docs: def f2tc(f,base=25):
      """Converts frames to timecode"""
      try:
          f = int(f)
      except:
          return "--:--:--:--"
      hh = int((f / base) / 3600)
      mm = int(((f / base) / 60) - (hh*60))
      ss = int((f/base) - (hh*3600) - (mm*60))
      ff = int(f - (hh*3600*base) - (mm*60*base) - (ss*base))
      return "{:02d}:{:02d}:{:02d}:{:02d}".format(hh, mm, ss, ff)