As the title of this article suggests I am going to pen my attempts of streaming / broadcasting Live Video WebRTC call to non WebRTC supported browsers and media players such as VLC , ffplay , default video player in Linux etc.
Some of the high level archietctures for streaming Webrtc Video to multiple endpoints can be viewed in the post below.
Aim : I will be attempting to create a lightweight WebRTC to raw/h264 transcoder by making my own media engine which takes input from WebRTC peerconnection or getusermedia. I am sharing my past experiments in hope of helping someone whose objective may be to acheive the same since many non webrtc supported endpoints ( Rpi , kisosks , mobile browsers ) could benifit heavily from webrtc streaming . Even if your objective is not the same as mine, you may gain some insigh on what not to do when making a media transcoder.
Attempt 1 : use one to many brodcasting API in js
<table class=”visible”><tr><td style=”text-align: right;”><input type=”text” id=”conference-name” placeholder=”Broadcast Name”> </td><td> <select id=”broadcasting-option”> <option>Audio + Video</option> <option>Only Audio</option> <option>Screen</option> </select> </td><td> <button id=”start-conferencing”>Start Broadcasting</button> </td> </tr></table><table id=”rooms-list” class=”visible”></table><div id=”participants”></div>http://âRTCPeerConnection-v1.5.jsâ http://âfirebase.jsâhttp://âbroadcast.jsâhttp://âbroadcast-ui.jsâ
It uses API fromwebrtc-experiment.com. The broadcast is in one direction only where the viewrs are never asked for their mic / webcam permission .
problem : The broadcast is for WebRTC browsers only and doesnt support non webrtc players / browsers
Attempt 1.1: Stream the media directly to nodejs through websocke
window.addEventListener('DOMContentLoaded', function () {
var v = document.getElementById('v');
navigator.getUserMedia = (navigator.getUserMedia ||
navigator.webkitGetUserMedia ||
navigator.mozGetUserMedia ||
navigator.msGetUserMedia);
if (navigator.getUserMedia) {
// Request access to video only
navigator.getUserMedia(
{
video: true,
audio: false
},
function (stream) {
var url = window.URL || window.webkitURL;
v.src = url ? url.createObjectURL(stream) : stream;
v.play();
var ws = new WebSocket('ws://localhost:3000', 'echo-protocol');
waitForSocketConnection(ws, function () {
console.log(" url.createObjectURL(stream)-----", url.createObjectURL(stream))
ws.send(stream);
console.log("message sent!!!");
});
},
function (error) {
alert('Something went wrong. (error code ' + error.code + ')');
return;
}
);
} else {
alert('Sorry, the browser you are using doesn\'t support getUserMedia');
return;
}
});
//Make the function wait until the connection is made...
function waitForSocketConnection(socket, callback) {
setTimeout(
function () {
if (socket.readyState === 1) {
console.log("Connection is made")
if (callback != null) {
callback();
}
return;
} else {
console.log("wait for connection...")
waitForSocketConnection(socket, callback);
}
}, 5); // wait 5 milisecond for the connection...
}
Problem : The video is in form of buffer and doesnot play
Attempt 2: Record the WebRTC media ( 5 secs each ) into chunks of webm format-> transfer them to other end -> append the chunks together like a regular file
This process involved the following components :
- Recorder Javascript library : RecordJs
- Transfer mechanism : Record using RecordRTC.js -> send to other end for media server -> stitching together the small webm files into big one at runtime and play
- Programs :
Code for video recorder
navigator.getUserMedia(videoConstraints, function (stream) {
video.onloadedmetadata = function () {
video.width = 320;
video.height = 240;
var options = {
type: isRecordVideo ? 'video' : 'gif',
video: video,
canvas: {
width: canvasWidth_input.value,
height: canvasHeight_input.value
}
};
recorder = window.RecordRTC(stream, options);
recorder.startRecording();
};
video.src = URL.createObjectURL(stream);
}, function () {
if (document.getElementById('record-screen').checked) {
if (location.protocol === 'http:')
alert('https is mandatory to capture screen.');
else
alert('Multi-capturing of screen is not allowed.Have you enabled flag: "Enable screen capture support in getUserMedia"?');
} else
alert('Webcam access is denied.');
});
Code for video append-er
var FILE1 = '1.webm';
var FILE2 = '2.webm';
var FILE3 = '3.webm';
var FILE4 = '4.webm';
var FILE5 = '5.webm';
var NUM_CHUNKS = 5;
var video = document.querySelector('video');
window.MediaSource = window.MediaSource || window.WebKitMediaSource;
if (!!!window.MediaSource) {
alert('MediaSource API is not available');
}
var mediaSource = new MediaSource();
video.src = window.URL.createObjectURL(mediaSource);
function callback(e) {
var sourceBuffer = mediaSource.addSourceBuffer('video/webm; codecs="vorbis,vp8"');
GET(FILE1, function (uInt8Array) {
var file = new Blob([uInt8Array], {type: 'video/webm'});
var i = 1;
(function readChunk_(i) {
var reader = new FileReader();
reader.onload = function (e) {
sourceBuffer.appendBuffer(new Uint8Array(e.target.result));
if (i == NUM_CHUNKS) mediaSource.endOfStream();
else {
if (video.paused) {
video.play(); // Start playing after 1st chunk is appended.
}
readChunk_(++i);
}
};
reader.readAsArrayBuffer(file);
})(i); // Start the recursive call by self calling.
});
}
mediaSource.addEventListener('sourceopen', callback, false);
mediaSource.addEventListener('webkitsourceopen', callback, false);
mediaSource.addEventListener('webkitsourceended', function (e) {
logger.log('mediaSource readyState: ' + this.readyState);
}, false);
// function get the video via XHR
function GET(url, callback) {
var xhr = new XMLHttpRequest();
xhr.open('GET', url, true);
xhr.responseType = 'arraybuffer';
xhr.send();
xhr.onload = function (e) {
if (xhr.status != 200) {
alert("Unexpected status code " + xhr.status + " for " + url);
return false;
}
callback(new Uint8Array(xhr.response));
};
}
Shortcoming of this approach
- The webm files failed to play on most of the media players
- The recorder can only either record video or audio file at a time .
Attempt 2.Chunking and media proxy
Since the previous approach failed to support on webrtc endpoinst , the next iteration of this approach was to channel the webrtc media via a nodejs server thus disrupting the peer to peer media strem in favour of centralized / proxied emdia stream. This would enable me to obtain raw media packets form teh stream using low level C based vp8 decoder libraries and then re encode them to h364 or other media formats suitable for endpoints .
In theory media could be reencoded jusing openH264 library and the frame could be then send to players
let mediaSource = new MediaSource();
let sourceBuffer = mediaSource.addSourceBuffer('video/mp4; codecs=vp9',
new VP9Decoder());
let buffer = await loadBuffer();
sourceBuffer.appendBuffer(buffer);
Further extending for uncompressed video
let mediaSource = new MediaSource();
let sourceBuffer = mediaSource.addSourceBuffer('video/raw; codecs=yuv420p');
for (let p in demuxPAckets()) {
let frame = await codec.decode(p);
sourceBuffer.appendBuffer(frame);
}
Atleast that was the plan .
Attempt 2.1: Record the WebRTC media ( 5 secs each ) into chunks of webm format ( RecordRTC.js) > Use Kurento JS script ( kws-media-api,js) to make a HTTP Endpoint to recorded Webm files -> append the chunks together like a regular file at runtime
// UI elements
function getByID(id) {
return document.getElementById(id);
}
var recordAudio = getByID('record-audio'),
recordVideo = getByID('record-video'),
stopRecordingAudio = getByID('stop-recording-audio'),
stopRecordingVideo = getByID('stop-recording-video'),
broadcasting = getByID('broadcasting');
var canvasWidth_input = getByID('canvas-width-input'),
canvasHeight_input = getByID('canvas-height-input');
var video = getByID('video');
var audio = getByID('audio');
// Audio video constraints
var videoConstraints = {
audio: false,
video: {
mandatory: {},
optional: []
}
};
var audioConstraints = {
audio: true,
video: false
};
// Recording and stop recording - to be convrted into real time capture and chunking
const ws_uri = 'ws://localhost:8888/kurento';
var URL_SMALL = "http://localhost:8080/streamtomp4/approach1/5561840332.webm";
var audioStream;
var recorder;
recordAudio.onclick = function () {
if (!audioStream)
navigator.getUserMedia(audioConstraints, function (stream) {
if (window.IsChrome) stream = new window.MediaStream(stream.getAudioTracks());
audioStream = stream;
audio.src = URL.createObjectURL(audioStream);
audio.muted = true;
audio.play();
// "audio" is a default type
recorder = window.RecordRTC(stream, {
type: 'audio'
});
recorder.startRecording();
}, function () {
});
else {
audio.src = URL.createObjectURL(audioStream);
audio.muted = true;
audio.play();
if (recorder) recorder.startRecording();
}
window.isAudio = true;
this.disabled = true;
stopRecordingAudio.disabled = false;
};
Recording and stop recording video inot small media files ( chunks )
recordVideo.onclick = function () {
recordVideoOrGIF(true);
};
stopRecordingAudio.onclick = function () {
this.disabled = true;
recordAudio.disabled = false;
audio.src = '';
if (recorder)
recorder.stopRecording(function (url) {
audio.src = url;
audio.muted = false;
audio.play();
document.getElementById('audio-url-preview').innerHTML = '&amp;amp;amp;lt;a href="' + url + '" target="_blank"&amp;amp;amp;gt;Recorded Audio URL&amp;amp;amp;lt;/a&amp;amp;amp;gt;';
});
};
function recordVideoOrGIF(isRecordVideo) {
navigator.getUserMedia(videoConstraints, function (stream) {
video.onloadedmetadata = function () {
video.width = 320;
video.height = 240;
var options = {
type: isRecordVideo ? 'video' : 'gif',
video: video,
canvas: {
width: canvasWidth_input.value,
height: canvasHeight_input.value
}
};
recorder = window.RecordRTC(stream, options);
recorder.startRecording();
};
video.src = URL.createObjectURL(stream);
}, function () {
if (document.getElementById('record-screen').checked) {
if (location.protocol === 'http:')
alert('&amp;amp;amp;lt;https&amp;amp;amp;gt; is mandatory to capture screen.');
else
alert('Multi-capturing of screen is not allowed. Capturing process is denied. Are you enabled flag: "Enable screen capture support in getUserMedia"?');
} else
alert('Webcam access is denied.');
});
window.isAudio = false;
if (isRecordVideo) {
recordVideo.disabled = true;
stopRecordingVideo.disabled = false;
} else {
recordGIF.disabled = true;
stopRecordingGIF.disabled = false;
}
}
stopRecordingVideo.onclick = function () {
this.disabled = true;
recordVideo.disabled = false;
if (recorder)
recorder.stopRecording(function (url) {
video.src = url;
video.play();
document.getElementById('video-url-preview').innerHTML = '&amp;amp;amp;lt;a href="' + url + '" target="_blank"&amp;amp;amp;gt;Recorded Video URL&amp;amp;amp;lt;/a&amp;amp;amp;gt;';
});
};
Broadcasting the chunks to media engine
function onerror(error) {
console.log(" error occured");
console.error(error);
}
broadcast.onclick = function () {
var videoOutput = document.getElementById("videoOutput");
KwsMedia(ws_uri, function (error, kwsMedia) {
if (error) return onerror(error);
// Create pipeline
kwsMedia.create('MediaPipeline', function (error, pipeline) {
if (error) return onerror(error);
// Create pipeline media elements (endpoints &amp;amp;amp;amp; filters)
pipeline.create('PlayerEndpoint', {uri: URL_SMALL}, function (error, player) {
if (error) return console.error(error);
pipeline.create('HttpGetEndpoint', function (error, httpGet) {
if (error) return onerror(error);
// Connect media element between them
player.connect(httpGet, function (error, pipeline) {
if (error) return onerror(error);
// Set the video on the video tag
httpGet.getUrl(function (error, url) {
if (error) return onerror(error);
videoOutput.src = url;
console.log(url);
// Start player
player.play(function (error) {
if (error) return onerror(error);
console.log('player.play');
});
});
});
// Subscribe to HttpGetEndpoint EOS event
httpGet.on('EndOfStream', function (event) {
console.log("EndOfStream event:", event);
});
});
});
});
}, onerror);
}
problem : dissecting the live video into small the files and appending to each other on reception is an expensive , time and resource consuming process . Also involves heavy buffering and other problems pertaining to real-time streaming .
Attempt 2.2 : Send the recorded chunks of webm to a port on linux server. Use socket programming to pick up these individual files and play using VLC player from UDP port of the Linux Server
End Result : Small file containers play but slow buffering makes this approach non compatible for streaming files chunks and appending as single file.
Attempt 2.3: Send the recorded chunks of webm to a port on linux server socket . Use socket programming to pick up these individual webm files and convert to H264 format so that they can be send to a media server.
This process involved the following components :
- Recorder Javascript library : RecordJs
- Transfer mechanism :WebRTC endpoint -> Call handler ( Record in chunks ) -> ffmpeg / gstreamer to put it on RTP -> streaming server like wowza – > viewers
- Programs : Use HTML webpage Webscoket connection -> nodejs program to write content from websocket to linux socket -> nodejs program to read that socket and print the content on console
Snippet to transfer the webm recorder files over websocket to nodejs program
// Make the function wait until the connection is made.
function waitForSocketConnection(socket, callback) {
setTimeout(
function () {
if (socket.readyState === 1) {
console.log("Connection is made")
if (callback != null)
callback();
} else {
console.log("wait for connection...")
waitForSocketConnection(socket, callback);
}
}, 5); // wait 5 milisecond for the connection...
}
function previewFile() {
var preview = document.querySelector('img');
var file = document.querySelector('input[type=file]').files[0];
var reader = new FileReader();
reader.onloadend = function () {
preview.src = reader.result;
console.log(" reader result ", reader.result);
var video = document.getElementById("v");
video.src = reader.result;
console.log(" video played ");
var ws = new WebSocket('ws://localhost:3000', 'echo-protocol');
waitForSocketConnection(ws, function () {
ws.send(reader.result);
console.log("message sent!!!");
});
}
if (file) {
// converts to base64 encoded string of the file data
//reader.readAsDataURL(file);
reader.readAsBinaryString(file);
} else {
preview.src = "";
}
}
Program for Linux Sockets sender which creates the socket for the webm files in nodejs
var net = require('net');
var fs = require('fs');
var socketPath = '/tmp/tfxsocket';
var http = require('http');
var stream = require('stream');
var util = require('util');
var WebSocketServer = require('ws').Server;
var port = 3000;
var serverUrl = "localhost";
var socket;
/*----------http server -----------*/
var server = http.createServer(function (request, response) {});
server.listen(port, serverUrl);
console.log('HTTP Server running at ', serverUrl, port);
/*------websocket server ----------*/
var wss = new WebSocketServer({server: server});
wss.on("connection", function (ws) {
console.log("websocket connection open");
ws.on('message', function (message) {
console.log(" stream recived from broadcast client on port 3000 ");
var s = require('net').Socket();
s.connect(socketPath);
s.write(message);
console.log(" send the stream to socketPath", socketPath);
});
ws.on("close", function () {
console.log("websocket connection close")
});
});
Program for Linux Socket Listener using nodejs and socket . Here the socket is in node /tmp/mysocket
var net = require('net');
var client = net.createConnection("/tmp/mysocket");
client.on("connect", function() {
console.log("connected to mysocket");
});
client.on("data", function(data) {
console.log(data);
});
client.on('end', function() {
console.log('server disconnected');
});
Output 1: Video Buffer displayed
Output 2 : Payload from Video displayed that shows the pipeline works but no output yet.
ffmpeg format of transfering the content from socket to UDP IP and port
ffmpeg -i unix://tmp/mysocket -f format udp://192.168.0.119:8083
problems of this approach : The video was on a passing stage from the socket and contained no information as such when tried to play / show console.
Attempt 3 : Use existing media engine like kurento to do the transocding for me
Send the live WebRTC stream from Kurento WebRTC endpoint to Kurento HTTP endpoint then play using Mozilla VLC web plugin
VLC mozilla plugin can be embedded by :
name="video2"
autoplay="yes" loop="no" hidden="no"
target="rtp://@192.165.0.119:8086" />
screenshot of failure on part of Mozilla VLC plugin to play from a WebRTC endpoint
problem : VLC mozilla plugin was unable to play the video and mozilla playback only was a difficult optio for most consumers .
Contnued on next article : continue : Streaming / broadcasting Live Video call to non webrtc supported browsers and media players
More article on simmilar topics
Telecom R & D 
great article . helped me a lot to complete my assignment .
especially the description of
Attempt 2.1: Record the WebRTC media ( 5 secs each ) into chunks of webm format ( RecordRTC.js) > Use Kurento JS script ( kws-media-api,js) to make a HTTP Endpoint to recorded Webm files -> append the chunks together like a regular file at runtime
However can u specify the Kurento version you are using for this ?
Thanks .
Hello robert I am using directly the master branch from kurento media server git repo . Right now the other stable branch is 4.3 .