Capture inputs have one or more input ports (instances of AVCaptureInput.Port). Capture outputs can accept data from one or more sources (for example, an AVCaptureMovieFileOutput object accepts both video and audio data).
You can add an AVCaptureConnection instance to a session using the addConnection(_:) method only if the canAddConnection(_:) method returns true.
When using the addInput(_:) or addOutput(_:) method, the session forms connections automatically between all compatible inputs and outputs.
You only need to add connections manually when adding an input or output with no connections.
You can also use connections to enable or disable the flow of data from a given input or to a given output.