diff --git a/encoder.go b/encoder.go
index 48f9cf2..22ccddf 100644
--- a/encoder.go
+++ b/encoder.go
@@ -44,6 +44,10 @@ func (e *FrameEncoder) GetInputSize() int {
 	return int(e.handle.input_packet_size)
 }
 
+func (e *FrameEncoder) GetSamplesPerPacket() int {
+	return int(e.handle.frames_per_packet)
+}
+
 func (e *FrameEncoder) WritePacket(pcm []byte) []byte {
 	output := make([]byte, int(e.handle.output_max_packet_size))
 	outBytes := C.alac_encoder_write(&e.handle, (*C.uchar)(unsafe.Pointer(&pcm[0])), C.int(len(pcm)), (*C.uchar)(unsafe.Pointer(&output[0])))
diff --git a/mp4.go b/mp4.go
index 27ecdf3..e287132 100644
--- a/mp4.go
+++ b/mp4.go
@@ -8,12 +8,16 @@ import (
 )
 
 type FormatEncoder struct {
-	encoder         *FrameEncoder
-	writer          io.Writer
-	buffer          []byte
-	segmentDuration int64
-	trackId         uint32
-	seqNumber       uint32
+	encoder          *FrameEncoder
+	writer           io.Writer
+	sampleRate       int
+	buffer           []byte
+	outputBuffer     [][]byte
+	segmentDuration  time.Duration
+	samplesPerPacket int
+	packetsWritten   int
+	trackId          uint32
+	seqNumber        uint32
 }
 
 type alacBox struct {
@@ -58,13 +62,16 @@ func NewFormatEncoder(writer io.Writer, sampleRate, channels, bitDepth int, fast
 	e := &FormatEncoder{
 		encoder:         NewFrameEncoder(sampleRate, channels, bitDepth, fastMode),
 		writer:          writer,
-		segmentDuration: segmentDuration.Milliseconds(),
+		sampleRate:      sampleRate,
+		segmentDuration: segmentDuration,
 	}
 
 	if e.encoder == nil {
 		return nil
 	}
 
+	e.samplesPerPacket = e.encoder.GetSamplesPerPacket()
+
 	init := mp4.CreateEmptyInit()
 	init.AddEmptyTrack(uint32(sampleRate), "audio", "en")
 	e.trackId = init.Moov.Mvhd.NextTrackID - 1
@@ -84,21 +91,39 @@ func NewFormatEncoder(writer io.Writer, sampleRate, channels, bitDepth int, fast
 }
 
 func (e *FormatEncoder) outputPacket(packet []byte) {
-	//TODO: more frames
+	e.outputBuffer = append(e.outputBuffer, packet)
+
+	if time.Duration(float64(time.Second)*(float64(e.samplesPerPacket*len(e.outputBuffer))/float64(e.sampleRate))) >= e.segmentDuration {
+		e.outputSegment()
+	}
+
+}
+
+func (e *FormatEncoder) outputSegment() {
+	if len(e.outputBuffer) == 0 {
+		return
+	}
+
 	seg := mp4.NewMediaSegment()
 	frag, _ := mp4.CreateFragment(e.seqNumber, e.trackId)
 	seg.AddFragment(frag)
-	frag.AddFullSampleToTrack(mp4.FullSample{
-		Sample: mp4.Sample{
-			Dur:  4096, //TODO
-			Size: uint32(len(packet)),
-		},
-		DecodeTime: uint64(4096 * e.seqNumber),
-		Data:       packet,
-	}, e.trackId)
+
+	for _, b := range e.outputBuffer {
+		frag.AddFullSampleToTrack(mp4.FullSample{
+			Sample: mp4.Sample{
+				Dur:  uint32(e.samplesPerPacket),
+				Size: uint32(len(b)),
+			},
+			DecodeTime: uint64(e.samplesPerPacket * e.packetsWritten),
+			Data:       b,
+		}, e.trackId)
+		e.packetsWritten++
+	}
 
 	seg.Encode(e.writer)
 	e.seqNumber++
+	e.outputBuffer = nil
+
 }
 
 func (e *FormatEncoder) Write(pcm []byte) {
diff --git a/mp4_test.go b/mp4_test.go
index 2d601c5..1cd3e01 100644
--- a/mp4_test.go
+++ b/mp4_test.go
@@ -30,7 +30,7 @@ func TestEncodeMP4(t *testing.T) {
 	}
 	defer o.Close()
 
-	encoder := NewFormatEncoder(o, 44100, 2, 16, false, time.Second)
+	encoder := NewFormatEncoder(o, 44100, 2, 16, false, time.Millisecond*100)
 
 	iterationSize := 65536
 	for len(data) > iterationSize {