.Write(b, binary.LittleEndian, []int16{l, r}); err != nil {
+			panic(err)
+		}
+	}
+	return b.Bytes()
+}
+
+type sample struct {
+	l []float32
+	r []float32
+}
+
 func initialize() {
 	ch := make(chan struct{})
 	go func() {
@@ -30,15 +55,50 @@ func initialize() {
 		context := device.CreateContext()
 		context.Activate()
 
-		buffer := openal.NewBuffer()
-		//buffer.SetData(openal.FormatStereo16)
-		_ = buffer
+		source := openal.NewSource()
+
+		if alErr := openal.GetError(); alErr != 0 {
+			panic(fmt.Sprintf("OpenAL initialize error: %d", alErr))
+		}
 
 		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 {
+			if source.State() != openal.Playing {
+				panic(fmt.Sprintf("invalid source state: %d (0x%[1]x)", source.State()))
+			}
+			processed := source.BuffersProcessed()
+			if processed == 0 {
+				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)
+			}
+		}
 	}()
 	<-ch
 }
 
 func start() {
-	// TODO: Implement
+	// Do nothing
 }