def callback(track_transfer_batch, entry, dest, user_param1, ...)

Emitted when a new entry is about to be transferred. This will be emitted for each entry in the batch, unless the batch is cancelled.

track_transfer_batch :

instance of RB.TrackTransferBatch that is emitting the signal

entry :

the RB.RhythmDBEntry being transferred

dest :

the destination URI for the transfer

user_param1 :

first user parameter (if any) specified with the connect() method

... :

additional user parameters (if any)