Factory
- get a list of available backends
- be able to choose the one you want to use, overriding the KTrader information
- test on the fly switching

Audio
- function to retrieve the PCM data that currently is played (could be done in
  the Channel as well as in the Player)

Video
- either a new interface or somehow integrate into the player
  If it's a new interface we have to copy most of the Player class, which I
  wouldn't like to see.

two wrapper APIs:
- for notifications
  play file and don't care
  automatically use the notification channel if present
- for simple players
  open file and provide seek and volume

Mixer abstraction
- provide access to the hardware mixer and/or the mixer of the backend
- provide access to software volume controls (like the Channels)

Record Interface
- simple PCM recording API