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Comment by sardine5 | Hacker News Reader

A bit different, as it's mainly for voice - but I made an app 'Murmur : Bluetooth Group Calls' - that lets you hold group voice calls and message via a mesh of Bluetooth LE connections. It's available on Android and iOS. https://apps.apple.com/gb/app/murmur-bluetooth-group-calls/i...

Doesn't really get any downloads, so not sure there's much demand for this - but I use it with some shokz bone conducting headphones for talking to my wife when we're cycling (also for wrangling our two small girls)

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I'd guess you're not getting downloads because you're not marketing it to people who want it. You mention a few use cases at the end of the short description and that's it.

For example, this completes with motorcycle communicators such as Sena. That dedicated hardware can be over $400. If your app is as easy to use as a Sena device and you market it to bikers looking for a cheaper alternative you'll get users.

LOL, no. You can't even hear a ok quality music further than 20 metres away. Class 2 devices (smartphones) have maximum theoretical range of 30 metres with 2.4mW (4dBm).

Sena or Cardo work in 2.4 Ghz (ISM) range as well, but as a class 1 devices, which with 100mW (20 dBm), they can allow for maximum range in excess of 1 mile.

I'd use Walkie - talkies (PMR 446 MHz, about half of a mile of the range in the town) before resorting to the smartphone bluetooth. Likely only feasible on the parking.

Smartphone bluetooth is fine for two bicycles but it does NOT compete with a purpose-built hardware, especially not with the top makers like Cardo or Sena, LOL.

Bluetooth LE which most smartphones support today is quite a bit different from Bluetooth classic. It typically runs at 1 or 2 Mbps and can trade bandwidth for error correction to get some impressive range. For example, this guy got 1.6 miles at 8dbm transmission power. https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/pos...

The audio codec on ble is more modern too.

> “You can't even hear a ok quality music further than 20 metres away” That smells like the SBC codec running on Bluetooth classic to me. Very different tech.

Okay, this is neat! A true mesh networking bluetooth app- The other one that's notable, Briar is super impressive - but i think it doesn't actually have proper mesh capability due to difficulties with how devices handle things

(See: https://old.reddit.com/r/Briar/comments/gxiffy/what_exactly_...

https://news.ycombinator.com/item?id=43363031 }

Anyway, -Question: I take it Murmur is end to end encrypted fully? Also, just curious if this is open source?

This could become SUPER useful- having a actual mesh networking Bluetooth app , if it's open source/E2EE!

It's AES128 encrypted with a key derived from the group password.

I'll try this app because Briar never worked between any of my devices (all Androids)

How's the range on BLE? I was looking at this app for exactly the use case you mentioned but was curious if it worked with varying distances on bike rides

It's somewhat device dependant - but between her Pixel 6 and my Pixel 7 - if we've got line of sight and the handset's not being held to our body (so in a handlebar mount or saddle bag) - 50-75m? I've been victim to the recent Microsoft layoffs, so have a bit of time to work on it at the moment - looking at adding longer range CodedPhy support this week (though that would only be available on Android)

It works best if there's 3 phones though - as it can route via the other if a link drops.

Any chance it could use seamless transport switching? It would be so awesome if it could switch to cellular(if available) or wifi-direct as needed on the fly. I have been thinking about creating such an app but lacked the time.

If it's open source, I would love to help.

I will give your app a try.

I actually have this kind of working on a branch - really don't fancy hosting any infrastructure myself though - so I was intending it to be a Windows service or docker container you have to setup and pair with. Once you've done that - the endpoint is included in any group you create, and treated as an extra node in the graph. If available and lower latency than other routes, it'll be used.

Was trying to keep things simple though - the separate server seemed a step too far for most people I talked to about it.

This sounds perfect for my use case. I'm a mountain biker who doesn't mind setting up hosting infra. It's fairly common when mountain biking to unintentionally get separated by line-of-sight or more than 75M even among very similarly skilled riders. Even on straight easy trails, just the dust cloud generated by the rider ahead can cause you to back off significant distance if it's dusty.

I've used these[0] in the past and they worked ok. I lost the pair I bought when traveling and thought using the plethora of radios I have with me anyway on my phone with an earbud headphone would be much better replacement. Would be great for group rides to just send an app link instead of suggesting they all buy $100 hardware.

Honestly I think a well marketed and polished commercial app would have both Sena and Cardo[1] both quite existentially scared.

[0]: https://www.sena.com/en-us/product/pi/ [1]: https://cardosystems.com/

App will be held down by the hardware. Smartphones are not meant to transmit with the necessary power, and you also don't get direct access to the radio, so you can't run custom protocols like Sena/Cardo, but you must transmit over the actual bluetooth or actual WiFi.

They're not really a competition.

I'd stayed away from WiFi Direct because Android and iOS don't play nicely with it - but looks like the EU has forced Apple to support WiFi Aware in iOS 26. It still looks like it would require A LOT of manual pairing through the system UI if you join a group with new people though. I really wanted to keep the single password (or qr code scan/NFC tap) to join.

Totally missed this news. EU will mandate it indeed

Cool technology, but what is the usecase? I can imagine traveling abroad without a sim and using it as described. But is it any better than using the cellular network (when you have access to it)?

I possibly live more remote than you do - but mobile data isn't really a thing (in the UK at least) you can rely on continuously when you're cycling, or visiting the supermarket and you've lost your partner near the cheese aisle...

I mean it is in most of the UK. Maybe not in remote areas of Scotland or Wales.

In most of the supermarkets down here, couple of miles from M25. I mean, outside, so its probably considered third-world country, but no, no need to reduce the argument ad absurdum.

Or 2 metres from the window a mile from Hammersmith. If not for WiFi calling I'd have to leave my phones on the windowsill.

I've still got dead zones near me. If I were cycling with someone, and we wanted to chat on headsets, there's at least a few places I might ride where we'd hit dead air. If we're on different networks, then we both need coverage to communicate with cellular.

Might be more reasonable to use higher bandwidth, lower latency codecs over bluetooth as well?

For this use case, old fashioned radio is a lot more reliable.

Quite likely, but then you need to carry that radio. And probably still carry a phone in case you split up and want to communicate.

You raised reliability issue, you've got a solution, now you're moving a goalpost and raising a convenience argument.

Decide which one is it.

PS Motorola talkabout T62 or T42 - small, light, reliable. Retevis h777: sturdy, reliable. You can just drop them in the bag.

On festival sites and other crowded events, cellular sometimes gets quite saturated and slow. This might be a good alternative.

Also, I could see it as a useful tool in emergency situations. But a lot of people would need to use it to be actually useful.

When I last had a university workshop where 20 people in a room worked on a bluetooth protocol I also noticed bluetooth is quickly saturated with many participants. Hopefully that changed in the last 15 years since...

I commonly Signal call my partner when we are at opposite ends of the house. I can see something like this being useful to prevent using some remote Internet server to facilitate a very local call.

I wonder if there's a home lab / self hosted solution for this.

Bluetooth to reach and reliably hold a high throughout connection to the device across the house?

I don't think so.

You can do a surprising amount with a low throughput connection though. I've been playing with Google's Lyra V2 codec - it chews up a fair bit of CPU, but 3.2kbps over a CodedPhy link sounds fine.

I would love to use it to talk to my girlfriend when we go bike riding. I was shocked by the price tag for all the motorcycle helmet comms systems.

If you're looking at the premium segment then yeah, when you're going out with your several mates and need to be able to hear every one of them.

For one rider to one rider you can get a very decent set well under $100 (Lexin b4fm, FredConn, even Thokwok is well reviewed).

Cardo uses a similar tech for a dynamic mesh network, using Bluetooth I think, in their helmet comms. So if you are out on motorcycles or ATVs you can still talk without needing a cellular network. It makes things a lot more stable and not use any data. In these scenarios you'd struggle to talk face to face wearing helmets without some sort of comm. So if you can remove the need to buy a specialized comm device to do it, sounds great.

You can't. Smartphones are Class 2 devices (weak), and you must use radio the way firmware let's you.

Purpose-built hardware is Class 1 (much stronger, 100 mW/20dBm vs 2.4mW/4dBm), and they can use sophisticated protocols to keep the connection stable. And that's Bluetooth.

If they're not playing Bluetooth but go general ISM, they can emit whole 1W on 2.4GHz or 915 MHz.

They're not really alike.

Unfortunately you have generated a name collision: the server component of the Mumble VoIP is also called "Murmur", for a long time: https://en.m.wikipedia.org/wiki/Mumble_(software)

Yeah, I think that fully explain apparent disinterest of users. No way nobody is looking for this app, but there is also no way this one shows up on searches over the other one.

This is really interesting! Will have a look!

This looks really cool. I'd see it being useful as a headset to talk to camera people and others during a live stream. We already have hardware for this, but if we didn't it would be great.

For my use, I'd like to be able to join and monitor multiple groups at once (cameras, presenters, certain others individually), and select which I talk to (including being able to talk to several or all groups at once).

Another feature idea, if you are out of range, it would be good if there was an option to save the message until you come back and replay it.

Thanks! The protocol it uses does allow broadcasting to a subset of the group - I haven't hooked that up to the UI yet, but it's on the todo list (after CodedPhy and IP fallback).

Re. Messages - if you're not in range, as long as you don't leave the call, it'll send as soon as you reconnect. Messages are not currently persisted to a database though (- unsure if that's a feature or not?). I'd wanted to hold off on that until I was sure I'd covered everything I needed for the schema - they're currently encoded with ITA-2 (which is why some punctuation and emoticons go missing) - but I've made some improvements to the protocol, and intend to move to UTF-8 for broader character/language support.

The current protocol is very much designed to work around all the ways streaming audio really isn't a good fit for Bluetooth LE GATT. It does things which don't really make sense for messages, so I'm intending to separate messages from the live call.

The current focus is trying to make it play a little better with wireless headphones though. I started the app back in the days when phones had 3.5mm headphone jacks. If you've an Android phone and can use LE Audio headphones - they work much better, but wired headphones work best.

Looks interesting, especially that use case. May I ask which headphone you are using? I have the older openmove from shokzs and voice isn't really understandable while riding a bike.

We've got Openrun Pros - wind can be a problem, but if you cover the mics with a head band, it actually works pretty well. (To act as a crude wind muff)

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