Design
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Dub Playlist
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Dub considers the filesystem as its database. User specifies one or more directories
as the directories in which dub will scan for all or particular media types.

The scanning is initiated on demand, so that dub does not perform redundant disk
access which is expensive.

Design Goals
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v1.0
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User interface:

 * settings: select directories that contain media files.

 * tree view to browse files: this should scan directories like a file manager would,
  consider re-using code from file manager.

 * add file: symlink to a directory as Njaard suggests

v2.0
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implement filters: directory-wise filtering of media types.

implement database: for storing properties of media files, such as tags in mp3s so that
alternative queries can be made.

user interface: improved tree view that accesses the db to fetch info about files

v3.0
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music playing: implement an automated dj process.
