Use MediaEngine in janus-gateway/streaming

Since we are answering we should not depend on hardcoded PayloadTypes.
We should explore if we can move this internally, and figure out if we
can implement this without copying user input if PayloadType isn't know
at track creation time.

Resolves pion#35

Author: Sean-Der

janus-gateway/streaming/main.go

@@ -53,52 +53,6 @@ func watchHandle(handle *janus.Handle) {
 func main() {
 	// Everything below is the pion-WebRTC API! Thanks for using it ❤️.
 
-	// Prepare the configuration
-	config := webrtc.Configuration{
-		ICEServers: []webrtc.ICEServer{
-			{
-				URLs: []string{"stun:stun.l.google.com:19302"},
-			},
-		},
-		SDPSemantics: webrtc.SDPSemanticsUnifiedPlanWithFallback,
-	}
-
-	// Create a new RTCPeerConnection
-	peerConnection, err := webrtc.NewPeerConnection(config)
-	if err != nil {
-		panic(err)
-	}
-
-	// Allow us to receive 1 audio track, and 1 video track
-	if _, err = peerConnection.AddTransceiver(webrtc.RTPCodecTypeAudio); err != nil {
-		panic(err)
-	} else if _, err = peerConnection.AddTransceiver(webrtc.RTPCodecTypeVideo); err != nil {
-		panic(err)
-	}
-
-	peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
-		fmt.Printf("Connection State has changed %s \n", connectionState.String())
-	})
-
-	peerConnection.OnTrack(func(track *webrtc.Track, receiver *webrtc.RTPReceiver) {
-		codec := track.Codec()
-		if codec.Name == webrtc.Opus {
-			fmt.Println("Got Opus track, saving to disk as output.ogg")
-			i, oggNewErr := oggwriter.New("output.ogg", codec.ClockRate, codec.Channels)
-			if oggNewErr != nil {
-				panic(oggNewErr)
-			}
-			saveToDisk(i, track)
-		} else if codec.Name == webrtc.VP8 {
-			fmt.Println("Got VP8 track, saving to disk as output.ivf")
-			i, ivfNewErr := ivfwriter.New("output.ivf")
-			if ivfNewErr != nil {
-				panic(ivfNewErr)
-			}
-			saveToDisk(i, track)
-		}
-	})
-
 	// Janus
 	gateway, err := janus.Connect("ws://localhost:8188/")
 	if err != nil {
@@ -137,14 +91,64 @@ func main() {
 	}
 
 	if msg.Jsep != nil {
-		err = peerConnection.SetRemoteDescription(webrtc.SessionDescription{
+		offer := webrtc.SessionDescription{
 			Type: webrtc.SDPTypeOffer,
 			SDP:  msg.Jsep["sdp"].(string),
+		}
+
+		mediaEngine := webrtc.MediaEngine{}
+		if err = mediaEngine.PopulateFromSDP(offer); err != nil {
+			panic(err)
+		}
+
+		// Create a new RTCPeerConnection
+		var peerConnection *webrtc.PeerConnection
+		peerConnection, err = webrtc.NewAPI(webrtc.WithMediaEngine(mediaEngine)).NewPeerConnection(webrtc.Configuration{
+			ICEServers: []webrtc.ICEServer{
+				{
+					URLs: []string{"stun:stun.l.google.com:19302"},
+				},
+			},
+			SDPSemantics: webrtc.SDPSemanticsUnifiedPlanWithFallback,
 		})
 		if err != nil {
 			panic(err)
 		}
 
+		// Allow us to receive 1 audio track, and 1 video track
+		if _, err = peerConnection.AddTransceiver(webrtc.RTPCodecTypeAudio); err != nil {
+			panic(err)
+		} else if _, err = peerConnection.AddTransceiver(webrtc.RTPCodecTypeVideo); err != nil {
+			panic(err)
+		}
+
+		peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
+			fmt.Printf("Connection State has changed %s \n", connectionState.String())
+		})
+
+		peerConnection.OnTrack(func(track *webrtc.Track, receiver *webrtc.RTPReceiver) {
+			codec := track.Codec()
+			if codec.Name == webrtc.Opus {
+				fmt.Println("Got Opus track, saving to disk as output.ogg")
+				i, oggNewErr := oggwriter.New("output.ogg", codec.ClockRate, codec.Channels)
+				if oggNewErr != nil {
+					panic(oggNewErr)
+				}
+				saveToDisk(i, track)
+			} else if codec.Name == webrtc.VP8 {
+				fmt.Println("Got VP8 track, saving to disk as output.ivf")
+				i, ivfNewErr := ivfwriter.New("output.ivf")
+				if ivfNewErr != nil {
+					panic(ivfNewErr)
+				}
+				saveToDisk(i, track)
+			}
+		})
+
+		if err = peerConnection.SetRemoteDescription(offer); err != nil {
+			panic(err)
+		}
+
 		answer, answerErr := peerConnection.CreateAnswer(nil)
 		if answerErr != nil {
 			panic(answerErr)