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configuration.md

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Configuration

Sources

Audio sources are added to the server as source in the [stream] section of the configuration file /etc/snapserver.conf. Every source must be fed with a fixed sample format, that can be configured per stream (e.g. 48000:16:2).

The following notation is used in this paragraph:

  • <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"

The general format of an audio source is:

TYPE://host/path?name=<name>[&codec=<codec>][&sampleformat=<sampleformat>][&chunk_ms=<chunk ms>]

parameters have the form key=value, they are concatenated with an & character. Parameter name is mandatory for all sources, while codec, sampleformat and chunk_ms are optional and will override the default codec, sampleformat or chunk_ms settings. Non blocking sources support the dryout_ms parameter: when no new data is read from the source, send silence to the clients

Available audio source types are:

pipe

Captures audio from a named pipe

pipe:///<path/to/pipe>?name=<name>[&mode=create][&dryout_ms=2000]

mode can be create or read. Sometimes your audio source might insist in creating the pipe itself. So the pipe creation mode can by changed to "not create, but only read mode", using the mode option set to read

librespot

Launches librespot and reads audio from stdout

librespot:///<path/to/librespot>?name=<name>[&dryout_ms=2000][&username=<my username>&password=<my password>][&devicename=Snapcast][&bitrate=320][&wd_timeout=7800][&volume=100][&onevent=""][&normalize=false][&autoplay=false]

Note that you need to have the librespot binary on your machine and the sampleformat will be set to 44100:16:2

TODO: description of the parameters

airplay

Launches airplay and reads audio from stdout

airplay:///<path/to/airplay>?name=<name>[&dryout_ms=2000][&port=5000]

Note that you need to have the airplay binary on your machine and the sampleformat will be set to 44100:16:2

TODO: description of the parameters

file

Reads PCM audio from a file

file:///<path/to/PCM/file>?name=<name>

process

Launches a process and reads audio from stdout

process:///<path/to/process>?name=<name>[&dryout_ms=2000][&wd_timeout=0][&log_stderr=false][&params=<process arguments>]

TODO: description of the parameters

tcp server

Receives audio from a TCP socket (acting as server)

tcp://<listen IP, e.g. 127.0.0.1>:<port>?name=<name>[&mode=server]

default for port (if omitted) is 4953, default for mode is server

Mopdiy configuration would look like this (running GStreamer in client mode)

[audio]
output = audioresample ! audioconvert ! audio/x-raw,rate=48000,channels=2,format=S16LE ! wavenc ! tcpclientsink

tcp client

Receives audio from a TCP socket (acting as client)

tcp://<server IP, e.g. 127.0.0.1>:<port>?name=<name>&mode=client

Mopdiy configuration would look like this (running GStreamer in server mode):

[audio]
output = audioresample ! audioconvert ! audio/x-raw,rate=48000,channels=2,format=S16LE ! wavenc ! tcpserversink

alsa

Captures audio from an alsa device

alsa://?name=<name>&device=<alsa device>

device is an alsa device name or identifier, e.g. default or hw:0,0

The output of any audio player that uses alsa can be redirected to Snapcast by using an alsa loopback device:

  1. Setup the alsa loopback device by loading the kernel module:

    sudo modprobe snd-aloop

    The loopback device can be created during boot by adding snd-aloop to /etc/modules

  2. The loopback device should show up in aplay -l

    aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
Subdevices: 8/8
Subdevice #0: subdevice #0
Subdevice #1: subdevice #1
Subdevice #2: subdevice #2
Subdevice #3: subdevice #3
Subdevice #4: subdevice #4
Subdevice #5: subdevice #5
Subdevice #6: subdevice #6
Subdevice #7: subdevice #7
card 0: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
Subdevices: 8/8
Subdevice #0: subdevice #0
Subdevice #1: subdevice #1
Subdevice #2: subdevice #2
Subdevice #3: subdevice #3
Subdevice #4: subdevice #4
Subdevice #5: subdevice #5
Subdevice #6: subdevice #6
Subdevice #7: subdevice #7
card 1: Intel [HDA Intel], device 0: CX20561 Analog [CX20561 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: Intel [HDA Intel], device 1: CX20561 Digital [CX20561 Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 2: CODEC [USB Audio CODEC], device 0: USB Audio [USB Audio]
Subdevices: 0/1
Subdevice #0: subdevice #0

    In this example the loopback device is card 0 with devices 0 and 1, each having 8 subdevices.
    The devices are addressed with hw:<card idx>,<device idx>,<subdevice num>, e.g. hw:0,0,0.
    If a process plays audio using hw:0,0,x, then the audio will be looped back to hw:0,1,x

  3. Configure your player to use a loopback device

    For mopidy (gstreamer) in mopidy.conf:

    output = audioresample ! audioconvert ! audio/x-raw,rate=48000,channels=2,format=S16LE ! alsasink device=hw:0,0,0

    For mpd: in mpd.conf

    audio_output_format            "48000:16:2"
audio_output {
        type            "alsa"
        name            "My ALSA Device"
        device          "hw:0,0,0"      # optional
#       auto_resample   "no"
#       mixer_type      "hardware"      # optional
#       mixer_device    "default"       # optional
#       mixer_control   "PCM"           # optional
#       mixer_index     "0"             # optional
}

  4. Configure Snapserver to capture the loopback device:

    [stream]
stream = alsa://?name=SomeName&sampleformat=48000:16:2&device=hw:0,1,0