Add examples/rtcp-processing

rtcp-processing demonstrates how to access RTCP Packets via ReadRTCP

Resolves #2027

examples/rtcp-processing/README.md

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+# rtcp-processing
+rtcp-processing demonstrates the Public API for processing RTCP packets in Pion WebRTC.
+
+This example is only processing messages for a RTPReceiver. A RTPReceiver is used for accepting
+media from a remote peer.  These APIs also exist on the RTPSender when sending media to a remote peer.
+
+RTCP is used for statistics and control information for media in WebRTC. Using these messages
+you can get information about the quality of the media, round trip time and packet loss. You can
+also craft messages to influence the media quality.
+
+## Instructions
+### Download rtcp-processing
+```
+export GO111MODULE=on
+go get github.com/pion/webrtc/v3/examples/rtcp-processing
+```
+
+### Open rtcp-processing example page
+[jsfiddle.net](https://jsfiddle.net/Le3zg7sd/) you should see two text-areas, 'Start Session' button and 'Copy browser SessionDescription to clipboard'
+
+### Run rtcp-processing with your browsers Session Description as stdin
+In the jsfiddle press 'Copy browser Session Description to clipboard' or copy the base64 string manually.
+
+Now use this value you just copied as the input to `rtcp-processing`
+
+#### Linux/macOS
+Run `echo $BROWSER_SDP | rtcp-processing`
+#### Windows
+1. Paste the SessionDescription into a file.
+1. Run `rtcp-processing < my_file`
+
+### Input rtcp-processing's Session Description into your browser
+Copy the text that `rtcp-processing` just emitted and copy into the second text area in the jsfiddle
+
+### Hit 'Start Session' in jsfiddle
+You will see console messages for each inbound RTCP message from the remote peer.
+
+Congrats, you have used Pion WebRTC! Now start building something cool

examples/rtcp-processing/jsfiddle/demo.css

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+textarea {
+    width: 500px;
+    min-height: 75px;
+}

examples/rtcp-processing/jsfiddle/demo.details

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+---
+ name: rtcp-processing
+ description: play-from-disk demonstrates how to process RTCP messages from Pion WebRTC
+ authors:
+   - Sean DuBois

examples/rtcp-processing/jsfiddle/demo.html

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+Browser Session Description
+<br/>
+<textarea id="localSessionDescription" readonly="true"></textarea>
+<br/>
+
+<button onclick="window.copySessionDescription()">Copy browser Session Description to clipboard</button>
+
+<br/>
+<br/>
+<br/>
+
+Remote Session Description
+<br/>
+<textarea id="remoteSessionDescription"></textarea>
+<br/>
+<button onclick="window.startSession()">Start Session</button>
+<br/>
+<br/>
+
+Video<br />
+<video id="video1" width="160" height="120" autoplay muted></video> <br />
+
+Logs
+<br/>
+<div id="div"></div>

examples/rtcp-processing/jsfiddle/demo.js

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+/* eslint-env browser */
+
+const pc = new RTCPeerConnection({
+  iceServers: [{
+    urls: 'stun:stun.l.google.com:19302'
+  }]
+})
+const log = msg => {
+  document.getElementById('div').innerHTML += msg + '<br>'
+}
+
+pc.ontrack = function (event) {
+  const el = document.createElement(event.track.kind)
+  el.srcObject = event.streams[0]
+  el.autoplay = true
+  el.controls = true
+
+  document.getElementById('remoteVideos').appendChild(el)
+}
+
+pc.oniceconnectionstatechange = e => log(pc.iceConnectionState)
+pc.onicecandidate = event => {
+  if (event.candidate === null) {
+    document.getElementById('localSessionDescription').value = btoa(JSON.stringify(pc.localDescription))
+  }
+}
+
+navigator.mediaDevices.getUserMedia({ video: true, audio: true })
+  .then(stream => {
+    document.getElementById('video1').srcObject = stream
+    stream.getTracks().forEach(track => pc.addTrack(track, stream))
+
+    pc.createOffer().then(d => pc.setLocalDescription(d)).catch(log)
+  }).catch(log)
+
+window.startSession = () => {
+  const sd = document.getElementById('remoteSessionDescription').value
+  if (sd === '') {
+    return alert('Session Description must not be empty')
+  }
+
+  try {
+    pc.setRemoteDescription(new RTCSessionDescription(JSON.parse(atob(sd))))
+  } catch (e) {
+    alert(e)
+  }
+}
+
+window.copySessionDescription = () => {
+  const browserSessionDescription = document.getElementById('localSessionDescription')
+
+  browserSessionDescription.focus()
+  browserSessionDescription.select()
+
+  try {
+    const successful = document.execCommand('copy')
+    const msg = successful ? 'successful' : 'unsuccessful'
+    log('Copying SessionDescription was ' + msg)
+  } catch (err) {
+    log('Oops, unable to copy SessionDescription ' + err)
+  }
+}

examples/rtcp-processing/main.go

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+// +build !js
+
+package main
+
+import (
+	"fmt"
+
+	"github.com/pion/webrtc/v3"
+	"github.com/pion/webrtc/v3/examples/internal/signal"
+)
+
+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"},
+			},
+		},
+	}
+
+	// Create a new RTCPeerConnection
+	peerConnection, err := webrtc.NewPeerConnection(config)
+	if err != nil {
+		panic(err)
+	}
+
+	// Set a handler for when a new remote track starts
+	peerConnection.OnTrack(func(track *webrtc.TrackRemote, receiver *webrtc.RTPReceiver) {
+		fmt.Printf("Track has started streamId(%s) id(%s) rid(%s) \n", track.StreamID(), track.ID(), track.RID())
+
+		for {
+			// Read the RTCP packets as they become available for our new remote track
+			rtcpPackets, _, rtcpErr := receiver.ReadRTCP()
+			if rtcpErr != nil {
+				panic(rtcpErr)
+			}
+
+			for _, r := range rtcpPackets {
+				// Print a string description of the packets
+				if stringer, canString := r.(fmt.Stringer); canString {
+					fmt.Printf("Received RTCP Packet: %v", stringer.String())
+				}
+			}
+		}
+	})
+
+	// Set the handler for ICE connection state
+	// This will notify you when the peer has connected/disconnected
+	peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
+		fmt.Printf("Connection State has changed %s \n", connectionState.String())
+	})
+
+	// Wait for the offer to be pasted
+	offer := webrtc.SessionDescription{}
+	signal.Decode(signal.MustReadStdin(), &offer)
+
+	// Set the remote SessionDescription
+	err = peerConnection.SetRemoteDescription(offer)
+	if err != nil {
+		panic(err)
+	}
+
+	// Create answer
+	answer, err := peerConnection.CreateAnswer(nil)
+	if err != nil {
+		panic(err)
+	}
+
+	// Create channel that is blocked until ICE Gathering is complete
+	gatherComplete := webrtc.GatheringCompletePromise(peerConnection)
+
+	// Sets the LocalDescription, and starts our UDP listeners
+	err = peerConnection.SetLocalDescription(answer)
+	if err != nil {
+		panic(err)
+	}
+
+	// Block until ICE Gathering is complete, disabling trickle ICE
+	// we do this because we only can exchange one signaling message
+	// in a production application you should exchange ICE Candidates via OnICECandidate
+	<-gatherComplete
+
+	// Output the answer in base64 so we can paste it in browser
+	fmt.Println(signal.Encode(*peerConnection.LocalDescription()))
+
+	// Block forever
+	select {}
+}