Snapcast Server in a Container

In this blog, let's look at using snapcast server software in a container.

Snapcast is a synchronous multiroom client-server audio player. While Snapcast server has multiple configurable options for stream sources, this setup will use a named pipe as a source, from which Snapcast reads PCM chunks of audio data. Using named pipe as a source extends the ability to configure multiple audio sources - like Librespot (see Librespot Docker container) to send audio output.

|Librespot|---write to---> /tmp/snapcast/fifo <---read from--- |snapcast server| ~~~ network ~~~ |[snapcast clients]|

Setup¶

The snapcast-server docker image is available on docker hub. The container requires two inputs - a snapserver.conf file and fifo pipe file. The files on the filesystem are passed to the containers via docker volumes.

Assuming smarthome is a your home-automation directory, create a directory with the name snapcast and create a file called docker-compose.yml with the following contents.

---
services:
  snapcast-server:
    image: jbollineni/snapcast-server:latest
    network_mode: "host"        
    restart: on-failure
    volumes:
      - /opt/smarthome/snapcast/snapserver.conf:/etc/snapserver.conf:ro
      - /tmp/snapcast/fifo:/tmp/snapcast/fifo

Add another file called snapserver.conf to snapcast directory with the following contents, which tells snapcast server the path to the named fifo pipe as well as the audio sample format. See Snapcast documentation for more options on setting up sources.

[stream]
stream = pipe:///tmp/snapcast/fifo?name=Librespot-docker&sampleformat=44100:16:2

Note: The sample format is set to 44100:16:2 to match the Librespot source's sample format.

Create a named pipe file

mkdir -p /tmp/snapcast
mkfifo /tmp/snapcast/fifo

Run container¶

Navigate to the snapcast directory and run docker compose command

cd /opt/smarthome/snapcast
docker compose up -d

Verify container¶

[violet@home snapcast]$ docker ps | grep snapcast
d8fd172f8f34   jbollineni/snapcast-server:latest   "/bin/sh -c 'rm /var…"   3 weeks ago   Up 3 weeks                       snapcast-snapcast-server-1
[violet@home snapcast]$

Dockerfile¶

FROM alpine:edge

MAINTAINER Jana Bollineni (jana@neni.io)

LABEL version="1.2"
LABEL org.label-schema.name="Snapcast Server Docker" \
      org.label-schema.description="Snapcast server on alpine image with Avahi and D-Bus support" \
      org.label-schema.schema-version="1.0"

RUN apk -U add snapcast-server \
    && mkdir -p /tmp/snapcast/ \
    && apk add -U avahi \
    && apk add dbus \
    && dbus-uuidgen > /var/lib/dbus/machine-id \
    && mkdir -p /var/run/dbus \
    && rm -rf /etc/ssl /var/cache/apk/* /lib/apk/db/*

CMD dbus-daemon --config-file=/usr/share/dbus-1/system.conf --print-address; avahi-daemon -D; snapserver