static S witAI_recognizeMP3(File mp3File) ctex {
  if (mp3File.length() == 0) fail("No file: " + mp3File);
  print("Calling wit.ai with " + toK(mp3File.length()) + " K mp3...");
  
  S token = witAIToken();
  URL url = new URL("https://api.wit.ai/speech?v=20160526");
  URLConnection con = url.openConnection();
  con.setRequestProperty("Authorization", "Bearer " + token);
  con.setRequestProperty("Content-Type", "audio/mpeg3");
  
  con.setDoOutput(true);
  OutputStream out = con.getOutputStream();
  file2stream(mp3File, out);
  out.flush();

  S json = loadPage(con, url);
  out.close();
  ret getString(jsonDecodeMap(json), "_text");
}