          if self.args.action in self._actions_have_print_output:
              self.print_ = True
  
          self.effmpeg_process()
  
      def effmpeg_process(self):
          kwargs = {"input_": self.input,
                    "output": self.output,
                    "ref_vid": self.ref_vid,
 
</s> remove     def extract(input_=None, output=None, fps=None, extract_ext=None,
 </s> add     def extract(input_=None, output=None, fps=None, extract_ext=None, start=None, duration=None,
        logger.debug("Finished Effmpeg process")
          if self.args.action in self._actions_have_print_output:
              self.print_ = True
  
          self.effmpeg_process()
        logger.debug("Finished Effmpeg process")
  
      def effmpeg_process(self):
          kwargs = {"input_": self.input,
                    "output": self.output,
                    "ref_vid": self.ref_vid,
keep keep keep add keep keep keep keep keep
 Fix duration for effmpeg extract 
tools/effmpeg.py