let to_string v =
    Printf.sprintf
    "%%opus(%s,%schannels=%d,%s%s%s%ssamplerate=%d,frame_size=%.02f)"
      (string_of_mode v.mode)
      (string_of_bitrate v.bitrate)
      v.channels
      (string_of_application v.application)
      (match v.complexity with None -> "" | Some i -> (Printf.sprintf "complexity=\"%d\"," i))
      (string_of_bandwidth v.max_bandwidth)
      (string_of_signal v.signal)
      v.samplerate
      v.frame_size