Implement Interceptors

Provide API so that handling around RTP can be easily defined by the
user. See the design doc here[0]

[0] https://github.com/pion/webrtc-v3-design/issues/34

api.go

@@ -3,6 +3,7 @@
 package webrtc
 
 import (
+	"github.com/pion/interceptor"
 	"github.com/pion/logging"
 )
 
@@ -13,6 +14,7 @@ import (
 type API struct {
 	settingEngine *SettingEngine
 	mediaEngine   *MediaEngine
+	interceptor   interceptor.Interceptor
 }
 
 // NewAPI Creates a new API object for keeping semi-global settings to WebRTC objects
@@ -35,6 +37,10 @@ func NewAPI(options ...func(*API)) *API {
 		a.mediaEngine = &MediaEngine{}
 	}
 
+	if a.interceptor == nil {
+		a.interceptor = &interceptor.NoOp{}
+	}
+
 	return a
 }
 
@@ -57,3 +63,11 @@ func WithSettingEngine(s SettingEngine) func(a *API) {
 		a.settingEngine = &s
 	}
 }
+
+// WithInterceptorRegistry allows providing Interceptors to the API.
+// Settings should not be changed after passing the registry to an API.
+func WithInterceptorRegistry(interceptorRegistry *interceptor.Registry) func(a *API) {
+	return func(a *API) {
+		a.interceptor = interceptorRegistry.Build()
+	}
+}

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/pion/datachannel v1.4.21
 	github.com/pion/dtls/v2 v2.0.3
 	github.com/pion/ice/v2 v2.0.11
+	github.com/pion/interceptor v0.0.3
 	github.com/pion/logging v0.2.2
 	github.com/pion/quic v0.1.4
 	github.com/pion/randutil v0.1.0

go.sum

@@ -106,6 +106,8 @@ github.com/pion/dtls/v2 v2.0.3 h1:3qQ0s4+TXD00rsllL8g8KQcxAs+Y/Z6oz618RXX6p14=
 github.com/pion/dtls/v2 v2.0.3/go.mod h1:TUjyL8bf8LH95h81Xj7kATmzMRt29F/4lxpIPj2Xe4Y=
 github.com/pion/ice/v2 v2.0.11 h1:XAKZPtglESY/w18eHJR8YLWx3sS8ms7LbWvtOpEM1Dg=
 github.com/pion/ice/v2 v2.0.11/go.mod h1:Sqdo0oy3ZkaOCsK7Ai9ksLpJkREG03R3fHMJ0PXmHO8=
+github.com/pion/interceptor v0.0.3 h1:VQtmPts/2IgYQtb9sZLTp6B0kIdHE5zBMQ6tCcgdJcM=
+github.com/pion/interceptor v0.0.3/go.mod h1:lPVrf5xfosI989ZcmgPS4WwwRhd+XAyTFaYI2wHf7nU=
 github.com/pion/logging v0.2.2 h1:M9+AIj/+pxNsDfAT64+MAVgJO0rsyLnoJKCqf//DoeY=
 github.com/pion/logging v0.2.2/go.mod h1:k0/tDVsRCX2Mb2ZEmTqNa7CWsQPc+YYCB7Q+5pahoms=
 github.com/pion/mdns v0.0.4 h1:O4vvVqr4DGX63vzmO6Fw9vpy3lfztVWHGCQfyw0ZLSY=

interceptor.go

@@ -0,0 +1,26 @@
+// +build !js
+
+package webrtc
+
+import (
+	"github.com/pion/interceptor"
+)
+
+// RegisterDefaultInterceptors will register some useful interceptors. If you want to customize which interceptors are loaded,
+// you should copy the code from this method and remove unwanted interceptors.
+func RegisterDefaultInterceptors(mediaEngine *MediaEngine, interceptorRegistry *interceptor.Registry) error {
+	err := ConfigureNack(mediaEngine, interceptorRegistry)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// ConfigureNack will setup everything necessary for handling generating/responding to nack messages.
+func ConfigureNack(mediaEngine *MediaEngine, interceptorRegistry *interceptor.Registry) error {
+	mediaEngine.RegisterFeedback(RTCPFeedback{Type: "nack"}, RTPCodecTypeVideo)
+	mediaEngine.RegisterFeedback(RTCPFeedback{Type: "nack", Parameter: "pli"}, RTPCodecTypeVideo)
+	interceptorRegistry.Add(&interceptor.NACK{})
+	return nil
+}

interceptor_test.go

@@ -0,0 +1,188 @@
+// +build !js
+
+package webrtc
+
+import (
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/pion/interceptor"
+	"github.com/pion/rtcp"
+	"github.com/pion/rtp"
+	"github.com/pion/transport/test"
+	"github.com/pion/webrtc/v3/pkg/media"
+	"github.com/stretchr/testify/assert"
+)
+
+type testInterceptor struct {
+	t           *testing.T
+	extensionID uint8
+	rtcpWriter  atomic.Value
+	lastRTCP    atomic.Value
+	interceptor.NoOp
+}
+
+func (t *testInterceptor) BindLocalStream(_ *interceptor.StreamInfo, writer interceptor.RTPWriter) interceptor.RTPWriter {
+	return interceptor.RTPWriterFunc(func(p *rtp.Packet, attributes interceptor.Attributes) (int, error) {
+		// set extension on outgoing packet
+		p.Header.Extension = true
+		p.Header.ExtensionProfile = 0xBEDE
+		assert.NoError(t.t, p.Header.SetExtension(t.extensionID, []byte("write")))
+
+		return writer.Write(p, attributes)
+	})
+}
+
+func (t *testInterceptor) BindRemoteStream(info *interceptor.StreamInfo, reader interceptor.RTPReader) interceptor.RTPReader {
+	return interceptor.RTPReaderFunc(func() (*rtp.Packet, interceptor.Attributes, error) {
+		p, attributes, err := reader.Read()
+		if err != nil {
+			return nil, nil, err
+		}
+		// set extension on incoming packet
+		p.Header.Extension = true
+		p.Header.ExtensionProfile = 0xBEDE
+		assert.NoError(t.t, p.Header.SetExtension(t.extensionID, []byte("read")))
+
+		// write back a pli
+		rtcpWriter := t.rtcpWriter.Load().(interceptor.RTCPWriter)
+		pli := &rtcp.PictureLossIndication{SenderSSRC: info.SSRC, MediaSSRC: info.SSRC}
+		_, err = rtcpWriter.Write([]rtcp.Packet{pli}, make(interceptor.Attributes))
+		assert.NoError(t.t, err)
+
+		return p, attributes, nil
+	})
+}
+
+func (t *testInterceptor) BindRTCPReader(reader interceptor.RTCPReader) interceptor.RTCPReader {
+	return interceptor.RTCPReaderFunc(func() ([]rtcp.Packet, interceptor.Attributes, error) {
+		pkts, attributes, err := reader.Read()
+		if err != nil {
+			return nil, nil, err
+		}
+
+		t.lastRTCP.Store(pkts[0])
+
+		return pkts, attributes, nil
+	})
+}
+
+func (t *testInterceptor) lastReadRTCP() rtcp.Packet {
+	p, _ := t.lastRTCP.Load().(rtcp.Packet)
+	return p
+}
+
+func (t *testInterceptor) BindRTCPWriter(writer interceptor.RTCPWriter) interceptor.RTCPWriter {
+	t.rtcpWriter.Store(writer)
+	return writer
+}
+
+func TestPeerConnection_Interceptor(t *testing.T) {
+	to := test.TimeOut(time.Second * 20)
+	defer to.Stop()
+
+	report := test.CheckRoutines(t)
+	defer report()
+
+	createPC := func(i interceptor.Interceptor) *PeerConnection {
+		m := &MediaEngine{}
+		err := m.RegisterDefaultCodecs()
+		if err != nil {
+			t.Fatal(err)
+		}
+		ir := &interceptor.Registry{}
+		ir.Add(i)
+		pc, err := NewAPI(WithMediaEngine(m), WithInterceptorRegistry(ir)).NewPeerConnection(Configuration{})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		return pc
+	}
+
+	sendInterceptor := &testInterceptor{t: t, extensionID: 1}
+	senderPC := createPC(sendInterceptor)
+	receiverPC := createPC(&testInterceptor{t: t, extensionID: 2})
+
+	track, err := NewTrackLocalStaticSample(RTPCodecCapability{MimeType: "video/vp8"}, "video", "pion")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	sender, err := senderPC.AddTrack(track)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pending := new(int32)
+	wg := &sync.WaitGroup{}
+
+	wg.Add(1)
+	*pending++
+	receiverPC.OnTrack(func(track *TrackRemote, receiver *RTPReceiver) {
+		p, readErr := track.ReadRTP()
+		if readErr != nil {
+			t.Fatal(readErr)
+		}
+		assert.Equal(t, p.Extension, true)
+		assert.Equal(t, "write", string(p.GetExtension(1)))
+		assert.Equal(t, "read", string(p.GetExtension(2)))
+		atomic.AddInt32(pending, -1)
+		wg.Done()
+
+		for {
+			_, readErr = track.ReadRTP()
+			if readErr != nil {
+				return
+			}
+		}
+	})
+
+	wg.Add(1)
+	*pending++
+	go func() {
+		_, readErr := sender.ReadRTCP()
+		assert.NoError(t, readErr)
+		atomic.AddInt32(pending, -1)
+		wg.Done()
+
+		for {
+			_, readErr = sender.ReadRTCP()
+			if readErr != nil {
+				return
+			}
+		}
+	}()
+
+	err = signalPair(senderPC, receiverPC)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			time.Sleep(time.Millisecond * 100)
+			if routineErr := track.WriteSample(media.Sample{Data: []byte{0x00}, Duration: time.Second}); routineErr != nil {
+				t.Error(routineErr)
+				return
+			}
+
+			if atomic.LoadInt32(pending) == 0 {
+				return
+			}
+		}
+	}()
+
+	wg.Wait()
+	assert.NoError(t, senderPC.Close())
+	assert.NoError(t, receiverPC.Close())
+
+	pli, _ := sendInterceptor.lastReadRTCP().(*rtcp.PictureLossIndication)
+	if pli == nil || pli.SenderSSRC == 0 {
+		t.Errorf("pli not found by send interceptor")
+	}
+}

interceptor_track_local.go

@@ -0,0 +1,29 @@
+// +build !js
+
+package webrtc
+
+import (
+	"sync/atomic"
+
+	"github.com/pion/interceptor"
+	"github.com/pion/rtp"
+)
+
+type interceptorTrackLocalWriter struct {
+	TrackLocalWriter
+	rtpWriter atomic.Value
+}
+
+func (i *interceptorTrackLocalWriter) setRTPWriter(writer interceptor.RTPWriter) {
+	i.rtpWriter.Store(writer)
+}
+
+func (i *interceptorTrackLocalWriter) WriteRTP(header *rtp.Header, payload []byte) (int, error) {
+	writer := i.rtpWriter.Load().(interceptor.RTPWriter)
+
+	if writer == nil {
+		return 0, nil
+	}
+
+	return writer.Write(&rtp.Packet{Header: *header, Payload: payload}, make(interceptor.Attributes))
+}

mediaengine.go

@@ -233,6 +233,22 @@ func (m *MediaEngine) RegisterHeaderExtension(extension RTPHeaderExtensionCapabi
 	return nil
 }
 
+// RegisterFeedback adds feedback mechanism to already registered codecs.
+func (m *MediaEngine) RegisterFeedback(feedback RTCPFeedback, typ RTPCodecType) {
+	switch typ {
+	case RTPCodecTypeVideo:
+		for i, v := range m.videoCodecs {
+			v.RTCPFeedback = append(v.RTCPFeedback, feedback)
+			m.videoCodecs[i] = v
+		}
+	case RTPCodecTypeAudio:
+		for i, v := range m.audioCodecs {
+			v.RTCPFeedback = append(v.RTCPFeedback, feedback)
+			m.audioCodecs[i] = v
+		}
+	}
+}
+
 // GetHeaderExtensionID returns the negotiated ID for a header extension.
 // If the Header Extension isn't enabled ok will be false
 func (m *MediaEngine) GetHeaderExtensionID(extension RTPHeaderExtensionCapability) (val int, audioNegotiated, videoNegotiated bool) {
@@ -249,19 +265,19 @@ func (m *MediaEngine) GetHeaderExtensionID(extension RTPHeaderExtensionCapabilit
 	return
 }
 
-func (m *MediaEngine) getCodecByPayload(payloadType PayloadType) (RTPCodecParameters, error) {
+func (m *MediaEngine) getCodecByPayload(payloadType PayloadType) (RTPCodecParameters, RTPCodecType, error) {
 	for _, codec := range m.negotiatedVideoCodecs {
 		if codec.PayloadType == payloadType {
-			return codec, nil
+			return codec, RTPCodecTypeVideo, nil
 		}
 	}
 	for _, codec := range m.negotiatedAudioCodecs {
 		if codec.PayloadType == payloadType {
-			return codec, nil
+			return codec, RTPCodecTypeAudio, nil
 		}
 	}
 
-	return RTPCodecParameters{}, ErrCodecNotFound
+	return RTPCodecParameters{}, 0, ErrCodecNotFound
 }
 
 func (m *MediaEngine) collectStats(collector *statsReportCollector) {
@@ -309,7 +325,7 @@ func (m *MediaEngine) updateCodecParameters(remoteCodec RTPCodecParameters, typ
 			return err
 		}
 
-		if _, err = m.getCodecByPayload(PayloadType(payloadType)); err != nil {
+		if _, _, err = m.getCodecByPayload(PayloadType(payloadType)); err != nil {
 			return nil // not an error, we just ignore this codec we don't support
 		}
 	}
@@ -378,8 +394,8 @@ func (m *MediaEngine) updateFromRemoteDescription(desc sdp.SessionDescription) e
 			return err
 		}
 
-		for id, extension := range extensions {
-			if err = m.updateHeaderExtension(extension, id, typ); err != nil {
+		for extension, id := range extensions {
+			if err = m.updateHeaderExtension(id, extension, typ); err != nil {
 				return err
 			}
 		}
@@ -405,6 +421,39 @@ func (m *MediaEngine) getCodecsByKind(typ RTPCodecType) []RTPCodecParameters {
 	return nil
 }
 
+func (m *MediaEngine) getRTPParametersByKind(typ RTPCodecType) RTPParameters {
+	headerExtensions := make([]RTPHeaderExtensionParameter, 0)
+	for id, e := range m.negotiatedHeaderExtensions {
+		if e.isAudio && typ == RTPCodecTypeAudio || e.isVideo && typ == RTPCodecTypeVideo {
+			headerExtensions = append(headerExtensions, RTPHeaderExtensionParameter{ID: id, URI: e.uri})
+		}
+	}
+
+	return RTPParameters{
+		HeaderExtensions: headerExtensions,
+		Codecs:           m.getCodecsByKind(typ),
+	}
+}
+
+func (m *MediaEngine) getRTPParametersByPayloadType(payloadType PayloadType) (RTPParameters, error) {
+	codec, typ, err := m.getCodecByPayload(payloadType)
+	if err != nil {
+		return RTPParameters{}, err
+	}
+
+	headerExtensions := make([]RTPHeaderExtensionParameter, 0)
+	for id, e := range m.negotiatedHeaderExtensions {
+		if e.isAudio && typ == RTPCodecTypeAudio || e.isVideo && typ == RTPCodecTypeVideo {
+			headerExtensions = append(headerExtensions, RTPHeaderExtensionParameter{ID: id, URI: e.uri})
+		}
+	}
+
+	return RTPParameters{
+		HeaderExtensions: headerExtensions,
+		Codecs:           []RTPCodecParameters{codec},
+	}, nil
+}
+
 func (m *MediaEngine) negotiatedHeaderExtensionsForType(typ RTPCodecType) map[int]mediaEngineHeaderExtension {
 	headerExtensions := map[int]mediaEngineHeaderExtension{}
 	for id, e := range m.negotiatedHeaderExtensions {

mediaengine_test.go

@@ -63,7 +63,7 @@ a=fmtp:111 minptime=10; useinbandfec=1
 		assert.False(t, m.negotiatedVideo)
 		assert.True(t, m.negotiatedAudio)
 
-		opusCodec, err := m.getCodecByPayload(111)
+		opusCodec, _, err := m.getCodecByPayload(111)
 		assert.NoError(t, err)
 		assert.Equal(t, opusCodec.MimeType, mimeTypeOpus)
 	})
@@ -85,10 +85,10 @@ a=fmtp:112 minptime=10; useinbandfec=1
 		assert.False(t, m.negotiatedVideo)
 		assert.True(t, m.negotiatedAudio)
 
-		_, err := m.getCodecByPayload(111)
+		_, _, err := m.getCodecByPayload(111)
 		assert.Error(t, err)
 
-		opusCodec, err := m.getCodecByPayload(112)
+		opusCodec, _, err := m.getCodecByPayload(112)
 		assert.NoError(t, err)
 		assert.Equal(t, opusCodec.MimeType, mimeTypeOpus)
 	})
@@ -110,7 +110,7 @@ a=fmtp:111 minptime=10; useinbandfec=1
 		assert.False(t, m.negotiatedVideo)
 		assert.True(t, m.negotiatedAudio)
 
-		opusCodec, err := m.getCodecByPayload(111)
+		opusCodec, _, err := m.getCodecByPayload(111)
 		assert.NoError(t, err)
 		assert.Equal(t, opusCodec.MimeType, "audio/OPUS")
 	})
@@ -131,7 +131,7 @@ a=rtpmap:111 opus/48000/2
 		assert.False(t, m.negotiatedVideo)
 		assert.True(t, m.negotiatedAudio)
 
-		opusCodec, err := m.getCodecByPayload(111)
+		opusCodec, _, err := m.getCodecByPayload(111)
 		assert.NoError(t, err)
 		assert.Equal(t, opusCodec.MimeType, mimeTypeOpus)
 	})

peerconnection.go

@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/pion/ice/v2"
+	"github.com/pion/interceptor"
 	"github.com/pion/logging"
 	"github.com/pion/rtcp"
 	"github.com/pion/sdp/v3"
@@ -76,6 +77,8 @@ type PeerConnection struct {
 	// A reference to the associated API state used by this connection
 	api *API
 	log logging.LeveledLogger
+
+	interceptorRTCPWriter interceptor.RTCPWriter
 }
 
 // NewPeerConnection creates a peerconnection with the default
@@ -119,6 +122,8 @@ func (api *API) NewPeerConnection(configuration Configuration) (*PeerConnection,
 		log: api.settingEngine.LoggerFactory.NewLogger("pc"),
 	}
 
+	pc.interceptorRTCPWriter = api.interceptor.BindRTCPWriter(interceptor.RTCPWriterFunc(pc.writeRTCP))
+
 	var err error
 	if err = pc.initConfiguration(configuration); err != nil {
 		return nil, err
@@ -1125,7 +1130,7 @@ func (pc *PeerConnection) startReceiver(incoming trackDetails, receiver *RTPRece
 			return
 		}
 
-		codec, err := pc.api.mediaEngine.getCodecByPayload(receiver.Track().PayloadType())
+		params, err := pc.api.mediaEngine.getRTPParametersByPayloadType(receiver.Track().PayloadType())
 		if err != nil {
 			pc.log.Warnf("no codec could be found for payloadType %d", receiver.Track().PayloadType())
 			return
@@ -1133,7 +1138,9 @@ func (pc *PeerConnection) startReceiver(incoming trackDetails, receiver *RTPRece
 
 		receiver.Track().mu.Lock()
 		receiver.Track().kind = receiver.kind
-		receiver.Track().codec = codec
+		receiver.Track().codec = params.Codecs[0]
+		receiver.Track().params = params
+		receiver.Track().bindInterceptor()
 		receiver.Track().mu.Unlock()
 
 		pc.onTrack(receiver.Track(), receiver)
@@ -1335,7 +1342,7 @@ func (pc *PeerConnection) handleUndeclaredSSRC(rtpStream io.Reader, ssrc SSRC) e
 			continue
 		}
 
-		codec, err := pc.api.mediaEngine.getCodecByPayload(payloadType)
+		params, err := pc.api.mediaEngine.getRTPParametersByPayloadType(payloadType)
 		if err != nil {
 			return err
 		}
@@ -1345,7 +1352,7 @@ func (pc *PeerConnection) handleUndeclaredSSRC(rtpStream io.Reader, ssrc SSRC) e
 				continue
 			}
 
-			track, err := t.Receiver().receiveForRid(rid, codec, ssrc)
+			track, err := t.Receiver().receiveForRid(rid, params, ssrc)
 			if err != nil {
 				return err
 			}
@@ -1730,28 +1737,33 @@ func (pc *PeerConnection) SetIdentityProvider(provider string) error {
 	return errPeerConnSetIdentityProviderNotImplemented
 }
 
-// WriteRTCP sends a user provided RTCP packet to the connected peer
-// If no peer is connected the packet is discarded
+// WriteRTCP sends a user provided RTCP packet to the connected peer. If no peer is connected the
+// packet is discarded. It also runs any configured interceptors.
 func (pc *PeerConnection) WriteRTCP(pkts []rtcp.Packet) error {
+	_, err := pc.interceptorRTCPWriter.Write(pkts, make(interceptor.Attributes))
+	return err
+}
+
+func (pc *PeerConnection) writeRTCP(pkts []rtcp.Packet, _ interceptor.Attributes) (int, error) {
 	raw, err := rtcp.Marshal(pkts)
 	if err != nil {
-		return err
+		return 0, err
 	}
 
 	srtcpSession, err := pc.dtlsTransport.getSRTCPSession()
 	if err != nil {
-		return nil
+		return 0, nil
 	}
 
 	writeStream, err := srtcpSession.OpenWriteStream()
 	if err != nil {
-		return fmt.Errorf("%w: %v", errPeerConnWriteRTCPOpenWriteStream, err)
+		return 0, fmt.Errorf("%w: %v", errPeerConnWriteRTCPOpenWriteStream, err)
 	}
 
-	if _, err := writeStream.Write(raw); err != nil {
-		return err
+	if n, err := writeStream.Write(raw); err != nil {
+		return n, err
 	}
-	return nil
+	return 0, nil
 }
 
 // Close ends the PeerConnection
@@ -1775,6 +1787,8 @@ func (pc *PeerConnection) Close() error {
 	//    continue the chain the Mux has to be closed.
 	closeErrs := make([]error, 4)
 
+	closeErrs = append(closeErrs, pc.api.interceptor.Close())
+
 	// https://www.w3.org/TR/webrtc/#dom-rtcpeerconnection-close (step #4)
 	for _, t := range pc.GetTransceivers() {
 		if !t.stopped {

rtpcodec.go

@@ -57,6 +57,14 @@ type RTPHeaderExtensionCapability struct {
 	URI string
 }
 
+// RTPHeaderExtensionParameter represents a negotiated RFC5285 RTP header extension.
+//
+// https://w3c.github.io/webrtc-pc/#dictionary-rtcrtpheaderextensionparameters-members
+type RTPHeaderExtensionParameter struct {
+	URI string
+	ID  int
+}
+
 // RTPCodecParameters is a sequence containing the media codecs that an RtpSender
 // will choose from, as well as entries for RTX, RED and FEC mechanisms. This also
 // includes the PayloadType that has been negotiated
@@ -77,6 +85,14 @@ type RTCRtpCapabilities struct {
 	Codecs           []RTPCodecCapability
 }
 
+// RTPParameters is a list of negotiated codecs and header extensions
+//
+// https://w3c.github.io/webrtc-pc/#dictionary-rtcrtpparameters-members
+type RTPParameters struct {
+	HeaderExtensions []RTPHeaderExtensionParameter
+	Codecs           []RTPCodecParameters
+}
+
 // Do a fuzzy find for a codec in the list of codecs
 // Used for lookup up a codec in an existing list to find a match
 func codecParametersFuzzySearch(needle RTPCodecParameters, haystack []RTPCodecParameters) (RTPCodecParameters, error) {

rtpreceiver.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"sync"
 
+	"github.com/pion/interceptor"
 	"github.com/pion/rtcp"
 	"github.com/pion/srtp"
 )
@@ -31,6 +32,8 @@ type RTPReceiver struct {
 
 	// A reference to the associated api object
 	api *API
+
+	interceptorRTCPReader interceptor.RTCPReader
 }
 
 // NewRTPReceiver constructs a new RTPReceiver
@@ -39,14 +42,17 @@ func (api *API) NewRTPReceiver(kind RTPCodecType, transport *DTLSTransport) (*RT
 		return nil, errRTPReceiverDTLSTransportNil
 	}
 
-	return &RTPReceiver{
+	r := &RTPReceiver{
 		kind:      kind,
 		transport: transport,
 		api:       api,
 		closed:    make(chan interface{}),
 		received:  make(chan interface{}),
 		tracks:    []trackStreams{},
-	}, nil
+	}
+	r.interceptorRTCPReader = api.interceptor.BindRTCPReader(interceptor.RTCPReaderFunc(r.readRTCP))
+
+	return r, nil
 }
 
 // Transport returns the currently-configured *DTLSTransport or nil
@@ -94,11 +100,12 @@ func (r *RTPReceiver) Receive(parameters RTPReceiveParameters) error {
 
 	if len(parameters.Encodings) == 1 && parameters.Encodings[0].SSRC != 0 {
 		t := trackStreams{
-			track: &TrackRemote{
-				kind:     r.kind,
-				ssrc:     parameters.Encodings[0].SSRC,
-				receiver: r,
-			},
+			track: newTrackRemote(
+				r.kind,
+				parameters.Encodings[0].SSRC,
+				"",
+				r,
+			),
 		}
 
 		var err error
@@ -111,11 +118,12 @@ func (r *RTPReceiver) Receive(parameters RTPReceiveParameters) error {
 	} else {
 		for _, encoding := range parameters.Encodings {
 			r.tracks = append(r.tracks, trackStreams{
-				track: &TrackRemote{
-					kind:     r.kind,
-					rid:      encoding.RID,
-					receiver: r,
-				},
+				track: newTrackRemote(
+					r.kind,
+					0,
+					encoding.RID,
+					r,
+				),
 			})
 		}
 	}
@@ -148,15 +156,27 @@ func (r *RTPReceiver) ReadSimulcast(b []byte, rid string) (n int, err error) {
 	}
 }
 
-// ReadRTCP is a convenience method that wraps Read and unmarshal for you
+// ReadRTCP is a convenience method that wraps Read and unmarshal for you.
+// It also runs any configured interceptors.
 func (r *RTPReceiver) ReadRTCP() ([]rtcp.Packet, error) {
+	pkts, _, err := r.interceptorRTCPReader.Read()
+	return pkts, err
+}
+
+// ReadRTCP is a convenience method that wraps Read and unmarshal for you
+func (r *RTPReceiver) readRTCP() ([]rtcp.Packet, interceptor.Attributes, error) {
 	b := make([]byte, receiveMTU)
 	i, err := r.Read(b)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
-	return rtcp.Unmarshal(b[:i])
+	pkts, err := rtcp.Unmarshal(b[:i])
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return pkts, make(interceptor.Attributes), nil
 }
 
 // ReadSimulcastRTCP is a convenience method that wraps ReadSimulcast and unmarshal for you
@@ -232,7 +252,7 @@ func (r *RTPReceiver) readRTP(b []byte, reader *TrackRemote) (n int, err error)
 
 // receiveForRid is the sibling of Receive expect for RIDs instead of SSRCs
 // It populates all the internal state for the given RID
-func (r *RTPReceiver) receiveForRid(rid string, codec RTPCodecParameters, ssrc SSRC) (*TrackRemote, error) {
+func (r *RTPReceiver) receiveForRid(rid string, params RTPParameters, ssrc SSRC) (*TrackRemote, error) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 
@@ -240,8 +260,10 @@ func (r *RTPReceiver) receiveForRid(rid string, codec RTPCodecParameters, ssrc S
 		if r.tracks[i].track.RID() == rid {
 			r.tracks[i].track.mu.Lock()
 			r.tracks[i].track.kind = r.kind
-			r.tracks[i].track.codec = codec
+			r.tracks[i].track.codec = params.Codecs[0]
+			r.tracks[i].track.params = params
 			r.tracks[i].track.ssrc = ssrc
+			r.tracks[i].track.bindInterceptor()
 			r.tracks[i].track.mu.Unlock()
 
 			var err error

rtpsender.go

@@ -6,8 +6,10 @@ import (
 	"io"
 	"sync"
 
+	"github.com/pion/interceptor"
 	"github.com/pion/randutil"
 	"github.com/pion/rtcp"
+	"github.com/pion/rtp"
 	"github.com/pion/srtp"
 )
 
@@ -16,13 +18,12 @@ type RTPSender struct {
 	track TrackLocal
 
 	rtcpReadStream *srtp.ReadStreamSRTCP
-	rtpWriteStream *srtp.WriteStreamSRTP
+	context        TrackLocalContext
 
 	transport *DTLSTransport
 
 	payloadType PayloadType
 	ssrc        SSRC
-	codec       RTPCodecParameters
 
 	// nolint:godox
 	// TODO(sgotti) remove this when in future we'll avoid replacing
@@ -36,6 +37,8 @@ type RTPSender struct {
 
 	mu                     sync.RWMutex
 	sendCalled, stopCalled chan interface{}
+
+	interceptorRTCPReader interceptor.RTCPReader
 }
 
 // NewRTPSender constructs a new RTPSender
@@ -51,7 +54,7 @@ func (api *API) NewRTPSender(track TrackLocal, transport *DTLSTransport) (*RTPSe
 		return nil, err
 	}
 
-	return &RTPSender{
+	r := &RTPSender{
 		track:      track,
 		transport:  transport,
 		api:        api,
@@ -59,7 +62,10 @@ func (api *API) NewRTPSender(track TrackLocal, transport *DTLSTransport) (*RTPSe
 		stopCalled: make(chan interface{}),
 		ssrc:       SSRC(randutil.NewMathRandomGenerator().Uint32()),
 		id:         id,
-	}, nil
+	}
+	r.interceptorRTCPReader = api.interceptor.BindRTCPReader(interceptor.RTCPReaderFunc(r.readRTCP))
+
+	return r, nil
 }
 
 func (r *RTPSender) isNegotiated() bool {
@@ -97,11 +103,7 @@ func (r *RTPSender) ReplaceTrack(track TrackLocal) error {
 	defer r.mu.Unlock()
 
 	if r.hasSent() {
-		if err := r.track.Unbind(TrackLocalContext{
-			id:          r.id,
-			ssrc:        r.ssrc,
-			writeStream: r.rtpWriteStream,
-		}); err != nil {
+		if err := r.track.Unbind(r.context); err != nil {
 			return err
 		}
 	}
@@ -111,12 +113,7 @@ func (r *RTPSender) ReplaceTrack(track TrackLocal) error {
 		return nil
 	}
 
-	if _, err := track.Bind(TrackLocalContext{
-		id:          r.id,
-		codecs:      []RTPCodecParameters{r.codec},
-		ssrc:        r.ssrc,
-		writeStream: r.rtpWriteStream,
-	}); err != nil {
+	if _, err := track.Bind(r.context); err != nil {
 		return err
 	}
 
@@ -148,18 +145,53 @@ func (r *RTPSender) Send(parameters RTPSendParameters) error {
 		return err
 	}
 
-	if r.rtpWriteStream, err = srtpSession.OpenWriteStream(); err != nil {
+	rtpWriteStream, err := srtpSession.OpenWriteStream()
+	if err != nil {
 		return err
 	}
 
-	if r.codec, err = r.track.Bind(TrackLocalContext{
+	writeStream := &interceptorTrackLocalWriter{TrackLocalWriter: rtpWriteStream}
+
+	r.context = TrackLocalContext{
 		id:          r.id,
-		codecs:      r.api.mediaEngine.getCodecsByKind(r.track.Kind()),
+		params:      r.api.mediaEngine.getRTPParametersByKind(r.track.Kind()),
 		ssrc:        parameters.Encodings.SSRC,
-		writeStream: r.rtpWriteStream,
-	}); err != nil {
+		writeStream: writeStream,
+	}
+
+	codec, err := r.track.Bind(r.context)
+	if err != nil {
 		return err
 	}
+	r.context.params.Codecs = []RTPCodecParameters{codec}
+
+	headerExtensions := make([]interceptor.RTPHeaderExtension, 0, len(r.context.params.HeaderExtensions))
+	for _, h := range r.context.params.HeaderExtensions {
+		headerExtensions = append(headerExtensions, interceptor.RTPHeaderExtension{ID: h.ID, URI: h.URI})
+	}
+	feedbacks := make([]interceptor.RTCPFeedback, 0, len(codec.RTCPFeedback))
+	for _, f := range codec.RTCPFeedback {
+		feedbacks = append(feedbacks, interceptor.RTCPFeedback{Type: f.Type, Parameter: f.Parameter})
+	}
+	info := &interceptor.StreamInfo{
+		ID:                  r.context.id,
+		Attributes:          interceptor.Attributes{},
+		SSRC:                uint32(r.context.ssrc),
+		PayloadType:         uint8(codec.PayloadType),
+		RTPHeaderExtensions: headerExtensions,
+		MimeType:            codec.MimeType,
+		ClockRate:           codec.ClockRate,
+		Channels:            codec.Channels,
+		SDPFmtpLine:         codec.SDPFmtpLine,
+		RTCPFeedback:        feedbacks,
+	}
+	writeStream.setRTPWriter(
+		r.api.interceptor.BindLocalStream(
+			info,
+			interceptor.RTPWriterFunc(func(p *rtp.Packet, attributes interceptor.Attributes) (int, error) {
+				return rtpWriteStream.WriteRTP(&p.Header, p.Payload)
+			}),
+		))
 
 	close(r.sendCalled)
 	return nil
@@ -194,15 +226,26 @@ func (r *RTPSender) Read(b []byte) (n int, err error) {
 	}
 }
 
-// ReadRTCP is a convenience method that wraps Read and unmarshals for you
+// ReadRTCP is a convenience method that wraps Read and unmarshals for you.
+// It also runs any configured interceptors.
 func (r *RTPSender) ReadRTCP() ([]rtcp.Packet, error) {
+	pkts, _, err := r.interceptorRTCPReader.Read()
+	return pkts, err
+}
+
+func (r *RTPSender) readRTCP() ([]rtcp.Packet, interceptor.Attributes, error) {
 	b := make([]byte, receiveMTU)
 	i, err := r.Read(b)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
-	return rtcp.Unmarshal(b[:i])
+	pkts, err := rtcp.Unmarshal(b[:i])
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return pkts, make(interceptor.Attributes), nil
 }
 
 // hasSent tells if data has been ever sent for this instance

track_local.go

@@ -11,10 +11,11 @@ type TrackLocalWriter interface {
 	Write(b []byte) (int, error)
 }
 
-// TrackLocalContext is the Context passed when a TrackLocal has been Binded/Unbinded from a PeerConnection
+// TrackLocalContext is the Context passed when a TrackLocal has been Binded/Unbinded from a PeerConnection, and used
+// in Interceptors.
 type TrackLocalContext struct {
 	id          string
-	codecs      []RTPCodecParameters
+	params      RTPParameters
 	ssrc        SSRC
 	writeStream TrackLocalWriter
 }
@@ -22,7 +23,13 @@ type TrackLocalContext struct {
 // CodecParameters returns the negotiated RTPCodecParameters. These are the codecs supported by both
 // PeerConnections and the SSRC/PayloadTypes
 func (t *TrackLocalContext) CodecParameters() []RTPCodecParameters {
-	return t.codecs
+	return t.params.Codecs
+}
+
+// HeaderExtensions returns the negotiated RTPHeaderExtensionParameters. These are the header extensions supported by
+// both PeerConnections and the SSRC/PayloadTypes
+func (t *TrackLocalContext) HeaderExtensions() []RTPHeaderExtensionParameter {
+	return t.params.HeaderExtensions
 }
 
 // SSRC requires the negotiated SSRC of this track

track_remote.go

@@ -5,6 +5,7 @@ package webrtc
 import (
 	"sync"
 
+	"github.com/pion/interceptor"
 	"github.com/pion/rtp"
 )
 
@@ -19,10 +20,49 @@ type TrackRemote struct {
 	kind        RTPCodecType
 	ssrc        SSRC
 	codec       RTPCodecParameters
+	params      RTPParameters
 	rid         string
 
 	receiver *RTPReceiver
 	peeked   []byte
+
+	interceptorRTPReader interceptor.RTPReader
+}
+
+func newTrackRemote(kind RTPCodecType, ssrc SSRC, rid string, receiver *RTPReceiver) *TrackRemote {
+	t := &TrackRemote{
+		kind:     kind,
+		ssrc:     ssrc,
+		rid:      rid,
+		receiver: receiver,
+	}
+	t.interceptorRTPReader = interceptor.RTPReaderFunc(t.readRTP)
+
+	return t
+}
+
+func (t *TrackRemote) bindInterceptor() {
+	headerExtensions := make([]interceptor.RTPHeaderExtension, 0, len(t.params.HeaderExtensions))
+	for _, h := range t.params.HeaderExtensions {
+		headerExtensions = append(headerExtensions, interceptor.RTPHeaderExtension{ID: h.ID, URI: h.URI})
+	}
+	feedbacks := make([]interceptor.RTCPFeedback, 0, len(t.codec.RTCPFeedback))
+	for _, f := range t.codec.RTCPFeedback {
+		feedbacks = append(feedbacks, interceptor.RTCPFeedback{Type: f.Type, Parameter: f.Parameter})
+	}
+	info := &interceptor.StreamInfo{
+		ID:                  t.id,
+		Attributes:          interceptor.Attributes{},
+		SSRC:                uint32(t.ssrc),
+		PayloadType:         uint8(t.payloadType),
+		RTPHeaderExtensions: headerExtensions,
+		MimeType:            t.codec.MimeType,
+		ClockRate:           t.codec.ClockRate,
+		Channels:            t.codec.Channels,
+		SDPFmtpLine:         t.codec.SDPFmtpLine,
+		RTCPFeedback:        feedbacks,
+	}
+	t.interceptorRTPReader = t.receiver.api.interceptor.BindRemoteStream(info, interceptor.RTPReaderFunc(t.readRTP))
 }
 
 // ID is the unique identifier for this Track. This should be unique for the
@@ -125,19 +165,25 @@ func (t *TrackRemote) peek(b []byte) (n int, err error) {
 	return
 }
 
-// ReadRTP is a convenience method that wraps Read and unmarshals for you
+// ReadRTP is a convenience method that wraps Read and unmarshals for you.
+// It also runs any configured interceptors.
 func (t *TrackRemote) ReadRTP() (*rtp.Packet, error) {
+	p, _, err := t.interceptorRTPReader.Read()
+	return p, err
+}
+
+func (t *TrackRemote) readRTP() (*rtp.Packet, interceptor.Attributes, error) {
 	b := make([]byte, receiveMTU)
 	i, err := t.Read(b)
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
 	r := &rtp.Packet{}
 	if err := r.Unmarshal(b[:i]); err != nil {
-		return nil, err
+		return nil, nil, err
 	}
-	return r, nil
+	return r, interceptor.Attributes{}, nil
 }
 
 // determinePayloadType blocks and reads a single packet to determine the PayloadType for this Track