audio: Discard audio data when queue seems full

audio/audio.go

@@ -177,6 +177,7 @@ type Context struct {
 	sampleRate     int
 	frames         int64
 	writtenBytes   int64
+	unwrittenCount int
 }
 
 var (
@@ -223,8 +224,7 @@ func (c *Context) Update() error {
 	// e.g. a variable for JVM on Android might not be set.
 	if c.playerWriteCh == nil {
 		init := make(chan error)
-		// 4 is (buffer size) / (bytes for 1 frame).
-		c.playerWriteCh = make(chan []uint8, 4)
+		c.playerWriteCh = make(chan []uint8)
 		c.playerErrCh = make(chan error, 1)
 		c.playerCloseCh = make(chan struct{})
 		go func() {
@@ -269,10 +269,18 @@ func (c *Context) Update() error {
 		close(c.playerCloseCh)
 		return err
 	}
+	// Discard when the buffer queue seems full.
+	if c.unwrittenCount > 0 {
+		c.unwrittenCount--
+		return nil
+	}
 	select {
 	case c.playerWriteCh <- buf:
 		// Writing can block. Don't wait for the result here.
 	default:
+		// The current buffer size is 1/15 [sec] = 4 [frames].
+		// Wait for 5 [frames] which is more than 4.
+		c.unwrittenCount = 5
 	}
 	return nil
 }