linux mpd 音乐播放守护程序

### 一、mpd和mpc 安装和配置

下载安装 mpd 和 mpc 
```
sudo apt install mpd mpc -y
```

修改 mpd 启动配置环境 /etc/default/mpd 
```
pi@raspberrypi:~/Workship/mpd_audio/ympd-1.3.0/build $ cat /etc/default/mpd 
## Defaults for the MPD init script, sourced by /etc/init.d/mpd on Debian
## systems.  Uncomment (remove the leading '#') and change values as needed.

## If you don't want MPD to be started as a system service (for example, if
## you want to run it from a regular user account), disable it using the
## command 'update-rc.d mpd disable' (or 'systemctl disable mpd' for systemd).

## The configuration file location for mpd:
# MPDCONF=/etc/mpd.conf
MPDCONF=/home/pi/.config/mpd/mpd.conf
```

位于软件包的 MPD 配置示例提供了一个创建用户配置的案例
```
sudo gzip -d /usr/share/doc/mpd/mpdconf.example.gz
cp /usr/share/doc/mpd/mpdconf.example ~/.config/mpd/mpd.conf
```

编辑配置文件 ~/.config/mpd/mpd.conf
```bash
# An example configuration file for MPD.
# Read the user manual for documentation: http://www.musicpd.org/doc/user/

# Files and directories #######################################################
#
# This setting controls the top directory which MPD will search to discover the
# available audio files and add them to the daemon's online database. This
# setting defaults to the XDG directory, otherwise the music directory will be
# be disabled and audio files will only be accepted over ipc socket (using
# file:// protocol) or streaming files over an accepted protocol.
#
music_directory         "~/music"
#
# This setting sets the MPD internal playlist directory. The purpose of this
# directory is storage for playlists created by MPD. The server will use
# playlist files not created by the server but only if they are in the MPD
# format. This setting defaults to playlist saving being disabled.
#
playlist_directory              "~/.config/mpd/playlists"
#
# This setting sets the location of the MPD database. This file is used to
# load the database at server start up and store the database while the
# server is not up. This setting defaults to disabled which will allow
# MPD to accept files over ipc socket (using file:// protocol) or streaming
# files over an accepted protocol.
#
db_file                 "~/.config/mpd/mpd.db"

# These settings are the locations for the daemon log files for the daemon.
#
# The special value "syslog" makes MPD use the local syslog daemon. This
# setting defaults to logging to syslog.
#
# If you use systemd, do not configure a log_file.  With systemd, MPD
# defaults to the systemd journal, which is fine.
#
log_file                        "~/.config/mpd/log"

# This setting sets the location of the file which stores the process ID
# for use of mpd --kill and some init scripts. This setting is disabled by
# default and the pid file will not be stored.
#
# If you use systemd, do not configure a pid_file.
#
pid_file                        "~/.config/mpd/pid"

# This setting sets the location of the file which contains information about
# most variables to get MPD back into the same general shape it was in before
# it was brought down. This setting is disabled by default and the server
# state will be reset on server start up.
#
state_file                      "~/.config/mpd/state"
#
# The location of the sticker database.  This is a database which
# manages dynamic information attached to songs.
#
#sticker_file                   "~/.config/mpd/sticker.sql"
#
###############################################################################

# General music daemon options ################################################
#
# This setting specifies the user that MPD will run as. MPD should never run as
# root and you may use this setting to make MPD change its user ID after
# initialization. This setting is disabled by default and MPD is run as the
# current user.
#
user                            "pi"
#
# This setting specifies the group that MPD will run as. If not specified
# primary group of user specified with "user" setting will be used (if set).
# This is useful if MPD needs to be a member of group such as "audio" to
# have permission to use sound card.
#
group                           "pi"
#
# This setting sets the address for the daemon to listen on. Careful attention
# should be paid if this is assigned to anything other than the default, any.
# This setting can deny access to control of the daemon. Not effective if
# systemd socket activation is in use.
#
# For network
bind_to_address         "0.0.0.0"
#
# And for Unix Socket
bind_to_address         "~/.config/mpd/socket"
#
# This setting is the TCP port that is desired for the daemon to get assigned
# to.
#
port                            "6600"
#
# Suppress all messages below the given threshold.  Use "verbose" for
# troubleshooting. Available setting arguments are "notice", "info", "verbose",
# "warning" and "error".
#
#log_level                      "notice"
#
# Setting "restore_paused" to "yes" puts MPD into pause mode instead
# of starting playback after startup.
#
#restore_paused "no"
#
# This setting enables MPD to create playlists in a format usable by other
# music players.
#
#save_absolute_paths_in_playlists       "no"
#
# This setting defines a list of tag types that will be extracted during the
# audio file discovery process. The complete list of possible values can be
# found in the user manual.
#metadata_to_use        "artist,album,title,track,name,genre,date,composer,performer,disc"
#
# This example just enables the "comment" tag without disabling all
# the other supported tags:
#metadata_to_use "+comment"
#
# This setting enables automatic update of MPD's database when files in
# music_directory are changed.
#
#auto_update    "yes"
#
# Limit the depth of the directories being watched, 0 means only watch
# the music directory itself.  There is no limit by default.
#
#auto_update_depth "3"
#
###############################################################################

# Symbolic link behavior ######################################################
#
# If this setting is set to "yes", MPD will discover audio files by following
# symbolic links outside of the configured music_directory.
#
#follow_outside_symlinks        "yes"   # 允许跟随指向主目录外部的符号链接
#
# If this setting is set to "yes", MPD will discover audio files by following
# symbolic links inside of the configured music_directory.
#
#follow_inside_symlinks         "yes"   # 允许跟随主音乐目录内部的符号链接（递归扫描）
#
###############################################################################

# Zeroconf / Avahi Service Discovery ##########################################
#
# If this setting is set to "yes", service information will be published with
# Zeroconf / Avahi.
#
#zeroconf_enabled               "yes"
#
# The argument to this setting will be the Zeroconf / Avahi unique name for
# this MPD server on the network. %h will be replaced with the hostname.
#
#zeroconf_name                  "Music Player @ %h"
#
###############################################################################

# Permissions #################################################################
#
# If this setting is set, MPD will require password authorization. The password
# setting can be specified multiple times for different password profiles.
#
#password                        "password@read,add,control,admin"
#
# This setting specifies the permissions a user has who has not yet logged in.
#
#default_permissions             "read,add,control,admin"
#
###############################################################################

# Database #######################################################################
#
# An example of a database section instead of the old 'db_file' setting.
# It enables mounting other storages into the music directory.
#
#database {
#       plugin "simple"
#       path "~/.local/share/mpd/db
#       cache_directory "~/.local/share/mpd/cache"
#}
#
# An example of database config for a satellite setup
#
#music_directory "nfs://fileserver.local/srv/mp3"
#database {
#       plugin "proxy"
#       host "other.mpd.host"
#       port "6600"
#}

# Input #######################################################################
#
input {
        plugin "curl"
#       proxy "proxy.isp.com:8080"
#       proxy_user "user"
#       proxy_password "password"
}

#
###############################################################################

# Decoder #####################################################################
#

decoder {
        plugin                  "hybrid_dsd"
        enabled                 "no"
#       gapless                 "no"
}

# 强制禁用 wildmidi 插件
# 如果希望保留 MIDI 文件支持，安装 wildmidi 所需依赖：
# sudo apt install wildmidi
decoder {
        plugin        "wildmidi"
        enabled       "no"
        #config_file "/etc/timidity/timidity.cfg"
}

# Audio Output ################################################################
#
# MPD supports various audio output types, as well as playing through multiple
# audio outputs at the same time, through multiple audio_output settings
# blocks. Setting this block is optional, though the server will only attempt
# autodetection for one sound card.
#
# An example of an ALSA output:
#
audio_output {
        type            "alsa"
        name            "My ALSA Device"
        device          "hw:0,0"        # optional
        #mixer_type      "hardware"     # optional
        mixer_type      "software"      # optional
        mixer_device    "default"       # optional
        mixer_control   "PCM"           # optional
        mixer_index     "0"             # optional
}
#
# An example of an OSS output:
#
#audio_output {
#       type            "oss"
#       name            "My OSS Device"
##      device          "/dev/dsp"      # optional
##      mixer_type      "hardware"      # optional
##      mixer_device    "/dev/mixer"    # optional
##      mixer_control   "PCM"           # optional
#}
#
# An example of a shout output (for streaming to Icecast):
#
#audio_output {
#       type            "shout"
#       encoder         "vorbis"                # optional
#       name            "My Shout Stream"
#       host            "localhost"
#       port            "8000"
#       mount           "/mpd.ogg"
#       password        "hackme"
#       quality         "5.0"
#       bitrate         "128"
#       format          "44100:16:1"
##      protocol        "icecast2"              # optional
##      user            "source"                # optional
##      description     "My Stream Description" # optional
##      url             "http://example.com"    # optional
##      genre           "jazz"                  # optional
##      public          "no"                    # optional
##      timeout         "2"                     # optional
##      mixer_type      "software"              # optional
#}
#
# An example of a recorder output:
#
#audio_output {
#       type            "recorder"
#       name            "My recorder"
#       encoder         "vorbis"                # optional, vorbis or lame
#       path            "/var/lib/mpd/recorder/mpd.ogg"
##      quality         "5.0"                   # do not define if bitrate is defined
#       bitrate         "128"                   # do not define if quality is defined
#       format          "44100:16:1"
#}
#
# An example of a httpd output (built-in HTTP streaming server):
#
#audio_output {
#       type            "httpd"
#       name            "My HTTP Stream"
#       encoder         "vorbis"                # optional, vorbis or lame
#       port            "8000"
#       bind_to_address "0.0.0.0"               # optional, IPv4 or IPv6
##      quality         "5.0"                   # do not define if bitrate is defined
#       bitrate         "128"                   # do not define if quality is defined
#       format          "44100:16:1"
#       max_clients     "0"                     # optional 0=no limit
#}
#
# An example of a pulseaudio output (streaming to a remote pulseaudio server)
#
#audio_output {
#       type            "pulse"
#       name            "My Pulse Output"
##      server          "remote_server"         # optional
##      sink            "remote_server_sink"    # optional
##      media_role      "media_role"            #optional
#}
#
# An example of a winmm output (Windows multimedia API).
#
#audio_output {
#       type            "winmm"
#       name            "My WinMM output"
##      device          "Digital Audio (S/PDIF) (High Definition Audio Device)" # optional
#               or
##      device          "0"             # optional
##      mixer_type      "hardware"      # optional
#}
#
# An example of a wasapi output (Windows multimedia API).
#
#audio_output {
#       type            "wasapi"
#       name            "My WASAPI output"
##      device          "Digital Audio (S/PDIF) (High Definition Audio Device)" # optional
#               or
##      device          "0"             # optional
## Exclusive mode blocks all other audio source, and get best audio quality without resampling.
##      exclusive       "no"            # optional
## Enumerate all devices in log.
##      enumerate       "no"            # optional
#}
#
# An example of an openal output.
#
#audio_output {
#       type            "openal"
#       name            "My OpenAL output"
##      device          "Digital Audio (S/PDIF) (High Definition Audio Device)" # optional
#}
#
# An example of an sndio output.
#
#audio_output {
#       type            "sndio"
#       name            "sndio output"
#       mixer_type      "hardware"
#}
#
# An example of an OS X output:
#
#audio_output {
#       type            "osx"
#       name            "My OS X Device"
##      device          "Built-in Output"       # optional
##      channel_map      "-1,-1,0,1"    # optional
#}
#
## Example "pipe" output:
#
#audio_output {
#       type            "pipe"
#       name            "my pipe"
#       command         "aplay -f cd 2>/dev/null"
## Or if you're want to use AudioCompress
#       command         "AudioCompress -m | aplay -f cd 2>/dev/null"
## Or to send raw PCM stream through PCM:
#       command         "nc example.org 8765"
#       format          "44100:16:2"
#}
#
## An example of a null output (for no audio output):
#
#audio_output {
#       type            "null"
#       name            "My Null Output"
#       mixer_type      "none"                  # optional
#}
#
###############################################################################

# Normalization automatic volume adjustments ##################################
#
# This setting specifies the type of ReplayGain to use. This setting can have
# the argument "off", "album", "track" or "auto". "auto" is a special mode that
# chooses between "track" and "album" depending on the current state of
# random playback. If random playback is enabled then "track" mode is used.
# See <https://wiki.hydrogenaud.io/index.php?title=Replaygain> for
# more details about ReplayGain.
# This setting is off by default.
#
#replaygain                     "album"
#
# This setting sets the pre-amp used for files that have ReplayGain tags. By
# default this setting is disabled.
#
#replaygain_preamp              "0"
#
# This setting sets the pre-amp used for files that do NOT have ReplayGain tags.
# By default this setting is disabled.
#
#replaygain_missing_preamp      "0"
#
# This setting enables or disables ReplayGain limiting.
# MPD calculates actual amplification based on the ReplayGain tags
# and replaygain_preamp / replaygain_missing_preamp setting.
# If replaygain_limit is enabled MPD will never amplify audio signal
# above its original level. If replaygain_limit is disabled such amplification
# might occur. By default this setting is enabled.
#
#replaygain_limit               "yes"
#
# This setting enables on-the-fly normalization volume adjustment. This will
# result in the volume of all playing audio to be adjusted so the output has
# equal "loudness". This setting is disabled by default.
#
#volume_normalization           "no"
#
###############################################################################

# Character Encoding ##########################################################
#
# If file or directory names do not display correctly for your locale then you
# may need to modify this setting.
#
filesystem_charset              "UTF-8"
#
###############################################################################
```

### 二、mpc 控制

mpc 常用指令
```bash
man mpc      # 查看文档

mpc update
mpc listall
mpc add
mpc listall |mpc add
mpc playlist
mpc play
mpc stop
mpc next
mpc prev
mpc volume [+/-][num]        # 加减音量
mpc volume  [num]            # 设置音量

```

创建所需目录及文件:
```bash
mkdir -p ~/.config/mpd/playlists
touch ~/.config/mpd/{mpd.db,log,state}  # 数据库、日志和状态文件[6](@ref)
```
MPD 需要扫描上述定义的 music_directory 目录，才能建立数据库文件。为完成这一任务，需要使用一个 MPD#客户端。例如，对于 mpc，执行命令是：
```bash
mpc update
```

**systemd  用户级服务自启动**
修改 /etc/default/mpd 文件 中的# MPDCONF=/etc/mpd.conf  为 ~/.config/mpd/mpd.conf
修改 /usr/lib/systemd/user/mpd.service 用户级启动配置文件
```
[Unit]
Description=Music Player Daemon
Documentation=man:mpd(1) man:mpd.conf(5)
Documentation=file:///usr/share/doc/mpd/html/user.html
After=network.target sound.target

[Service]
Type=notify
# 增加指定启动配置文件变量
EnvironmentFile=/etc/default/mpd     
ExecStart=/usr/bin/mpd --systemd $MPDCONF

# Enable this setting to ask systemd to watch over MPD, see
# systemd.service(5).  This is disabled by default because it causes
# periodic wakeups which are unnecessary if MPD is not playing.
#WatchdogSec=120

# allow MPD to use real-time priority 40
LimitRTPRIO=40
LimitRTTIME=infinity

# for io_uring
LimitMEMLOCK=64M

# disallow writing to /usr, /bin, /sbin, ...
ProtectSystem=yes

# more paranoid security settings
NoNewPrivileges=yes
ProtectKernelTunables=yes
ProtectControlGroups=yes
# AF_NETLINK is required by libsmbclient, or it will exit() .. *sigh*
RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX AF_NETLINK
RestrictNamespaces=yes

# Note that "ProtectKernelModules=yes" is missing in the user unit
# because systemd 232 is unable to reduce its own capabilities
# ("Failed at step CAPABILITIES spawning /usr/bin/mpd: Operation not
# permitted")

[Install]
WantedBy=default.target
```

```bash
systemctl --user enable mpd.service
```

### 参考文档
[Arch linux mpd wiki](https://wiki.archlinuxcn.org/wiki/MPD)
[音乐守护进程mpd，mpc和ncmpcpp - 播放器三重奏](https://www.bilibili.com/video/BV1vo2tYhEmR/?spm_id_from=333.337.search-card.all.click&vd_source=64bcdab1e8263295a838d5e4a0fab29c)
[Standalone MPD Web GUI written in C, utilizing Websockets and Bootstrap/JS](https://github.com/notandy/ympd)

Plattenalbum — 小巧而现代化的 GTK4 界面客户端，用 Python 编写而成。
https://github.com/SoongNoonien/plattenalbum || plattenalbumAUR
[mpc doc](https://www.musicpd.org/doc/mpc/html/)