docs: def hms2frame(hms, fps):
          """
          :param hms: a string, e.g. "01:23:15" for one hour, 23 minutes 15 seconds 
          :param fps: framerate 
          :return: frame number
          """
          import time
          t = time.strptime(hms, "%H:%M:%S")
          return (t.tm_hour * 60 * 60 + t.tm_min * 60 + t.tm_sec) * fps