READY_TO_PAUSED

state change from READY to PAUSED.

* The element pads are activated in order to receive data in PAUSED. Streaming threads are started. * Some elements might need to return gst_state_change_async and complete the state change when they have enough information. It is a requirement for sinks to return gst_state_change_async and complete the state change when they receive the first buffer or gst_event_eos (preroll). Sinks also block the dataflow when in PAUSED. * A pipeline resets the running_time to 0. * Live sources return gst_state_change_no_preroll and don't generate data.