This article is to introduce Janus based SFU media architecture for WebRTC systems. It also aims at evaluating the performance of the VP9 simulcast p2p model with Janus based SFU system.


We know Janus is a popular small footprint gateway/media Server with support for WebRTC features like JSEP/SDP, ICE, DTLS-SRTP, DataChannels. Its plugins expose Janus API over different transports – HTTP, WS, rabbitMQ, Unix sockets, MQTT so on. Other plugins provide deeper modifications such as Video SFU, Audio MCU, SIP/RTSP gateways, broadcasting etc.

Centralised media conferencing / mixing service using Janus

Streaming Video via CDN

Tip : use mixing for Audio and Relay for video in large participant sessions.

Server Selection and Setup from source

Janus Setup on public ec2 isntance. Since the a media server can clog the server space make sure to choose alarge instance like c5.large. Sample log file size

Install prerequisite libraries

sudo apt-get install libmicrohttpd-dev libjansson-dev libnice-dev libssl-dev libsrtp-dev libsofia-sip-ua-dev libglib2.0-dev libopus-dev libogg-dev libini-config-dev libcollection-dev libwebsockets-dev pkg-config gengetopt automake libtool doxygen graphviz git libconfig-dev cmake

Make Sure libsrtp v2.x is installed instead of existing 1.4 in debain /ubuntu default such as

libsrtp0-dev is already the newest version (1.4.5~20130609~dfsg-2ubuntu1).

Manually installing libsrtp2 from https://github.com/cisco/libsrtp

wget https://github.com/cisco/libsrtp/archive/v2.2.0.tar.gz
tar xfv v2.2.0.tar.gz
cd libsrtp-2.2.0
./configure --prefix=/usr --enable-openssl
make shared_library && sudo make install

Since we are going to use websocket as signalling, ensure lws (libwebsocket) >= 2.0.0 is installed

git clone https://libwebsockets.org/repo/libwebsockets
cd libwebsockets
mkdir build
cd build
make && sudo make install

Also libnice (at least v0.1.16) need to be installed

Get Janus source code and configure

git clone git://github.com/meetecho/janus-gateway.git
cd janus-gateway
sh autogen.sh
--prefix=/opt/janus LDFLAGS="-L/usr/local/lib -Wl,-rpath=/usr/local/lib" CFLAGS="-I/usr/local/include"

At this point Janus prinst a config detail such as below and asks if its ok . Ensure Websocket is yes. One can start the make process if it is

Compiler:                  gcc
libsrtp version:           2.x
SSL/crypto library:        OpenSSL
DTLS set-timeout:          not available
Mutex implementation:      GMutex (native futex on Linux)
DataChannels support:      no
Recordings post-processor: no
TURN REST API client:      no
Doxygen documentation:     no
    REST (HTTP/HTTPS):     yes
    WebSockets:            yes
    RabbitMQ:              no
    MQTT:                  no
    Unix Sockets:          yes
    Nanomsg:               no
    Echo Test:             yes
    Streaming:             yes
    Video Call:            yes
    SIP Gateway:           yes
    NoSIP (RTP Bridge):    yes
    Audio Bridge:          yes
    Video Room:            yes
    Voice Mail:            yes
    Record&Play:           yes
    Text Room:             yes
    Lua Interpreter:       no
    Duktape Interpreter:   no
Event handlers:
    Sample event handler:  no
    WebSocket ev. handler: yes
    RabbitMQ event handler:no
    MQTT event handler:    no
    Nanomsg event handler: no
    GELF event handler:    yes
External loggers:
    JSON file logger:      no
JavaScript modules:        no

Make and install

make && sudo make install

Making configs

sudo make configs

For details refer to actual README on Janus git repo https://github.com/meetecho/janus-gateway


By default, Janus starts in foreground, as a console application that stop with Ctrl + c command


Starting janus as backvroudn or daemon service

sudo ./janus -N -d 0 --daemon --log-file /var/log/janus

tailing the log file

> tail -f /var/log/janus
  Starting Meetecho Janus (WebRTC Server) v0.11.1

Checking command line arguments...
Debug/log level is 0
Debug/log timestamps are disabled
Debug/log colors are enabled

references : https://janus.conf.meetecho.com/docs/service.html

Issues with installation of janus

Before resolving any issue, it is important to verify whether you are runing multiple versions of janus on your system

altanai@xx:~/janus-gateway$ janus --version
Janus commit: bed081c03ad4854f3956898646198100a8ed82cf
Compiled on:  Fri Apr  2 07:28:14 UTC 2021

janus 0.11.1

altanai@xx:~/janus-gateway$ ./janus --version
Janus commit: c970528037d46d52a4bc1fd7db2a44c900c2baf2
Compiled on:  Thu Apr  8 18:01:36 UTC 2021

janus 0.10.8

If this is so, delete the one you dont require. I’d go with rmeoove the one installed globally.

Cmake version error

If you see an error in rabbitmq instalation , which is part of janus installation

CMake 3.12...3.18 or higher is required.  You are running version 3.10.2

then proceed to remove existing version and install updates ne by first removing tghe existing cmake version

sudo apt remove cmake
wget https://github.com/Kitware/CMake/releases/download/v3.20.1/cmake-3.20.1-linux-x86_64.sh
sh cmake-3.20.1-linux-x86_64.sh

check version

>> cmake-3.20.1-linux-x86_64/bin/cmake --version
cmake version 3.20.1

lib websocket error in libjanus_websockets.so

Couldn't load transport plugin 'libjanus_websockets.so': /opt/janus/lib/janus/transports/libjanus_websockets.so: undefined symbol: lws_hdr_custom_length

Libwebsockets (LWS) is a flexible, lightweight pure C library for implementing modern network protocols easily with a tiny footprint, using a nonblocking event loop.

Fisrt check the version of libwebsockets u have on ur machine . If it is lesse that 2.0.0 version

>> apt show libwebsockets-dev

Package: libwebsockets-dev
Version: 2.0.3-3build1
Priority: optional
Section: universe/libdevel
Source: libwebsockets
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: Laszlo Boszormenyi (GCS) <gcs@debian.org>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 502 kB
Depends: libwebsockets8 (= 2.0.3-3build1), libev-dev, libssl-dev, libuv1-dev, zlib1g-dev
Homepage: https://libwebsockets.org/
Download-Size: 133 kB
APT-Manual-Installed: yes
APT-Sources: http://us-west-1.ec2.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
Description: lightweight C websockets library - development files
 Libwebsockets is a lightweight pure C library for both websockets
 clients and servers built to use minimal CPU and memory resources
 and provide fast throughput in both directions.
 This package contains the header files needed for developing programs
 using libwebsockets and a static library.

Follow the steps to install libwebsocket ,  libwebsockets >= 2.0.0, the current v3.2-stable is good http://libwebsockets.org/

Failures due to ICE

ICE failed for component 1 in stream 1… 
No WebRTC media anymore
 WebRTC resources freed;

Self Signed SSL certs

Make a new directory for SSL certs

mkdir /home/ubuntu/ssl

generate certs 

openssl req -new -newkey rsa:4096 -nodes -keyout key.pem -out cert.csr
openssl x509 -req -sha256 -days 365 -in cert.csr -signkey key.pem -out cert.pem
chmod 600 cert.csr
chmod 600 cert.pem
chmod 600 key.pem

Remember to allow advanced access if the ssl are self signed and not from a varified CA

Update janus config

Path for Janus configuration is usually /opt/janus/etc/janus/janus.jcfg as given by the prefix during instalation. some of the types of config are

>> vi /opt/janus/etc/janus/janus.jcfg
general: {
   configs_folder = "/opt/janus/etc/janus" # Configuration files folder
   plugins_folder = "/opt/janus/lib/janus/plugins" # Plugins folder
   transports_folder = "/opt/janus/lib/janus/transports" # Transports folder
   events_folder = "/opt/janus/lib/janus/events" # Event handlers folder
   loggers_folder = "/opt/janus/lib/janus/loggers" # External loggers folder
  • SSL certs for DTLS can also be specified under certificates
  • Restricting media ports between a range . Comes in handy when u have to selectively open ports ona cloud instance such as AWS instance
media: {
        ipv6 = false
        #min_nack_queue = 500
        rtp_port_range = "20000-40000"
        #dtls_mtu = 1200
        #no_media_timer = 1
        #slowlink_threshold = 4
        #twcc_period = 100
        #dtls_timeout = 500
  • changing NAT for STUN/TURN servers to gather ICE

using 1:1 NAT( suited to Amzon EC2) requires specifying public address

nat_1_1_mapping = ""
  • To change transport http , set http to true from false

goto installation location for janus config

cd /opt/janus/etc/janus/
> vi /opt/janus/etc/janus/janus.transport.http.jcfg

general: {
    #events = true                 # Whether to notify event handlers about transport events (default=true)
    json = "indented"              # Whether the JSON messages should be indented (default),
                                   # plain (no indentation) or compact (no indentation and no spaces)
    base_path = "/janus"           # Base path to bind to in the web server (plain HTTP only)
    http = true                    # Whether to enable the plain HTTP interface
    port = 8088                    # Web server HTTP port
    #interface = "eth0"            # Whether we should bind this server to a specific interface onlya
    #ip = "x.x.x.x"                # Whether we should bind this server to a specific IP address (v4 or v6) only
    https = true                   # Whether to enable HTTPS (default=false)
    secure_port = 8089             # Web server HTTPS port, if enabled
    #secure_interface = "eth0"     # Whether we should bind this server to a specific interface only
    #secure_ip = ""     # Whether we should bind this server to a specific IP address (v4 or v6) only
    #acl = "127.,192.168.0."       # Only allow requests coming from this comma separated list of addresses

Change path for certs and key pem files

> vi janus.jcfg

certificates: {
        cert_pem = "/home/ubuntu/ssl/cert.pem"
        cert_key = "/home/ubutu/ssl/key.pem"
        #cert_pwd = "secretpassphrase"
        #dtls_accept_selfsigned = false
        #dtls_ciphers = "your-desired-openssl-ciphers"
        #rsa_private_key = false
      #ciphers = "PFS:-VERS-TLS1.0:-VERS-TLS1.1:-3DES-CBC:-ARCFOUR-128"

There are options for other ciphers and passphrass , leave them for now.

  • To change transport ws for websocket
general: {
        #events = true            # Whether to notify event handlers about transport events (default=true)
        json = "indented"         # Whether the JSON messages should be indented (default),
                                  # plain (no indentation) or compact (no indentation and no spaces)
        #pingpong_trigger = 30    # After how many seconds of idle, a PING should be sent
        #pingpong_timeout = 10    # After how many seconds of not getting a PONG, a timeout should be detected

        ws = true                 # Whether to enable the WebSockets API
        ws_port = 8188            # WebSockets server port
        #ws_interface = "eth0"    # Whether we should bind this server to a specific interface only
        #ws_ip = ""    # Whether we should bind this server to a specific IP address only
        wss = true                # Whether to enable secure WebSockets
        wss_port = 8989           # WebSockets server secure port, if enabled
        #wss_interface = "eth0"   # Whether we should bind this server to a specific interface only
        #wss_ip = ""   # Whether we should bind this server to a specific IP address only
        #ws_logging = "err,warn"  # libwebsockets debugging level as a comma separated list of things
                                  # to debug, supported values: err, warn, notice, info, debug, parser,
                                  # header, ext, client, latency, user, count (plus 'none' and 'all')
        #ws_acl = "127.,192.168.0." # Only allow requests coming from this comma separated list of addresses

Simillar to http transport conf above , also update the certs section with valid path for ssl certs

Check Janus Running

Running ports check ( http )

> sudo lsof -i  | grep janus
janus     26450          ubuntu    7u  IPv6 418550      0t0  UDP *:rfe 
janus     26450          ubuntu    8u  IPv6 418551      0t0  UDP *:5004 
janus     26450          ubuntu   17u  IPv6 418557      0t0  TCP *:omniorb (LISTEN)
janus     26450          ubuntu   20u  IPv6 672518      0t0  TCP *:8089 (LISTEN)
janus     26450          ubuntu   24u  IPv4 672519      0t0  TCP *:8188 (LISTEN)
janus     26450          ubuntu   25u  IPv4 672520      0t0  TCP *:8989 (LISTEN) 

Janus INFO

Going to deployed janus URL like http://x.x.x.x:8088/janus/info

   "janus": "server_info",
   "transaction": "rGuo8HNI4wu",
   "name": "Janus WebRTC Gateway",
   "version": 26,
   "version_string": "0.2.6",
   "author": "Meetecho s.r.l.",
   "commit-hash": "not-a-git-repo",
   "compile-time": "Wed Feb 28 07:02:15 UTC 2018",
   "log-to-stdout": true,
   "log-to-file": false,
   "data_channels": false,
   "session-timeout": 60,
   "server-name": "MyJanusInstance",
   "local-ip": "x.x.x.x",
   "ipv6": false,
   "ice-lite": false,
   "ice-tcp": false,
   "api_secret": false,
   "auth_token": false,
   "event_handlers": false,
   "transports": {
      "janus.transport.http": {
         "name": "JANUS REST (HTTP/HTTPS) transport plugin",
         "author": "Meetecho s.r.l.",
         "description": "This transport plugin adds REST (HTTP/HTTPS) support to the Janus API via libmicrohttpd.",
         "version_string": "0.0.2",
         "version": 2
      "janus.transport.websockets": {
         "name": "JANUS WebSockets transport plugin",
         "author": "Meetecho s.r.l.",
         "description": "This transport plugin adds WebSockets support to the Janus API via libwebsockets.",
         "version_string": "0.0.1",
         "version": 1
   "events": {},
   "plugins": {
      "janus.plugin.voicemail": {
         "name": "JANUS VoiceMail plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a plugin implementing a very simple VoiceMail service for Janus, recording Opus streams.",
         "version_string": "0.0.6",
         "version": 6
      "janus.plugin.audiobridge": {
         "name": "JANUS AudioBridge plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a plugin implementing an audio conference bridge for Janus, mixing Opus streams.",
         "version_string": "0.0.10",
         "version": 10
      "janus.plugin.echotest": {
         "name": "JANUS EchoTest plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a trivial EchoTest plugin for Janus, just used to showcase the plugin interface.",
         "version_string": "0.0.7",
         "version": 7
      "janus.plugin.recordplay": {
         "name": "JANUS Record&amp;Play plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a trivial Record&amp;Play plugin for Janus, to record WebRTC sessions and replay them.",
         "version_string": "0.0.4",
         "version": 4
      "janus.plugin.textroom": {
         "name": "JANUS TextRoom plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a plugin implementing a text-only room for Janus, using DataChannels.",
         "version_string": "0.0.2",
         "version": 2
      "janus.plugin.videoroom": {
         "name": "JANUS VideoRoom plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a plugin implementing a videoconferencing SFU (Selective Forwarding Unit) for Janus, that is an audio/video router.",
         "version_string": "0.0.9",
         "version": 9
      "janus.plugin.sipre": {
         "name": "JANUS SIPre plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a simple SIP plugin for Janus (based on libre instead of Sofia), allowing WebRTC peers to register at a SIP server and call SIP user agents through the gateway.",
         "version_string": "0.0.1",
         "version": 1
      "janus.plugin.videocall": {
         "name": "JANUS VideoCall plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a simple video call plugin for Janus, allowing two WebRTC peers to call each other through the gateway.",
         "version_string": "0.0.6",
         "version": 6
      "janus.plugin.streaming": {
         "name": "JANUS Streaming plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a streaming plugin for Janus, allowing WebRTC peers to watch/listen to pre-recorded files or media generated by gstreamer.",
         "version_string": "0.0.8",
         "version": 8
      "janus.plugin.nosip": {
         "name": "JANUS NoSIP plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a simple RTP bridging plugin that leaves signalling details (e.g., SIP) up to the application.",
         "version_string": "0.0.1",
         "version": 1
      "janus.plugin.sip": {
         "name": "JANUS SIP plugin",
         "author": "Meetecho s.r.l.",
         "description": "This is a simple SIP plugin for Janus, allowing WebRTC peers to register at a SIP server and call SIP user agents through the gateway.",
         "version_string": "0.0.7",
         "version": 7


An Echo test is part of Janus and can be done via reached via deployed server url https://x.x.x.x:8084/echotest.html

For a valid SDP message notice the contact headers in chrome://webrtc-internals

Local Description (mungled)

O line represents origin

type: offer, sdp: v=0
o=- 1331622865522329207 2 IN IP4

Audio Media stream in m line 

m=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 0 8 106 105 13 110 112 113 126
c=IN IP4

Video media stream in m line 

m=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 100 101 102 122 127 121 125 107 108 109 124 120 123
c=IN IP4


m=application 9 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4

Remote Description

Origin Line

type: answer, sdp: v=0
o=- 6397148042001786590 2 IN IP4

Audio Stream

m=audio 9 UDP/TLS/RTP/SAVPF 111 9 0 8 106 105 13 110 112 113
c=IN IP4

Video Stream

m=video 9 UDP/TLS/RTP/SAVPF 96 98 100 102 127 125 108 97 99 101 122 121 107 109
c=IN IP4


m=application 0 UDP/DTLS/SCTP 0
c=IN IP4

VideoCall – https://x.x.x.x:8084/videocalltest.html



Plugin (above ) and then procceeds to join the room ( screenshot below)

After this Janus procced to do JSEP offer / answer signalling with ICE checks and then does keepalive checks for the duraion of the session .

Stream Types





LD Libbary Path Exception

If you see an missing encryption exception , start janus with LD_LIBRARY_PATH

export LD_LIBRARY_PATH=/usr/lib && /opt/janus/bin/janus --debug-level=7 --stun-server=stun.l.google.com:19302 --event-handlers --full-trickle

ICE resolution in Runtime

Trickle ICE Command Line params give console output as

    general: {
        debug_level: 7
    certificates: {
    nat: {
        stun_server: stun.l.google.com
        stun_port: 19302
        full_trickle: true
    media: {
    transports: {
    plugins: {
    events: {
        broadcast: yes
    loggers: {

With NAT 1:1 mapping

export LD_LIBRARY_PATH=/usr/lib && /opt/janus/bin/janus --debug-level=7 --nat-1-1= --stun-server=stun.l.google.com:19302 --rtp-port-range=20000-50000 

1 to 1 NAT mpapping coordinates with amazon ec2

    general: {
        debug_level: 7
    certificates: {
    nat: {
    media: {
        rtp_port_range: 20000-50000
    transports: {
    plugins: {
    events: {
    loggers: {

WebRTC Client for Janus System

Test client

Using the html sample clients

cd html
admin.html            citeus.html      e2etest.html   index.html      nosiptest.html          siptest.html        textroomtest.html   voicemailtest.html audiobridgetest.html  demos.html       echotest.html  multiopus.html  recordplaytest.html     streamingtest.html  videocalltest.html  vp9svctest.html canvas.html           devicetest.html  footer.html    navbar.html     screensharingtest.html  support.html        videoroomtest.html

check lsb release and then Install Nodejs to host client page

>> lsb_release -a
curl -sL https://deb.nodesource.com/setup_15.x | sudo -E bash -
sudo apt-get install -y nodejs

Http WebServer

npm init
npm install http-server

To be able to compile native addons from npm you’ll need to install the development tools:

sudo apt install build-essential

open the client in webrtc supported browser at http://x.x.x.x:8080/videoroomtest.html

If you see a issues

 No WebRTC media anymore; 0x7fbe20001a40 0x7fbe20002440
 WebRTC resources freed; 0x7fbe20001a40 0x7fbe20001320
 Handle and related resources freed; 0x7fbe20001a40 0x7fbe20001320

Then it is likley a NAT issues and you should look at jcfg config file to see whether the interface is specified corectly

# Generic settings
interface = "x.x.x.x"                                     # Interface to use (will be used in SDP)
server_name = "WebrtcMCUJanus"                                  # Public name of this Janus instance

Security consideration before taking janus live

Hide the dependencies

hide_dependencies = true  

By default, a call to the “info” endpoint of either the Janus or Admin API now als returns the versions of the main dependencies (e.g., libnice, libsrtp, which crypto library is in use and so on). Should you want that info not to be disclose, set ‘hide_dependencies’ to true.

Common spam attack. source https://groups.google.com/g/meetecho-janus/c/IcJd3e4V1F8

Issues : Janus is throwing an error Invalid url /ws/v1/cluster/apps/new-application

Possible solution : changing port of http transport


To read more about Media Archietctures and topologies such as point-point , point-to-multipoint , multicast , translators, mixers and SFU goto :

Media Architecture, RTP topologies

With the sudden onset of Covid-19 and building trend of working-from-home , the demand for building scalable conferncing solution and virtual meeting room has skyrocketed . Here is my advice if you are building a auto- scalable conferencing solution

To read more on the topologies of conferencing systems ( Mesh vs Star , Unicast vs Multicast and SVC) read :

SIP conferencing and Media Bridges

SIP is the most popular signalling protocol in VOIP ecosystem. It is most suited to a caller-callee scenario , yet however supporting scalable conferences on VOIP is a market demand. It is desired that SIP must for multimedia stream but also provide conference control for building communication and collaboration apps for new and customisable solutions.

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