Mumble Discord Bridge

Mumble Discord Bridge is an open source Go application to bridge the audio and chat between Mumble and Discord.

It was built with the idea that people can continue to use the voice application of their choice.

New BridgeLib Architecture

The project now includes a modular library (pkg/bridgelib) that enables multiple bridge instances to share a single Discord client.

Key features of the new architecture:

• Shared Discord client (bot) for multiple bridge instances
• Proper message routing between Discord and bridge instances
• Consistent behavior between single and multi-bridge deployments
• DAVE E2EE support (Discord Audio & Video End-to-End Encryption)
• Used by the patchcord.io multi-bridge service 😄

PatchCord.io

Mumble Discord Bridge can be hosted on any server or computer and ships in a Docker container for convenience.

For those looking for SaaS solution take a look at patchcord.io. patchcord.io offers a free tier for those who want to try out Mumble Discord Bridge, and paid tiers for those who want to handle larger communities.

Usage

Several configuration variables are required to run the bridge. All variables can be set using command line flags or in the environment. The variable can also be specified in an .env file located in the working directory. See the help documentation for all the options

./mumble-discord-bridge --help

The bridge can be run with the follow modes:

   auto
       The bot starts up but does not connect audio channels immediately. It can be either manually linked (see below) or will join the voice channels when there's at least one person on each side.
       The audio bridge will leave both voice channels once there is no one on either end
   manual
       The bot starts up but does not connect immediately. It will join the voice channels when issued the link command via chat and will leave with the unlink command
   constant (default)
       The bridge starts up and immediately connects to both Discord and Mumble voice channels. It can not be controlled in this mode and quits when the program is stopped

In "auto" or "manual" modes, the bridge can be controlled in Discord with the following commands.

Important: Discord commands only work when sent from the configured channel (DISCORD_CID). Commands from other channels are ignored. This ensures proper isolation in multi-bridge deployments.

!COMMAND link
 (Discord Only) Commands the bridge to join Discord voice and Mumble.
 The user must be in the configured voice channel (DISCORD_CID) for this to work.

!COMMAND unlink
 (Discord Only) Commands the bridge to leave Discord voice and Mumble.

!COMMAND refresh
 (Discord Only) Commands the bridge to unlink, then link again.

There are additional commands that can be called from either Mumble or Discord.

!COMMAND help
 Print help text

!COMMAND version
 Print the version

!COMMAND restart
 Restart the bridge

!COMMAND status
 Show bridge status, uptime, and mode

!COMMAND list
 List all connected users in both Mumble and Discord.

Setup

Creating a Discord Bot

A Discord Bot is required to authenticate this application with Discord. The guide below provides information on how to create a Discord bot.

Create a Discord Bot

Individual Discord servers need to invite the bot before it can connect.
The bot requires the following permissions:

General Permissions

• View Channels

Text Permissions

• Send Messages
• Read Message History

Voice Permissions

• Connect
• Speak
• Use Voice Activity

Permission integer 36768768.

Finding Discord CID and GID

Discord GID is a unique ID linked to one Discord Server, also called Guild. CID is similarly a unique ID for a Discord Channel. To find these you need to set Discord into developer Mode.

Instructions to enable Discord Developer Mode

Then you can get the GID by right-clicking your server and selecting Copy-ID. Similarly the CID can be found right clicking the voice channel and selecting Copy ID.

Generating Mumble Client (Optional)

Optionally you can specify a client certificate for mumble Mumble Certificates If you don't have a client certificate, you can generate one with this command:

openssl req -x509 -nodes -days 3650 -newkey rsa:2048 -keyout cert.pem -out cert.pem -subj "/CN=mumble-discord-bridge"

Binary

Prebuilt binaries are available. The binaries require the opus and libdave runtime libraries to be installed.

# Ubuntu — install runtime dependencies
sudo apt install libopus0

# Install libdave runtime library
# Option A: use the Makefile target (requires cmake, g++)
make install-libdave

# Option B: manually copy libdave.so to /usr/lib
# See the godave repository for details: https://github.com/disgoorg/godave

# Ensure the linker can find libdave
export LD_LIBRARY_PATH="$HOME/.local/lib:$LD_LIBRARY_PATH"

curl -s https://api.github.com/repos/stieneee/mumble-discord-bridge/releases/latest | grep "mumble-discord-bridge" | grep "browser_download_url" | cut -d '"' -f 4 | wget -qi -

Docker

This project is built and distributed in a docker container. A sample docker command can be copied from below. This service command will always attempt to restart the service due to the --restart=always flag even when the server is restarted. For testing purposes it may be best to remove the restart flag.

Replace the environment variables with variable for the desired mumble server, discord bot and discord server/channel.

# Sample for testing
docker docker run -e MUMBLE_ADDRESS=example.com -e MUMBLE_PASSWORD=optional -e DISCORD_TOKEN=TOKEN -e DISCORD_GID=GID -e DISCORD_CID=CID stieneee/mumble-discord-bridge

# Run as a service
docker docker run -e MUMBLE_ADDRESS=example.com -e MUMBLE_PASSWORD=optional -e DISCORD_TOKEN=TOKEN -e DISCORD_GID=GID -e DISCORD_CID=CID --restart=always --name=mumble-discord-bridge -d stieneee/mumble-discord-bridge

# Stop the service
docker stop mumble-discord-bridge && docker rm mumble-discord-bridge

MDB Bridge Options

The following options can be set using environment variables or with command line options.

Note boolean values are flags when set via command line, example -mumble-insecure -mumble-disable-text not -mumble-insecure true -mumble-disable-text true.

Environment Variable	CLI	Type	Default	Description
CHAT_BRIDGE	-chat-bridge	flag	false	enable text chat bridge
COMMAND	-command	string	"mumble-discord"	command phrase '!mumble-discord help' to control the bridge via text channels
COMMAND_MODE	-command-mode	string	"both"	[both, mumble, discord, none] determine which side of the bridge will respond to commands
DEBUG_LEVEL	-debug-level	int	1	discord debug level
DISCORD_CID	-discord-cid	string	""	discord cid, required
DISCORD_TEXT_MODE	-discord-text-mode	string	"channel"	disable sending direct messages to discord
DISCORD_GID	-discord-gid	string	""	discord gid, required
DISCORD_TOKEN	-discord-token	string	""	discord bot token, required
MODE	-mode	string	"constant"	[constant, manual, auto] determine which mode the bridge starts in
MUMBLE_ADDRESS	-mumble-address	string	""	mumble server address, example example.com, required
MUMBLE_CERTIFICATE	-mumble-certificate	string	""	client certificate to use when connecting to the Mumble server
MUMBLE_CHANNEL	-mumble-channel	string	""	mumble channel to start in, using '/' to separate nested channels, optional
MUMBLE_DISABLE_TEXT	-mumble-disable-text	flag	false	disable sending text to mumble
MUMBLE_INSECURE	-mumble-insecure	flag	false	mumble insecure, ignore ssl certificates issues
MUMBLE_PASSWORD	-mumble-password	string	""	mumble password
MUMBLE_PORT	-mumble-port	int	64738	mumble port
MUMBLE_USERNAME	-mumble-username	string	"Discord"	mumble username
MUMBLE_BOT	-mumble-bot	flag	false	exclude bot from mumble user count, optional, requires mumble v1.5 or later
PROMETHEUS_ENABLE	-prometheus-enable	flag	false	enable prometheus metrics
PROMETHEUS_PORT	-prometheus-port	int	9559	prometheus metrics port
TO_DISCORD_BUFFER	-to-discord-buffer	int	50	jitter buffer from Mumble to Discord to absorb timing issues related to network, OS and hardware quality. (Increments of 10ms)
TO_MUMBLE_BUFFER	-to-mumble-buffer	int	50	jitter buffer from Discord to Mumble to absorb timing issues related to network, OS and hardware quality. (Increments of 10ms)

Mumbler Server Setting

To ensure compatibility please edit your murmur configuration and add the following

opusthreshold=0

This ensures all packets are opus encoded and should not cause any compatibility issues if your users are using up to date clients.

Chat Bridge

The chat bridge feature will relay chat messages between mumble and discord channels. To enable the feature the MUMBLE_DISABLE_TEXT must be false and DISCORD_TEXT_MODE must be set to "channel" (the default state). Finally the CHAT_BRIDGE variable must be set to true.

Building From Source

This project requires Go and CGO to build from source. Two system libraries are required:

• libopus — Opus audio codec
• libdave — Discord Audio & Video End-to-End Encryption (DAVE) protocol

# Ubuntu/Debian
sudo apt install libopus-dev cmake g++ pkg-config

# Install libdave (downloads prebuilt binary or builds from source)
make install-libdave

# Ensure pkg-config can find libdave (add to your shell profile)
export PKG_CONFIG_PATH="$HOME/.local/lib/pkgconfig:$PKG_CONFIG_PATH"
export LD_LIBRARY_PATH="$HOME/.local/lib:$LD_LIBRARY_PATH"

# Build
make

OpenBSD Users

OpenBSD users should consider compiling a custom kernel to use 1000 ticks for the best possible performance. See issue 20 for the latest discussion about this topic.

Jitter Buffer

The bridge implements simple jitter buffers that attempt to compensate for network, OS and hardware related jitter. These jitter buffers are configurable in both directions. A jitter buffer will slightly the delay the transmission of audio in order to have audio packets buffered for the next time step. The Mumble client itself includes a jitter buffer for similar reasons. A default jitter of 50ms should be adequate for most scenarios. A warning will be logged if short burst or audio are seen. A single warning can be ignored multiple warnings in short time spans would suggest the need for a larger jitter buffer.

Monitoring the Bridge (Optional)

The bridge can be started with a Prometheus metrics endpoint enabled. The example folder contains the a docker-compose file that will spawn the bridge, Prometheus and Grafana configured to serve a single a pre-configured dashboard.

The endpoint exposes /live and /ready for use with Kubernetes.

Known Issues

Delays in connecting to Mumble (such as from external authentication plugins) may result in extra error messages on initial connection.

There is an issue seen with Mumble-Server (murmur) 1.3.0 in which the bridge will lose the ability to send messages client after prolonged periods of connectivity. This issue appears to be resolved by murmur 1.3.4.

Breaking Config Changes

Version 0.7

Command Behavior Changes:

• Discord commands (link, unlink, refresh) now only work when sent from the configured channel (DISCORD_CID). Commands from other text channels are ignored.
• The link command now requires the user to be in the configured voice channel (DISCORD_CID). Previously, the bridge would join whichever voice channel the user was in. This change ensures proper isolation in multi-bridge deployments where multiple bridges may exist in the same guild.

Removed Features:

• Bot status updates removed. The bridge no longer updates Discord's "Listening to..." status with Mumble user counts. The DISCORD_DISABLE_BOT_STATUS / -discord-disable-bot-status config option has been removed along with this functionality.

BridgeLib API Changes (for library users):

• DiscordDisableBotStatus removed from BridgeConfig (feature removed)
• Logger interface moved to pkg/logger package - use logger.Logger instead of bridgelib.Logger
• JoinVoiceChannel removed from DiscordProvider interface - voice connections are now managed internally by connection managers
• New EventDispatcher system for subscribing to bridge events (connection status, user join/leave, etc.)

Version 0.6

DISCORD_DISABLE_TEXT has been replaced with DISCORD_TEXT_MODE. As a result the default behavior has been change from direct messages to users "user" to "channel".

DISCORD_COMMAND has been replace with COMMAND and COMMAND_MODE. The feature now supports both mumble and discord. The default command phrase remains "!mumble-discord".

License

Distributed under the MIT License. See LICENSE for more information.

Contributing

Issues and PRs are welcome and encouraged. Please consider opening an issue to discuss features and ideas.

Acknowledgement

The project would not have been possible without:

• gumble
• disgo
• godave — Go bindings for Discord's DAVE E2EE protocol
• discordgo (used in earlier versions)