add sinusoid tone generation

examples/tone-player/main.go

@@ -0,0 +1,20 @@
+package main
+
+import "os"
+import "fmt"
+import "github.com/faiface/beep"
+import "github.com/faiface/beep/speaker"
+import "strconv"
+
+func main() {
+f,_ := strconv.Atoi(os.Args[1])
+speaker.Init(beep.SampleRate(48000), 4800)
+s := beep.SinTone(beep.SampleRate(48000), f)
+rb := make([][2]float64,20)
+s.Stream(rb)
+fmt.Println(rb)
+speaker.Play(s)
+for {
+
+}
+}

toner.go

@@ -0,0 +1,45 @@
+// tones generator
+
+
+package beep
+
+import "math"
+
+// simple sinusoid tone generator
+type toneStreamer struct {
+stat float64
+delta float64
+}
+
+// create streamer which will produce infinite sinusoid tone with the given frequency
+// use other wrappers of this package to change amplitude or add time limit
+// sampleRate must be at least two times grater then frequency, otherwise this function will panic
+func SinTone(sr SampleRate, freq int) Streamer {
+if int(sr) / freq < 2 {
+panic("samplerate must be at least 2 times grater then frequency")
+}
+r := new(toneStreamer)
+r.stat = 0.0
+srf := float64(sr)
+ff := float64(freq)
+steps := srf / ff
+r.delta = 1.0 / steps
+return r
+}
+
+func (c *toneStreamer) nextSample() float64 {
+r := math.Sin(c.stat * 2.0 * math.Pi)
+_,c.stat = math.Modf(c.stat + c.delta)
+return r
+}
+
+func (c *toneStreamer) Stream(buf [][2]float64) (int, bool) {
+for i := 0; i < len(buf); i++ {
+s := c.nextSample()
+buf[i] = [2]float64{s,s}
+}
+return len(buf),true
+}
+func (_ *toneStreamer) Err() error {
+return nil
+}