val tracks : ?format:format->string ->((string * string) list * string) list
tracks data performs whole process and outputs a list of metadatas,uri from given xml data string
All metadatas are what is provided by the playlist The only variable name that is changed is the author because each formats has its own field for that. The module will use "artist".
Order of tracks is preserved.
format is an optional argument, used to force format detection. Otherwise. detect_format is used.