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Strobe Audio

Strobe Hub

This is the umbrella project for the code that comprises the Strobe Audio hub.

Strobe is a multi-room audio system built from scratch in Elixir by @magnetised.


Strobe is comprised of this 'hub' or 'broadcaster' (or 'server'). This acts as both a store of music and also the means for playing it.

Connecting to the hub are some number of 'receivers'. These are Raspberry Pis with IQaudIO DACs connected to some kind of hi-fi amplifier and speakers.

In order to play your music Strobe is currently* modelled around the following core concepts:

  • Music is stored in a set of 'libraries'.

    There are currently only two libraries: a disk-based 'your music' library (think iTunes) and a set of live BBC radio streams. This should change with time.

  • Tracks are added from libraries to named 'channels'.

  • Receivers are attached to channels.

│                                 Strobe Hub                                 │
│                                                                            │
│ ┌─────────────────────────────────┐ ┌─────────────────────────────────┐    │
│ │                                 │ │                                 │    │
│ │                                 │ │                                 │    │
│ │             Library             │ │             Library             │    │
│ │                                 │ │                                 │    │
│ │                                 │ │                                 │    │
│ └─────────────────────────────────┘ └─────────────────────────────────┘    │
│ ┌─────────────────────┐ ┌─────────────────────┐ ┌─────────────────────┐    │
│ │                     │ │                     │ │                     │    │
│ │                     │ │                     │ │                     │    │
│ │       Channel       │ │       Channel       │ │       Channel       │    │
│ │                     │ │                     │ │                     │    │
│ │                     │ │                     │ │                     │    │
│ └─────────────────────┘ └─────────────────────┘ └─────────────────────┘    │
│            ▲                       ▲                                       │
│            │                       │                                       │
             │                       │
             │                       │
             │                       │
         ┌───┘               ┌───────┴───────────┬───────────────────┐
         │                   │                   │                   │
         │                   │                   │                   │
         │                   │                   │                   │
         │                   │                   │                   │
         │                   │                   │                   │
         │                   │                   │                   │
┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐
│                 │ │                 │ │                 │ │                 │
│                 │ │                 │ │                 │ │                 │
│    Reciever     │ │    Reciever     │ │    Reciever     │ │    Reciever     │
│                 │ │                 │ │                 │ │                 │
│                 │ │                 │ │                 │ │                 │
└─────────────────┘ └─────────────────┘ └─────────────────┘ └─────────────────┘

Channels are the core of the strobe system. Strobe is capable of playing multiple channels at the same time (hence the name). For instance you may want to listen to your music downstairs so you add your songs to a channel named "Jane's Music" and attach the "Kitchen" and "Living room" receivers, however your partner may want to listen to the radio upstairs, so they use the existing "Radio 6" channel and attach the "Bedroom" and "Bathroom" receivers to it.

Later if your partner goes out and you want to listen to your music throughout the house you can reattach the "Bedroom" and "Bathroom" receivers to your music channel.

Part of the purpose of channels is to persist before and after they are in active use and also provide convenient shortcuts for often used live streams. For example if you suddenly remember that album you want to listen to at the weekend, then you can add the album you want to some channel and then, when the weekend comes, the music you wanted is there waiting for you.

* 'Currently' because this mode of interaction is still in proof of concept phase. Though powerful and not overly complex, I'm still deciding if there isn't something simpler lurking. The only way to decide this is to gather more experience of using the system from both myself and others.


Strobe is still in relatively early stages. Although the back-end functions are fairly solid (music playback is fully functional and extremely reliable) the user-facing side of things is still in their infancy. This extends from the installation experience to the UI.

Note that ongoing development is also a form of extreme 'mobile first'. To the extent that the current UI doesn't work well in desktop browsers. This is just a temporary glitch while I work out the last details of the library interaction.


This is a very high-level overview of the project aims over the short- to mid-term:

  • Complete basic interaction design (including wifi settings and music library configuration)
  • Skin UI with reasonable & consistent visual design
  • Package hub for embedded deployment using Nerves
  • Manage music library through e.g. webdav
  • Expand library access:
    • DNLA renderer (to enable playback of audio files from a NAS)
    • add Shairport receiver (so a single channel can be setup to play music from iOS/macOS device)
    • Add more radio options
    • Google Music (using gmusicapi)

The longer term aim is to provide some, potentially paid, form of over-the-air updates for both hub and receiver.


If you'd like to contribute then please, be my guest.

I'm particularly keen on finding a front-end designer to help me transform a functional but very rough user interface into something beautiful.


Generating pre-built images is a WIP.

Strobe requires the following dependencies to run.



An up-to-date homebrew installation is the easiest/recommended route to install the required dependencies.

be sure to brew update before installation to get the latest versions.

Erlang 19


brew install erlang

Elixir 1.4

Install the latest Elixir using the installation instructions on the Elixir website.

Elm 0.18

Follow the instructions for your platform at the elm-lang website.

This should give you the elm-package command.

cd apps/elvis
elm-package install


The UI is compiled using Webpack. To install this and its dependencies use Yarn.

cd apps/elvis
yarn install

SQLite 3

Strobe is backed by a SQLite database and you'll need the development libraries to compile the bindings.


macOS comes with SQLite 3 pre-installed.


Strobe uses ffmpeg to transcode all audio into 16-bit 44,100 kHz PCM streams:


brew install ffmpeg


Currently during music library import Strobe uses the mediainfo binary to extract music metadata.


brew install mediainfo


Recievers use various techniques to discover the active hub. One of those techniques is to register a service using mDNS backed by Bonjour on macOS and Avahi on linux.


No installation necessary -- macOS comes preinstalled with an mDNS framework.


apt-get install avahi-daemon libavahi-compat-libdnssd-dev



You need to retrieve the Elixir dependencies:

mix deps.get


Strobe maintains two databases: the hub state and your music library.

Both of these databases require initialization.

From the root of the project directory run

mix ecto.create -r Otis.State.Repo
mix ecto.migrate -r Otis.State.Repo

mix ecto.create -r Peel.Repo
mix ecto.migrate -r Peel.Repo

Importing your music

There is currently no UI for adding music to your library. To do this we must run a command from the terminal which tells Peel to recursively scan a particular directory for music files and import them into your library.

mix run --eval 'Peel.scan(["/path/to/music..."])'

This may take some time.

The import will also attempt to provide cover art for any tracks that are missing it. This uses the musicbrainz cover art API which is rate-limited to 1 request per second. You can safely ctrl-c ctrl-c out of this part though as the update will proceed in the background next time (and any time) you start the server.


From the root of the project directory run

mix phoenix.server

all being well this should launch a HTML ui on http://localhost:4000


Stobe Audio Hub Copyright (C) 2017 Garry Hill

This program is free software: you can redistribute it and/or modify it under the terms of the GNU 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 General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see


The server for the strobe audio system








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