Transcoding in Subsonic is a way to re-encode music on the fly to a format
your listening device supports. A common use is transcoding FLAC, WMA,
and Vorbis audio to MP3 for devices supporting only that codec.

Configuring transcoding uses up to three commands one would use on a normal
command line pipe but with a whitelist of executables installed or linked into
%%SUBSONIC_HOME%%/transcode. The transcoding configuration page takes
transcoding rules in the form of:

  [rule name] [convert from] [convert to] [command 1] [command 2] [command 3]

The most compatible single audio transcoding command is with FFmpeg, transcoding
any input to MP3, mapping all streams to output, and limiting metadata to the
more-compatible ID3v2.3:

  [All to MP3] [ogg flac wma aiff m4a] [mp3] ...
    [ffmpeg -i %s -ab %bk -id3v2_version 3 -map_metadata 0 -map 0:0 -ar 44100 -ac 2 -v 0 -f mp3 -]

You can also transcode with multiple single-codec commands to avoid
the heavy FFmpeg dependency:

  [FLAC to MP3] [flac] [mp3] ...
    [flac --silent --decode --stdout %s] [lame --silent -h -b %b -]

  [AAC to MP3] [m4a] [mp3] ...
    [faad -s -o - %s] [lame --silent -h -b %b -]

  [Vorbis to MP3] [ogg] [mp3] ...
    [oggdec -Q -o /dev/stdout %s] [lame --silent -h -b %b -]

  [MPC to MP3] [mpc] [mp3] ...
    [mpcdec %s -] [lame --silent -h -b %b -]

  [APE to MP3] [ape] [mp3] ...
    [mac %s - -d] [lame --silent -h -b %b -]

  [Trackers to MP3] [mod s3m xm it] [mp3] ...
    [xmp -q -c %s] [lame --silent -h -b %b -]