static DownloadedMedia downloadAudio(S url) 
File dir = javaxDataDir("Downloaded Audio");

S fn = md5FileName(url);
saveTextFile(newFile(dir, fn + ".url"), url);
S options = "-U --no-playlist --no-mtime --write-description --write-info-json"
  + " --write-annotations --write-thumbnail --print-json --restrict-filenames";
options += " -x"; // audio only
options += " --audio-format opus"; // demand opus

S output = backtick_verbose(pqO(installYouTubeDL())
  + " " + options
  + " -o " + pqO(newFile(dir, youTubeDLDefaultFileNameTemplate()))
  + " " + pqO(url));
saveTextFile(newFile(dir, fn + ".info"), output);
pnl(jsonDecodeMap(output));