zTunes is a system for ingesting and synchronizing digital media libraries
in multiple media formats and for multiple devices.  I built it so that
we could play all the music in our library on all of our devices (iPods,
Squeezebox, other MP3 players) without having to transcode everything down
to the least-common-denominator.

Configuring zTunes:

Copy the configuration file config.rb from the GEM and put it somewhere.
Edit it according to the descriptions below, and invoke zTunes with:

    ztunes -c /path/to/config.rb target...

There are three kinds of directories in a zTunes configuration:
 - Media folders -- these are the authoritative copies of your media,
using their media tags to structure the subdirectories (e.g.,
"The Who/Who's Next/Baba O'Reilly.flac").
 - Drop folders -- these are directories into which you drop new media
files, to be filed into your media directories.  Filing may simply involve
copying, or it could involve transcoding or compression.  My metaphor
for drop folders is the gas tank of an M1 -- you can pour any combustible
material into it, and the fuel sensors figure out how to burn it.
 - View folders -- these are directories that are targeted at a
specific device whose supported media types are known.  For example, you
might have an iPod directory.  Since iPods can play m4a and mp3 natively,
the iPod view directory would contain symlinks back to the authoritative
copy for these files, plus transcoded versions of other files (such as flac
or wma) in a format that iPod likes.

Here's an example of how you might configure zTunes where you have one
main media directory for audio files, a single drop folder, and view
folders for iPod and Squeezebox.  First you configure your directories:

# Drop folder
DROP = "/home/media/drop"

# Media folders
AUDIO = "/home/media/music"
VIDEO = "/home/media/video"

# View folders
MP3 = "/home/media/views/mp3"
IPOD = "/home/media/views/ipod"
SQUEEZEBOX = "/home/media/views/squeezebox"

# The staging directory is a temporary folder for use by zTunes
STAGE = "/home/media/stage"

Then, you configure your drop folders.  Here, we only have one drop
folder, which supports wav, mp3, wma, flac, and m4a.  All these files
will be swept to the AUDIO directory after being processed by the
specified handler.  For flac, m4a, wma, and mp3, the handler just copies
the file; for WAV files, the handler encodes it with flac and extracts
the metadata from the file name (using a naming convention specific to
the handler).

DROP_FOLDERS = {
        DROP => {
                "wav"  => { :handler => WavToFlacDropHandler.new,  :toDir => AUDIO },
                "mp3"  => { :handler => SimpleDropHandler.new("mp3"),  :toDir => AUDIO },
                "wma"  => { :handler => WmaDropHandler.new,  :toDir => AUDIO },
                "flac" => { :handler => SimpleDropHandler.new("flac"), :toDir => AUDIO },
                "m4a"  => { :handler => SimpleDropHandler.new("m4a"),  :toDir => AUDIO }
        }
}

The view folders are the most complicated part.  A view is a directory tree filled with
symlinks back to the media folders, or transcoded versions of files from the media folders.
It is allowable to have views of views; the example below shows that.

VIEW_FOLDERS = {
        MP3 => { :target => :mp3,
                 :fromDirs => [ AUDIO ],
                 :supportedTypes => [ "mp3" ],
                 :transcode => { "flac" => FlacToMp3.new,
                                 "wma" => WmaToMp3.new,
                                 "m4a" => M4aToMp3.new }
        },
        IPOD => { :target => :ipod,
                  :fromDirs => [ AUDIO, MP3 ],
                  :supportedTypes => [ "m4a", "mp3" ],
                  :transcode => { "mp4" => Mp4ForIpod.new }
        },
        SQUEEZEBOX => { :target => :squeezebox,
                        :fromDirs => [ AUDIO, MP3 ],
                        :supportedTypes => [ "flac", "wma", "mp3" ]
        }
}

Here, we have three view folders -- one consisting of MP3s versions of all the flac,
wma, and m4a files (this view is then used by both the other views), one for iPod
(which supports m4a and mp3), and one for Squeezebox (which supports flac, wma, and
mp3.)

For each view folder, the :fromDirs key points to a list of media folders to
form a view overs.  The :supportedTypes key points to a list of media types that
are supported natively; if it finds any of this type in the media directories, it
creates a symbolic link.  The :transcode key points to a hash of file types and
transcoding handlers; if it finds any of these types in the media folders, it
transcodes them.  Supported types take precedence over transcoding, and directories
earlier in the list of media folders take precedence over those that come later.
So in this example, even through there is going to be an MP3 version in the MP3
view for every M4A file in the AUDIO folder, if it finds an M4A version of a track,
it doesn't also link in the MP3 version.  Careful ordering of the :fromDirs, :transcode,
and :supportedTypes lists can generally create the result you want.

Other applications:
 - You may want to keep multiple resolutions of video files, such as one for iPod
nano-sized devices, another for iPhone, and another for pushing to Myth.  Views
can do this for you.
 - You may want to segregate media files by owner, but provide aggregated views.
For example, maybe your kids rip files using a crappy ripper, and you don't want
to pollute your main media store.  In that case, you have separate drop and media
folders for the main store and for the kids store, and then a view that ties them
together.


zTunes is based on rake, so different functionality is invoked through different rake
targets.  There are three basic classes of targets:

 - Drop targets -- process files from the drop folders
 - View targets -- generate views from the media folders
 - Sync targets -- synchronize media folders and views

The :drop target processes all the drop folders.  You can configure a MAX_THREADS
parameter, which should generally be set to the number of cores your system has,
so that CPU-intensive activities can take advantage of all available CPUs.

The :views target processes all the view folders.  You can also process the view
folders individually by invoking the value of the :target key from the view folders
config.

The :rename target will rename all files in the media folders to follow the naming
convention #{ARTIST}/#{ALBUM}/#{TRACK}.#{FILETYPE}.  This is helpful after you've
edited the metadata using a tool like Tag&Rename and want to get the directory
structure back in sync with the metadata tags.

Executing :rename may create empty directories or break symlinks; the :prune
target will prune out empty directories and kill dead symlinks in the media and
view directories.

A sensible order for processing everything is:

  ztunes drop rename prune views

The :checktags target will crawl the media folders and complain about any files
that have empty artist, album, track number, genre, or title tags.

Any target can be "pre-flighted" by specifying the :preview target at the start
of the target list:

  ztunes preview rename

to see what it is going to do.

Things to be added very soon:
 - Video transcoding support

Things to be added eventually:
 - iTunes integration
 - Web app for content ingestion, library management