Implement SFU example

`sfu` example shows how to build a simple broadcast only SFU

Resolves #63

examples/README.md

@@ -9,6 +9,7 @@ We've build an extensive collection of examples covering common use-cases. Modif
 * [save-to-disk](save-to-disk/README.md): Save video from your Webcam to disk
 * [data-channels](data-channels/README.md): Use data channels to send text between Pion WebRTC and your browser
 * [data-channels-create](data-channels/README.md): Similar to data channels but now Pion initiates the creation of the data channel.
+* [sfu](sfu/README.md): Broadcast a video to many peers, while only requiring the broadcaster to upload once
 * [WIP] [pion-to-pion](pion-to-pion/README.md): An example of two Pion instances communicating directly.
 
 All examples can be executed on your local machine.

examples/examples.json

@@ -28,5 +28,11 @@
 		"link": "save-to-disk",
 		"description": "save-to-disk is a simple application that shows how to record your webcam using pion-WebRTC and save to disk.",
 		"type": "browser"
+	},
+	{
+		"title": "SFU",
+		"link": "sfu",
+		"description": "sfu is a pion-WebRTC application that demonstrates how to broadcast a video to many peers, while only requiring the broadcaster to upload once.",
+		"type": "browser"
 	}
-]
+]

examples/sfu/README.md

@@ -0,0 +1,27 @@
+# sfu
+sfu is a pion-WebRTC application that demonstrates how to broadcast a video to many peers, while only requiring the broadcaster to upload once.
+
+This could serve as the building block to building conferencing software, and other applications where publishers are bandwidth constrained.
+
+## Instructions
+### Download sfu
+```
+go get github.com/pions/webrtc/examples/sfu
+```
+
+### Open sfu example page
+[jsfiddle.net](https://jsfiddle.net/5cwx0rns/) You should see two buttons 'Publish a Broadcast' and 'Join a Broadcast'
+
+### Run SFU
+#### Linux/macOS
+Run `sfu` OR run `main.go` in `github.com/pions/webrtc/examples/sfu`
+
+### Start a publisher
+Click `Publish a Broadcast` and paste the SDP into your terminal. The `sfu` application will respond with an offer, paste this into the second input field. Then press `Start Session`
+
+### Join the broadcast
+Click `Join a Broadcast` and paste the SDP into your terminal. The `sfu` application will respond with an offer, paste this into the second input field. Then press `Start Session`
+
+You can `Join the broadcast` as many times as you want. The `sfu` Golang application is relaying all traffic, so your browser only has to upload once.
+
+Congrats, you have used pion-WebRTC! Now start building something cool

examples/sfu/jsfiddle/demo.css

@@ -0,0 +1 @@
+

examples/sfu/jsfiddle/demo.details

@@ -0,0 +1,5 @@
+---
+ name: gstreamer-receive
+ description: Example of using pion-WebRTC to play video using GStreamer
+ authors:
+   - Sean DuBois

examples/sfu/jsfiddle/demo.html

@@ -0,0 +1,13 @@
+<video id="video1" width="160" height="120" autoplay muted></video> <br />
+
+
+<button class="createSessionButton" onclick="window.createSession(true)"> Publish a Broadcast </button>
+<button class="createSessionButton" onclick="window.createSession(false)"> Join a Broadcast </button>
+
+<div id="signalingContainer" style="display: none">
+  Browser base64 Session Description <textarea id="localSessionDescription" readonly="true"></textarea> <br />
+  Golang base64 Session Description: <textarea id="remoteSessionDescription"></textarea> <br/>
+  <button onclick="window.startSession()"> Start Session </button>
+</div>
+
+<div id="logs"></div>

examples/sfu/jsfiddle/demo.js

@@ -0,0 +1,62 @@
+/* eslint-env browser */
+var log = msg => {
+  document.getElementById('logs').innerHTML += msg + '<br>'
+}
+
+window.createSession = isPublisher => {
+  let pc = new RTCPeerConnection({
+    iceServers: [
+      {
+        urls: 'stun:stun.l.google.com:19302'
+      }
+    ]
+  })
+  pc.oniceconnectionstatechange = e => log(pc.iceConnectionState)
+  pc.onicecandidate = event => {
+    if (event.candidate === null) {
+      document.getElementById('localSessionDescription').value = btoa(pc.localDescription.sdp)
+    }
+  }
+
+  if (isPublisher) {
+    navigator.mediaDevices.getUserMedia({video: true, audio: false})
+      .then(stream => pc.addStream(document.getElementById('video1').srcObject = stream))
+      .catch(log)
+    pc.onnegotiationneeded = e => {
+      pc.createOffer()
+        .then(d => pc.setLocalDescription(d))
+        .catch(log)
+    }
+  } else {
+    pc.createOffer({offerToReceiveVideo: true})
+      .then(d => pc.setLocalDescription(d))
+      .catch(log)
+
+    pc.ontrack = function (event) {
+      var el = document.getElementById('video1')
+      el.srcObject = event.streams[0]
+      el.autoplay = true
+      el.controls = true
+    }
+  }
+
+  window.startSession = () => {
+    let sd = document.getElementById('remoteSessionDescription').value
+    if (sd === '') {
+      return alert('Session Description must not be empty')
+    }
+
+    try {
+      pc.setRemoteDescription(new RTCSessionDescription({type: 'answer', sdp: atob(sd)}))
+    } catch (e) {
+      alert(e)
+    }
+  }
+
+  let btns = document.getElementsByClassName('createSessionButton')
+  for (let i = 0; i < btns.length; i++) {
+    btns[i].style = 'display: none'
+  }
+
+  document.getElementById('signalingContainer').style = 'display: block'
+}

examples/sfu/main.go

@@ -0,0 +1,142 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"sync"
+	"time"
+
+	"bufio"
+	"encoding/base64"
+
+	"github.com/pions/webrtc"
+	"github.com/pions/webrtc/pkg/media"
+	"github.com/pions/webrtc/pkg/media/samplebuilder"
+	"github.com/pions/webrtc/pkg/rtcp"
+	"github.com/pions/webrtc/pkg/rtp/codecs"
+)
+
+var peerConnectionConfig = webrtc.RTCConfiguration{
+	IceServers: []webrtc.RTCIceServer{
+		{
+			URLs: []string{"stun:stun.l.google.com:19302"},
+		},
+	},
+}
+
+func check(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func mustReadStdin(reader *bufio.Reader) string {
+	rawSd, err := reader.ReadString('\n')
+	check(err)
+
+	fmt.Println("")
+	sd, err := base64.StdEncoding.DecodeString(rawSd)
+	check(err)
+
+	return string(sd)
+}
+
+const (
+	rtcpPLIInterval = time.Second * 3
+)
+
+func main() {
+	reader := bufio.NewReader(os.Stdin)
+	sd := mustReadStdin(reader)
+	fmt.Println("")
+
+	/* Everything below is the pion-WebRTC API, thanks for using it! */
+
+	// Only support VP8, this makes our proxying code simpler
+	webrtc.RegisterCodec(webrtc.NewRTCRtpVP8Codec(webrtc.DefaultPayloadTypeVP8, 90000))
+
+	// Create a new RTCPeerConnection
+	peerConnection, err := webrtc.New(peerConnectionConfig)
+	check(err)
+
+	outboundSamples := []chan<- media.RTCSample{}
+	var outboundSamplesLock sync.RWMutex
+	// Set a handler for when a new remote track starts, this just distributes all our packets
+	// to connected peers
+	peerConnection.OnTrack = func(track *webrtc.RTCTrack) {
+		// Send a PLI on an interval so that the publisher is pushing a keyframe every rtcpPLIInterval
+		// This is a temporary fix until we implement incoming RTCP events, then we would push a PLI only when a viewer requests it
+		go func() {
+			ticker := time.NewTicker(rtcpPLIInterval)
+			for {
+				select {
+				case <-ticker.C:
+					err := peerConnection.SendRTCP(&rtcp.PictureLossIndication{MediaSSRC: track.Ssrc})
+					if err != nil {
+						fmt.Println(err)
+					}
+				}
+			}
+		}()
+
+		// Transform RTP packets into samples, allowing us to distribute incoming packets from the publisher to everyone who has joined the broadcast
+		builder := samplebuilder.New(256, &codecs.VP8Packet{})
+		for {
+			outboundSamplesLock.RLock()
+			builder.Push(<-track.Packets)
+			for s := builder.Pop(); s != nil; s = builder.Pop() {
+				for _, outChan := range outboundSamples {
+					outChan <- *s
+				}
+			}
+			outboundSamplesLock.RUnlock()
+		}
+	}
+
+	// Set the remote SessionDescription
+	check(peerConnection.SetRemoteDescription(webrtc.RTCSessionDescription{
+		Type: webrtc.RTCSdpTypeOffer,
+		Sdp:  string(sd),
+	}))
+
+	// Sets the LocalDescription, and starts our UDP listeners
+	answer, err := peerConnection.CreateAnswer(nil)
+	check(err)
+
+	// Get the LocalDescription and take it to base64 so we can paste in browser
+	fmt.Println(base64.StdEncoding.EncodeToString([]byte(answer.Sdp)))
+
+	for {
+		fmt.Println("")
+		fmt.Println("Paste an SDP to start sendonly peer connection")
+		recvOnlyOffer := mustReadStdin(reader)
+
+		// Create a new RTCPeerConnection
+		peerConnection, err := webrtc.New(peerConnectionConfig)
+		check(err)
+
+		// Create a single VP8 Track to send videa
+		vp8Track, err := peerConnection.NewRTCTrack(webrtc.DefaultPayloadTypeVP8, "video", "pion2")
+		check(err)
+
+		_, err = peerConnection.AddTrack(vp8Track)
+		check(err)
+
+		outboundSamplesLock.Lock()
+		outboundSamples = append(outboundSamples, vp8Track.Samples)
+		outboundSamplesLock.Unlock()
+
+		// Set the remote SessionDescription
+		check(peerConnection.SetRemoteDescription(webrtc.RTCSessionDescription{
+			Type: webrtc.RTCSdpTypeOffer,
+			Sdp:  string(recvOnlyOffer),
+		}))
+
+		// Sets the LocalDescription, and starts our UDP listeners
+		answer, err := peerConnection.CreateAnswer(nil)
+		check(err)
+
+		// Get the LocalDescription and take it to base64 so we can paste in browser
+		fmt.Println(base64.StdEncoding.EncodeToString([]byte(answer.Sdp)))
+	}
+}