audio: add Ctrl decorator

audio/ctrl.go

@@ -0,0 +1,24 @@
+package audio
+
+import "time"
+
+type Ctrl struct {
+	Streamer Streamer
+	Paused   bool
+	Duration time.Duration
+}
+
+func (c *Ctrl) Stream(samples [][2]float64) (n int, ok bool) {
+	if c.Streamer == nil {
+		return 0, false
+	}
+	if c.Paused {
+		for i := range samples {
+			samples[i] = [2]float64{}
+		}
+		return len(samples), true
+	}
+	n, ok = c.Streamer.Stream(samples)
+	c.Duration += time.Duration(n) * time.Second / time.Duration(SampleRate)
+	return n, ok
+}