If the GstBaseSrcClas.create|GstBaseSrcClas.creates method performs its own synchronisation
against the clock it must unblock when going from PLAYING to the PAUSED state
and call this method before continuing to produce the remaining data.
This function will block until a state change to PLAYING happens (in which
case this function returns GST_FLOW_OK) or the processing must be stopped due
to a state change to READY or a FLUSH event (in which case this function
returns GST_FLOW_FLUSHING).
If the GstBaseSrcClas.create|GstBaseSrcClas.creates method performs its own synchronisation against the clock it must unblock when going from PLAYING to the PAUSED state and call this method before continuing to produce the remaining data.
This function will block until a state change to PLAYING happens (in which case this function returns GST_FLOW_OK) or the processing must be stopped due to a state change to READY or a FLUSH event (in which case this function returns GST_FLOW_FLUSHING).