User’s Manual¶
Introduction¶
Music Player Daemon (MPD) is a flexible, powerful, server-side application for playing music. Through plugins and libraries it can play a variety of sound files while being controlled by its network protocol.
This document is work in progress. Most of it may be incomplete yet. Please help!
Installation¶
Installing on Debian/Ubuntu¶
Install the package mpd
via apt:
apt install mpd
When installed this way, MPD by default looks for music in /var/lib/mpd/music/
; this may not be correct. Look at your /etc/mpd.conf
file…
Note
Debian and Ubuntu are infamous for shipping heavily outdated software. The MPD version in their respective stable releases are usually too old to be supported by this project. Ironically, the MPD version in Debian “unstable” is more stable than the version in Debian “stable”.
Installing on Android¶
An experimental Android build is available on Google Play. After installing and launching it, MPD will scan the music in your Music directory and you can control it as usual with a MPD client.
If you need to tweak the configuration, you can create a file called
mpd.conf
in MPD’s data directory on the external storage
(usually Android/data/org.musicpd/files/mpd.conf
).
ALSA is not available on Android; only the OpenSL ES output plugin can be used for local playback.
Compiling from source¶
Download the source tarball and unpack it (or clone the git repository):
tar xf mpd-version.tar.xz
cd mpd-version
In any case, you need:
a C++17 compiler (e.g. GCC 8 or clang 7)
Meson 0.56.0 and Ninja
Boost 1.58
pkg-config
Each plugin usually needs a codec library, which you also need to install. Check the Plugin reference for details about required libraries
For example, the following installs a fairly complete list of build dependencies on Debian Bullseye:
apt install meson g++ \
libfmt-dev \
libpcre2-dev \
libmad0-dev libmpg123-dev libid3tag0-dev \
libflac-dev libvorbis-dev libopus-dev libogg-dev \
libadplug-dev libaudiofile-dev libsndfile1-dev libfaad-dev \
libfluidsynth-dev libgme-dev libmikmod-dev libmodplug-dev \
libmpcdec-dev libwavpack-dev libwildmidi-dev \
libsidplay2-dev libsidutils-dev libresid-builder-dev \
libavcodec-dev libavformat-dev \
libmp3lame-dev libtwolame-dev libshine-dev \
libsamplerate0-dev libsoxr-dev \
libbz2-dev libcdio-paranoia-dev libiso9660-dev libmms-dev \
libzzip-dev \
libcurl4-gnutls-dev libyajl-dev libexpat-dev \
libasound2-dev libao-dev libjack-jackd2-dev libopenal-dev \
libpulse-dev libshout3-dev \
libsndio-dev \
libmpdclient-dev \
libnfs-dev \
libupnp-dev \
libavahi-client-dev \
libsqlite3-dev \
libsystemd-dev \
libgtest-dev \
libboost-dev \
libicu-dev \
libchromaprint-dev \
libgcrypt20-dev
Now configure the source tree:
meson . output/release --buildtype=debugoptimized -Db_ndebug=true
The following command shows a list of compile-time options:
meson configure output/release
NB: Check the sysconfdir setting to determine where mpd will look for mpd.conf; if you expect mpd to look for /etc/mpd.conf the sysconfdir must be ‘/etc’ (i.e., not ‘etc’ which will result in mpd looking for /usr/local/etc/mpd.conf):
meson configure output/release |grep sysconfdir
If this is not /etc (or another path you wish to specify):
$ meson configure output/release -Dsysconfdir='/etc' ; meson configure output/release |grep syscon
sysconfdir /etc Sysconf data directory
When everything is ready and configured, compile:
ninja -C output/release
And install:
ninja -C output/release install
Compiling for Windows¶
Even though it does not “feel” like a Windows application, MPD works well under Windows. Its build process follows the “Linux style” and may seem awkward for Windows people (who are not used to compiling their software, anyway).
Basically, there are two ways to compile MPD for Windows:
Build as described above: with meson and ninja. To cross-compile from Linux, you need a Meson cross file.
The remaining difficulty is installing all the external libraries. And MPD usually needs many, making this method cumbersome for the casual user.
Build on Linux for Windows using MPD’s library build script.
This section is about the latter.
You need:
Meson 0.56.0 and Ninja
cmake
pkg-config
quilt
Just like with the native build, unpack the MPD source tarball and change into the directory. Then, instead of meson, type:
mkdir -p output/win64
cd output/win64
../../win32/build.py --64 \
--buildtype=debugoptimized -Db_ndebug=true \
-Dwrap_mode=forcefallback
This downloads various library sources, and then configures and builds
MPD (for x64; to build a 32 bit binary, pass
--32
). The resulting EXE files is linked statically, i.e. it
contains all the libraries already and you do not need carry DLLs
around. It is large, but easy to use. If you wish to have a small
mpd.exe with DLLs, you need to compile manually, without the
build.py
script.
The option -Dwrap_mode=forcefallback
tells Meson to download and
cross-compile several libraries used by MPD instead of looking for
them on your computer.
Compiling for Android¶
MPD can be compiled as an Android app. It can be installed easily with Google Play, but if you want to build it from source, follow this section.
You need:
Android SDK
Meson 0.56.0 and Ninja
cmake
pkg-config
quilt
Just like with the native build, unpack the MPD source tarball and change into the directory. Then, instead of meson, type:
mkdir -p output/android
cd output/android
../../android/build.py SDK_PATH NDK_PATH ABI \
--buildtype=debugoptimized -Db_ndebug=true \
-Dwrap_mode=forcefallback \
-Dandroid_debug_keystore=$HOME/.android/debug.keystore
ninja android/apk/mpd-debug.apk
SDK_PATH
is the absolute path where you installed the
Android SDK; NDK_PATH
is the Android NDK installation path;
ABI is the Android ABI to be built, e.g. “arm64-v8a
”.
This downloads various library sources, and then configures and builds MPD.
Configuration¶
The Configuration File¶
MPD reads its configuration from a text file. Usually, that is /etc/mpd.conf
, unless a different path is specified on the command line. If you run MPD as a user daemon (and not as a system daemon), the configuration is read from $XDG_CONFIG_HOME/mpd/mpd.conf
(usually ~/.config/mpd/mpd.conf
). On Android, mpd.conf
will be loaded from the top-level directory of the data partition.
Each line in the configuration file contains a setting name and its value, e.g.:
connection_timeout "5"
For settings which specify a filesystem path, the tilde is expanded:
music_directory "~/Music"
Some of the settings are grouped in blocks with curly braces, e.g. per-plugin settings:
audio_output {
type "alsa"
name "My ALSA output"
device "iec958:CARD=Intel,DEV=0"
mixer_control "PCM"
}
The include
directive can be used to include settings from
another file; the given file name is relative to the current file:
include "other.conf"
You can use include_optional
instead if you want the included file
to be optional; the directive will be ignored if the file does not exist:
include_optional "may_not_exist.conf"
Configuring the music directory¶
When you play local files, you should organize them within a directory called the “music directory”. This is configured in MPD with the music_directory setting.
By default, MPD follows symbolic links in the music directory. This behavior can be switched off: follow_outside_symlinks
controls whether MPD follows links pointing to files outside of the music directory, and follow_inside_symlinks
lets you disable symlinks to files inside the music directory.
Instead of using local files, you can use storage plugins to access
files on a remote file server. For example, to use music from the
SMB/CIFS server “myfileserver
” on the share called “Music”,
configure the music directory “smb://myfileserver/Music
”. For
a recipe, read the Satellite MPD section Satellite setup.
You can also use multiple storage plugins to assemble a virtual music directory consisting of multiple storages.
Configuring database plugins¶
If a music directory is configured, one database plugin is used. To
configure this plugin, add a database
block to
mpd.conf
:
database {
plugin "simple"
path "/var/lib/mpd/db"
}
More information can be found in the Database plugins reference.
Configuring neighbor plugins¶
All neighbor plugins are disabled by default to avoid unwanted
overhead. To enable (and configure) a plugin, add a neighbors
block to mpd.conf
:
neighbors {
plugin "smbclient"
}
More information can be found in the Neighbor plugins reference.
Configuring input plugins¶
To configure an input plugin, add an input
block to
mpd.conf
:
input {
plugin "curl"
proxy "proxy.local"
}
The following table lists the input options valid for all plugins:
Name |
Description |
---|---|
plugin |
The name of the plugin |
enabled yes|no |
Allows you to disable a input plugin without recompiling. By default, all plugins are enabled. |
More information can be found in the Input plugins reference.
Configuring the Input Cache¶
The input cache prefetches queued song files before they are going to be played. This has several advantages:
risk of buffer underruns during playback is reduced because this decouples playback from disk (or network) I/O
bulk transfers may be faster and more energy efficient than loading small chunks on-the-fly
by prefetching several songs at a time, the hard disk can spin down for longer periods of time
This comes at a cost:
memory usage
bulk transfers may reduce the performance of other applications which also want to access the disk (if the kernel’s I/O scheduler isn’t doing its job properly)
To enable the input cache, add an input_cache
block to the
configuration file:
input_cache {
size "1 GB"
}
This allocates a cache of 1 GB. If the cache grows larger than that, older files will be evicted.
You can flush the cache at any time by sending SIGHUP
to the
MPD process, see Signals.
Configuring decoder plugins¶
Most decoder plugins do not need any special configuration. To
configure a decoder, add a decoder
block to mpd.conf
:
decoder {
plugin "wildmidi"
config_file "/etc/timidity/timidity.cfg"
}
The following table lists the decoder options valid for all plugins:
Name |
Description |
---|---|
plugin |
The name of the plugin |
enabled yes|no |
Allows you to disable a decoder plugin without recompiling. By default, all plugins are enabled. |
More information can be found in the Decoder plugins reference.
Configuring encoder plugins¶
Encoders are used by some of the output plugins (such as shout). The
encoder settings are included in the audio_output
section, see Configuring audio outputs.
More information can be found in the Encoder plugins reference.
Configuring audio outputs¶
Audio outputs are devices which actually play the audio chunks produced by MPD. You can configure any number of audio output devices, but there must be at least one. If none is configured, MPD attempts to auto-detect. Usually, this works quite well with ALSA, OSS and on Mac OS X.
To configure an audio output manually, add one or more
audio_output
blocks to mpd.conf
:
audio_output {
type "alsa"
name "my ALSA device"
device "hw:0"
}
The following table lists the audio_output options valid for all plugins:
Name |
Description |
---|---|
type |
The name of the plugin |
name |
The name of the audio output. It is visible to the client. Some plugins also use it internally, e.g. as a name registered in the PULSE server. |
format samplerate:bits:channels |
Always open the audio output with the specified audio format, regardless of the format of the input file. This is optional for most plugins. See Global Audio Format for a detailed description of the value. |
enabled yes|no |
Specifies whether this audio output is enabled when MPD is started. By default, all audio outputs are enabled. This is just the default setting when there is no state file; with a state file, the previous state is restored. |
tags yes|no |
If set to no, then MPD will not send tags to this output. This is only useful for output plugins that can receive tags, for example the httpd output plugin. |
always_on yes|no |
If set to yes, then MPD attempts to keep this audio output always open. This may be useful for streaming servers, when you don’t want to disconnect all listeners even when playback is accidentally stopped. |
mixer_type hardware|software|null|none |
Specifies which mixer should be used for this audio output: the
hardware mixer (available for ALSA alsa, OSS
oss and PulseAudio pulse), the
software mixer, the “ |
replay_gain_handler software|mixer|none |
Specifies how Replay Gain is applied. The default is
|
filters “name,…” |
The specified configured filters are instantiated in the given
order. Each filter name refers to a |
More information can be found in the Output plugins reference.
Configuring filters¶
Filters are plugins which modify an audio stream.
To configure a filter, add a filter
block to mpd.conf
:
filter {
plugin "volume"
name "software volume"
}
Configured filters may then be added to the filters
setting of an
audio_output
section, see Configuring audio outputs.
The following table lists the filter options valid for all plugins:
Name |
Description |
---|---|
plugin |
The name of the plugin |
name |
The name of the filter |
More information can be found in the Filter plugins reference.
Configuring playlist plugins¶
Playlist plugins are used to load remote playlists (protocol commands load, listplaylist and listplaylistinfo). This is not related to MPD’s playlist directory.
To configure a playlist plugin, add a playlist_plugin
block to
mpd.conf
:
playlist_plugin {
name "m3u"
enabled "true"
}
The following table lists the playlist_plugin options valid for all plugins:
Name |
Description |
---|---|
name |
The name of the plugin |
enabled yes|no |
Allows you to disable a playlist plugin without recompiling. By default, all plugins are enabled. |
as_directory yes|no |
With this option, a playlist file of this type is parsed during database update and converted to a virtual directory, allowing MPD clients to access individual entries. By default, this is only enabled for the cue plugin. |
More information can be found in the Playlist plugins reference.
Audio Format Settings¶
Global Audio Format¶
The setting audio_output_format
forces MPD to use one
audio format for all outputs. Doing that is usually not a good idea.
The value is specified as samplerate:bits:channels
.
Any of the three attributes may be an asterisk to specify that this
attribute should not be enforced, example: 48000:16:*
.
*:*:*
is equal to not having a format specification.
The following values are valid for bits: 8
(signed 8 bit integer
samples), 16
, 24
(signed 24 bit integer samples padded to 32
bit), 32
(signed 32 bit integer samples), f
(32 bit floating
point, -1.0 to 1.0), dsd
means DSD (Direct Stream Digital). For
DSD, there are special cases such as dsd64
, which allows you to
omit the sample rate (e.g. dsd512:2
for stereo DSD512,
i.e. 22.5792 MHz).
The sample rate is special for DSD: MPD counts the number of bytes, not bits. Thus, a DSD “bit” rate of 22.5792 MHz (DSD512) is 2822400 from MPD’s point of view (44100*512/8).
Resampler¶
Sometimes, music needs to be resampled before it can be played; for example, CDs use a sample rate of 44,100 Hz while many cheap audio chips can only handle 48,000 Hz. Resampling reduces the quality and consumes a lot of CPU. There are different options, some of them optimized for high quality and others for low CPU usage, but you can’t have both at the same time. Often, the resampler is the component that is responsible for most of MPD’s CPU usage. Since MPD comes with high quality defaults, it may appear that MPD consumes more CPU than other software.
Check the Resampler plugins reference for a list of resamplers and how to configure them.
Volume Normalization Settings¶
Replay Gain¶
The setting replaygain
specifies whether MPD shall adjust the
volume of songs played using ReplayGain tags.
Setting this to album
will adjust volume using the album’s
ReplayGain tags, while setting it to track
will adjust it using
the “track” ReplayGain tags. auto
uses the track ReplayGain tags
if random play is activated otherwise the album ReplayGain
tags.
If ReplayGain is enabled, then the setting replaygain_preamp
is
set to a value (in dB) between -15
and 15
. This is the gain
applied to songs with ReplayGain tags.
On songs without ReplayGain tags, the setting
replaygain_missing_preamp
is used instead. If this setting is not
configured, then no ReplayGain is applied to such songs, and they will
appear too loud.
ReplayGain is usually implemented with a software volume filter (which
prevents Bit-perfect playback). To use a hardware mixer, set
replay_gain_handler
to mixer
in the audio_output
section
(see Configuring audio outputs for details).
Simple Volume Normalization¶
MPD implements a very simple volume normalization method which can be
enabled by setting volume_normalization
to yes
. It supports
16 bit PCM only.
Cross-Fading¶
If crossfade
is set to a positive number, then adjacent songs are
cross-faded by this number of seconds. This is a run-time setting
which can be controlled by clients,
e.g. with mpc:
mpc crossfade 10
mpc crossfade 0
Zero means cross-fading is disabled.
Cross-fading is only possible if both songs have the same audio format. At the cost of quality loss and higher CPU usage, you can make sure this is always given by configuring Global Audio Format.
MixRamp¶
MixRamp tags describe the loudness levels at start and end of a song and can be used by MPD to find the best time to begin cross-fading. MPD enables MixRamp if:
Cross-fade is enabled
mixrampdelay is set to a positive value, e.g.:
mpc mixrampdelay 1
mixrampdb is set to a reasonable value, e.g.:
mpc mixrampdb -17
both songs have MixRamp tags
both songs have the same audio format (or Global Audio Format is configured)
The MixRamp tool can be used to add MixRamp tags to your song files.
Client Connections¶
Listeners¶
The setting bind_to_address
specifies which addresses
MPD listens on for connections from clients. It can be
used multiple times to bind to more than one address. Example:
bind_to_address "192.168.1.42"
bind_to_address "127.0.0.1"
The default is “any”, which binds to all available addresses.
Additionally, MPD binds to $XDG_RUNTIME_DIR/mpd/socket
(if it
was launched as a per-user daemon and no bind_to_address
setting exists).
You can set a port that is different from the global port setting, e.g. “localhost:6602”. IPv6 addresses must be enclosed in square brackets if you want to configure a port:
bind_to_address "[::1]:6602"
To bind to a local socket (UNIX domain socket), specify an absolute
path or a path starting with a tilde (~). Some clients default to
connecting to /var/run/mpd/socket
so this may be a good
choice:
bind_to_address "/var/run/mpd/socket"
On Linux, local sockets can be bound to a name without a socket inode
on the filesystem; MPD implements this by prepending @
to the
address:
bind_to_address "@mpd"
If no port is specified, the default port is 6600. This default can be changed with the port setting:
port "6601"
These settings will be ignored if systemd socket activation is used.
Permissions and Passwords¶
By default, all clients are unauthenticated and have a full set of permissions. This can be restricted with the settings default_permissions
and password
.
default_permissions
controls the permissions of a new client. Its value is a comma-separated list of permissions:
Name |
Description |
---|---|
read |
Allows reading of the database, displaying the current playlist, and current status of MPD. |
add |
Allows adding songs and loading playlists. |
player |
Allows any player and queue manipulation (start/pause/stop playback etc.). |
control |
Allows all other player and playlist manipulations. |
admin |
Allows manipulating outputs, stickers and partitions, mounting/unmounting storage and shutting down MPD. |
local_permissions
may be used to assign other permissions to clients connecting on a local socket.
host_permissions
may be used to assign permissions to clients
with a certain IP address.
password
allows the client to send a password to gain other permissions. This option may be specified multiple times with different passwords.
Note that the password
option is not secure: passwords are sent in clear-text over the connection, and the client cannot verify the server’s identity.
Example:
default_permissions "read"
host_permissions "192.168.0.100 read,add,control,admin"
host_permissions "2003:1234:4567::1 read,add,control,admin"
password "the_password@read,add,control"
password "the_admin_password@read,add,control,admin"
Other Settings¶
Setting |
Description |
---|---|
metadata_to_use TAG1,TAG2,… |
Use only the specified tags, and ignore the others. This setting can reduce the database size and MPD’s memory usage by omitting unused tags. By default, all tags but comment are enabled. The special value “none” disables all tags. If the setting starts with
Section Tags contains a list of supported tags. |
The State File¶
The state file is a file where MPD saves and restores its state (play queue, playback position etc.) to keep it persistent across restarts and reboots. It is an optional setting.
MPD will attempt to load the state file during startup, and will save it when shutting down the daemon. Additionally, the state file is refreshed every two minutes (after each state change).
Setting |
Description |
---|---|
state_file PATH |
Specify the state file location. The parent directory must be writable by the MPD user (+wx). |
state_file_interval SECONDS |
Auto-save the state file this number of seconds after each state change. Defaults to 120 (2 minutes). |
restore_paused yes|no |
If set to |
The Sticker Database¶
“Stickers” are pieces of information attached to songs. Some clients
use them to store ratings and other volatile data. This feature
requires SQLite, compile-time configure option
-Dsqlite=...
.
Setting |
Description |
---|---|
sticker_file PATH |
The location of the sticker database. |
Resource Limitations¶
These settings are various limitations to prevent MPD from using too many resources (denial of service).
Setting |
Description |
---|---|
connection_timeout SECONDS |
If a client does not send any new data in this time period, the connection is closed. Clients waiting in “idle” mode are excluded from this. Default is 60. |
max_connections NUMBER |
This specifies the maximum number of clients that can be connected to MPD at the same time. Default is 100. |
max_playlist_length NUMBER |
The maximum number of songs that can be in the playlist. Default is 16384. |
max_command_list_size KBYTES |
The maximum size a command list. Default is 2048 (2 MiB). |
max_output_buffer_size KBYTES |
The maximum size of the output buffer to a client (maximum response size). Default is 8192 (8 MiB). |
Buffer Settings¶
Do not change these unless you know what you are doing.
Setting |
Description |
---|---|
audio_buffer_size SIZE |
Adjust the size of the internal audio buffer. Default is
|
Zeroconf¶
If Zeroconf support (Avahi or Apple’s Bonjour)
was enabled at compile time with -Dzeroconf=...
,
MPD can announce its presence on the network. The following
settings control this feature:
Setting |
Description |
---|---|
zeroconf_enabled yes|no |
Enables or disables this feature. Default is yes. |
zeroconf_name NAME |
The service name to publish via Zeroconf. The default is “Music Player @ %h”. %h will be replaced with the hostname of the machine running MPD. |
Advanced configuration¶
Satellite setup¶
MPD runs well on weak machines such as the Raspberry Pi. However, such hardware tends to not have storage big enough to hold a music collection. Mounting music from a file server can be very slow, especially when updating the database.
One approach for optimization is running MPD on the file server, which not only exports raw files, but also provides access to a readily scanned database. Example configuration:
music_directory "nfs://fileserver.local/srv/mp3"
#music_directory "smb://fileserver.local/mp3"
database {
plugin "proxy"
host "fileserver.local"
}
The music_directory
setting tells MPD to read files from the given NFS server. It does this by connecting to the server from userspace. This does not actually mount the file server into the kernel’s virtual file system, and thus requires no kernel cooperation and no special privileges. It does not even require a kernel with NFS support, only the nfs storage plugin (using the libnfs userspace library). The same can be done with SMB/CIFS using the smbclient storage plugin (using libsmbclient).
The database setting tells MPD to pass all database queries on to the MPD instance running on the file server (using the proxy plugin).
Real-Time Scheduling¶
On Linux, MPD attempts to configure real-time scheduling for some threads that benefit from it.
This is only possible if you allow MPD to do it. This privilege is controlled by RLIMIT_RTPRIO
RLIMIT_RTTIME
. You can configure this privilege with ulimit before launching MPD:
ulimit -HS -r 40; mpd
Or you can use the prlimit program from the util-linux package:
prlimit --rtprio=40 --rttime=unlimited mpd
The systemd service file shipped with MPD comes with this setting.
This works only if the Linux kernel was compiled with CONFIG_RT_GROUP_SCHED disabled. Use the following command to check this option for your current kernel:
zgrep ^CONFIG_RT_GROUP_SCHED /proc/config.gz
You can verify whether the real-time scheduler is active with the ps command:
# ps H -q `pidof -s mpd` -o 'pid,tid,cls,rtprio,comm'
PID TID CLS RTPRIO COMMAND
16257 16257 TS - mpd
16257 16258 TS - io
16257 16259 FF 40 rtio
16257 16260 TS - player
16257 16261 TS - decoder
16257 16262 FF 40 output:ALSA
16257 16263 IDL 0 update
The CLS column shows the CPU scheduler; TS is the normal scheduler; FF and RR are real-time schedulers. In this example, two threads use the real-time scheduler: the output thread and the rtio (real-time I/O) thread; these two are the important ones. The database update thread uses the idle scheduler (“IDL in ps), which only gets CPU when no other process needs it.
Note
There is a rumor that real-time scheduling improves audio quality. That is not true. All it does is reduce the probability of skipping (audio buffer xruns) when the computer is under heavy load.
Using MPD¶
Starting and Stopping MPD¶
The simplest (but not the best) way to start MPD is to simply type:
mpd
This will start MPD as a daemon process (which means it
detaches from your terminal and continues to run in background). To
stop it, send SIGTERM
to the process; if you have configured a
pid_file
, you can use the --kill
option:
mpd --kill
The best way to manage MPD processes is to use a service manager such as systemd.
systemd¶
MPD ships with systemd service units.
If you have installed MPD with your operating system’s package manager, these are probably preinstalled, so you can start and stop MPD this way (like any other service):
systemctl start mpd
systemctl stop mpd
systemd socket activation¶
Using systemd, you can launch MPD on demand when the first client attempts to connect.
MPD comes with two systemd unit files: a “service” unit and
a “socket” unit. These will be installed to the directory specified
with -Dsystemd_system_unit_dir=...
,
e.g. /lib/systemd/system
.
To enable socket activation, type:
systemctl enable mpd.socket
systemctl start mpd.socket
In this configuration, MPD will ignore the listener
settings (bind_to_address
and port
).
systemd user unit¶
You can launch MPD as a systemd user unit. These will be
installed to the directory specified with
-Dsystemd_user_unit_dir=...
,
e.g. /usr/lib/systemd/user
or
$HOME/.local/share/systemd/user
.
Once the user unit is installed, you can start and stop MPD like any other service:
systemctl --user start mpd
To auto-start MPD upon login, type:
systemctl --user enable mpd
Signals¶
MPD understands the following UNIX signals:
SIGTERM
,SIGINT
: shut down MPDSIGHUP
: reopen log files (send this after log rotation) and flush caches (see Configuring the Input Cache)
The client¶
After you have installed, configured and started MPD, you choose a client to control the playback.
The most basic client is mpc, which provides a command line interface. It is useful in shell scripts. Many people bind specific mpc commands to hotkeys.
The MPD Wiki contains an extensive list of clients to choose from.
The music directory and the database¶
The “music directory” is where you store your music files. MPD stores all relevant meta information about all songs in its “database”. Whenever you add, modify or remove songs in the music directory, you have to update the database, for example with mpc:
mpc update
Depending on the size of your music collection and the speed of the storage, this can take a while.
To exclude a file from the update, create a file called
.mpdignore
in its parent directory. Each line of that file
may contain a list of shell wildcards. Matching files (or
directories) in the current directory and all subdirectories are
excluded. Example:
*.opus
99*
Subject to pattern matching is the file/directory name. It is (not
yet) possible to match nested path names, e.g. something like
foo/*.flac
is not possible.
Mounting other storages into the music directory¶
MPD has various storage plugins of which multiple instances can be “mounted” into the music directory. This way, you can use local music, file servers and USB sticks at the same time. Example:
mpc mount foo nfs://192.168.1.4/export/mp3
mpc mount usbstick udisks://by-uuid-2F2B-D136
mpc unmount usbstick
MPD’s neighbor plugins can be helpful with finding mountable storages:
mpc listneighbors
Mounting is only possible with the simple database plugin and a cache_directory
, e.g.:
database {
plugin "simple"
path "~/.mpd/db"
cache_directory "~/.mpd/cache"
}
This requires migrating from the old db_file
setting to a database section. The cache directory must exist, and MPD will put one file per mount there, which will be reused when the same storage is used again later.
Metadata¶
When scanning or playing a song, MPD parses its metadata. See Tags for a list of supported tags.
The metadata_to_use setting can be used to enable or disable certain tags.
Note that MPD may not necessarily read metadata itself, instead relying on data reported by the decoder that was used to read a file. For example, this is the case for the FFmpeg decoder: both MPD and FFmpeg need to support a given metadata format in order for metadata to be picked up correctly.
Only if a decoder does not have metadata support will MPD attempt to parse a song’s metadata itself.
The queue¶
The queue (sometimes called “current playlist”) is a list of songs to be played by MPD. To play a song, add it to the queue and start playback. Most clients offer an interface to edit the queue.
Stored Playlists¶
Stored playlists are some kind of secondary playlists which can be
created, saved, edited and deleted by the client. They are addressed
by their names. Its contents can be loaded into the queue, to be
played back. The playlist_directory
setting specifies where
those playlists are stored.
Advanced usage¶
Bit-perfect playback¶
“Bit-perfect playback” is a phrase used by audiophiles to describe a setup that plays back digital music as-is, without applying any modifications such as resampling, format conversion or software volume. Naturally, this implies a lossless codec.
By default, MPD attempts to do bit-perfect playback, unless you tell it not to. Precondition is a sound chip that supports the audio format of your music files. If the audio format is not supported, MPD attempts to fall back to the nearest supported audio format, trying to lose as little quality as possible.
To verify if MPD converts the audio format, enable verbose logging, and watch for these lines:
decoder: audio_format=44100:24:2, seekable=true
output: opened plugin=alsa name="An ALSA output" audio_format=44100:16:2
output: converting from 44100:24:2
This example shows that a 24 bit file is being played, but the sound chip cannot play 24 bit. It falls back to 16 bit, discarding 8 bit.
However, this does not yet prove bit-perfect playback; ALSA may be fooling MPD that the audio format is supported. To verify the format really being sent to the physical sound chip, try:
cat /proc/asound/card*/pcm*p/sub*/hw_params
access: RW_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 44100 (44100/1)
period_size: 4096
buffer_size: 16384
Obey the “format” row, which indicates that the current playback format is 16 bit (signed 16 bit integer, little endian).
Check list for bit-perfect playback:
Use the ALSA output plugin.
Disable sound processing inside ALSA by configuring a “hardware” device (
hw:0,0
or similar).Don’t use software volume (setting
mixer_type
).Don’t use Replay Gain.
Don’t force MPD to use a specific audio format (settings
format
, audio_output_format).Verify that you are really doing bit-perfect playback using MPD’s verbose log and
/proc/asound/card*/pcm*p/sub*/hw_params
. Some DACs can also indicate the audio format.
Direct Stream Digital (DSD)¶
DSD (Direct Stream Digital) is a digital format that stores audio as a sequence of single-bit values at a very high sampling rate. It is the sample format used on Super Audio CDs.
MPD understands the file formats DSDIFF and DSF. There are three ways to play back DSD:
Native DSD playback. Requires ALSA 1.0.27.1 or later, a sound driver/chip that supports DSD and of course a DAC that supports DSD.
DoP (DSD over PCM) playback. This wraps DSD inside fake 24 bit PCM according to the DoP standard. Requires a DAC that supports DSD. No support from ALSA and the sound chip required (except for bit-perfect 24 bit PCM support).
Convert DSD to PCM on-the-fly.
Native DSD playback is used automatically if available. DoP is only
used if enabled explicitly using the dop
option, because there
is no way for MPD to find out whether the DAC supports
it. DSD to PCM conversion is the fallback if DSD cannot be used
directly.
ICY-MetaData¶
Some MP3 streams send information about the current song with a
protocol named “ICY-MetaData”.
MPD makes its StreamTitle
value available as Title
tag.
By default, MPD assumes this tag is UTF-8-encoded. To tell
MPD to assume a different character set, specify it in the
charset
URL fragment parameter, e.g.:
mpc add 'http://radio.example.com/stream#charset=cp1251'
Client Hacks¶
External Mixer¶
The setting mixer_type "null"
asks MPD to pretend that there is a mixer, but not actually do something. This allows you to implement a MPD client which listens for mixer events, queries the current (fake) volume, and uses it to program an external mixer. For example, your client can forward this setting to your amplifier.
Troubleshooting¶
Where to start¶
Make sure you have the latest MPD version (via mpd --version
, not mpc version). All the time, bugs are found and fixed, and your problem might be a bug that is fixed already. Do not ask for help unless you have the latest MPD version. The most common excuse is when your distribution ships an old MPD version - in that case, please ask your distribution for help, and not the MPD project.
Check the log file. Configure log_level "verbose"
or pass --verbose
to mpd.
Sometimes, it is helpful to run MPD in a terminal and follow what happens. This is how to do it:
mpd --stderr --no-daemon --verbose
Support¶
Getting Help¶
The MPD project runs a forum and an IRC channel (#mpd on Libera.Chat) for requesting help. Visit the MPD help page for details on how to get help.
Common Problems¶
Startup¶
Error “could not get realtime scheduling”¶
See Real-Time Scheduling. You can safely ignore this, but you won’t benefit from real-time scheduling. This only makes a difference if your computer runs programs other than MPD.
Error “Failed to initialize io_uring”¶
Linux specific: the io_uring subsystem could not be initialized. This is not a critical error - MPD will fall back to “classic” blocking disk I/O. You can safely ignore this error, but you won’t benefit from io_uring’s advantages.
“Cannot allocate memory” usually means that your memlock limit (
ulimit -l
in bash orLimitMEMLOCK
in systemd) is too low. 64 MB is a reasonable value for this limit.Your Linux kernel might be too old and does not support io_uring.
Error “bind to ‘0.0.0.0:6600’ failed (continuing anyway, because binding to ‘[::]:6600’ succeeded)”¶
This happens on Linux when /proc/sys/net/ipv6/bindv6only
is
disabled. MPD first binds to IPv6, and this automatically binds to
IPv4 as well; after that, MPD binds to IPv4, but that fails. You can
safely ignore this, because MPD works on both IPv4 and IPv6.
Database¶
I can’t see my music in the MPD database¶
Check your
music_directory
setting.Does the MPD user have read permission on all music files, and read+execute permission on all music directories (and all of their parent directories)?
Did you update the database? (mpc update)
Did you enable all relevant decoder plugins at compile time? mpd --version will tell you.
Playback¶
I can’t hear music on my client¶
That problem usually follows a misunderstanding of the nature of MPD. MPD is a remote-controlled music player, not a music distribution system. Usually, the speakers are connected to the box where MPD runs, and the MPD client only sends control commands, but the client does not actually play your music.
MPD has output plugins which allow hearing music on a remote host (such as httpd), but that is not MPD’s primary design goal.
Error “Device or resource busy”¶
This ALSA error means that another program uses your sound hardware exclusively. You can stop that program to allow MPD to use it.
Sometimes, this other program is PulseAudio, which can multiplex sound from several applications, to allow them to share your sound chip. In this case, it might be a good idea for MPD to use PulseAudio as well, instead of using ALSA directly.
Reporting Bugs¶
If you believe you found a bug in MPD, report it on the bug tracker.
Your bug report should contain:
the output of mpd --version
your configuration file (
mpd.conf
)relevant portions of the log file (
--verbose
)be clear about what you expect MPD to do, and what is actually happening
Too Much CPU Usage¶
If you believe MPD consumes too much CPU, write a bug report with a profiling information.
On Linux, this can be obtained with perf (on Debian,
installed the package linux-perf
), for example:
perf record -p `pidof mpd`
Run this command while MPD consumes much CPU, let it run for a minute
or so, and stop it by pressing Ctrl-C
. Then type:
perf report >mpd_perf.txt
Upload the output file to the bug report.
Note
This requires having debug symbols for MPD and all relevant libraries. See MPD crashes for details.
MPD crashes¶
All MPD crashes are bugs which must be fixed by a developer, and you should write a bug report. (Many crash bugs are caused by codec libraries used by MPD, and then that library must be fixed; but in any case, the MPD bug tracker is a good place to report it first if you don’t know.)
A crash bug report needs to contain a “backtrace”.
First of all, your MPD executable must not be “stripped”
(i.e. debug information deleted). The executables shipped with Linux
distributions are usually stripped, but some have so-called “debug”
packages (package mpd-dbgsym
or mpd-dbg
on Debian,
mpd-debug
on other distributions). Make sure this package is
installed.
If you built MPD from sources, please recompile with Meson
option “--buildtype=debug -Db_ndebug=false
”, because this will
add more helpful information to the backtrace.
You can extract the backtrace from a core dump, or by running MPD in a debugger, e.g.:
gdb --args mpd --stderr --no-daemon --verbose
run
As soon as you have reproduced the crash, type “bt” on the gdb command prompt. Copy the output to your bug report.