Janus FTL Plugin

This is a work-in-progress Janus plugin to support the FTL "Faster-Than-Light" protocol developed for the Mixer live streaming service.

This protocol lets streamers deliver media to browser viewers with very low, often sub-second latency.

See my notes on the FTL protocol here.

Building

Dependencies

First, compile and install Janus.

Get Meson for building.

See the Dockerfile for the full set of dependencies.

Building

By default during build we look for Janus in /opt/janus (the default install path), but this can be configured with the JANUS_PATH env var.

mkdir build/
meson build/
cd build
ninja

Use GCC 10 compiler

This project utilizes some C++20 features available only in GCC 10 or newer.

If you are building on a recent Ubuntu distribution, you can install the gcc-10 and g++-10 packages and configure meson to use them for compilation:

CC=gcc-10 CXX=g++-10 meson build/

Building for production

To enable optimizations, set meson to build in debugoptimized mode (recommended over release mode so you can use the debug information to diagnose issues).

meson --buildtype=debugoptimized build/

If you've already previously configured meson, you can reconfigure it:

meson --reconfigure --buildtype=debugoptimized build/

Building on resource-constrained machines

Some machines (like the teensy tiny DigitalOcean droplet) will fail to finish building with the default Ninja build configuration.

Consider configuring Ninja to disable parallel builds to allow the build to finish successfully:

cd build
ninja -j 1

Also consider adding swap space if you have <2GB of RAM available.

Installing

(from build/ directory)

sudo ninja install

Running

Just fire up Janus (/opt/janus/bin/janus), and the FTL plugin should automatically load - you should see this output:

FTL: Plugin initialized!
[...]
FTL: Ingest server is listening on port 8084

Now you ought to be able to point an FTL client at the ingest server and start streaming.

The default stream key is 123456789-aBcDeFgHiJkLmNoPqRsTuVwXyZ123456.

123456789 can be whatever "Channel ID" you'd like.

aBcDeFgHiJkLmNoPqRsTuVwXyZ123456 can be overridden by setting the FTL_SERVICE_DUMMY_HMAC_KEY environment variable.

See DummyServiceConnection.cpp for the default stream key retrieval mechanism.

For watching your stream from a browser, see janus-ftl-player.

Configuration

Configuration is achieved through environment variables.

Dockering

docker build -t janus-ftl .
docker run --rm -p 8084:8084/tcp -p 8088:8088/tcp -p 9000-9100:9000-9100/udp -p 20000-20100:20000-20100/udp -e "DOCKER_IP=HOST.IP.ADDRESS.HERE" janus-ftl

systemd

This plugin will have systemd watchdog support if the libsystemd-dev package is installed. To enable this integration set WatchdogSec in your service unit file. The following is a sample service unit for running this plugin under systemd with reasonable defaults.

[Unit]
Description=Janus WebRTC Server with FTL support
Requires=network.target
After=syslog.target network.target

[Service]
Type=notify
ExecStart=/opt/janus/bin/janus -o
Restart=on-failure
RestartSec=10
WatchdogSec=60

LimitNOFILE=65536

[Install]
WantedBy=multi-user.target

Misc Notes

Streaming from OBS

Currently, there is no UI in OBS to set a custom FTL ingest endpoint.

In order to specify a custom FTL ingest server, you will need to edit the plugin_config\rtmp-services\services.json file. This is located in %AppData%\obs-studio\plugin_config\rtmp-services\services.json on Windows.

Add the following to the "services" array:

{
    "name": "YOUR NAME HERE",
    "common": false,
    "servers": [
        {
            "name": "SERVER NAME HERE",
            "url": "your.janus.hostname"
        }
    ],
    "recommended": {
        "keyint": 2,
        "output": "ftl_output",
        "max audio bitrate": 160,
        "max video bitrate": 8000,
        "profile": "main",
        "bframes": 0
    }
},

After you've made this change, you can start OBS and find your service listed in the OBS settings UI.

Include paths

If you use VS code with the C++ extension, these include paths should make intellisense happy.

"includePath": [
    "${workspaceFolder}/**",
    "/opt/janus/include/janus",
    "/usr/include/glib-2.0",
    "/usr/lib/x86_64-linux-gnu/glib-2.0/include"
]

License

Copyright (C) 2020  Hayden McAfee

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.