Some might have noticed that the editor of this article was not very active on the ZS Link Group Nets the past three week. Well there was good reason for this. I in collaboration with AI have been working on a project relating to create a analog to digital bridge network between AllStarLink3 (ASL3) and Mumble. I now do have the pleasure to announce a new addition / extension to the ZS1I Hub Network in Mossel Bay:
The new "KID" = The ZS1I AllStarLink3 (ASL3) to ZS1I Mumble Bridge now incorporated into the ZS1I Hub Network in Mossel Bay.Before I tell you more about the new "KID" on the block, it is important to first provide some information on Mumble.
Background:
Now why on earth would one want to use Mumble, firstly in general and amateur radio and secondly use a commercial software application when there are more than enough amateur radio software applications available and thirdly build a bridge between ASL3 and Mumble?
Firstly:
Mumble is fundamentally a digital voice application.
It uses AREDN, your computer or phone's internet connection to transmit compressed, digital voice data, unlike the analog streams typically processed by AllStarLink (ASL3). However, in amateur radio, I used software like DVSwitch and Analog_Bridge as well as a Mumble_Bridge.py script to bridge Mumble and other digital networks into analog ASL3 nodes.
• ASL3: Connects via analog radios and repeaters
(FM), though the system relies on digital servers, the internet and
AREDN to link nodes together.
• Mumble: Transmits over Voice over
IP (VoIP), capturing and compressing your voice into digital packets
right from the start.
Let's look further at Mumble:
Mumble
is a free, open-source, and highly secure Voice over Internet Protocol
(VoIP) application primarily designed for real-time voice
communication. It is celebrated for its incredibly low audio latency
and high sound clarity, offering a self-hosted alternative to platforms
like Discord or TeamSpeak.
Because
it relies on a decentralized, client-server model rather than
centralized corporate servers, Mumble offers a unique set of features
and capabilities for its users:
Key Features
- Extremely Low Latency: Mumble was engineered to transmit voice packets with virtually zero delay, making it vital for fast-paced, competitive applications where split-second communication matters.
- High-Quality Audio: It utilizes advanced, royalty-free audio codecs (like Opus and CELT) to ensure crystal clear, wide-band voice communication without heavy resource usage.
- Positional (Spatial) Audio: In certain supported applications, Mumble uses 3D listening technology that simulates a 360-degree soundscape.
- Privacy and Security: All Mumble communications are encrypted by default. Because the software is open-source, it contains no ads or user-tracking mechanics.
How It Works
Mumble uses a two-part architecture:
- The Client (Mumble): The desktop or mobile application you use to log in and talk.
- The Server (Murmur): The back-end software that routes the voice data.
Unlike
Discord, where you hop into a server hosted by a single company, anyone
can download the Murmur server software and host their own private
Mumble server on their own hardware. This gives server administrators
complete control over user data, privacy, permissions, and complex
channel setups.
Who Uses It?
While originally built for gamers, Mumble's reliability and self-hosting capabilities have made it popular in other fields:
- Podcast Recording: Its high fidelity and multi-channel audio recording make it a popular tool for podcasters recording remote interviews.
- Radio Enthusiasts: Amateur radio operators use it to bridge internet-based communications with physical radio nodes and AREDN.
- Workplaces: Teams requiring highly secure, self-hosted, or on-premises voice communication networks.
Now that we know a little bit more about Mumble let's move on to the second part as stated in the the background heading above.
Secondly:
Why use a "commercial" software application when there are more than enough amateur radio software applications available out there?
In
the early 2000's I started to create a HSMM and later a AREDN Mesh Network in the Mossel Bay area. I decided to use Mumble over the mesh
network and it is important to mention it here as Mumble plays an
important roll in AREDN. I therefor wanted to use Mumble as an ASL3 /
Mumble bridge and to conform to software already in use.
Here are the reasons for using Mumble in Amateur Radio:
- Extremely low latency - Important if you run any amateur radio network.
- High-Quality Audio - Need I say anything? Maybe just that Mumble uses advanced audio codecs to transmit pristine, natural sounding voice.
- Privacy and Security: Mumble communications are safe and open source. It contains no ads or user-tracking mechanics.
- Mumble channels function like isolated virtual rooms where connected users can speak to one another. Creating of different channels for different uses in amateur radio. In my AREDN setup I also use Mumble and I created several channels (chat-rooms) for different services like Amateur Radio Emergency Coms Channel, Citadel Email and Client Channel, Digital Radio Mode Channel, Echolink Relay/Listen Channel, Emergency JOC Channel, General Voice Chat Channel etc.
- Remote Audio Bridging - Amateurs use Mumble to stream audio directly from remove transceivers of Software-Defined Radios (SDR's)
- Bandwidth Efficiency - It allows remote multi-operator teams to listen to or control stations without needing heavy, complicated port forwarding on routers.
- Repeater and Cross Band Linking - Mumble acts as a central hub or "rendezvous server" to bridge analog repeaters, AllStar nodes and Digital modes via the Internet, AREDN and interconnected networks.
- Cross-linking - It handles multiple users speaking simultaneously without Garbling, which is ideal for broad group communications or net check-ins.
- Emergency Communications - During a disaster or emergency responses or power grid outages, radio amateurs can set up self-hosted local servers that auto-reconnect reliably. (Author's AREDN Network a good example of this.)
- Low CPU usage - One can use a Raspberry Pi to host the software.
- Highly Reliable Application Software - Been using it for years!
- Can be used for remote station Control/Audio - HF Remote Control Station
- Can be used for multi-operator contesting - Setup and win contests!
- Can be used for multi-channel operations in Amateur Radio - Already discussed above. Definitely a big plus point!
Thirdly:
I in collaboration with AI has successfully created a Mumble_Bridge.py script that establish a bridge between ASL3 and Mumble. I am not going to provide more detail in this part but will provide full information in future parts of this article.
An ASL3/Mumble bridge script (often utilizing the Analog_Bridge software from the DVSwitch project) is a utility that connects your amateur radio system to a Mumble VoIP server. It allows you to relay audio seamlessly both ways between physical radio nodes and internet-linked computers or mobile devices.
The ASL3 (AllStarLink 3) environment connects amateur radio repeaters, nodes, and hotspots. By adding a Mumble bridge, the script performs several key functions:
Two-Way Audio Relaying: It encodes and decodes audio so that when someone speaks into a radio connected to your ASL3 node, the audio is streamed into Mumble. Conversely, when a Mumble user talks, it is pushed out over your RF node.
Protocol Translation: The script translates between the VoIP protocols used by Mumble and the audio formats (like ULAW) that Asterisk (which powers ASL3) natively uses.
User Accessibility: It allows radio amateurs and other operators who might not be near a radio to participate in local net check-ins or general conversations using a simple Mumble client on their PC, Mac, or Android device.
Bridging Software: These integration scripts utilize tools developed by the DVSwitch ecosystem to link different digital modes together, creating a unified communication space.
I in collaboration with AI has successfully created a Mumble_Bridge.py script that establish a bridge between ASL3 and Mumble. I am not going to provide more detail in this part but will provide full information in future parts of this article.
An ASL3/Mumble bridge script (often utilizing the Analog_Bridge software from the DVSwitch project) is a utility that connects your amateur radio system to a Mumble VoIP server. It allows you to relay audio seamlessly both ways between physical radio nodes and internet-linked computers or mobile devices.
The ASL3 (AllStarLink 3) environment connects amateur radio repeaters, nodes, and hotspots. By adding a Mumble bridge, the script performs several key functions:
Two-Way Audio Relaying: It encodes and decodes audio so that when someone speaks into a radio connected to your ASL3 node, the audio is streamed into Mumble. Conversely, when a Mumble user talks, it is pushed out over your RF node.
Protocol Translation: The script translates between the VoIP protocols used by Mumble and the audio formats (like ULAW) that Asterisk (which powers ASL3) natively uses.
User Accessibility: It allows radio amateurs and other operators who might not be near a radio to participate in local net check-ins or general conversations using a simple Mumble client on their PC, Mac, or Android device.
Bridging Software: These integration scripts utilize tools developed by the DVSwitch ecosystem to link different digital modes together, creating a unified communication space.
Short Overview of the script: This script successfully handles bidirectional audio streaming. It processes incoming 352-byte DVSwitch frames from Asterisk, strips the 32-byte header, up-samples the audio to 48kHz, and packs it into 20ms blocks for Mumble For outbound audio (phone/PC to radio), it down-samples to 8kHz and constructs a valid big-endian sequential DVSwitch header to trip the Asterisk TX gate.
Well this is enough for Part 1. In future parts I will describe the working components and configurations that successfully established the ZS1I AllStarLink3 (ASL3) to Mumble Bridge.
The ZS1I ASL3 to Mumble Bridge is currently fully operational on the ZS1I Hub Network in the Mossel Bay area. Fine tuning the set-up and audio loudness will be an ongoing task until optimal results are achieved, but so far reports indicate that the setup is working great.
Plans are already underway to expand the radio stack even further by adding:
- Configure automated backups for the system.
- Set up real-time system alerts if the bridge drops offline.
- Integrate additional digital modes to the network.
Images (Click on images for larger view.)
