Difference between revisions of "Music Player Daemon"

Revision as of 14:32, 25 February 2014

zh-CN:Music Player Daemon

MPD (music player daemon) is an audio player that has a server-client architecture. It plays audio files, organizes playlists and maintains a music database all while using very few resources. In order to interface with it, a separate client is needed.

Installation

The latest stable version of mpd is available in the official repositories.

Should users wish to run an experimental version, the AUR offers several from which to choose. For example, mpd-git^AUR.

Setup

MPD is able to run locally (per user settings), globally (settings apply to all users), and in multiple instances. The way of setting up mpd depends on the way it is intended to be used: a local configuration may prove more useful on a desktop system, for example.

In order for MPD to be able to play back audio, ALSA or OSS (optionally with PulseAudio) needs to be setup and working.

MPD is configured in mpd.conf. The location of this file depends on how you want to run MPD (see the sections below). These are commonly used configuration options:

• pid_file - The file where mpd stores its process ID
• db_file - The music database
• state_file - MPD's current state is noted here
• playlist_directory - The folder where playlists are saved into
• music_directory - The folder that MPD scans for music
• sticker_file - The sticker database

Global configuration

The default /etc/mpd.conf keeps the setup in /var/lib/mpd and uses mpd as default user. However, /var/lib/mpd is owned by root by default, we need to change this so mpd can write here:

# chown -R mpd /var/lib/mpd

Edit /etc/mpd.conf and add a music_directory line with the path to your music directory:

music_directory /path/to/music

Music directory

MPD needs to have +x permissions on all parent directories to the music collection.

If the music directory is located outside of /var/lib/mpd, you will most likely need to remount the music directory under a directory that the MPD user (mpd by default) has access to:

# mkdir /var/lib/mpd/music
# echo "/path/to/music/dir /var/lib/mpd/music none bind" >> /etc/fstab
# mount -a

Also see this forum thread.

An additional solution would be to just create a symbolic link into /var/lib/mpd/music.

# mkdir /var/lib/mpd/music
# ln -s /path/to/music/dir /var/lib/mpd/music/

If the music collection is contained under multiple directories, create symbolic links under the main music directory in /var/lib/mpd. Remember to set permissions accordingly on the directories being linked.

Start MPD

MPD can be controlled with mpd.service using systemd. The first startup can take some time as MPD will scan your music directory.

Test everything by starting a client application (ncmpc is a light and easy to use client), and play some music!

Configure audio

To change the volume for mpd independent from other programs, uncomment or add this switch in mpd.conf:

/etc/mpd.conf

mixer_type			"software"

Users of ALSA will want to have the following device definition, which allows software volume control in the MPD client to control the volume separately from other applications.

/etc/mpd.conf

audio_output {
        type            "alsa"
        name            "My Sound Card"
        mixer_type      "software"      # optional
}

Users of PulseAudio will need to make the following modification:

/etc/mpd.conf

audio_output {
        type            "pulse"
        name            "pulse audio"
}

PulseAudio supports multiple advanced operations, e.g. transferring the audio to a different machine. For advanced configuration with MPD see Music Player Daemon Community Wiki.

Changing user

Changing the group that MPD runs as may result in errors like output: Failed to open "My ALSA Device", [alsa]: Failed to open ALSA device "default": No such file or directory or player_thread: problems opening audio device while playing "Song Name.mp3".

This is because the MPD users need to be part of the audio group to access sound devices under /dev/snd/. To fix it add user make the MPD user part of the audio group:

# gpasswd -a mpd audio

Timeline of MPD startup

To depict when MPD drops its superuser privileges and assumes those of the user set in the configuration, the timeline of a normal MPD startup is listed here:

1. Since MPD is started as root by systemd, it first reads the /etc/mpd.conf file.
2. MPD reads the user variable in the /etc/mpd.conf file, and changes from root to this user.
3. MPD then reads the contents of the /etc/mpd.conf file and configures itself accordingly.

Notice that MPD changes the running user from root to the one named in the /etc/mpd.conf file. This way, uses of ~ in the configuration file point correctly to the home user's directory, and not root's directory. It may be worthwhile to change all uses of ~ to /home/username to avoid any confusion over this aspect of MPD's behavior.

Local configuration (per user)

MPD can be configured per user (rather than the typical method of configuring MPD globally). Running MPD as a normal user has the benefits of:

• A single directory ~/.config/mpd/ (or any other directory under $HOME) that will contain all the MPD configuration files.
• Easier to avoid unforeseen read/write permission errors.

Good practice is to create a single directory for the required files and playlists. It can be any directory for which you have read and write access, e.g. ~/.config/mpd/ or ~/.mpd/. This section assumes it is ~/.config/mpd/, which corresponds to the default value of $XDG_CONFIG_HOME (part of XDG Base Directory Specification).

MPD searches for a config file in $XDG_CONFIG_HOME/mpd/mpd.conf and then ~/.mpdconf. It is also possible to pass other path as command line argument.

Copy the example configuration file to desired location, for example:

$ cp /usr/share/doc/mpd/mpdconf.example ~/.config/mpd/mpd.conf

Edit ~/.config/mpd/mpd.conf and specify the required files:

~/.config/mpd/mpd.conf

# Required files
db_file            "~/.config/mpd/database"
log_file           "~/.config/mpd/log"

# Optional
music_directory    "~/music"
playlist_directory "~/.config/mpd/playlists"
pid_file           "~/.config/mpd/pid"
state_file         "~/.config/mpd/state"
sticker_file       "~/.config/mpd/sticker.sql"

Create all the files and directories as configured above:

$ mkdir ~/.config/mpd/playlists
$ touch ~/.config/mpd/{database,log,pid,state,sticker.sql}

When the paths of required files are configured, MPD can be started. To specify custom location of the configuration file:

$ mpd config_file

Autostart on tty login

To start MPD on login add the following to ~/.profile (or another autostart file):

# MPD daemon start (if no other user instance exists)
[ ! -s ~/.config/mpd/pid ] && mpd

Autostart in X

If you use a desktop environment, place the following file in ~/.config/autostart/:

~/.config/autostart/mpd.desktop

[Desktop Entry]
Encoding=UTF-8
Type=Application
Name=Music Player Daemon
Comment=Server for playing audio files
Exec=mpd
StartupNotify=false
Terminal=false
Hidden=false
X-GNOME-Autostart-enabled=false

If you do not use a DE, place the line from #Autostart on tty login in your autostart file.

Autostart with systemd

The package mpd provides user service file in /usr/lib/systemd/user/mpd.service. The configuration file is expected to exist either in ~/.mpdconf or ~/.config/mpd/mpd.conf, see systemd#Editing provided unit files if you would like to use different path. The process is not started as root, so you should not use the user and group variables in the MPD configuration file, the process already has user permissions and therefore it is not necessary to change them further.

All you have to do is enable and start the mpd user service.

Scripted configuration

Rasi has written a script that will create the proper directory structure, configuration files and prompt for the location of the user's Music directory; it can be downloaded here.

Multi-mpd setup

Useful if running an icecast server.

For a second MPD (e.g., with icecast output to share music over the network) using the same music and playlist as the one above, simply copy the above configuration file and make a new file (e.g., /home/username/.mpd/config-icecast), and only change the log_file, error_file, pid_file, and state_file parameters (e.g., mpd-icecast.log, mpd-icecast.error, and so on); using the same directory paths for the music and playlist directories would ensure that this second mpd would use the same music collection as the first one e.g., creating and editing a playlist under the first daemon would affect the second daemon as well. Users do not have to create the same playlists all over again for the second daemon. Call this second daemon the same way from ~/.xinitrc above. (Just be sure to have a different port number, so as to not conflict with the first mpd daemon).

Clients

A separate client is needed to control mpd. See a long list of clients at the mpd wiki. Popular options are:

Console

• mpc — Simple KISS client. All basic functionality available

http://mpd.wikia.com/wiki/Client:Mpc || mpc

• ncmpc — Ncurses client for mpd

http://mpd.wikia.com/wiki/Client:Ncmpc || ncmpc

• ncmpcpp — Almost exact clone of ncmpc with some new features written in C++ (tag editor, search engine)

http://unkart.ovh.org/ncmpcpp/ || ncmpcpp

• pms — Highly configurable and accessible ncurses client

http://pms.sourceforge.net/ || pmus^AUR

• vimpc — Ncurses based MPD client with vi-like key bindings

http://sourceforge.net/projects/vimpc/ || vimpc^AUR

Graphical

• Ario — Very feature-rich GTK2 GUI client for mpd, inspired by Rhythmbox

http://ario-player.sourceforge.net/ || ario

• QmpdClient — GUI client written with Qt 4.x

http://bitcheese.net/wiki/QMPDClient || qmpdclient

• Sonata — Elegant Python GTK+ client

http://sonata.berlios.de/ || sonata

• gmpc — GTK2 frontend for Music Player Daemon. It is designed to be lightweight and easy to use, while providing full access to all of MPD's features. Users are presented with several different methods to browse through their music. It can be extended by plugins, of which many are available.

http://gmpc.wikia.com/wiki/Gnome_Music_Player_Client || gmpc

• Dmpc — Dmenu-based MPC client with a playlist manager and state-saving on playlist changes

http://wintervenom.mine.nu/ || dmpc^AUR

• Cantata — High-feature, Qt4/KDE4 client for MPD with very configurable interface

https://code.google.com/p/cantata/ || cantata-qt^AUR

Web

• Patchfork — Web client for MPD written in PHP and Ajax

http://mpd.wikia.com/wiki/Client:Pitchfork || patchfork-git^AUR.

See also

• MPD Forum
• MPD User Manual
• Wikipedia article