def METHOD_NAME(file_name):
  command_line = ["ffmpeg"]
  command_line += ["-i", file_name]
  command_line += ["-c", "copy"]
  command_line += ["-map", "0"]
  command_line += ["-f", "mp4"]
  command_line += ["-movflags", "empty_moov"]
  command_line += ["-"]
  return subprocess.Popen(
    command_line, stdout=subprocess.PIPE
  )