diff --git a/disk.go b/disk.go
new file mode 100644
index 0000000..fd364e3
--- /dev/null
+++ b/disk.go
@@ -0,0 +1,335 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/at-wat/ebml-go/webm"
+	"github.com/pion/rtp"
+	"github.com/pion/rtp/codecs"
+	"github.com/pion/webrtc/v2"
+	"github.com/pion/webrtc/v2/pkg/media/samplebuilder"
+)
+
+type diskClient struct {
+	group  *group
+	id     string
+	down   []*diskConn
+	closed bool
+}
+
+func (client *diskClient) getGroup() *group {
+	return client.group
+}
+
+func (client *diskClient) getId() string {
+	return client.id
+}
+
+func (client *diskClient) getUsername() string {
+	return "RECORDING"
+}
+
+func (client *diskClient) Close() error {
+	for _, down := range client.down {
+		down.Close()
+	}
+	client.down = nil
+	client.closed = true
+	return nil
+}
+
+func (client *diskClient) pushConn(conn *upConnection, tracks []*upTrack, label string) error {
+	if client.closed {
+		return errors.New("disk client is closed")
+	}
+
+	directory := filepath.Join(recordingsDir, client.group.name)
+	err := os.MkdirAll(directory, 0700)
+	if err != nil {
+		return err
+	}
+
+	down, err := newDiskConn(directory, label, conn, tracks)
+	if err != nil {
+		return err
+	}
+
+	client.down = append(client.down, down)
+	return nil
+}
+
+var _ client = &diskClient{}
+
+type diskConn struct {
+	directory     string
+	label         string
+	file          *os.File
+	remote        *upConnection
+	tracks        []*diskTrack
+	width, height uint32
+}
+
+func (conn *diskConn) reopen() error {
+	for _, t := range conn.tracks {
+		if t.writer != nil {
+			t.writer.Close()
+			t.writer = nil
+		}
+	}
+	conn.file = nil
+
+	file, err := openDiskFile(conn.directory, conn.label)
+	if err != nil {
+		return err
+	}
+
+	conn.file = file
+	return nil
+}
+
+func (conn *diskConn) Close() error {
+	conn.remote.delLocal(conn)
+
+	for _, t := range conn.tracks {
+		if t.writer != nil {
+			t.writer.Close()
+			t.writer = nil
+		}
+		t.remote.delLocal(t)
+	}
+	return nil
+}
+
+func openDiskFile(directory, label string) (*os.File, error) {
+	filename := time.Now().Format("2006-01-02T15:04:05")
+	if label != "" {
+		filename = filename + "-" + label
+	}
+	for counter := 0; counter < 100; counter++ {
+		var fn string
+		if counter == 0 {
+			fn = fmt.Sprintf("%v.webm", filename)
+		} else {
+			fn = fmt.Sprintf("%v-%02d.webm", filename, counter)
+		}
+
+		fn = filepath.Join(directory, fn)
+		f, err := os.OpenFile(
+			fn, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600,
+		)
+		if err == nil {
+			return f, nil
+		} else if !os.IsExist(err) {
+			return nil, err
+		}
+	}
+	return nil, errors.New("couldn't create file")
+}
+
+type diskTrack struct {
+	remote    *upTrack
+	writer    webm.BlockWriteCloser
+	builder   *samplebuilder.SampleBuilder
+	timestamp uint32
+	conn      *diskConn
+}
+
+func newDiskConn(directory, label string, up *upConnection, remoteTracks []*upTrack) (*diskConn, error) {
+	conn := diskConn{
+		directory: directory,
+		label:     label,
+		tracks:    make([]*diskTrack, 0, len(remoteTracks)),
+		remote:    up,
+	}
+	video := false
+	for _, remote := range remoteTracks {
+		var builder *samplebuilder.SampleBuilder
+		switch remote.track.Codec().Name {
+		case webrtc.Opus:
+			builder = samplebuilder.New(16, &codecs.OpusPacket{})
+		case webrtc.VP8:
+			if video {
+				return nil, errors.New("multiple video tracks not supported")
+			}
+			builder = samplebuilder.New(32, &codecs.VP8Packet{})
+			video = true
+		}
+		track := &diskTrack{
+			remote:  remote,
+			builder: builder,
+			conn:    &conn,
+		}
+		conn.tracks = append(conn.tracks, track)
+		remote.addLocal(track)
+	}
+
+	if !video {
+		err := conn.initWriter(0, 0)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+
+	up.addLocal(&conn)
+
+	return &conn, nil
+}
+
+func clonePacket(packet *rtp.Packet) *rtp.Packet {
+	buf, err := packet.Marshal()
+	if err != nil {
+		return nil
+	}
+	var p rtp.Packet
+	err = p.Unmarshal(buf)
+	if err != nil {
+		return nil
+	}
+	return &p
+}
+
+func (t *diskTrack) WriteRTP(packet *rtp.Packet) error {
+	if t.builder == nil {
+		return nil
+	}
+
+	p := clonePacket(packet)
+	if p == nil {
+		return nil
+	}
+
+	t.builder.Push(p)
+
+	for {
+		sample := t.builder.Pop()
+		if sample == nil {
+			return nil
+		}
+
+		t.timestamp += sample.Samples
+
+		keyframe := true
+
+		switch t.remote.track.Codec().Name {
+		case webrtc.VP8:
+			if len(sample.Data) < 1 {
+				return nil
+			}
+			keyframe = (sample.Data[0]&0x1 == 0)
+			if keyframe {
+				err := t.initWriter(sample.Data)
+				if err != nil {
+					return err
+				}
+			}
+		}
+		if t.writer == nil {
+			if !keyframe {
+				return ErrKeyframeNeeded
+			}
+			return nil
+		}
+
+		tm := t.timestamp / (t.remote.track.Codec().ClockRate / 1000)
+		_, err := t.writer.Write(keyframe, int64(tm), sample.Data)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (t *diskTrack) initWriter(data []byte) error {
+	switch t.remote.track.Codec().Name {
+	case webrtc.VP8:
+		if len(data) < 10 {
+			return nil
+		}
+		keyframe := (data[0]&0x1 == 0)
+		if !keyframe {
+			return nil
+		}
+		raw := uint32(data[6]) | uint32(data[7])<<8 |
+			uint32(data[8])<<16 | uint32(data[9])<<24
+		width := raw & 0x3FFF
+		height := (raw >> 16) & 0x3FFF
+		return t.conn.initWriter(width, height)
+	}
+	return nil
+}
+
+func (conn *diskConn) initWriter(width, height uint32) error {
+	if conn.file != nil && width == conn.width && height == conn.height {
+		return nil
+	}
+	var entries []webm.TrackEntry
+	for i, t := range conn.tracks {
+		codec := t.remote.track.Codec()
+		var entry webm.TrackEntry
+		switch t.remote.track.Codec().Name {
+		case webrtc.Opus:
+			entry = webm.TrackEntry{
+				Name:        "Audio",
+				TrackNumber: uint64(i + 1),
+				CodecID:     "A_OPUS",
+				TrackType:   2,
+				Audio: &webm.Audio{
+					SamplingFrequency: float64(codec.ClockRate),
+					Channels:          uint64(codec.Channels),
+				},
+			}
+		case webrtc.VP8:
+			entry = webm.TrackEntry{
+				Name:        "Video",
+				TrackNumber: uint64(i + 1),
+				CodecID:     "V_VP8",
+				TrackType:   1,
+				Video: &webm.Video{
+					PixelWidth:  uint64(width),
+					PixelHeight: uint64(height),
+				},
+			}
+		default:
+			return errors.New("unknown track type")
+		}
+		entries = append(entries, entry)
+	}
+
+	err := conn.reopen()
+	if err != nil {
+		return err
+	}
+
+	writers, err := webm.NewSimpleBlockWriter(conn.file, entries)
+	if err != nil {
+		conn.file.Close()
+		conn.file = nil
+		return err
+	}
+
+	if len(writers) != len(conn.tracks) {
+		conn.file.Close()
+		conn.file = nil
+		return errors.New("unexpected number of writers")
+	}
+
+	conn.width = width
+	conn.height = height
+
+	for i, t := range conn.tracks {
+		t.writer = writers[i]
+	}
+	return nil
+}
+
+func (t *diskTrack) Accumulate(bytes uint32) {
+	return
+}
+
+func (down *diskTrack) GetMaxBitrate(now uint64) uint64 {
+	return ^uint64(0)
+}
diff --git a/go.mod b/go.mod
index 706f49e..a989fff 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module sfu
 go 1.13
 
 require (
+	github.com/at-wat/ebml-go v0.11.0
 	github.com/gorilla/websocket v1.4.2
 	github.com/pion/rtcp v1.2.2
 	github.com/pion/rtp v1.5.4
diff --git a/go.sum b/go.sum
index 721d175..44b5443 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/at-wat/ebml-go v0.11.0 h1:E6V+h/XWDhAdbphMIYIa3B61kaeU4lnNfKLSy0wLP4o=
+github.com/at-wat/ebml-go v0.11.0/go.mod h1:w1cJs7zmGsb5nnSvhWGKLCxvfu4FVx5ERvYDIalj1ww=
 github.com/cheekybits/genny v1.0.0 h1:uGGa4nei+j20rOSeDeP5Of12XVm7TGUd4dJA9RDitfE=
 github.com/cheekybits/genny v1.0.0/go.mod h1:+tQajlRqAUrPI7DOSpB0XAqZYtQakVtB7wXkRAgjxjQ=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
diff --git a/sfu.go b/sfu.go
index 824f3e6..38bffbb 100644
--- a/sfu.go
+++ b/sfu.go
@@ -31,6 +31,7 @@ var httpAddr string
 var staticRoot string
 var dataDir string
 var groupsDir string
+var recordingsDir string
 var iceFilename string
 
 func main() {
@@ -43,6 +44,8 @@ func main() {
 		"data `directory`")
 	flag.StringVar(&groupsDir, "groups", "./groups/",
 		"group description `directory`")
+	flag.StringVar(&recordingsDir, "recordings", "./recordings/",
+		"recordings `directory`")
 	flag.StringVar(&cpuprofile, "cpuprofile", "",
 		"store CPU profile in `file`")
 	flag.StringVar(&memprofile, "memprofile", "",