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<?xml version='1.0' encoding="utf-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
                      "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">

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<book>
  <title>The Music Player Daemon - User's Manual</title>

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  <chapter id="intro">
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    <title>Introduction</title>

    <para>
      This document is work in progress.  Most of it may be incomplete
      yet.  Please help!
    </para>

    <para>
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      <application>MPD</application> (Music Player Daemon) is, as the
      name suggests, a server software allowing you to remotely play
      your music, handle playlists, deliver music (HTTP streams with
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      various sub-protocols) and organize playlists.
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    </para>

    <para>
      It has been written with minimal resource usage and stability in
      mind!  Infact, it runs fine on a Pentium 75, allowing you to use
      your cheap old PC to create a stereo system!
    </para>

    <para>
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      <application>MPD</application> supports also gapless playback,
      buffered audio output, and crossfading!
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    </para>

    <para>
      The separate client and server design allows users to choose a
      user interface that best suites their tastes independently of
      the underlying daemon, which actually plays music!
    </para>
  </chapter>

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  <chapter id="install">
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    <title>Installation</title>

    <para>
      We recommend that you use the software installation routines of
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      your distribution to install <application>MPD</application>.
      Most operating systems have a <application>MPD</application>
      package, which is very easy to install.
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    </para>

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    <section id="install_debian">
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      <title>Installing on Debian/Ubuntu</title>

      <para>
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        Install the package <application>MPD</application> via APT:
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      </para>

      <programlisting>apt-get install mpd</programlisting>

      <para>
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        When installed this way, <application>MPD</application> by
        default looks for music in
        <filename>/var/lib/mpd/music/</filename>; this may not be
        correct. Look at your <filename>/etc/mpd.conf</filename>
        file...
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      </para>
    </section>

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    <section id="install_android">
      <title>Installing on Android</title>

      <para>
        An experimental Android build is available on <ulink
        url="https://play.google.com/store/apps/details?id=org.musicpd">Google
        Play</ulink>.  After installing and launching it, MPD will
        scan the music in your <filename>Music</filename> directory
        and you can control it as usual with a MPD client.
      </para>

      <para>
        If you need to tweak the configuration, you can create a file
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        called <filename>mpd.conf</filename> on the data partition
        (the directory which is returned by Android's <ulink
        url="https://developer.android.com/reference/android/os/Environment.html#getExternalStorageDirectory()">getExternalStorageDirectory()</ulink>
        API function).
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      </para>
    </section>

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    <section id="install_source">
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      <title>Compiling from source</title>

      <para>
        Download the source tarball from <ulink
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        url="http://www.musicpd.org/download.html">the
        <application>MPD</application> home page</ulink> and unpack
        it:
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      </para>

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      <programlisting>tar xf mpd-version.tar.xz
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cd mpd-version</programlisting>

      <para>
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        In any case, you need:
      </para>

      <itemizedlist>
        <listitem>
          <para>
            a C++14 compiler (e.g. <ulink
            url="http://gcc.gnu.org/">gcc 4.9</ulink> or <ulink
            url="http://clang.llvm.org/">clang 3.9</ulink>)
          </para>
        </listitem>

        <listitem>
          <para>
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            <ulink url="http://www.boost.org/">Boost 1.54</ulink>
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          </para>
        </listitem>

        <listitem>
          <para>
            <ulink url="https://www.freedesktop.org/wiki/Software/pkg-config/">pkg-config</ulink>
          </para>
        </listitem>
      </itemizedlist>

      <para>
        Each plugin usually needs a codec library, which you also need
        to install.  Check the plugin reference for details about
        required libraries.
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      </para>

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      <para>
        For example, the following installs a fairly complete list of
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        build dependencies on Debian Jessie:
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      </para>

      <programlisting>
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apt-get install g++ \
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  libmad0-dev libmpg123-dev libid3tag0-dev \
  libflac-dev libvorbis-dev libopus-dev \
  libadplug-dev libaudiofile-dev libsndfile1-dev libfaad-dev \
  libfluidsynth-dev libgme-dev libmikmod2-dev libmodplug-dev \
  libmpcdec-dev libwavpack-dev libwildmidi-dev \
  libsidplay2-dev libsidutils-dev libresid-builder-dev \
  libavcodec-dev libavformat-dev \
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  libmp3lame-dev libtwolame-dev libshine-dev \
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  libsamplerate0-dev libsoxr-dev \
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  libbz2-dev libcdio-paranoia-dev libiso9660-dev libmms-dev \
  libzzip-dev \
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  libcurl4-gnutls-dev libyajl-dev libexpat-dev \
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  libasound2-dev libao-dev libjack-jackd2-dev libopenal-dev \
  libpulse-dev libroar-dev libshout3-dev \
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  libsndio-dev \
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  libmpdclient-dev \
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  libnfs-dev libsmbclient-dev \
  libupnp-dev \
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  libavahi-client-dev \
  libsqlite3-dev \
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  libsystemd-dev libwrap0-dev \
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  libcppunit-dev xmlto \
  libboost-dev \
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  libicu-dev
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      </programlisting>

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      <para>
        Now configure the source tree:
      </para>

      <programlisting>./configure</programlisting>

      <para>
        The <parameter>--help</parameter> argument shows a list of
        compile-time options.  When everything is ready and
        configured, compile:
      </para>

      <programlisting>make</programlisting>

      <para>
        And install:
      </para>

      <programlisting>make install</programlisting>
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      <section id="windows_build">
        <title>Compiling for Windows</title>

        <para>
          Even though it does not "feel" like a Windows application,
          <application>MPD</application> 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).
        </para>

        <para>
          Basically, there are three ways to compile
          <application>MPD</application> for Windows:
        </para>

        <orderedlist>
          <listitem>
            <para>
              Build on Windows for Windows.  All you need to do is
              described above already: configure and make.
            </para>

            <para>
              For Windows users, this is kind of unusual, because few
              Windows users have a GNU toolchain and a UNIX shell
              installed.
            </para>
          </listitem>

          <listitem>
            <para>
              Build on Linux for Windows.  This is described above
              already: configure and make.  You need the <ulink
              url="https://mingw-w64.org/"><application>mingw-w64</application>
              cross compiler</ulink>.  Pass
              <parameter>--host=i686-w64-mingw32</parameter> (32 bit)
              or <parameter>--host=x86_64-w64-mingw32</parameter> (64
              bit) to configure.
            </para>

            <para>
              This is somewhat natural for Linux users.  Many
              distributions have <application>mingw-w64</application>
              packages.  The remaining difficulty here is installing
              all the external libraries.  And
              <application>MPD</application> usually needs many,
              making this method cumbersome for the casual user.
            </para>
          </listitem>

          <listitem>
            <para>
              Build on Linux for Windows using the
              <application>MPD</application>'s library build script.
            </para>
          </listitem>
        </orderedlist>

        <para>
          This section is about the latter.
        </para>

        <para>
          Just like with the native build, unpack the
          <application>MPD</application> source tarball and change
          into the directory.  Then, instead of
          <command>./configure</command>, type:
        </para>

        <programlisting>./win32/build.py --64</programlisting>

        <para>
          This downloads various library sources, and then configures
          and builds <application>MPD</application> (for x64; to build
          a 32 bit binary, pass <parameter>--32</parameter>).  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 <filename>mpd.exe</filename> with DLLs, you need to
          compile manually, without the <filename>build.py</filename>
          script.
        </para>
      </section>
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      <section id="android_build">
        <title>Compiling for Android</title>

        <para>
          MPD can be compiled as an Android app.  It can be installed
          easily with <link linkend="install_android">Google
          Play</link>, but if you want to build it from source, follow
          this section.
        </para>

        <para>
          You need:
        </para>

        <itemizedlist>
          <listitem>
            <para>
              Android SDK
            </para>
          </listitem>

          <listitem>
            <para>
              <ulink
              url="https://developer.android.com/ndk/downloads/index.html">Android
              NDK</ulink>
            </para>
          </listitem>
        </itemizedlist>

        <para>
          Just like with the native build, unpack the
          <application>MPD</application> source tarball and change
          into the directory.  Then, instead of
          <command>./configure</command>, type:
        </para>

        <programlisting>./android/build.py SDK_PATH NDK_PATH ABI
make android/build/mpd-debug.apk</programlisting>

        <para>
          <varname>SDK_PATH</varname> is the absolute path where you
          installed the Android SDK; <varname>NDK_PATH</varname> is
          the Android NDK installation path; <varname>ABI</varname> is
          the Android ABI to be built, e.g. "armeabi-v7a".
        </para>

        <para>
          This downloads various library sources, and then configures
          and builds <application>MPD</application>.
        </para>
      </section>
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    </section>
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    <section id="systemd_socket">
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      <title><filename>systemd</filename> socket activation</title>

      <para>
        Using <filename>systemd</filename>, you can launch
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        <application>MPD</application> on demand when the first client
        attempts to connect.
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      </para>

      <para>
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        <application>MPD</application> comes with two
        <application>systemd</application> unit files: a "service"
        unit and a "socket" unit.  These will only be installed when
        <application>MPD</application> was configured with
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        <parameter>--with-systemdsystemunitdir=/lib/systemd/system</parameter>.
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      </para>

      <para>
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        To enable socket activation, type:
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      </para>

      <programlisting>systemctl enable mpd.socket
systemctl start mpd.socket</programlisting>

      <para>
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        In this configuration, <application>MPD</application> will
        ignore the <varname>bind_to_address</varname> and
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        <varname>port</varname> settings.
      </para>
    </section>
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    <section id="systemd_user">
      <title><filename>systemd</filename> user unit</title>

      <para>
        You can launch <application>MPD</application> as a
        <filename>systemd</filename> user unit.  The service file will
        only be installed when <application>MPD</application> was
        configured with
        <parameter>--with-systemduserunitdir=/usr/lib/systemd/user</parameter>
        or
        <parameter>--with-systemduserunitdir=$HOME/.local/share/systemd/user</parameter>.
      </para>

      <para>
        Once the user unit is installed, you can start and stop
        <application>MPD</application> like any other service:
      </para>

      <programlisting>systemctl --user start mpd</programlisting>

      <para>
        To auto-start <application>MPD</application> upon login, type:
      </para>

      <programlisting>systemctl --user enable mpd</programlisting>
    </section>
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  </chapter>

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  <chapter id="config">
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    <title>Configuration</title>

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    <section id="config_file">
      <title>The Configuration File</title>

      <para>
        <application>MPD</application> reads its configuration from a
        text file.  Usually, that is
        <filename>/etc/mpd.conf</filename>, unless a different path is
        specified on the command line.  If you run
        <application>MPD</application> as a user daemon (and not as a
        system daemon), the configuration is read from
        <filename>$XDG_CONFIG_HOME/mpd/mpd.conf</filename> (usually
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        <filename>~/.config/mpd/mpd.conf</filename>).  On Android,
        <filename>mpd.conf</filename> will be loaded from the
        top-level directory of the data partition.
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      </para>

      <para>
        Each line in the configuration file contains a setting name
        and its value, e.g.:
      </para>

      <programlisting>connection_timeout "5"</programlisting>

      <para>
        For settings which specify a filesystem path, the tilde is
        expanded:
      </para>

      <programlisting>music_directory "~/Music"</programlisting>

      <para>
        Some of the settings are grouped in blocks with curly braces,
        e.g. per-plugin settings:
      </para>

      <programlisting>audio_output {
    type "alsa"
    name "My ALSA output"
    device "iec958:CARD=Intel,DEV=0"
    mixer_control "PCM"
}</programlisting>
    </section>

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    <section id="config_music_directory">
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      <title>Configuring the music directory</title>

      <para>
        When you play local files, you should organize them within a
        directory called the "music directory".  This is configured in
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        <application>MPD</application> with the
        <varname>music_directory</varname> setting.
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      </para>

      <para>
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        By default, <application>MPD</application> follows symbolic
        links in the music directory.  This behavior can be switched
        off: <varname>follow_outside_symlinks</varname> controls
        whether <application>MPD</application> follows links pointing
        to files outside of the music directory, and
        <varname>follow_inside_symlinks</varname> lets you disable
        symlinks to files inside the music directory.
      </para>

      <para>
        Instead of using local files, you can use <link
        linkend="storage_plugins">storage plugins</link> 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
        "<parameter>smb://myfileserver/Music</parameter>".  For a
        recipe, read the <link linkend="satellite">Satellite
        MPD</link> section.
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      </para>
    </section>

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    <section id="config_database_plugins">
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      <title>Configuring database plugins</title>

      <para>
        If a music directory is configured, one database plugin is
        used.  To configure this plugin, add a
        <varname>database</varname> block to
        <filename>mpd.conf</filename>:
      </para>

      <programlisting>database {
    plugin "simple"
    path "/var/lib/mpd/db"
}
      </programlisting>

      <para>
        The following table lists the <varname>database</varname>
        options valid for all plugins:
      </para>

      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>
                Name
              </entry>
              <entry>
                Description
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>plugin</varname>
              </entry>
              <entry>
                The name of the plugin.
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
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      <para>
        More information can be found in the <link
        linkend="database_plugins">database plugin reference</link>.
      </para>
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    </section>

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    <section id="config_neighbor_plugins">
      <title>Configuring neighbor plugins</title>

      <para>
        All neighbor plugins are disabled by default to avoid unwanted
        overhead.  To enable (and configure) a plugin, add a
        <varname>neighbor</varname> block to
        <filename>mpd.conf</filename>:
      </para>

      <programlisting>neighbors {
    plugin "smbclient"
}
      </programlisting>

      <para>
        The following table lists the <varname>neighbor</varname>
        options valid for all plugins:
      </para>

      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>
                Name
              </entry>
              <entry>
                Description
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>plugin</varname>
              </entry>
              <entry>
                The name of the plugin.
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>

      <para>
        More information can be found in the <link
        linkend="neighbor_plugins">neighbor plugin reference</link>.
      </para>
    </section>

    <section id="config_input_plugins">
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      <title>Configuring input plugins</title>

      <para>
        To configure an input plugin, add a <varname>input</varname>
        block to <filename>mpd.conf</filename>:
      </para>

      <programlisting>input {
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    plugin "curl"
    proxy "proxy.local"
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}
      </programlisting>

      <para>
        The following table lists the <varname>input</varname> options
        valid for all plugins:
      </para>

      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>
                Name
              </entry>
              <entry>
                Description
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>plugin</varname>
              </entry>
              <entry>
                The name of the plugin.
              </entry>
            </row>
            <row>
              <entry>
                <varname>enabled</varname>
                <parameter>yes|no</parameter>
              </entry>
              <entry>
                Allows you to disable a input plugin without
                recompiling.  By default, all plugins are enabled.
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
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      <para>
        More information can be found in the <link
        linkend="input_plugins">input plugin reference</link>.
      </para>
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    </section>

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    <section id="config_decoder_plugins">
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      <title>Configuring decoder plugins</title>

      <para>
        Most decoder plugins do not need any special configuration.
        To configure a decoder, add a <varname>decoder</varname> block
        to <filename>mpd.conf</filename>:
      </para>

      <programlisting>decoder {
    plugin "wildmidi"
    config_file "/etc/timidity/timidity.cfg"
}
      </programlisting>

      <para>
        The following table lists the <varname>decoder</varname>
        options valid for all plugins:
      </para>

      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>
                Name
              </entry>
              <entry>
                Description
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>plugin</varname>
              </entry>
              <entry>
                The name of the plugin.
              </entry>
            </row>
            <row>
              <entry>
                <varname>enabled</varname>
                <parameter>yes|no</parameter>
              </entry>
              <entry>
                Allows you to disable a decoder plugin without
                recompiling.  By default, all plugins are enabled.
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
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      <para>
        More information can be found in the <link
        linkend="decoder_plugins">decoder plugin reference</link>.
      </para>
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    </section>

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    <section id="config_encoder_plugins">
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      <title>Configuring encoder plugins</title>

      <para>
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        Encoders are used by some of the output plugins (such as <link
        linkend="shout_output"><varname>shout</varname></link>).  The
        encoder settings are included in the
        <varname>audio_output</varname> section.  More information can
        be found in the <link linkend="encoder_plugins">encoder plugin
        reference</link>.
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      </para>
    </section>

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    <section id="config_audio_outputs">
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      <title>Configuring audio outputs</title>

      <para>
        Audio outputs are devices which actually play the audio chunks
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        produced by <application>MPD</application>.  You can configure
        any number of audio output devices, but there must be at least
        one.  If none is configured, <application>MPD</application>
        attempts to auto-detect.  Usually, this works quite well with
        ALSA, OSS and on Mac OS X.
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      </para>

      <para>
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        To configure an audio output manually, add one or more
        <varname>audio_output</varname> blocks to
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        <filename>mpd.conf</filename>:
      </para>

      <programlisting>audio_output {
    type "alsa"
    name "my ALSA device"
    device "hw:0"
}
      </programlisting>

      <para>
        The following table lists the <varname>audio_output</varname>
        options valid for all plugins:
      </para>

      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>
                Name
              </entry>
              <entry>
                Description
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>type</varname>
              </entry>
              <entry>
                The name of the plugin.
              </entry>
            </row>
            <row>
              <entry>
                <varname>name</varname>
              </entry>
              <entry>
                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.
              </entry>
            </row>
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            <row id="ao_format">
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              <entry>
                <varname>format</varname>
              </entry>
              <entry>
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                <para>
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                  Always open the audio output with the specified
                  audio format
                  (<replaceable>samplerate:bits:channels</replaceable>),
                  regardless of the format of the input file.  This is
                  optional for most plugins.
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                </para>
                <para>
                  Any of the three attributes may be an asterisk to
                  specify that this attribute should not be enforced,
                  example: <parameter>48000:16:*</parameter>.
                  <parameter>*:*:*</parameter> is equal to not having
                  a <varname>format</varname> specification.
                </para>
                <para>
                  The following values are valid for
                  <varname>bits</varname>: <varname>8</varname>
                  (signed 8 bit integer samples),
                  <varname>16</varname>, <varname>24</varname> (signed
                  24 bit integer samples padded to 32 bit),
                  <varname>32</varname> (signed 32 bit integer
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                  samples), <varname>f</varname> (32 bit floating
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                  point, -1.0 to 1.0), "<varname>dsd</varname>" means
                  DSD (Direct Stream Digital).  For DSD, there are
                  special cases such as "<varname>dsd64</varname>",
                  which allows you to omit the sample rate
                  (e.g. <parameter>dsd512:2</parameter> for stereo
                  DSD512, i.e. 22.5792 MHz).
                </para>
                <para>
                  The sample rate is special for DSD:
                  <application>MPD</application> counts the number of
                  bytes, not bits.  Thus, a DSD "bit" rate of 22.5792
                  MHz (DSD512) is 2822400 from
                  <application>MPD</application>'s point of view
                  (44100*512/8).
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                </para>
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              </entry>
            </row>
            <row>
              <entry>
                <varname>enabled</varname>
                  <parameter>yes|no</parameter>
              </entry>
              <entry>
                Specifies whether this audio output is enabled when
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                <application>MPD</application> is started.  By
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                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.
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              </entry>
            </row>
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            <row>
              <entry>
                <varname>tags</varname>
                <parameter>yes|no</parameter>
              </entry>
              <entry>
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                If set to <parameter>no</parameter>, then
                <application>MPD</application> will not send tags to
                this output.  This is only useful for output plugins
                that can receive tags, for example the <link
                linkend="httpd_output"><varname>httpd</varname></link>
                output plugin.
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              </entry>
            </row>
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            <row>
              <entry>
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                <varname>always_on</varname>
                  <parameter>yes|no</parameter>
              </entry>
              <entry>
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                If set to <parameter>yes</parameter>, then
                <application>MPD</application> 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.
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              </entry>
            </row>
            <row>
              <entry>
                <varname>mixer_type</varname>
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                <parameter>hardware|software|null|none</parameter>
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              </entry>
              <entry>
                Specifies which mixer should be used for this audio
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                output: the hardware mixer (available for <link
                linkend="alsa_output">ALSA</link>, <link
                linkend="oss_output">OSS</link> and <link
                linkend="pulse_output">PulseAudio</link>), the
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                software mixer, the "null" mixer
                (<parameter>null</parameter>; allows setting the
                volume, but with no effect; this can be used as a
                trick to implement an <link
                linkend="external_mixer">external mixer</link>) or no
                mixer (<parameter>none</parameter>).  By default, the
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                hardware mixer is used for devices which support it,
                and none for the others.
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              </entry>
            </row>
            <row>
              <entry>
                <varname>replay_gain_handler</varname>
                <parameter>software|mixer|none</parameter>
              </entry>
              <entry>
                Specifies how replay gain is applied.  The default is
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                <parameter>software</parameter>, which uses an
                internal software volume control.
                <parameter>mixer</parameter> uses the configured
                (hardware) mixer control.  <parameter>none</parameter>
                disables replay gain on this audio output.
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              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
    </section>

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    <section id="config_filters">
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      <title>Configuring filters</title>

      <para>
        Filters are plugins which modify an audio stream.
      </para>

      <para>
        To configure a filter, add a <varname>filter</varname> block
        to <filename>mpd.conf</filename>:
      </para>

      <programlisting>filter {
    plugin "volume"
    name "software volume"
}
      </programlisting>

      <para>
        The following table lists the <varname>filter</varname>
        options valid for all plugins:
      </para>

      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>
                Name
              </entry>
              <entry>
                Description
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>plugin</varname>
              </entry>
              <entry>
                The name of the plugin.
              </entry>
            </row>
            <row>
              <entry>
                <varname>name</varname>
              </entry>
              <entry>
                The name of the filter.
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
    </section>

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    <section id="config_playlist_plugins">
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      <title>Configuring playlist plugins</title>

      <para>
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        Playlist plugins are used to load remote playlists (protocol
        commands <command>load</command>,
        <command>listplaylist</command> and
        <command>listplaylistinfo</command>).  This is not related to
        <application>MPD</application>'s playlist directory.
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      </para>

      <para>
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        To configure a playlist plugin, add a
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        <varname>playlist_plugin</varname> block to
        <filename>mpd.conf</filename>:
      </para>

      <programlisting>playlist_plugin {
    name "m3u"
    enabled "true"
}
      </programlisting>

      <para>
        The following table lists the
        <varname>playlist_plugin</varname> options valid for all
        plugins:
      </para>

      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>
                Name
              </entry>
              <entry>
                Description
              </entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>name</varname>
              </entry>
              <entry>
                The name of the plugin.
              </entry>
            </row>
            <row>
              <entry>
                <varname>enabled</varname>
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                <parameter>yes|no</parameter>
              </entry>
              <entry>
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                Allows you to disable a input plugin without
                recompiling.  By default, all plugins are enabled.
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              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>
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      <para>
        More information can be found in the <link
        linkend="playlist_plugins">playlist plugin reference</link>.
      </para>
    </section>

    <section id="config_audio_format">
      <title>Audio Format Settings</title>

      <section id="config_global_audio_format">
        <title>Global Audio Format</title>

        <para>
          The setting <varname>audio_output_format</varname> forces
          <application>MPD</application> to use one audio format for
          all outputs.  Doing that is usually not a good idea.  The
          values are the same as in <link
          linkend="ao_format"><varname>format</varname> in the <link
          linkend="config_audio_outputs"><varname>audio_output</varname></link>
          section</link>.
        </para>
      </section>

      <section>
        <title>Resampler</title>

        <para>
          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
          <application>MPD</application>'s CPU usage.  Since
          <application>MPD</application> comes with high quality
          defaults, it may appear that <application>MPD</application>
          consumes more CPU than other software.
        </para>

        <para>
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          Check the <link linkend="resampler_plugins">resampler plugin
          reference</link> for a list of resamplers and how to
          configure them.
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        </para>
      </section>
    </section>

    <section id="config_other">
      <title>Other Settings</title>

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      <informaltable>
        <tgroup cols="2">
          <thead>
            <row>
              <entry>Setting</entry>
              <entry>Description</entry>
            </row>
          </thead>
          <tbody>
            <row>
              <entry>
                <varname>metadata_to_use</varname>
                <parameter>TAG1,TAG2,...</parameter>
              </entry>
              <entry>
                Use only the specified tags, and ignore the others.
                This setting can reduce the database size and
                <application>MPD</application>'s memory usage by
                omitting unused tags.  By default, all tags but
                <varname>comment</varname> are enabled.  The special
                value "none" disables all tags.
              </entry>
            </row>
          </tbody>
        </tgroup>
      </informaltable>

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      <section>
        <title>The State File</title>

        <para>
          The <emphasis>state file</emphasis> is a file where
          <application>MPD</application> saves and restores its state
          (play queue, playback position etc.) to keep it persistent
          across restarts and reboots.  It is an optional setting.
        </para>

        <para>
          <application>MPD</application> 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).
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>state_file</varname>
                  <parameter>PATH</parameter>
                </entry>
                <entry>
                  Specify the state file location.  The parent
                  directory must be writable by the
                  <application>MPD</application> user
                  (<parameter>+wx</parameter>).
                </entry>
              </row>

              <row>
                <entry>
                  <varname>state_file_interval</varname>
                  <parameter>SECONDS</parameter>
                </entry>
                <entry>
                  Auto-save the state file this number of seconds
                  after each state change.  Defaults to
                  <parameter>120</parameter> (2 minutes).
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>

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      <section id="stickers">
        <title>The Sticker Database</title>

        <para>
          "Stickers" are pieces of information attached to songs.
          Some clients use them to store ratings and other volatile
          data.  This feature requires <ulink
          url="http://www.sqlite.org/">SQLite</ulink>, compile-time
          configure option <parameter>--enable-sqlite</parameter>.
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>sticker_file</varname>
                  <parameter>PATH</parameter>
                </entry>
                <entry>
                  The location of the sticker database.
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>

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      <section>
        <title>Resource Limitations</title>

        <para>
          These settings are various limitations to prevent
          <application>MPD</application> from using too many
          resources (denial of service).
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>

              <row>
                <entry>
                  <varname>connection_timeout</varname>
                  <parameter>SECONDS</parameter>
                </entry>
                <entry>
                  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
                  <parameter>60</parameter>.
                </entry>
              </row>

              <row>
                <entry>
                  <varname>max_connections</varname>
                  <parameter>NUMBER</parameter>
                </entry>
                <entry>
                  This specifies the maximum number of clients that
                  can be connected to <application>MPD</application>
                  at the same time.  Default is
                  <parameter>5</parameter>.
                </entry>
              </row>

              <row>
                <entry>
                  <varname>max_playlist_length</varname>
                  <parameter>NUMBER</parameter>
                </entry>
                <entry>
                  The maximum number of songs that can be in the
                  playlist.  Default is <parameter>16384</parameter>.
                </entry>
              </row>

              <row>
                <entry>
                  <varname>max_command_list_size</varname>
                  <parameter>KBYTES</parameter>
                </entry>
                <entry>
                  The maximum size a command list.  Default is
                  <parameter>2048</parameter> (2 MiB).
                </entry>
              </row>

              <row>
                <entry>
                  <varname>max_output_buffer_size</varname>
                  <parameter>KBYTES</parameter>
                </entry>
                <entry>
                  The maximum size of the output buffer to a client
                  (maximum response size).  Default is
                  <parameter>8192</parameter> (8 MiB).
                </entry>
              </row>

            </tbody>
          </tgroup>
        </informaltable>
      </section>

      <section>
        <title>Buffer Settings</title>

        <para>
          Do not change these unless you know what you are doing.
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>

              <row>
                <entry>
                  <varname>audio_buffer_size</varname>
                  <parameter>KBYTES</parameter>
                </entry>
                <entry>
                  Adjust the size of the internal audio buffer.
                  Default is <parameter>4096</parameter> (4 MiB).
                </entry>
              </row>

              <row>
                <entry>
                  <varname>buffer_before_play</varname>
                  <parameter>PERCENT</parameter>
                </entry>
                <entry>
                  Control the percentage of the buffer which is filled
                  before beginning to play.  Increasing this reduces
                  the chance of audio file skipping, at the cost of
                  increased time prior to audio playback.  Default is
                  <parameter>10%</parameter>.
                </entry>
              </row>

            </tbody>
          </tgroup>
        </informaltable>
      </section>
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      <section id="zeroconf">
        <title>Zeroconf</title>

        <para>
          If Zeroconf support (<ulink
          url="http://avahi.org/">Avahi</ulink> or Apple's Bonjour)
          was enabled at compile time with
          <parameter>--with-zeroconf=...</parameter>, MPD can announce
          its presence on the network.  The following settings control
          this feature:
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>

              <row>
                <entry>
                  <varname>zeroconf_enabled</varname>
                  <parameter>yes|no</parameter>
                </entry>
                <entry>
                  Enables or disables this feature.  Default is
                  <parameter>yes</parameter>.
                </entry>
              </row>

              <row>
                <entry>
                  <varname>zeroconf_name</varname>
                  <parameter>NAME</parameter>
                </entry>
                <entry>
                  The service name to publish via Zeroconf.  The
                  default is "<parameter>Music Player</parameter>".
                </entry>
              </row>

            </tbody>
          </tgroup>
        </informaltable>
      </section>
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    </section>
  </chapter>

  <chapter id="advanced_config">
    <title>Advanced configuration</title>

    <section id="satellite">
      <title>Satellite setup</title>

      <para>
        <application>MPD</application> runs well on weak machines such
        as the <ulink url="http://www.raspberrypi.org/">Raspberry
        Pi</ulink>.  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.
      </para>

      <para>
        One approach for optimization is running
        <application>MPD</application> on the file server, which not
        only exports raw files, but also provides access to a readily
        scanned database.  Example configuration:
      </para>

      <programlisting>music_directory "nfs://fileserver.local/srv/mp3"
#music_directory "smb://fileserver.local/mp3"

database {
    plugin "proxy"
    host "fileserver.local"
}
      </programlisting>

      <para>
        The <link
        linkend="config_music_directory"><varname>music_directory</varname></link>
        setting tells <application>MPD</application> 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
        <link linkend="nfs_storage"><filename>nfs</filename></link>
        storage plugin (using the <filename>libnfs</filename>
        userspace library).  The same can be done with SMB/CIFS using
        the <link
        linkend="smbclient_storage"><filename>smbclient</filename></link>
        storage plugin (using <filename>libsmbclient</filename>).
      </para>

      <para>
        The <link
        linkend="config_database_plugins"><varname>database</varname></link>
        setting tells <application>MPD</application> to pass all
        database queries on to the <application>MPD</application>
        instance running on the file server (using the <link
        linkend="proxy_database"><filename>proxy</filename></link>
        plugin).
      </para>
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    </section>
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    <section id="realtime">
      <title>Real-Time Scheduling</title>

      <para>
        On Linux, <application>MPD</application> attempts to configure
        <ulink
        url="https://en.wikipedia.org/wiki/Real-time_computing">real-time
        scheduling</ulink> for some threads that benefit from it.
      </para>

      <para>
        This is only possible you allow <application>MPD</application>
        to do it.  This privilege is controlled by
        <varname>RLIMIT_RTPRIO</varname>
        <varname>RLIMIT_RTTIME</varname>.  You can configure this
        privilege with <command>ulimit</command> before launching
        <application>MPD</application>:
      </para>

      <programlisting>ulimit -HS -r 50; mpd</programlisting>

      <para>
        Or you can use the <command>prlimit</command> program from the
        <application>util-linux</application> package:
      </para>

      <programlisting>prlimit --rtprio=50 --rttime=unlimited mpd</programlisting>

      <para>
        The <application>systemd</application> service file shipped
        with <application>MPD</application> comes with this setting.
      </para>

      <para>
        This works only if the Linux kernel was compiled with
        <varname>CONFIG_RT_GROUP_SCHED</varname> disabled.  Use the
        following command to check this option for your current
        kernel:
      </para>

      <programlisting>zgrep ^CONFIG_RT_GROUP_SCHED /proc/config.gz</programlisting>

      <note>
        <para>
          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.
        </para>
      </note>
    </section>
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  </chapter>

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  <chapter id="use">
    <title>Using <application>MPD</application></title>
1471

1472
    <section id="client">
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      <title>The client</title>

      <para>
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        After you have installed, configured and started
        <application>MPD</application>, you choose a client to control
        the playback.
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      </para>

      <para>
        The most basic client is <filename>mpc</filename>, which
        provides a command line interface.  It is useful in shell
        scripts.  Many people bind specific <filename>mpc</filename>
        commands to hotkeys.
      </para>

      <para>
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        The <ulink
        url="http://www.musicpd.org/clients/"><application>MPD</application>
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        Wiki</ulink> contains an extensive list of clients to choose
        from.
      </para>
    </section>

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    <section id="music_directory_and_database">
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      <title>The music directory and the database</title>

      <para>
        The "music directory" is where you store your music files.
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        <application>MPD</application> 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
        <filename>mpc</filename>:
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      </para>

      <programlisting>mpc update</programlisting>

      <para>
        Depending on the size of your music collection and the speed
        of the storage, this can take a while.
      </para>

      <para>
        To exclude a file from the update, create a file called
        <filename>.mpdignore</filename> in its parent directory.  Each
        line of that file may contain a list of shell wildcards.
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        Matching files in the current directory and all subdirectories
        are excluded.
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      </para>
    </section>

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    <section id="tags">
      <title>Metadata</title>

      <para>
        When scanning or playing a song,
        <application>MPD</application> parses its metadata.  The
        following tags are supported:
      </para>

      <xi:include href="include/tags.xml"
                  xmlns:xi="http://www.w3.org/2001/XInclude"/>
    </section>

1537
    <section id="queue">
1538 1539 1540 1541
      <title>The queue</title>

      <para>
        The queue (sometimes called "current playlist") is a list of
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        songs to be played by <application>MPD</application>.  To play
        a song, add it to the queue and start playback.  Most clients
        offer an interface to edit the queue.
      </para>
    </section>
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    <section id="stored_playlists">
      <title>Stored Playlists</title>

      <para>
        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
        <varname>playlist_directory</varname> setting specifies where
        those playlists are stored.
      </para>
    </section>
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  </chapter>

  <chapter id="advanced_usage">
    <title>Advanced usage</title>

    <section id="bit_perfect">
      <title>Bit-perfect playback</title>

      <para>
        "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.
      </para>

      <para>
        By default, <application>MPD</application> 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,
        <application>MPD</application> attempts to fall back to the
        nearest supported audio format, trying to lose as little
        quality as possible.
      </para>

      <para>
        To verify if <application>MPD</application> converts the audio
        format, enable verbose logging, and watch for these lines:
      </para>

      <programlisting>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</programlisting>

      <para>
        This example shows that a 24 bit file is being played, but the
        sond chip cannot play 24 bit.  It falls back to 16 bit,
        discarding 8 bit.
      </para>

      <para>
        However, this does not yet prove bit-perfect playback;
        <application>ALSA</application> may be fooling
        <application>MPD</application> that the audio format is
        supported.  To verify the format really being sent to the
        physical sound chip, try:
      </para>

      <programlisting>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</programlisting>

      <para>
        Obey the "format" row, which indicates that the current
        playback format is 16 bit (signed 16 bit integer, little
        endian).
      </para>

      <para>
        Check list for bit-perfect playback:
      </para>

      <itemizedlist>
        <listitem>
          <para>
            Use the <link linkend="alsa_output">ALSA</link> output
            plugin.
          </para>
        </listitem>

        <listitem>
          <para>
            Disable sound processing inside
            <application>ALSA</application> by configuring a
            "hardware" device (<parameter>hw:0,0</parameter> or
            similar).
          </para>
        </listitem>

        <listitem>
          <para>
            Don't use software volume (setting <link
            linkend="config_audio_outputs"><varname>mixer_type</varname></link>).
          </para>
        </listitem>

        <listitem>
          <para>
            Don't force <application>MPD</application> to use a
            specific audio format (settings <link
            linkend="config_audio_outputs"><varname>format</varname></link>,
            <link
            linkend="config_global_audio_format"><varname>audio_output_format</varname></link>).
          </para>
        </listitem>

        <listitem>
          <para>
            Verify that you are really doing bit-perfect playback
            using <application>MPD</application>'s verbose log and
            <filename>/proc/asound/card*/pcm*p/sub*/hw_params</filename>.
            Some DACs can also indicate the audio format.
          </para>
        </listitem>
      </itemizedlist>
    </section>

    <section id="dsd">
      <title>Direct Stream Digital (DSD)</title>

      <para>
        DSD (<ulink
        url="https://en.wikipedia.org/wiki/Direct_Stream_Digital">Direct
        Stream Digital</ulink>) is a digital format that stores audio
        as a sequence of single-bit values at a very high sampling
        rate.
      </para>

      <para>
        <application>MPD</application> understands the file formats
        <link linkend="dsdiff_decoder"><filename>dff</filename></link>
        and <link
        linkend="dsf_decoder"><filename>dsf</filename></link>.  There
        are three ways to play back DSD:
      </para>

      <itemizedlist>
        <listitem>
          <para>
            Native DSD playback.  Requires
            <application>ALSA</application> 1.0.27.1 or later, a sound
            driver/chip that supports DSD and of course a DAC that
            supports DSD.
          </para>
        </listitem>

        <listitem>
          <para>
            DoP (DSD over PCM) playback.  This wraps DSD inside fake
            24 bit PCM according to the <ulink
            url="http://dsd-guide.com/dop-open-standard">DoP
            standard</ulink>.  Requires a DAC that supports DSD.  No
            support from ALSA and the sound chip required (except for
            <link linkend="bit_perfect">bit-perfect</link> 24 bit PCM
            support).
          </para>
        </listitem>

        <listitem>
          <para>
            Convert DSD to PCM on-the-fly.
          </para>
        </listitem>
      </itemizedlist>

      <para>
        Native DSD playback is used automatically if available.  DoP
        is only used if enabled explicitly using the <link
        linkend="alsa_output"><varname>dop</varname></link> option,
        because there is no way for <application>MPD</application> to
        find out whether the DAC supports it.  DSD to PCM conversion
        is the fallback if DSD cannot be used directly.
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      </para>
    </section>
  </chapter>

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  <chapter id="client_hacks">
    <title>Client Hacks</title>

    <section id="external_mixer">
      <title>External Mixer</title>

      <para>
        The setting '<varname>mixer_type</varname>
        "<parameter>null</parameter>"' asks
        <application>MPD</application> to pretend that there is a
        mixer, but not actually do something.  This allows you to
        implement a <application>MPD</application> client which
        listens for <varname>mixer</varname> 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.
      </para>
    </section>
  </chapter>

  <chapter id="troubleshooting">
    <title>Troubleshooting</title>

    <section id="troubleshooting_start">
      <title>Where to start</title>

      <para>
        Make sure you have the latest <application>MPD</application>
        version (via <command>mpd --version</command>, not
        <command>mpc version</command>).  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
        <application>MPD</application> version.  The most common
        excuse is when your distribution ships an old
        <application>MPD</application> version - in that case, please
        ask your distribution for help, and not the
        <application>MPD</application> project.
      </para>

      <para>
        Check the log file.  Configure '<varname>log_level</varname>
        "<parameter>verbose</parameter>"' or pass
        <parameter>--verbose</parameter> to <filename>mpd</filename>.
      </para>

      <para>
        Sometimes, it is helpful to run <application>MPD</application>
        in a terminal and follow what happens.  This is how to do it:
      </para>

      <programlisting>mpd --stdout --no-daemon --verbose</programlisting>
    </section>

    <section id="support">
      <title>Support</title>

      <section id="help">
        <title>Getting Help</title>

        <para>
          The <application>MPD</application> project runs <ulink
          url="https://forum.musicpd.org/">a forum</ulink> and an IRC
          channel (<varname>#mpd</varname> on Freenode) for requesting
          help.  Visit <ulink url="https://www.musicpd.org/help/">the
          <application>MPD</application> help page</ulink> for details
          on how to get help.
        </para>
      </section>

      <section id="faq">
        <title>Common Problems</title>

        <qandaset defaultlabel='qanda'>
          <qandadiv>
            <title>Database</title>

            <qandaentry>
              <question>
                <para>
                  I can't see my music in the
                  <application>MPD</application> database!
                </para>
              </question>
              <answer>
                <itemizedlist>
                  <listitem>
                    <para>
                      Check your <varname>music_directory</varname>
                      setting.
                    </para>
                  </listitem>
                </itemizedlist>
                <itemizedlist>
                  <listitem>
                    <para>
                      Does the <application>MPD</application> user
                      have read permission on all music files, and
                      read+execute permission on all music directories
                      (and all of their parent directories)?
                    </para>
                  </listitem>
                </itemizedlist>
                <itemizedlist>
                  <listitem>
                    <para>
                      Did you update the database?  (<command>mpc
                      update</command>)
                    </para>
                  </listitem>
                </itemizedlist>
                <itemizedlist>
                  <listitem>
                    <para>
                      Did you enable all relevant decoder plugins at
                      compile time?  <command>mpd --version</command>
                      will tell you.
                    </para>
                  </listitem>
                </itemizedlist>
              </answer>
            </qandaentry>

            <qandaentry>
              <question>
                <para>
                  <application>MPD</application> doesn't read ID3
                  tags!
                </para>
              </question>
              <answer>
                <para>
                  You probably compiled <application>MPD</application>
                  without <filename>libid3tag</filename>.
                  <command>mpd --version</command> will tell you.
                </para>
              </answer>
            </qandaentry>
          </qandadiv>

          <qandadiv>
            <title>Playback</title>

            <qandaentry>
              <question>
                <para>I can't hear music on my client!</para>
              </question>
              <answer>
                <para>
                  That problem usually follows a misunderstanding of the
                  nature of <application>MPD</application>.
                  <application>MPD</application> is a remote-controlled
                  music player, not a music distribution system.
                  Usually, the speakers are connected to the box where
                  <application>MPD</application> runs, and the
                  <application>MPD</application> client only sends
                  control commands, but the client does not actually
                  play your music.
                </para>

                <para>
                  <application>MPD</application> has output plugins
                  which allow hearing music on a remote host (such as
                  <link
                      linkend="httpd_output"><varname>httpd</varname></link>),
                  but that is not <application>MPD</application>'s
                  primary design goal.
                </para>
              </answer>
            </qandaentry>

            <qandaentry>
              <question>
                <para>"Device or resource busy"</para>
              </question>
              <answer>
                <para>
                  This ALSA error means that another program uses your
                  sound hardware exclusively.  You can stop that
                  program to allow <application>MPD</application> to
                  use it.
                </para>
                <para>
                  Sometimes, this other program is
                  <application>PulseAudio</application>, 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 <link
                  linkend="pulse_output"><application>MPD</application>
                  to use <application>PulseAudio</application></link>
                  as well, instead of using ALSA directly.
                </para>
              </answer>
            </qandaentry>
          </qandadiv>
        </qandaset>
      </section>
    </section>

    <section id="bugs">
      <title>Reporting Bugs</title>

      <para>
        If you believe you found a bug in
        <application>MPD</application>, report it on <ulink
1936
        url="https://github.com/MusicPlayerDaemon/MPD/issues/">the bug
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        tracker</ulink>.
      </para>

      <para>
        Your bug report should contain:
      </para>

      <itemizedlist>
        <listitem>
          <para>
            the output of <command>mpd --version</command>
          </para>
        </listitem>

        <listitem>
          <para>
            your <link linkend="config_file">configuration file</link>
            (<filename>mpd.conf</filename>)
          </para>
        </listitem>

        <listitem>
          <para>
            relevant portions of the log file (--verbose)
          </para>
        </listitem>

        <listitem>
          <para>
            be clear about what you expect MPD to do, and what is
            actually happening
          </para>
        </listitem>
      </itemizedlist>

      <section id="crash">
        <title><application>MPD</application> crashes</title>

        <para>
          All <application>MPD</application> 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 <application>MPD</application>, and then that
          library must be fixed; but in any case, the
          <application>MPD</application> bug tracker is a good place
          to report it first if you don't know.)
        </para>

        <para>
          A crash bug report needs to contain a "backtrace".
        </para>

        <para>
          First of all, your <application>MPD</application> 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
          <filename>mpd-dbg</filename> or
          <filename>mpd-dbgsym</filename> on Debian,
          <filename>mpd-debug</filename> on other distributions).
          Make sure this package is installed.
        </para>

        <para>
          You can extract the backtrace from a core dump, or by
          running <application>MPD</application> in a debugger, e.g.:
        </para>

        <programlisting>gdb --args mpd --stdout --no-daemon --verbose
run</programlisting>

        <para>
          As soon as you have reproduced the crash, type
          "<command>bt</command>" on the <filename>gdb</filename>
          command prompt.  Copy the output to your bug report.
        </para>
      </section>
    </section>
  </chapter>

2017
  <chapter id="plugin_reference">
2018 2019
    <title>Plugin reference</title>

2020
    <section id="database_plugins">
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      <title>Database plugins</title>

      <section>
        <title><varname>simple</varname></title>

        <para>
          The default plugin.  Stores a copy of the database in
          memory.  A file is used for permanent storage.
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>path</varname>
                </entry>
                <entry>
                  The path of the database file.
                </entry>
              </row>
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              <row>
                <entry>
                  <varname>cache_directory</varname>
                </entry>
                <entry>
                  The path of the cache directory for additional
                  storages mounted at runtime.  This setting is
                  necessary for the <command>mount</command> protocol
                  command.
                </entry>
              </row>

              <row>
                <entry>
                  <varname>compress</varname>
                  <parameter>yes|no</parameter>
                </entry>
                <entry>
                  Compress the database file using
                  <filename>gzip</filename>?  Enabled by default (if
                  built with <filename>zlib</filename>).
                </entry>
              </row>
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            </tbody>
          </tgroup>
        </informaltable>
      </section>

2077
      <section id="proxy_database">
2078 2079 2080
        <title><varname>proxy</varname></title>

        <para>
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          Provides access to the database of another
          <application>MPD</application> instance using
          <filename>libmpdclient</filename>.  This is useful when you
          run mount the music directory via NFS/SMB, and the file
          server already runs a <application>MPD</application>
          instance.  Only the file server needs to update the
          database.
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        </para>

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        <para>
          Note that unless overridden by the below settings (e.g. by
          setting them to a blank value), general curl configuration
          from environment variables such as http_proxy or specified
          in ~/.curlrc will be in effect.
        </para>

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        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>host</varname>
                </entry>
                <entry>
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                  The host name of the "master"
                  <application>MPD</application> instance.
                </entry>
              </row>
              <row>
                <entry>
                  <varname>port</varname>
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                </entry>
2119 2120 2121 2122 2123
                <entry>
                  The port number of the "master"
                  <application>MPD</application> instance.
                </entry>
              </row>
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              <row>
                <entry>
                  <varname>keepalive</varname>
                  <parameter>yes|no</parameter>
                </entry>
                <entry>
                  Send TCP keepalive packets to the "master"
                  <application>MPD</application> instance?  This option can
                  help avoid certain firewalls dropping inactive
                  connections, at the expensive of a very small amount of
                  additional network traffic.  Disabled by default.
                </entry>
              </row>
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            </tbody>
          </tgroup>
        </informaltable>
      </section>

      <section>
        <title><varname>upnp</varname></title>

        <para>
          Provides access to UPnP media servers.
        </para>
      </section>
    </section>

    <section id="storage_plugins">
      <title>Storage plugins</title>

      <section>
        <title><varname>local</varname></title>

        <para>
          The default plugin which gives
          <application>MPD</application> access to local files.  It is
          used when <varname>music_directory</varname> refers to a
          local directory.
        </para>
      </section>

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      <section id="curl_storage">
        <title><varname>curl</varname></title>

        <para>
          A WebDAV client using <filename>libcurl</filename>.  It is
          used when <varname>music_directory</varname> contains a
          <parameter>http://</parameter> or
          <parameter>https://</parameter> URI, for example
          "<parameter>https://the.server/dav/</parameter>".
        </para>
      </section>

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      <section id="smbclient_storage">
        <title><varname>smbclient</varname></title>

        <para>
2181
          Load music files from a SMB/CIFS server.  It is used when
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          <varname>music_directory</varname> contains a
          <parameter>smb://</parameter> URI, for example
          "<parameter>smb://myfileserver/Music</parameter>".
        </para>
      </section>

      <section id="nfs_storage">
        <title><varname>nfs</varname></title>

        <para>
2192
          Load music files from a NFS server.  It is used when
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          <varname>music_directory</varname> contains a
          <parameter>nfs://</parameter> URI according to <ulink
          url="http://tools.ietf.org/html/rfc2224">RFC2224</ulink>,
          for example "<parameter>nfs://servername/path</parameter>".
        </para>

        <para>
          This plugin uses <ulink
          url="https://github.com/sahlberg/libnfs"><filename>libnfs</filename></ulink>,
          which supports only NFS version 3.  Since
          <application>MPD</application> is not allowed to bind to
          "privileged ports", the NFS server needs to enable the
          "insecure" setting; example
          <filename>/etc/exports</filename>:
        </para>

        <programlisting>/srv/mp3 192.168.1.55(ro,insecure)</programlisting>

        <para>
          Don't fear: "insecure" does not mean that your NFS server is
          insecure.  A few decades ago, people thought the concept of
          "privileged ports" would make network services "secure",
          which was a fallacy.  The absence of this obsolete
          "security" measure means little.
        </para>
      </section>
    </section>

    <section id="neighbor_plugins">
      <title>Neighbor plugins</title>

      <section id="smbclient_neighbor">
        <title><varname>smbclient</varname></title>

        <para>
          Provides a list of SMB/CIFS servers on the local network.
        </para>
      </section>

      <section id="upnp_neighbor">
        <title><varname>upnp</varname></title>

        <para>
          Provides a list of UPnP servers on the local network.
        </para>
      </section>
    </section>

    <section id="input_plugins">
      <title>Input plugins</title>

      <section>
        <title><varname>alsa</varname></title>

        <para>
          Allows <application>MPD</application> on Linux to play audio
          directly from a soundcard using the scheme
          <filename>alsa://</filename>. Audio is formatted as 44.1 kHz
          16-bit stereo (CD format). Examples:
        </para>

        <para>
          <filename>mpc add alsa://</filename> plays audio from device hw:0,0
        </para>
        <para>
          <filename>mpc add alsa://hw:1,0</filename> plays audio from device
          hw:1,0
        </para>
      </section>

      <section>
        <title><varname>cdio_paranoia</varname></title>

        <para>
2267 2268 2269
          Plays audio CDs using <ulink
          url="http://www.gnu.org/software/libcdio/"><filename>libcdio</filename></ulink>.
          The URI has the form:
2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280
          "<filename>cdda://[DEVICE][/TRACK]</filename>".  The
          simplest form <filename>cdda://</filename> plays the whole
          disc in the default drive.
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
2281
              </row>
2282 2283
            </thead>
            <tbody>
2284 2285
              <row>
                <entry>
2286 2287
                  <varname>default_byte_order</varname>
                <parameter>little_endian|big_endian</parameter>
2288 2289
                </entry>
                <entry>
2290 2291 2292 2293
                  If the CD drive does not specify a byte order,
                  <application>MPD</application> assumes it is the
                  CPU's native byte order.  This setting allows
                  overriding this.
2294 2295 2296 2297 2298 2299
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>
2300 2301 2302 2303 2304

      <section>
        <title><varname>curl</varname></title>

        <para>
2305 2306
          Opens remote files or streams over HTTP using <ulink
          url="http://curl.haxx.se/"><filename>libcurl</filename></ulink>.
2307 2308
        </para>

2309 2310 2311 2312 2313 2314 2315 2316
        <para>
          Note that unless overridden by the below settings (e.g. by
          setting them to a blank value), general curl configuration
          from environment variables such as
          <varname>http_proxy</varname> or specified in
          <filename>~/.curlrc</filename> will be in effect.
        </para>

2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342
        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>proxy</varname>
                </entry>
                <entry>
                  Sets the address of the HTTP proxy server.
                </entry>
              </row>
              <row>
                <entry>
                  <varname>proxy_user</varname>,
                  <varname>proxy_password</varname>
                </entry>
                <entry>
                  Configures proxy authentication.
                </entry>
              </row>
2343 2344

              <row>
2345 2346 2347 2348 2349 2350 2351 2352 2353
                <entry>
                  <varname>verify_peer</varname>
                  <parameter>yes|no</parameter>
                </entry>
                <entry>
                  Verify the peer's SSL certificate?  <ulink
                  url="http://curl.haxx.se/libcurl/c/CURLOPT_SSL_VERIFYPEER.html">More
                  information</ulink>.
                </entry>
2354
              </row>
2355

2356 2357
              <row>
                <entry>
2358 2359
                  <varname>verify_host</varname>
                  <parameter>yes|no</parameter>
2360 2361
                </entry>
                <entry>
2362 2363 2364
                  Verify the certificate's name against host?  <ulink
                  url="http://curl.haxx.se/libcurl/c/CURLOPT_SSL_VERIFYHOST.html">More
                  information</ulink>.
2365 2366 2367 2368 2369
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
2370 2371
      </section>

2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386
      <section id="ffmpeg_input">
        <title><varname>ffmpeg</varname></title>

        <para>
          Access to various network protocols implemented by the
          <application>FFmpeg</application> library:
          <filename>gopher://</filename>,
          <filename>rtp://</filename>,
          <filename>rtsp://</filename>,
          <filename>rtmp://</filename>,
          <filename>rtmpt://</filename>,
          <filename>rtmps://</filename>
        </para>
      </section>

2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398
      <section>
        <title><varname>file</varname></title>

        <para>
          Opens local files.
        </para>
      </section>

      <section>
        <title><varname>mms</varname></title>

        <para>
2399 2400
          Plays streams with the MMS protocol using <ulink
          url="https://launchpad.net/libmms"><filename>libmms</filename></ulink>.
2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446
        </para>
      </section>

      <section>
        <title><varname>nfs</varname></title>

        <para>
          Allows <application>MPD</application> to access files on
          NFSv3 servers without actually mounting them (i.e. in
          userspace, without help from the kernel's VFS layer).  All
          URIs with the <filename>nfs://</filename> scheme are used
          according to <ulink
          url="http://tools.ietf.org/html/rfc2224">RFC2224</ulink>.
          Example:
        </para>

        <para>
          <filename>mpc add nfs://servername/path/filename.ogg</filename>
        </para>

        <para>
          Note that this usually requires enabling the "insecure" flag
          in the server's <filename>/etc/exports</filename> file,
          because <application>MPD</application> cannot bind to
          so-called "privileged" ports.  Don't fear: this will not
          make your file server insecure; the flag was named in a time
          long ago when privileged ports were thought to be meaningful
          for security.  By today's standards, NFSv3 is not secure at
          all, and if you believe it is, you're already doomed.
        </para>
      </section>

      <section>
        <title><varname>smbclient</varname></title>

        <para>
          Allows <application>MPD</application> to access files on
          SMB/CIFS servers (e.g. Samba or Microsoft Windows).  All
          URIs with the <filename>smb://</filename> scheme are used.
          Example:
        </para>

        <para>
          <filename>mpc add smb://servername/sharename/filename.ogg</filename>
        </para>
      </section>
2447 2448
    </section>

2449
    <section id="decoder_plugins">
2450
      <title>Decoder plugins</title>
2451

2452 2453
      <section id="adplug_decoder">
        <title><varname>adplug</varname></title>
2454 2455

        <para>
2456 2457
          Decodes AdLib files using <ulink
          url="http://adplug.sourceforge.net/">libadplug</ulink>.
2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>sample_rate</varname>
                  <parameter></parameter>
                </entry>
                <entry>
                  The sample rate that shall be synthesized by the
                  plugin.  Defaults to 48000.
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>

      <section id="audiofile_decoder">
        <title><varname>audiofile</varname></title>

        <para>
2488 2489
          Decodes WAV and AIFF files using <ulink
          url="http://audiofile.68k.org/"><filename>libaudiofile</filename></ulink>.
2490 2491 2492 2493 2494 2495 2496
        </para>
      </section>

      <section id="faad_decoder">
        <title><varname>faad</varname></title>

        <para>
2497 2498
          Decodes AAC files using <ulink
          url="http://www.audiocoding.com/"><filename>libfaad</filename></ulink>.
2499 2500 2501 2502 2503 2504 2505
        </para>
      </section>

      <section id="ffmpeg_decoder">
        <title><varname>ffmpeg</varname></title>

        <para>
2506 2507
          Decodes various codecs using <ulink
          url="https://ffmpeg.org/"><application>FFmpeg</application></ulink>.
2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>analyzeduration</varname>
                  <parameter>VALUE</parameter>
                </entry>
                <entry>
                  Sets the FFmpeg muxer option
                  <varname>analyzeduration</varname>, which specifies
                  how many microseconds are analyzed to probe the
                  input.  The <ulink
                  url="https://ffmpeg.org/ffmpeg-formats.html">FFmpeg
                  formats documentation</ulink> has more information.
                </entry>
              </row>

              <row>
                <entry>
                  <varname>probesize</varname>
                  <parameter>VALUE</parameter>
                </entry>
                <entry>
                  Sets the FFmpeg muxer option
                  <varname>probesize</varname>, which specifies
                  probing size in bytes, i.e. the size of the data to
                  analyze to get stream information.  The <ulink
                  url="https://ffmpeg.org/ffmpeg-formats.html">FFmpeg
                  formats documentation</ulink> has more information.
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>

      <section id="flac_decoder">
        <title><varname>flac</varname></title>

        <para>
          Decodes FLAC files using
2558
          <ulink url="https://xiph.org/flac/"><application>libFLAC</application></ulink>.
2559 2560 2561 2562 2563 2564 2565 2566
        </para>
      </section>

      <section id="dsdiff_decoder">
        <title><varname>dsdiff</varname></title>

        <para>
          Decodes DFF files containing DSDIFF data (e.g. SACD rips).
2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>lsbitfirst</varname>
                  <parameter>yes|no</parameter>
                </entry>
                <entry>
                  Decode the least significant bit first.  Default is
2585
                  <parameter>no</parameter>.
2586 2587 2588 2589 2590 2591 2592
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>

2593
      <section id="dsf_decoder">
2594 2595 2596 2597 2598 2599 2600 2601
        <title><varname>dsf</varname></title>

        <para>
          Decodes DSF files containing DSDIFF data (e.g. SACD rips).
        </para>

      </section>

2602 2603 2604 2605
      <section>
        <title><varname>fluidsynth</varname></title>

        <para>
2606 2607
          MIDI decoder based on <ulink
          url="http://www.fluidsynth.org/"><application>FluidSynth</application></ulink>.
2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>sample_rate</varname>
                </entry>
                <entry>
                  The sample rate that shall be synthesized by the
                  plugin.  Defaults to 48000.
                </entry>
              </row>
              <row>
                <entry>
                  <varname>soundfont</varname>
                </entry>
                <entry>
                  The absolute path of the soundfont file.  Defaults
                  to
                  <filename>/usr/share/sounds/sf2/FluidR3_GM.sf2</filename>.
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>

2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677
      <section>
        <title><varname>gme</varname></title>

        <para>
          Video game music file emulator based on <ulink
          url="https://bitbucket.org/mpyne/game-music-emu/wiki/Home"><application>game-music-emu</application></ulink>.
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>accuracy</varname>
                  <parameter>yes|no</parameter>
                </entry>
                <entry>
                  Enable more accurate sound emulation.
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
      </section>

      <section id="mad_decoder">
        <title><varname>mad</varname></title>

        <para>
2678 2679
          Decodes MP3 files using <ulink
          url="http://www.underbit.com/products/mad/"><application>libmad</application></ulink>.
2680 2681 2682
        </para>
      </section>

2683
      <section>
2684
        <title><varname>mikmod</varname></title>
2685 2686

        <para>
2687 2688
          Module player based on <ulink
          url="http://mikmod.sourceforge.net/"><application>MikMod</application></ulink>.
2689
        </para>
2690 2691 2692 2693 2694 2695 2696 2697 2698 2699

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
2700 2701 2702 2703 2704 2705 2706 2707 2708 2709
              <row>
                <entry>
                  <varname>loop</varname>
                  <parameter>yes|no</parameter>
                </entry>
                <entry>
                  Allow backward loops in modules.  Default is
		  <parameter>no</parameter>.
                </entry>
              </row>
2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721
              <row>
                <entry>
                  <varname>sample_rate</varname>
                </entry>
                <entry>
                  Sets the sample rate generated by
                  <filename>libmikmod</filename>.  Default is 44100.
                </entry>
              </row>
            </tbody>
          </tgroup>
        </informaltable>
2722
      </section>
2723

2724 2725 2726 2727
      <section>
        <title><varname>modplug</varname></title>

        <para>
2728
          Module player based on <application>MODPlug</application>.
2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754
        </para>

        <informaltable>
          <tgroup cols="2">
            <thead>
              <row>
                <entry>Setting</entry>
                <entry>Description</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry>
                  <varname>loop_count</varname>
                </entry>
                <entry>
                  Number of times to loop the module if it uses backward loops.
                  Default is <parameter>0</parameter&