Make TrackLocalContext an interface

This allows external users to provide their own TrackLocalContext to be
bound to a track.

rtpsender.go

@@ -27,7 +27,7 @@ type trackEncoding struct {
 	rtcpInterceptor interceptor.RTCPReader
 	streamInfo      interceptor.StreamInfo
 
-	context TrackLocalContext
+	context *baseTrackLocalContext
 
 	ssrc SSRC
 }
@@ -242,13 +242,13 @@ func (r *RTPSender) ReplaceTrack(track TrackLocal) error {
 	}
 
 	var replacedTrack TrackLocal
-	var context *TrackLocalContext
+	var context *baseTrackLocalContext
 	if len(r.trackEncodings) != 0 {
 		replacedTrack = r.trackEncodings[0].track
-		context = &r.trackEncodings[0].context
+		context = r.trackEncodings[0].context
 	}
 	if r.hasSent() && replacedTrack != nil {
-		if err := replacedTrack.Unbind(*context); err != nil {
+		if err := replacedTrack.Unbind(context); err != nil {
 			return err
 		}
 	}
@@ -258,16 +258,16 @@ func (r *RTPSender) ReplaceTrack(track TrackLocal) error {
 		return nil
 	}
 
-	codec, err := track.Bind(TrackLocalContext{
-		id:              context.id,
+	codec, err := track.Bind(&baseTrackLocalContext{
+		id:              context.ID(),
 		params:          r.api.mediaEngine.getRTPParametersByKind(track.Kind(), []RTPTransceiverDirection{RTPTransceiverDirectionSendonly}),
-		ssrc:            context.ssrc,
-		writeStream:     context.writeStream,
-		rtcpInterceptor: context.rtcpInterceptor,
+		ssrc:            context.SSRC(),
+		writeStream:     context.WriteStream(),
+		rtcpInterceptor: context.RTCPReader(),
 	})
 	if err != nil {
 		// Re-bind the original track
-		if _, reBindErr := replacedTrack.Bind(*context); reBindErr != nil {
+		if _, reBindErr := replacedTrack.Bind(context); reBindErr != nil {
 			return reBindErr
 		}
 
@@ -297,7 +297,7 @@ func (r *RTPSender) Send(parameters RTPSendParameters) error {
 
 	for idx, trackEncoding := range r.trackEncodings {
 		writeStream := &interceptorToTrackLocalWriter{}
-		trackEncoding.context = TrackLocalContext{
+		trackEncoding.context = &baseTrackLocalContext{
 			id:              r.id,
 			params:          r.api.mediaEngine.getRTPParametersByKind(trackEncoding.track.Kind(), []RTPTransceiverDirection{RTPTransceiverDirectionSendonly}),
 			ssrc:            parameters.Encodings[idx].SSRC,

track_local.go

@@ -19,7 +19,31 @@ type TrackLocalWriter interface {
 
 // TrackLocalContext is the Context passed when a TrackLocal has been Binded/Unbinded from a PeerConnection, and used
 // in Interceptors.
-type TrackLocalContext struct {
+type TrackLocalContext interface {
+	// CodecParameters returns the negotiated RTPCodecParameters. These are the codecs supported by both
+	// PeerConnections and the SSRC/PayloadTypes
+	CodecParameters() []RTPCodecParameters
+
+	// HeaderExtensions returns the negotiated RTPHeaderExtensionParameters. These are the header extensions supported by
+	// both PeerConnections and the SSRC/PayloadTypes
+	HeaderExtensions() []RTPHeaderExtensionParameter
+
+	// SSRC requires the negotiated SSRC of this track
+	// This track may have multiple if RTX is enabled
+	SSRC() SSRC
+
+	// WriteStream returns the WriteStream for this TrackLocal. The implementer writes the outbound
+	// media packets to it
+	WriteStream() TrackLocalWriter
+
+	// ID is a unique identifier that is used for both Bind/Unbind
+	ID() string
+
+	// RTCPReader returns the RTCP interceptor for this TrackLocal. Used to read RTCP of this TrackLocal.
+	RTCPReader() interceptor.RTCPReader
+}
+
+type baseTrackLocalContext struct {
 	id              string
 	params          RTPParameters
 	ssrc            SSRC
@@ -29,35 +53,35 @@ 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 {
+func (t *baseTrackLocalContext) CodecParameters() []RTPCodecParameters {
 	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 {
+func (t *baseTrackLocalContext) HeaderExtensions() []RTPHeaderExtensionParameter {
 	return t.params.HeaderExtensions
 }
 
 // SSRC requires the negotiated SSRC of this track
 // This track may have multiple if RTX is enabled
-func (t *TrackLocalContext) SSRC() SSRC {
+func (t *baseTrackLocalContext) SSRC() SSRC {
 	return t.ssrc
 }
 
 // WriteStream returns the WriteStream for this TrackLocal. The implementer writes the outbound
 // media packets to it
-func (t *TrackLocalContext) WriteStream() TrackLocalWriter {
+func (t *baseTrackLocalContext) WriteStream() TrackLocalWriter {
 	return t.writeStream
 }
 
 // ID is a unique identifier that is used for both Bind/Unbind
-func (t *TrackLocalContext) ID() string {
+func (t *baseTrackLocalContext) ID() string {
 	return t.id
 }
 
 // RTCPReader returns the RTCP interceptor for this TrackLocal. Used to read RTCP of this TrackLocal.
-func (t *TrackLocalContext) RTCPReader() interceptor.RTCPReader {
+func (t *baseTrackLocalContext) RTCPReader() interceptor.RTCPReader {
 	return t.rtcpInterceptor
 }