Called by the event loop when it is started.

        Creates the output frame pools (if used) then calls
        :py:meth:`on_start`. Creating the output frame pools now allows
        their size to be configured before starting the component.

def start_event(self):
        """Called by the event loop when it is started.

        Creates the output frame pools (if used) then calls
        :py:meth:`on_start`. Creating the output frame pools now allows
        their size to be configured before starting the component.

        """
        # create object pool for each output
        if self.with_outframe_pool:
            self.update_config()
            for name in self.outputs:
                self.outframe_pool[name] = ObjectPool(
                    Frame, self.new_frame, self.config['outframe_pool_len'])
        try:
            self.on_start()
        except Exception as ex:
            self.logger.exception(ex)
            raise StopIteration()