Retrieves a new videoframe from the stream.

		Sets the frame as the __current_video_frame and passes it on to
		__videorenderfunc() if it is set.

def __render_videoframe(self):
		""" Retrieves a new videoframe from the stream.

		Sets the frame as the __current_video_frame and passes it on to
		__videorenderfunc() if it is set. """

		new_videoframe = self.clip.get_frame(self.clock.time)
		# Pass it to the callback function if this is set
		if callable(self.__videorenderfunc):
			self.__videorenderfunc(new_videoframe)
		# Set current_frame to current frame (...)
		self.__current_videoframe = new_videoframe