def process_mav(self, mlog, timeshift):
        '''process one file'''
        self.vars = {}
        while True:
            msg = mlog.recv_msg()
            if msg is None:
                break
            if msg.get_type() not in self.msg_types:
                continue
            if self.condition:
                if not mavutil.evaluate_condition(self.condition, mlog.messages):
                    continue
            tdays = matplotlib.dates.date2num(datetime.datetime.fromtimestamp(msg._timestamp+timeshift))
            self.add_data(tdays, msg, mlog.messages, mlog.flightmode)