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MQTT in Shairport Sync

To enable Shairport Sync to act as an MQTT publisher, you need to:

  1. Install the mosquitto library:
# apt install libmosquitto-dev
  1. Add the configuration flag --with-mqtt-client to the list of parameters to the ./configure... command. For example:
$ ./configure --with-mqtt-client --sysconfdir=/etc --with-alsa --with-avahi --with-ssl=openssl --with-systemd

If Shairport Sync has MQTT support, it will have the string mqtt in its configuration string. For example:

$ shairport-sync -V
3.3.8-OpenSSL-Avahi-ALSA-metadata-mqtt-sysconfdir:/etc

Note: The Docker image will have MQTT support enabled by default.

Setting Up MQTT Publishing

This is a rough guide on the setup of MQTT publishing in ShairPort Sync. The MQTT service listens for and publishes metadata generated by the AirPlay source and Shairport Sync.

Example Configuration

In the following example, Shairport Sync is configured to publish parsed metadata information and album-art to a MQTT server under the topic "shairport".

metadata =
{
	enabled = "yes"; // Set this to yes to get Shairport Sync to solicit metadata from the source and to pass it on via a pipe.
	include_cover_art = "yes"; // Set to "yes" to get Shairport Sync to solicit cover art from the source and pass it via the pipe. You must also set "enabled" to "yes".
	cover_art_cache_directory = "/tmp/shairport-sync/.cache/coverart"; // Artwork will be stored in this directory if the dbus or MPRIS interfaces are enabled or if the MQTT client is in use. Set it to "" to prevent caching, which may be useful on some systems.
	pipe_name = "/tmp/shairport-sync-metadata";
	pipe_timeout = 5000; // Wait for this number of milliseconds for a blocked pipe to unblock before giving up.
};


mqtt =
{
	enabled = "yes"; // Set this to yes to enable the mqtt-metadata-service.
	hostname = "192.168.1.111"; // Hostname of the MQTT Broker.
	port = 1883; // Port on the MQTT Broker to connect to.
	username = "username"; // Set this to your MQTT user's username in order to enable username authentication.
	password = "password"; // Set this to your MQTT user's password in order to enable username & password authentication.
	topic = "shairport"; // MQTT topic where this instance of Shairport Sync should publish. If not set, the general.name value is used.
//	publish_raw = "no"; // Whether to publish all available metadata under the codes given in the 'metadata' docs.
	publish_parsed = "yes"; // Whether to publish a small (but useful) subset of metadata under human-understandable topics.
	publish_cover = "yes"; // Whether to publish the cover over MQTT in binary form. This may lead to a bit of load on the broker.
//	enable_remote = "no"; // Whether to remote control via MQTT. RC is available under `topic`/remote.
};

Important: Either publish_raw, publish_parsed, or publish_cover need to be set in the MQTT configuration. Otherwise, no messages will be published.

Overall Active States

active_start and active_end represent a stable on/off flag for the current AirPlay session.

active_start is plublished when any new AirPlay session begins.

active_end will fire after a configured timeout period unless the AirPlay stream is resumed.

sessioncontrol =
{
//	"active" state starts when play begins, and ends when the active_state_timeout has elapsed after play ends, unless another play session starts before the timeout has fully elapsed.
	active_state_timeout = 30.0;
};

Metadata Parsing

Additional details regarding the metadata can be found at https://github.com/mikebrady/shairport-sync-metadata-reader.

Metadata is generated by both the stream source (iOS, iTunes, etc.) and by Shairport Sync itself. This data is coded as two 4-character codes to identify each piece of data, the type and the code.

The first 4-character code, called the type, is either:

  • core for all the regular metadadata coming from iTunes, etc., or
  • ssnc (for 'shairport-sync') for all metadata coming from Shairport Sync itself, such as start/end delimiters, etc.

Additionally:

  • For core metadata, the second 4-character code is the 4-character metadata code that comes from iTunes, etc. See, for example, https://code.google.com/p/ytrack/wiki/DMAP for information about the significance of the codes. The original data supplied by the source, if any, follows, and is encoded in base64 format. The length of the data is also provided.
  • For ssnc metadata, the second 4-character code is used to distinguish the messages. Cover art, coming from the source, is not tagged in the same way as other metadata, it seems, so is sent as an ssnc type metadata message with the code PICT. Progress information, similarly, is not tagged like other source-originated metadata, so it is sent as an ssnc type with the code prgr.

Here are some of the core codes commonly passed from the source:

  • asal -- album
  • asar -- artist
  • ascp -- composer
  • asgn -- genre
  • astm -- song time
  • caps -- play status (stopped, paused, playing)
  • minm -- title
  • mper -- track persistent id

Here are the 'ssnc' codes defined so far:

  • PICT -- the payload is a picture, either a JPEG or a PNG. Check the first few bytes to see which.
  • acre -- Active Remote
  • cdid -- Client advertised Device ID
  • clip -- the payload is the IP address of the client, i.e. the sender of audio. Can be an IPv4 or an IPv6 address.
  • cmac -- Client advertised MAC address
  • cmod -- Client advertised model ("iPhone14,2")
  • daid -- DACP ID
  • dapo -- DACP Port
  • mden -- a sequence of metadata has ended. The RTP timestamp associated with the metadata sequence is included as data, if available.
  • mdst -- a sequence of metadata is about to start. The RTP timestamp associated with the metadata sequence is included as data, if available.
  • pbeg -- play stream begin. No arguments
  • pcen -- a picture has been sent. The RTP timestamp associated with it is included as data, if available.
  • pcst -- a picture is about to be sent. The RTP timestamp associated with it is included as data, if available.
  • pend -- play stream end. No arguments
  • pfls -- play stream flush. No arguments
  • prsm -- play stream resume. No arguments
  • prgr -- progress -- this is metadata from AirPlay consisting of RTP timestamps for the start of the current play sequence, the current play point and the end of the play sequence.
  • pvol -- play volume. The volume is sent as a string -- "airplay_volume,volume,lowest_volume,highest_volume", where "volume", "lowest_volume" and "highest_volume" are given in dB. The "airplay_volume" is what's sent by the source (e.g. iTunes) to the player, and is from 0.00 down to -30.00, with -144.00 meaning "mute". This is linear on the volume control slider of iTunes or iOS AirPlay. If the volume setting is being ignored by Shairport Sync itself, the volume, lowest_volume and highest_volume values are zero.
  • snam -- a device e.g. "Joe's iPhone" has started a play session. Specifically, it's the "X-Apple-Client-Name" string for AP1, or direct from the configuration Plist for AP2.
  • snua -- a "user agent" e.g. "iTunes/12..." has started a play session. Specifically, it's the "User-Agent" string.
  • stal -- this is an error message meaning that reception of a large piece of metadata, usually a large picture, has stalled; bad things may happen.
  • svip -- the payload is the IP address of the server, i.e. shairport-sync. Can be an IPv4 or an IPv6 address.

Parsed Messages

The MQTT service can parse the above raw messages into a subset of human-readable topics that include:

  • active_remote_id -- Active Remote ID
  • artist -- text of artist name
  • album -- text of album name
  • client_ip -- IP address of the connected client
  • client_device_id -- Client advertised Device ID
  • client_mac_address -- Client advertised MAC address
  • client_model -- Client advertised model ("iPhone14,2")
  • client_name -- Client advertised name ("Joe's iPhone")
  • dacp_id -- DACP ID
  • format -- ??
  • genre -- text of genre
  • server_ip -- IP address of Shairport Sync that the client is connected to
  • songalbum --
  • title -- text of song title
  • volume -- The volume is sent as a string -- "airplay_volume,volume,lowest_volume,highest_volume", where "volume", "lowest_volume" and "highest_volume" are given in dB. (see above)

Additionally, empty messages (--) at the following topics are published.

  • play_start -- fired at the begining of every song
  • play_end -- fired at the end of every song
  • play_flush -- fired when song is skipped or on positional change
  • play_resume -- fired when song play resumes from pause
  • active_start -- fired when a new active AirPlay session begins
  • active_end -- fired after a configured timeout period after the stream ends (unless a new stream begins)

Consuming MQTT Data

MQTT provides users with the flexibility to consume the MQTT data in various home automation projects. If you have an interesting use, please raise a new issue to suggest adding it to the guide, or simply fork the development branch and create a pull request.

Home Assistant Examples

The active_start and active_end have good potential use as triggers to turn on and off various connected receivers/zones. Note that payload_off is set to prevent accidental triggering.

mqtt:
  - binary_sensor:
      name: "shairport active start"
      state_topic: "shairport/active_start"
      payload_on: "--"
      payload_off: "OFF"
      off_delay: 300
  - binary_sensor:
      name: "shairport active end"
      state_topic: "shairport/active_end"
      payload_on: "--"
      payload_off: "OFF"
      off_delay: 300

In the below example, the parsed data is saved into the Home Assistant database as sensor data. Please note the conversion of the volume from dB to percentage.

mqtt:
  sensor:
    - name: "shairport album"
      state_topic: "shairport/album"
      expire_after: 600

    - name: "shairport artist"
      state_topic: "shairport/artist"
      expire_after: 600

    - name: "shairport title"
      state_topic: "shairport/title"
      expire_after: 600

    - name: "shairport genre"
      state_topic: "shairport/genre"
      expire_after: 600

    - name: "shairport volume (dB)"
      state_topic: "shairport/volume"

    - name: "shairport volume (PCT)"
      state_topic: "shairport/volume"
      value_template: "{{ value |  regex_findall_index(find='^(.+?),', index=0, ignorecase=False) | float / 30 + 1  }}"
      unit_of_measurement: 'percent'