You're seeing just the callback handle_prepared_to_playing, go back to Membrane.Element.Base module for more information.
Link to this callback

handle_prepared_to_playing(context, state)

View Source (optional)


  context :: Membrane.Element.CallbackContext.PlaybackChange.t(),
  state :: Membrane.Element.state_t()
) :: callback_return_t()

Callback invoked when element is supposed to start playing (goes from state :prepared to :playing).

This is moment when initial demands are sent and first buffers are generated if there are any pads in the push mode.