Playback defines whether media is processed within a pipeline (:playing) or not (:stopped).

Component playback will not enter :playing state until its parent playback is playing and all components from the spec, that started this component have ended their setups and linked their pads.

By default, component setup ends with the end of handle_setup/2 callback. If {:setup, :incomplete} is returned there, setup lasts until {:setup, :complete} is returned from antoher callback.

Untils the setup lasts, the component won't enter :playing playback.