Media3PlaybackService is the active implementation, built on AndroidX Media3/ExoPlayer. PlaybackService is legacy and will throw an exception if started — it exists only during the transition period.

External callers should interact with the service through PlaybackController, which provides a bindToMedia3Service() helper that connects a MediaController and runs a callback on it. The MediaController exposes the standard Media3 Player interface: seekTo(positionMs), play(), pause(), getCurrentPosition(), getPlaybackParameters(), etc. Each call to bindToMedia3Service() creates a short-lived connection that is released after the callback returns.