# MPD (Music Player Daemon) #

MPD runs as a daemon.
Configure MPD to run either as a system service, or (more typically) run it directly as your user:

	$ mpd

MPD does many traditional music player things, like:

- maintain a database of music
- load and save playlists including the current play queue
- provide tools to search song metadata
- feed music files to the audio device to actually play songs

What MPD doesn't do is let a user directly control that stuff.
Sure, we could telnet to localhost:6600 (or wherever MPD is configured to listen), but generally we'll want to use on the numerous music player clients that provide an interface between the user and MPD.

	$ telnet localhost 6600
	Trying ::1...
	Connected to localhost.
	Escape character is '^]'.
	OK MPD 0.20.0
	stats
	uptime: 1412
	playtime: 16
	artists: 768
	albums: 540
	songs: 6801
	db_playtime: 1902630
	db_update: 1513708491
	OK
	^]
	telnet> Connection closed.

MPD comes with one very simple command-line client called `mpc`.
`mpc` may not be friendly enough to be your everyday music player, but it's great for learning about MPD.
Play with the commands described by `mpc help`.

	$ mpc
	Django Reinhardt - All the Things You Are
	[paused]  #7195/7773   0:03/2:55 (1%)
	volume: n/a   repeat: off   random: on    single: off   consume: off
	$ mpc help
	Usage: mpc [options] <command> [<arguments>]
	mpc version: 0.28
	
	Options:
	  -v, --verbose              Give verbose output
	  -q, --quiet                Suppress status message
	  -q, --no-status            synonym for --quiet
	  -h, --host=<host>          Connect to server on <host>
	  -P, --password=<password>  Connect to server using password <password>
	  -p, --port=<port>          Connect to server port <port>
	  -f, --format=<format>      Print status with format <format>
	  -w, --wait                 Wait for operation to finish (e.g. database update)

	Commands:
	  mpc                                                   Display status
	  mpc add <uri>                                         Add a song to the current playlist
	  mpc crop                                              Remove all but the currently playing song
	  mpc current                                           Show the currently playing song
	  [...]

Play some music:

```
$ mpc clear
$ mpc findadd genre Blues
$ mpc shuffle
$ mpc play
$ mpc help
```

## Configuration ##

Unless we specify a different configuration file when starting MPD, it looks for `$HOME/.mpdconf` and falls back to `/etc/mpd.conf`.
My `~/.mpdconf` file:

	# See mpd.conf(5).
	bind_to_address "~/.mpd/socket"
	bind_to_address "127.0.0.1"
	replaygain "off"
	music_directory "~/Music"
	playlist_directory "~/.mpd/playlists"
	db_file "~/.mpd/database"
	log_file "~/.mpd/log"
	pid_file "~/.mpd/pid"
	state_file "~/.mpd/state"
	sticker_file "~/.mpd/sticker.sql"

(MPD defaults assume the existence of the `~/.mpd/` directory. Maybe it creates it? To be safe `mkdir ~/.mpd`.)

See the [sample configuration file](https://github.com/MusicPlayerDaemon/MPD/blob/master/doc/mpdconf.example).

After modifying the configuration file, restart MPD:

	$ pkill -HUP mpd

## Database Updates ##

MPD should automatically update its database when files in its music directory change.
However, I sometimes need to prod it:

	$ mpc update

## Playlists ##

MPD has one active playlist at a time, also called the queue.
Save the current playlist to a file or load a different playlist:

	$ mpc lsplaylists
	$ mpc save myfavorites
	$ mpc load jazz

Show songs in the current playlist, and clear the current playlist ("clear" is safe — it doesn't destroy the contents of a saved playlist):

	$ mpc playlist
	$ mpc clear

Load every library song into the current playlist:

	$ mpc listall | mpc add

MPD loads and saves playlists in its `playlist_directory` (i.e. `~/.mpd/playlists/`).

If we want to manipulate playlists outside of an MPD client, or to interchange playlists with other programs, there are few things to know:

- MPD needs file names to have an `.m3u` extension, like `~/.mpd/playlists/myplaylist.m3u`.
- MPD generally notices if we drop a new playlist in its playlist directory, but sometimes we need to run `mpd update`.
- Most programs expect m3u playlists to include full file paths, but MPD uses paths relative to the music directory by default.
- We might want to change the above, but it's nice to be able to stuff like:

	$ mpc find genre Classical > ~/.mpd/playlists/Classical.m3u

## ncmpcpp ##

`ncmpcpp` is a powerful but horribly-named Curses client.
Also, it's default keybindings are not ideal for me.
See ncmpcpp(1) and `/usr/share/doc/ncmpcpp/bindings.gz`.

	$ zcat /usr/share/doc/ncmpcpp/bindings.gz > ~/.ncmpcpp/bindings

My more vim-like key bindings:

	def_key "k"
	  scroll_up
	def_key "j"
	  scroll_down
	def_key "ctrl-b"
	  page_up
	def_key "ctrl-f"
	  page_down
	def_key "l"
	  next_column
	def_key "h"
	  previous_column
	def_key "H"
	  show_help
	def_key "L"
	  show_lyrics

## Unix Socket ##

There are a couple of commands MPD only accepts over a unix socket connection.
Use `socat` to connect:

	$ socat - UNIX-CONNECT:$HOME/.mpd/socket
	OK MPD 0.20.0
	config
	music_directory: /home/paulgorman/Music
	OK

Some versions of `netcat` (e.g., OpenBSD's) also support this, like `nc -U ~/.mpd/socket`.

## Links ##

- https://www.musicpd.org/
- https://github.com/MusicPlayerDaemon/MPD/blob/master/doc/mpdconf.example
- https://github.com/pgorman/SpinMPC
- https://wiki.archlinux.org/index.php/Music_Player_Daemon
- https://help.ubuntu.com/community/MPD
- https://rybczak.net/ncmpcpp/
- https://wiki.archlinux.org/index.php/Ncmpcpp

Sun Dec 31 10:48:14 EST 2017