Add audio change detection

pkg/io/audio/detect.go

@@ -0,0 +1,46 @@
+package audio
+
+import (
+	"time"
+
+	"github.com/pion/mediadevices/pkg/prop"
+	"github.com/pion/mediadevices/pkg/wave"
+)
+
+// DetectChanges will detect chunk and audio property changes. For audio property detection,
+// since it's time related, interval will be used to determine the sample rate.
+func DetectChanges(interval time.Duration, onChange func(prop.Media)) TransformFunc {
+	return func(r Reader) Reader {
+		var currentProp prop.Media
+		var chunkCount uint
+		return ReaderFunc(func() (wave.Audio, error) {
+			var dirty bool
+
+			chunk, err := r.Read()
+			if err != nil {
+				return nil, err
+			}
+
+			info := chunk.ChunkInfo()
+			if currentProp.ChannelCount != info.Channels {
+				currentProp.ChannelCount = info.Channels
+				dirty = true
+			}
+
+			if currentProp.SampleRate != info.SamplingRate {
+				currentProp.SampleRate = info.SamplingRate
+				dirty = true
+			}
+
+			// TODO: Also detect sample format changes?
+			// TODO: Add audio detect changes. As of now, there's no useful property to track.
+
+			if dirty {
+				onChange(currentProp)
+			}
+
+			chunkCount++
+			return chunk, nil
+		})
+	}
+}

pkg/io/audio/detect_test.go

@@ -0,0 +1,77 @@
+package audio
+
+import (
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/pion/mediadevices/pkg/prop"
+	"github.com/pion/mediadevices/pkg/wave"
+)
+
+func TestDetectChanges(t *testing.T) {
+	buildSource := func(p prop.Media) (Reader, func(prop.Media)) {
+		return ReaderFunc(func() (wave.Audio, error) {
+				return wave.NewFloat32Interleaved(wave.ChunkInfo{
+					Len:          0,
+					Channels:     p.ChannelCount,
+					SamplingRate: p.SampleRate,
+				}), nil
+			}), func(newProp prop.Media) {
+				p = newProp
+			}
+	}
+
+	t.Run("OnChangeCalledBeforeFirstFrame", func(t *testing.T) {
+		var detectBeforeFirstChunk bool
+		var expected prop.Media
+		var actual prop.Media
+		expected.ChannelCount = 2
+		expected.SampleRate = 48000
+		src, _ := buildSource(expected)
+		src = DetectChanges(time.Second, func(p prop.Media) {
+			actual = p
+			detectBeforeFirstChunk = true
+		})(src)
+
+		_, err := src.Read()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !detectBeforeFirstChunk {
+			t.Fatal("on change callback should have called before first chunk")
+		}
+
+		if !reflect.DeepEqual(actual, expected) {
+			t.Fatalf("Received an unexpected prop\nExpected:\n%v\nActual:\n%v\n", expected, actual)
+		}
+	})
+
+	t.Run("DetectChangesOnEveryUpdate", func(t *testing.T) {
+		var expected prop.Media
+		var actual prop.Media
+		expected.ChannelCount = 2
+		expected.SampleRate = 48000
+		src, update := buildSource(expected)
+		src = DetectChanges(time.Second, func(p prop.Media) {
+			actual = p
+		})(src)
+
+		for channelCount := 1; channelCount < 8; channelCount++ {
+			for sampleRate := 12000; sampleRate <= 48000; sampleRate += 4000 {
+				expected.ChannelCount = channelCount
+				expected.SampleRate = sampleRate
+				update(expected)
+				_, err := src.Read()
+				if err != nil {
+					t.Fatal(err)
+				}
+
+				if !reflect.DeepEqual(actual, expected) {
+					t.Fatalf("Received an unexpected prop\nExpected:\n%v\nActual:\n%v\n", expected, actual)
+				}
+			}
+		}
+	})
+}