Convert Plugin
==============

The ``convert`` plugin lets you convert parts of your collection to a directory
of your choice, transcoding audio and embedding album art along the way. It can
transcode to and from any format using a configurable command line. Optionally
an m3u playlist file containing all the converted files can be saved to the
destination path.

Installation
------------

To use the ``convert`` plugin, first enable it in your configuration (see
:ref:`using-plugins`). By default, the plugin depends on FFmpeg_ to transcode
the audio, so you might want to install it.

.. _ffmpeg: https://ffmpeg.org

Usage
-----

To convert a part of your collection, run ``beet convert QUERY``. The command
will transcode all the files matching the query to the destination directory
given by the ``-d`` (``--dest``) option or the ``dest`` configuration. The path
layout mirrors that of your library, but it may be customized through the
``paths`` configuration. Files that have been previously converted---and thus
already exist in the destination directory---will be skipped.

The plugin uses a command-line program to transcode the audio. With the ``-f``
(``--format``) option you can choose the transcoding command and customize the
available commands :ref:`through the configuration <convert-format-config>`.

Unless the ``-y`` (``--yes``) flag is set, the command will list all the items
to be converted and ask for your confirmation.

The ``-a`` (or ``--album``) option causes the command to match albums instead of
tracks.

By default, the command places converted files into the destination directory
and leaves your library pristine. To instead back up your original files into
the destination directory and keep converted files in your library, use the
``-k`` (or ``--keep-new``) option.

To test your configuration without taking any actions, use the ``--pretend``
flag. The plugin will print out the commands it will run instead of executing
them.

By default, files that do not need to be transcoded will be copied to their
destination. Passing the ``-l`` (``--link``) flag creates symbolic links
instead, passing ``-H`` (``--hardlink``) creates hard links. Note that album art
embedding is disabled for files that are linked. Refer to the ``link`` and
``hardlink`` options below.

The ``-F`` (or ``--force``) option forces transcoding even when safety options
such as ``no_convert``, ``never_convert_lossy_files``, or ``max_bitrate`` would
normally cause a file to be copied or skipped instead. This can be combined with
``--format`` to explicitly transcode lossy inputs to a chosen target format.

The ``-m`` (or ``--playlist``) option enables the plugin to create an m3u8
playlist file in the destination folder given by the ``-d`` (``--dest``) option
or the ``dest`` configuration. The path to the playlist file can either be
absolute or relative to the ``dest`` directory. The contents will always be
relative paths to media files, which tries to ensure compatibility when read
from external drives or on computers other than the one used for the conversion.
There is one caveat though: A list generated on Unix/macOS can't be read on
Windows and vice versa.

Depending on the beets user's settings a generated playlist potentially could
contain unicode characters. This is supported, playlists are written in `M3U8
format`_.

Configuration
-------------

To configure the plugin, make a ``convert:`` section in your configuration file.
The available options are:

- **auto**: Import transcoded versions of your files automatically during
  imports. With this option enabled, the importer will transcode all (in the
  default configuration) non-MP3 files over the maximum bitrate before adding
  them to your library. Default: ``no``.
- **auto_keep**: Convert your files automatically on import to **dest** but
  import the non transcoded version. It uses the default format you have defined
  in your config file. Default: ``no``.

  .. note::

      You probably want to use only one of the ``auto`` and ``auto_keep``
      options, not both. Enabling both will convert your files twice on import,
      which you probably don't want.

- **tmpdir**: The directory where temporary files will be stored during import.
  Default: none (system default),
- **copy_album_art**: Copy album art when copying or transcoding albums matched
  using the ``-a`` option. Default: ``no``.
- **album_art_maxwidth**: Downscale album art if it's too big. The resize
  operation reduces image width to at most ``maxwidth`` pixels while preserving
  the aspect ratio. The specified image size will apply to both embedded album
  art and external image files.
- **dest**: The directory where the files will be converted (or copied) to.
  Default: none.
- **embed**: Embed album art in converted items. Default: ``yes``.
- **id3v23**: Can be used to override the global ``id3v23`` option. Default:
  ``inherit``.
- **write_metadata**: Can be used to disable writing metadata to converted
  files. Default: ``true``.
- **max_bitrate**: By default, the plugin does not transcode files that are
  already in the destination format. This option instead also transcodes files
  with high bitrates, even if they are already in the same format as the output.
  Note that this does not guarantee that all converted files will have a lower
  bitrate---that depends on the encoder and its configuration. Default: none.
  This option will be overridden by the ``--force`` flag
- **no_convert**: Does not transcode items matching the query string provided
  (see :doc:`/reference/query`). For example, to not convert AAC or WMA formats,
  you can use ``format:AAC, format:WMA`` or ``path::\.(m4a|wma)$``. If you only
  want to transcode WMA format, you can use a negative query, e.g.,
  ``^path::\.(wma)$``, to not convert any other format except WMA. This option
  will be overridden by the ``--force`` flag
- **never_convert_lossy_files**: Cross-conversions between lossy codecs---such
  as mp3, ogg vorbis, etc.---makes little sense as they will decrease quality
  even further. If set to ``yes``, lossy files are always copied. Default:
  ``no``. When ``never_convert_lossy_files`` is enabled, lossy source files (for
  example MP3 or Ogg Vorbis) are normally not transcoded and are instead copied
  or linked as-is. To explicitly transcode lossy files in spite of this, use the
  ``--force`` option with the ``convert`` command (optionally together with
  ``--format`` to choose a target format)
- **paths**: The directory structure and naming scheme for the converted files.
  Uses the same format as the top-level ``paths`` section (see
  :ref:`path-format-config`). Default: Reuse your top-level path format
  settings.
- **quiet**: Prevent the plugin from announcing every file it processes.
  Default: ``false``.
- **threads**: The number of threads to use for parallel encoding. By default,
  the plugin will detect the number of processors available and use them all.
- **link**: By default, files that do not need to be transcoded will be copied
  to their destination. This option creates symbolic links instead. Note that
  options such as ``embed`` that modify the output files after the transcoding
  step will cause the original files to be modified as well if ``link`` is
  enabled. For this reason, album-art embedding is disabled for files that are
  linked. Default: ``false``.
- **hardlink**: This options works similar to ``link``, but it creates hard
  links instead of symlinks. This option overrides ``link``. Only works when
  converting to a directory on the same filesystem as the library. Default:
  ``false``.
- **delete_originals**: Transcoded files will be copied or moved to their
  destination, depending on the import configuration. By default, the original
  files are not modified by the plugin. This option deletes the original files
  after the transcoding step has completed. Default: ``false``.
- **playlist**: The name of a playlist file that should be written on each run
  of the plugin. A relative file path (e.g ``playlists/mylist.m3u8``) is allowed
  as well. The final destination of the playlist file will always be relative to
  the destination path (``dest``, ``--dest``, ``-d``). This configuration is
  overridden by the ``-m`` (``--playlist``) command line option. Default: none.

You can also configure the format to use for transcoding (see the next section):

- **format**: The name of the format to transcode to when none is specified on
  the command line. Default: ``mp3``.
- **formats**: A set of formats and associated command lines for transcoding
  each.

.. _convert-format-config:

Configuring the transcoding command
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can customize the transcoding command through the ``formats`` map and select
a command with the ``--format`` command-line option or the ``format``
configuration.

::

    convert:
        format: speex
        formats:
            speex:
                command: ffmpeg -i $source -y -acodec speex $dest
                extension: spx
            wav: ffmpeg -i $source -y -acodec pcm_s16le $dest

In this example ``beet convert`` will use the *speex* command by default. To
convert the audio to ``wav``, run ``beet convert -f wav``. This will also use
the format key (``wav``) as the file extension.

Each entry in the ``formats`` map consists of a key (the name of the format) as
well as the command and optionally the file extension. ``extension`` is the
filename extension to be used for newly transcoded files. If only the command is
given as a string or the extension is not provided, the file extension defaults
to the format's name. ``command`` is the command to use to transcode audio. The
tokens ``$source`` and ``$dest`` in the command are replaced with the paths to
the existing and new file.

The plugin in comes with default commands for the most common audio formats:
``mp3``, ``alac``, ``flac``, ``aac``, ``opus``, ``ogg``, ``wma``. For details
have a look at the output of ``beet config -d``.

For a one-command-fits-all solution use the ``convert.command`` and
``convert.extension`` options. If these are set, the formats are ignored and the
given command is used for all conversions.

::

    convert:
        command: ffmpeg -i $source -y -vn -aq 2 $dest
        extension: mp3

Gapless MP3 encoding
~~~~~~~~~~~~~~~~~~~~

While FFmpeg cannot produce "gapless_" MP3s by itself, you can create them by
using LAME_ directly. Use a shell script like this to pipe the output of FFmpeg
into the LAME tool:

::

    #!/bin/sh
    ffmpeg -i "$1" -f wav - | lame -V 2 --noreplaygain - "$2"

Then configure the ``convert`` plugin to use the script:

::

    convert:
        command: /path/to/script.sh $source $dest
        extension: mp3

This strategy configures FFmpeg to produce a WAV file with an accurate length
header for LAME to use. Using ``--noreplaygain`` disables gain analysis; you can
use the :doc:`/plugins/replaygain` to do this analysis. See the LAME
documentation_ and the `HydrogenAudio wiki`_ for other LAME configuration
options and a thorough discussion of MP3 encoding.

.. _documentation: https://sourceforge.net/projects/lame/

.. _gapless: https://wiki.hydrogenaudio.org/index.php?title=Gapless_playback

.. _hydrogenaudio wiki: https://wiki.hydrogenaudio.org/index.php?title=LAME

.. _lame: https://sourceforge.net/projects/lame/

.. _m3u8 format: https://en.wikipedia.org/wiki/M3U#M3U8
