Merge pull request #127 from ilyapashuk/master

add sinusoid tone generation

examples/tone-player/main.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"fmt"
+	"github.com/faiface/beep"
+	"github.com/faiface/beep/generators"
+	"github.com/faiface/beep/speaker"
+	"os"
+	"strconv"
+)
+
+func usage() {
+	fmt.Printf("usage: %s freq\n", os.Args[0])
+	fmt.Println("where freq must be an integer from 1 to 24000")
+	fmt.Println("24000 because samplerate of 48000 is hardcoded")
+}
+func main() {
+	if len(os.Args) < 2 {
+		usage()
+		return
+	}
+	f, err := strconv.Atoi(os.Args[1])
+	if err != nil {
+		usage()
+		return
+	}
+	speaker.Init(beep.SampleRate(48000), 4800)
+	s, err := generators.SinTone(beep.SampleRate(48000), f)
+	if err != nil {
+		panic(err)
+	}
+	speaker.Play(s)
+	for {
+
+	}
+}

generators/toner.go

@@ -0,0 +1,48 @@
+// tones generator
+
+package generators
+
+import (
+	"math"
+	"errors"
+	. "github.com/faiface/beep"
+)
+
+// 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 return an error
+func SinTone(sr SampleRate, freq int) (Streamer, error) {
+	if int(sr)/freq < 2 {
+		return nil, errors.New("faiface beep tone generator: 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, nil
+}
+
+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
+}