Mpd2chromecast

mpd2chromecast

This is a python script and related systemd service that you can deploy on a Volumio or moOde installation and use it to integrate single and multi-room playback with Google Chromecast devices and all variants such as Google/Nest Home speakers.

The script uses an MPD client to monitor playback state of MPD, the underlying media player layer used by both Volumio and moOde. It then generates and sends a URL for the playing file to the target chromecast device or group. The chromecast then streams the file contents and plays the file.

As you invoke play, stop, pause, next/previous, seek actions & volume control on your media platform, these are detected by the MPD interface and then relayed to the Chromecast to match the behaviour. The script also provides album artwork support that will appear on screen for video-based chromecasts.

Note: Does not work with the official Volumio 2.x releases but works fine on the 3.0 beta/RC releases.

Note: MPD Volume control needs to be enabled for this script to then relay that value to the cast device. If your MPD setup via Volumio or moOde is set to not allow MPD volume control, it may result in MPD not reporting a volume level. When this happens, the script will just disable volume support.

Acknowledgements

The script would not be possible without the dedicated hard work of others who wrote various modules that made my job a lot easier:

• python-mp2 (https://github.com/Mic92/python-mpd2)
  This module implements an MPD client API that made everything very consistent. Prior to using this module, I was talking directly to the Volumio and moOde APIs but this approach is a lot better.

• pychromecast (https://github.com/balloob/pychromecast)
  With this module, we are able to detect and control Chromecast-based devices on the LAN.

• cherrypy (cherrypy.org)
  All URL serving provided by this script is made possible by the cherrypy module. Python does come with it's own HTTP libraries for client and server but they can be quite complex when playing a web server role. Cherrypy provides a much more mature and reliable framework for providing a directory URL server needed for the media and albumart files.

Installation

Bookworm images for Raspi-OS

New Bookworm (V12) releases of Raspi-OS are now encouraging no user accounts by default within images.

If working with the latest Moode, you will have to have installed the image using the Raspberry Pi Imager and selected custom install options to:

• enable SSH
• add a user account for your own use (can name it whatever you desire)

Then the custom user account is where mpd2chromecast is installed in the steps below. You may also be able to leverage the web SSH feature in Moode to setup this account now if you are already installed and do not wish to reflash the image.

Volumio (as of July 2024) is still working on a Buster image (V10) and is still creating a volumio user in the image. So for Volumio, you will first need to enable SSH (using the /dev URL from the volumio web page) and then login as volumio (password also volumio).

Install Steps

ssh into your user account:

ssh volumio@volumio.local
or 
ssh pi@moode.local (or whatever custom user you created)

Then start the install process as follows (you will be prompted for the password for sudo):

curl -s https://raw.githubusercontent.com/dresdner353/mpd2chromecast/master/install.sh | sudo bash

This command will:

• Install required packages..
  git, python3, pip3, pychromecast cherrypy python-mpd2
• Download mpd2chromecast
• Configure and start it as a background service (systemd)

Web Interface

Browse to http://[your device ip]:8090 and you will see a very simple web interface for managing the cast devices. The first drop-down combo shows all discovered Google cast-enabled devices. Select the desired device and it will set that as the active cast device.

Once you have selected the desired chromecast, playback should start trying to cast the current track to the selected chromecast. From you preferred UI (Volumio or Moode Web I/F, MPD client, apps etc), try playing tracks, playlists, changing tracks, pausing, skipping and changing volume and you should see the Chromecast react pretty quickly as the script detects local MPD playback changes and casts the new tracks.

Switch chromecast device and you should experience playback stopping on the current device and transferring to the new device. By setting the device to 'Disabled', you will disable the casting functionality.

The 2nd combo box (with play icon) can be used to toggle between two playback modes:

• Cast file URL
  This is the default mode which serves the playing track file as a URL to the cast device. The end device will stream the selected file directly and perform all decoding.

• Cast MPD Output Stream (experimental)
  This is experimental at present and can be enabled easily with moOde and with a bit more work on Volumio. When you select this streaming mode, it passes the fixed URL http://<IP>:8000 to the selected cast device. The end result is that the stream being played is the output stream from MPD and not the original file. This allows for integration of DSP modes in MPD, crossfade and even gapless playback. It's not perfect and mileage may vary depending on how well your network works. See below on how to enable this in moOde or Volumio.

Enabling/Disabling the Service and Troubleshooting

To see the running script. ssh into the pi and run:

ps -ef | grep mpd2chromecast

If running, you should see a running process like this:

pi       18160     1  5 21:41 ?        00:00:08 /usr/bin/python3 /home/pi/mpd2chromecast/mpd2chromecast.py

That script was run by the systemd service installed. You can stop and start this as required:

# stop the service
sudo systemctl stop mpd2chromecast

# start the service
sudo systemctl start mpd2chromecast

# restart the service
sudo systemctl restart mpd2chromecast

# disable the service
# This prevents the service restarting, even after a reboot
sudo systemctl stop mpd2chromecast
sudo systemctl disable mpd2chromecast

# enable the service 
sudo systemctl enable mpd2chromecast
sudo systemctl start mpd2chromecast

If asked to grab logs as part of troubleshooting, it's best to do something like the following:

sudo systemctl stop mpd2chromecast
python3 mpd2chromecast/mpd2chromecast.py

The above will stop the background service and let you run the script directly on the terminal and see any output it produces. You can also add the --verbose option to that command for more verbose output or even redirect the output to a file etc. Ctrl-C to stop the direct execution and run sudo systemctl start mpd2chromecast to return to the background service.

Configuring MPD Streaming (for DSP integration or gapless playback)

If you're interested in gapless playback or leveraging any kind of DSP effects/processing provided by moOde or Volumio, then you can use the following steps to get MPD streaming enabled. Then when casting select the "Cast MPD Output Stream" to ensure that the MPD stream is cast instead of the file URL.

moOde MPD Streaming

Navigate to Moode -> Configure -> Audio -> MPD Options -> HTTP streaming. Then enable the HTTP streaming on port 8000 with FLAC encoding (for lossless). Then click the set button to apply the change.

Volumio MPD Streaming

With Volumio, its a bit of command line lifting:

ssh volumio@volumio.local

# take a backup of the original file (needed for updates)
cp /volumio/app/plugins/music_service/mpd/mpd.conf.tmpl mpd.conf.tmpl_orig

sudo nano /volumio/app/plugins/music_service/mpd/mpd.conf.tmpl

Then paste in the following in the audio output section:

audio_output {
    type "httpd"
    name "HTTP Server"
    port "8000"
    encoder "flac"
    compression "0"
    tags "yes"
    always_on "yes"
}

Ctrl-X and enter y to save the file.

Then you need to restart volumio to have it regenerate the MPD file:

volumio vrestart

Note: Volumio will likely refuse to update when this file has been modified. So when performing an update, you may need to first restore the original as follows:

# take a backup of the current file (that has your MPD mods)
cp /volumio/app/plugins/music_service/mpd/mpd.conf.tmpl mpd.conf.tmpl_bkup

# restore original file
sudo cp mpd.conf.tmpl_orig /volumio/app/plugins/music_service/mpd/mpd.conf.tmpl 

# restart volumio, and then try the update again
volumio vrestart

# After update, take a copy again of the latest file 
# and restore customised file (or recreate edits from scratch)
cp /volumio/app/plugins/music_service/mpd/mpd.conf.tmpl mpd.conf.tmpl_orig
sudo cp mpd.conf.tmpl_bkup /volumio/app/plugins/music_service/mpd/mpd.conf.tmpl 

How it works

The script runs four threads:

• MPD/Chromecast
  This is to monitor the playback state of the server via MPD API allowing us to know what is playing and react to track changes, volume, pause/play/skip etc. It then passes these directives to the configured chromecast. It also monitors the chromecast status to ensure playback is operational. An albumart link is also passed if available.

• Cherrypy (web server)
  This thread provides a simple web server which is used to serve a file and albumart URLs for each track. It listens on port 8090 serving music URLs from /music. The chromecasts will use the URLs to stream the files for native playback. The same server is also used to provide the control interface hosted on /cast and / allowing a user to select the desired cast mode and target cast device from the list of discovered devices.

• Config
  This thread just monitors config (~/.mpd2chromecast) to track changes for the selected chromecast device or cast mode.

• Chromecast Discovery
  This thread runs cont