audio: Add Context

examples/audio/main.go

@@ -31,6 +31,12 @@ const (
 	sampleRate   = 44100
 )
 
+var audioContext *audio.Context
+
+func init() {
+	audioContext = audio.NewContext(sampleRate)
+}
+
 var frames = 0
 
 const (
@@ -116,7 +122,7 @@ func addNote() error {
 	square(l, vol, freq, 0.25)
 	square(r, vol, freq, 0.25)
 	b := toBytes(l, r)
-	p, err := audio.NewPlayer(bytes.NewReader(b), sampleRate)
+	p, err := audioContext.NewPlayer(bytes.NewReader(b))
 	if err != nil {
 		return err
 	}

examples/piano/main.go

@@ -33,6 +33,12 @@ const (
 	sampleRate   = 44100
 )
 
+var audioContext *audio.Context
+
+func init() {
+	audioContext = audio.NewContext(sampleRate)
+}
+
 var pcm = make([]float64, 4*sampleRate)
 
 const baseFreq = 220
@@ -81,7 +87,7 @@ func (s *stream) Close() error {
 func addNote(freq float64, vol float64) error {
 	f := int(freq)
 	if n, ok := noteCache[f]; ok {
-		p, err := audio.NewPlayer(&stream{bytes.NewReader(n)}, sampleRate)
+		p, err := audioContext.NewPlayer(&stream{bytes.NewReader(n)})
 		if err == audio.ErrTooManyPlayers {
 			return nil
 		}
@@ -105,7 +111,7 @@ func addNote(freq float64, vol float64) error {
 	}
 	n := toBytes(l, r)
 	noteCache[f] = n
-	p, err := audio.NewPlayer(&stream{bytes.NewReader(n)}, sampleRate)
+	p, err := audioContext.NewPlayer(&stream{bytes.NewReader(n)})
 	if err == audio.ErrTooManyPlayers {
 		return nil
 	}

examples/sinewave/main.go

@@ -32,6 +32,12 @@ const (
 	frequency    = 440
 )
 
+var audioContext *audio.Context
+
+func init() {
+	audioContext = audio.NewContext(sampleRate)
+}
+
 type stream struct {
 	position int64
 }
@@ -75,7 +81,7 @@ var player *audio.Player
 func update(screen *ebiten.Image) error {
 	if player == nil {
 		var err error
-		player, err = audio.NewPlayer(&stream{}, sampleRate)
+		player, err = audioContext.NewPlayer(&stream{})
 		if err != nil {
 			return err
 		}

exp/audio/audio.go

@@ -19,6 +19,18 @@ import (
 	"io"
 )
 
+// TODO: Enable to specify the format like Mono8?
+
+type Context struct {
+	sampleRate int
+}
+
+func NewContext(sampleRate int) *Context {
+	return &Context{
+		sampleRate: sampleRate,
+	}
+}
+
 type Player struct {
 	player *player
 }
@@ -31,8 +43,8 @@ type Player struct {
 // without a header (e.g. RIFF header).
 //
 // TODO: Pass sample rate and num of channels.
-func NewPlayer(src io.ReadSeeker, sampleRate int) (*Player, error) {
+func (c *Context) NewPlayer(src io.ReadSeeker) (*Player, error) {
-	return newPlayer(src, sampleRate)
+	return newPlayer(src, c.sampleRate)
 }
 
 var ErrTooManyPlayers = errors.New("audio: too many players exist")