Merge pull request #1 from faiface/audio

Audio

.travis.yml

@@ -9,6 +9,7 @@ addons:
             - libxinerama-dev
             - libxcursor-dev
             - libxi-dev
+            - libasound2-dev
 go:
 - 1.8
 - 1.7.4

audio/compositors.go

@@ -0,0 +1,40 @@
+package audio
+
+import (
+	"math"
+	"time"
+)
+
+// Take returns a Streamer which streams s for at most d duration.
+func Take(d time.Duration, s Streamer) Streamer {
+	currSample := 0
+	numSamples := int(math.Ceil(d.Seconds() * SampleRate))
+	return StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
+		if currSample >= numSamples {
+			return 0, false
+		}
+		toStream := numSamples - currSample
+		if len(samples) < toStream {
+			toStream = len(samples)
+		}
+		sn, sok := s.Stream(samples[:toStream])
+		currSample += sn
+		return sn, sok
+	})
+}
+
+// Seq takes zero or more Streamers and returns a Streamer which streams them one by one without pauses.
+func Seq(s ...Streamer) Streamer {
+	i := 0
+	return StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
+		for i < len(s) && len(samples) > 0 {
+			sn, sok := s[i].Stream(samples)
+			samples = samples[sn:]
+			n, ok = n+sn, ok || sok
+			if !sok {
+				i++
+			}
+		}
+		return n, ok
+	})
+}

audio/compositors_test.go

@@ -0,0 +1,79 @@
+package audio_test
+
+import (
+	"math"
+	"math/rand"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/faiface/pixel/audio"
+)
+
+// randomDataStreamer generates random samples of duration d and returns a Streamer which streams
+// them and the data itself.
+func randomDataStreamer(d time.Duration) (s audio.Streamer, data [][2]float64) {
+	numSamples := int(math.Ceil(d.Seconds() * audio.SampleRate))
+	data = make([][2]float64, numSamples)
+	for i := range data {
+		data[i][0] = rand.Float64()*2 - 1
+		data[i][1] = rand.Float64()*2 - 1
+	}
+	return audio.StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
+		if len(data) == 0 {
+			return 0, false
+		}
+		n = copy(samples, data)
+		data = data[n:]
+		return n, true
+	}), data
+}
+
+// collect drains Streamer s and returns all of the samples it streamed.
+func collect(s audio.Streamer) [][2]float64 {
+	var (
+		result [][2]float64
+		buf    [512][2]float64
+	)
+	for {
+		n, ok := s.Stream(buf[:])
+		if !ok {
+			return result
+		}
+		result = append(result, buf[:n]...)
+	}
+}
+
+func TestTake(t *testing.T) {
+	for i := 0; i < 7; i++ {
+		total := time.Nanosecond * time.Duration(1e8+rand.Intn(1e9))
+		s, data := randomDataStreamer(total)
+		d := time.Nanosecond * time.Duration(rand.Int63n(total.Nanoseconds()))
+		numSamples := int(math.Ceil(d.Seconds() * audio.SampleRate))
+
+		want := data[:numSamples]
+		got := collect(audio.Take(d, s))
+
+		if !reflect.DeepEqual(want, got) {
+			t.Error("Take not working correctly")
+		}
+	}
+}
+
+func TestSeq(t *testing.T) {
+	var (
+		s    = make([]audio.Streamer, 7)
+		want [][2]float64
+	)
+	for i := range s {
+		var data [][2]float64
+		s[i], data = randomDataStreamer(time.Nanosecond * time.Duration(1e8+rand.Intn(1e9)))
+		want = append(want, data...)
+	}
+
+	got := collect(audio.Seq(s...))
+
+	if !reflect.DeepEqual(want, got) {
+		t.Error("Seq not working correctly")
+	}
+}

audio/interface.go

@@ -2,9 +2,9 @@ package audio
 
 // SampleRate is the number of audio samples a Streamer should produce per one second of audio.
 //
-// This value should be set at most once before using audio package. It is safe to rely on the fact,
-// that this value does not change during runtime.
-var SampleRate = 48000
+// This value should be set at most once before using audio package. It is safe to assume that this
+// value does not change during runtime.
+var SampleRate float64 = 48000
 
 // Streamer is able to stream a finite or infinite sequence of audio samples.
 type Streamer interface {
@@ -36,3 +36,22 @@ type Streamer interface {
 	// following calls.
 	Stream(samples [][2]float64) (n int, ok bool)
 }
+
+// StreamerFunc is a Streamer created by simply wrapping a streaming function (usually a closure,
+// which encloses a time tracking variable). This sometimes simplifies creating new streamers.
+//
+// Example:
+//
+//   noise := StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
+//       for i := range samples {
+//           samples[i][0] = rand.Float64()*2 - 1
+//           samples[i][1] = rand.Float64()*2 - 1
+//       }
+//       return len(samples), true
+//   })
+type StreamerFunc func(samples [][2]float64) (n int, ok bool)
+
+// Stream calls the wrapped streaming function.
+func (sf StreamerFunc) Stream(samples [][2]float64) (n int, ok bool) {
+	return sf(samples)
+}