Updated segmenter

Author: djthorpe

pkg/segmenter/segmenter.go

@@ -31,13 +31,15 @@ type SegmentFunc func(time.Duration, []float32) error
 //////////////////////////////////////////////////////////////////////////////
 // LIFECYCLE
 
-// Create a new segmenter for a specific "dur" duration of samples with
-// a reader r. If dur is zero then no segmenting is performed, the whole
+// Create a new segmenter with a reader r which segments raw audio of 'dur'
+// length. If dur is zero then no segmenting is performed, the whole
 // audio file is read, which could cause some memory issues.
+//
 // The sample rate is the number of samples per second.
+//
 // At the moment, the audio format is auto-detected, but there should be
 // a way to specify the audio format.
-func New(r io.Reader, dur time.Duration, sample_rate int) (*Segmenter, error) {
+func NewReader(r io.Reader, dur time.Duration, sample_rate int) (*Segmenter, error) {
 	segmenter := new(Segmenter)
 
 	// Check arguments
@@ -136,12 +138,3 @@ func (s *Segmenter) Decode(ctx context.Context, fn SegmentFunc) error {
 	// Return success
 	return nil
 }
-
-// Return the file duration from the file or timestamp
-func (s *Segmenter) Duration() time.Duration {
-	if s.reader != nil {
-		return s.reader.Duration()
-	} else {
-		return s.ts + time.Duration(len(s.buf))*time.Second/time.Duration(s.sample_rate)
-	}
-}

pkg/segmenter/silence.go

@@ -0,0 +1,61 @@
+package segmenter
+
+import (
+	"math"
+	"time"
+	// Packages
+)
+
+////////////////////////////////////////////////////////////////////////////////
+// TYPES
+
+// silence is a silence detector and audio booster for raw samples
+// typical values are gain=20, threshold=0.003, timeout=2s
+type silence struct {
+	Gain      float64       // gain in decibels
+	Threshold float64       // threshold for silence
+	Timeout   time.Duration // duration of silence before stopping recording
+
+	// When we last started recording
+	t time.Time
+	r bool
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// PUBLIC METHODS
+
+// Increase gain and compute energy of a frame of audio data, return true
+// if the frame of data should be recorded, false if it should be ignored
+func (s *silence) Process(data []float32) bool {
+	energy := process(data, float32(math.Pow(10, s.Gain/20.0)))
+
+	// Compute the gain
+	if energy > s.Threshold {
+		if s.t.IsZero() {
+			// Transition from silence to recording
+			s.r = true
+		}
+		s.t = time.Now()
+	} else if !s.t.IsZero() {
+		if time.Since(s.t) > s.Timeout {
+			// Transition from recording to silence
+			s.t = time.Time{}
+			s.r = false
+		}
+	}
+	return s.r
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// PRIVATE METHODS
+
+// Increase gain and compute energy of a frame of audio data, return the
+// energy of the frame of data
+func process(data []float32, gain float32) float64 {
+	energy := float64(0)
+	for i := 0; i < len(data); i++ {
+		data[i] *= gain
+		energy += float64(data[i]) * float64(data[i])
+	}
+	return energy / math.Sqrt(float64(len(data)))
+}