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Setup of audio players/server

Snapcast can be used with a number of different audio players and servers, and so it can be integrated into your favorite audio-player solution and make it synced-multiroom capable. The only requirement is that the player's audio can be redirected into the Snapserver's fifo /tmp/snapfifo. In the following configuration hints for MPD and Mopidy are given, which are the base of other audio player solutions, like Volumio or RuneAudio (both MPD) or Pi MusicBox (Mopidy).

The goal is to build the following chain:

audio player software -> snapfifo -> snapserver -> network -> snapclient -> alsa

Streams

Snapserver can read audio from several sources, which are configured in the snapserver.conf file (default location is /etc/snapserver.conf); the config file can be changed with the -c parameter.
Within the config file a list of pcm sources can be configured in the [stream] section:

[stream]
...
# stream URI of the PCM input stream, can be configured multiple times
# Format: TYPE://host/path?name=NAME[&codec=CODEC][&sampleformat=SAMPLEFORMAT]
source = pipe:///tmp/snapfifo?name=default
...

The sampleformat is a triple of <samplerate>:<bit depth>:<channels>, e.g. 44100:16:2.
The PCM samples (bit depth) must be encoded signed, little endian in 8, 16, 24, or 32 bit, where 24 is expected to be encoded in the lower three bytes of a 32 bit word.

About the notation

In this document some expressions are in brackets:

  • <angle brackets>: the whole expression must be replaced with your specific setting
  • [square brackets]: the whole expression is optional and can be left out
    • [key=value]: if you leave this option out, value will be the default for key

For example:

source = spotify:///librespot?name=Spotify[&username=<my username>&password=<my password>][&devicename=Snapcast][&bitrate=320]
  • username and password are both optional in this case. You need to specify neither or both of them.
  • bitrate is optional. If not configured, 320 will be used.
  • devicename is optional. If not configured, Snapcast will be used.

For instance, a valid usage would be:

source = spotify:///librespot?name=Spotify&bitrate=160

MPD

To connect MPD to the Snapserver, edit /etc/mpd.conf, so that mpd will feed the audio into the snapserver's named pipe.

Disable alsa audio output by commenting out this section:

#audio_output {
#       type            "alsa"
#       name            "My ALSA Device"
#       device          "hw:0,0"        # optional
#       format          "48000:16:2"    # optional
#       mixer_device    "default"       # optional
#       mixer_control   "PCM"           # optional
#       mixer_index     "0"             # optional
#}

Add a new audio output of the type "fifo", which will let mpd play audio into the named pipe /tmp/snapfifo. Make sure that the "format" setting is the same as the format setting of the Snapserver (default is "48000:16:2", which should make resampling unnecessary in most cases).

audio_output {
    type            "fifo"
    name            "my pipe"
    path            "/tmp/snapfifo"
    format          "48000:16:2"
    mixer_type      "software"
}

To test your mpd installation, you can add a radio station by

sudo su
echo "http://wdr-1live-live.icecast.wdr.de/wdr/1live/live/mp3/128/stream.mp3" > /var/lib/mpd/playlists/einslive.m3u

Mopidy

Mopidy can stream the audio output into the Snapserver's fifo with a filesink as audio output in mopidy.conf:

[audio]
#output = autoaudiosink
output = audioresample ! audioconvert ! audio/x-raw,rate=48000,channels=2,format=S16LE ! filesink location=/tmp/snapfifo

With newer kernels one might also have to change this sysctl-setting, as default settings have changed recently: sudo sysctl fs.protected_fifos=0

See stackexchange for more details. You need to run this after each reboot or add it to /etc/sysctl.conf or /etc/sysctl.d/50-default.conf depending on distribution.

FFmpeg

Pipe FFmpeg's audio output to the snapfifo:

ffmpeg -y -i http://wms-15.streamsrus.com:11630 -f u16le -acodec pcm_s16le -ac 2 -ar 48000 /tmp/snapfifo

mpv

Pipe mpv's audio output to the snapfifo. For version < 0.21.0:

mpv http://wms-15.streamsrus.com:11630 --audio-display=no --audio-channels=stereo --audio-samplerate=48000 --audio-format=s16 --ao=pcm:file=/tmp/snapfifo

For version >= 0.21.0:

mpv http://wms-15.streamsrus.com:11630 --audio-display=no --audio-channels=stereo --audio-samplerate=48000 --audio-format=s16 --ao=pcm --ao-pcm-file=/tmp/snapfifo

MPlayer

Use -novideo and -ao to pipe MPlayer's audio output to the snapfifo:

mplayer http://wms-15.streamsrus.com:11630 -novideo -channels 2 -srate 48000 -af format=s16le -ao pcm:file=/tmp/snapfifo

Alsa

If the player cannot be configured to route the audio stream into the snapfifo, Alsa or PulseAudio can be redirected, resulting in this chain:

    audio player software -> Alsa -> Alsa file plugin -> snapfifo -> snapserver -> network -> snapclient -> Alsa

Edit or create your Alsa config /etc/asound.conf like this:

pcm.!default {
    type plug
    slave.pcm rate48000Hz
}

pcm.rate48000Hz {
    type rate
    slave {
        pcm writeFile # Direct to the plugin which will write to a file
        format S16_LE
        rate 48000
    }
}

pcm.writeFile {
    type file
    slave.pcm null
    file "/tmp/snapfifo"
    format "raw"
}

PulseAudio

Redirect the PulseAudio stream into the snapfifo:

audio player software -> PulseAudio -> PulseAudio pipe sink -> snapfifo -> snapserver -> network -> snapclient -> Alsa

PulseAudio will create the pipe file for itself and will fail if it already exists; see the Configuration section in the main README file on how to change the pipe creation mode to read-only.

Load the module pipe-sink like this:

pacmd load-module module-pipe-sink file=/tmp/snapfifo sink_name=Snapcast format=s16le rate=48000
pacmd update-sink-proplist Snapcast device.description=Snapcast

It might be neccessary to set the PulseAudio latency environment variable to 60 msec: PULSE_LATENCY_MSEC=60

AirPlay

Snapserver supports shairport-sync with the stdout backend and metadata support.

  1. Install dependencies. For debian derivates: apt-get install autoconf libpopt-dev libconfig-dev libssl-dev
  2. Build shairport-sync (version 3.3 or later) with stdout backend:
    • autoreconf -i -f
    • ./configure --with-stdout --with-avahi --with-ssl=openssl --with-metadata
  3. Copy the shairport-sync binary somewhere to your PATH, e.g. /usr/local/bin/
  4. Configure snapserver with source = airplay:///shairport-sync?name=Airplay[&devicename=Snapcast][&port=5000]

Spotify

Snapserver supports librespot with the pipe backend.

  1. Build and copy the librespot binary somewhere to your PATH, e.g. /usr/local/bin/
  2. Configure snapserver with source = spotify:///librespot?name=Spotify[&username=<my username>&password=<my password>][&devicename=Snapcast][&bitrate=320][&onstart=<start command>][&onstop=<stop command>][&volume=<volume in percent>][&cache=<cache dir>][&disable_audio_cache=false][&killall=false]
    • Valid bitrates are 96, 160, 320
    • start command and stop command are executed by Librespot at start/stop
      • For example: onstart=/usr/bin/logger -t Snapcast Starting spotify...
    • If killall is true, all running instances of Librespot will be killed. This MUST be disabled on all spotify streams by setting it to false if you want to use multiple spotify streams.
    • If disable_audio_cache is false (default), downloaded audio files are cached in <cache dir>. If set to true audio files will not be cached on disk.

Process

Snapserver can start any process and read PCM data from the stdout of the process:

Configure snapserver with source = process:///path/to/process?name=Process[&params=<--my list --of params>][&log_stderr=false]

For example, you could install the minimalist mpv media player to pick up WebRadio from a given url ...

[stream]
source = process:///usr/bin/mpv?name=Webradio&sampleformat=48000:16:2&params=http://129.122.92.10:88/broadwavehigh.mp3 --no-terminal --audio-display=no --audio-channels=stereo --audio-samplerate=48000 --audio-format=s16 --ao=pcm:file=/dev/stdout

Line-in

Audio captured from line-in can be redirected to the snapserver's pipe, e.g. by using:

cpiped

cpipe

PulseAudio

parec >/tmp/snapfifo (defaults to 44.1kHz, 16bit, stereo)

VLC

Use --aout afile and --audiofile-file to pipe VLC's audio output to the snapfifo:

vlc --no-video --aout afile --audiofile-file /tmp/snapfifo