code: function payloadNonStreamCheck(msg) {
        var message = '';
  
        // The input comes in on msg.payload, and can either be an audio file or a string
        // representing a URL.
        if (!msg.payload instanceof Buffer || !typeof msg.payload === 'string') {
          message = 'Invalid property: msg.payload, can only be a URL or a Buffer.';
        } else if (!(msg.payload instanceof Buffer)) {
          // This check is repeated just before the call to the service, but
          // its also performed here as a double check.
          if (typeof msg.payload === 'string' && !payloadutils.urlCheck(msg.payload)) {
            message = 'Invalid URL.';
          }
        } else {
          var f = 'txt', ft = '';
  
          ft = fileType(msg.payload);
          if (ft) {
            f = ft.ext;
          }
  
          switch (f) {
          case 'wav':
          case 'flac':
          case 'ogg':
          case 'mp3':
          case 'mpeg':
            break;
          default:
            if (! ft.mime.toLowerCase().includes('audio')) {
              message = 'Audio format (' + f + ') not supported, must be encoded as WAV, MP3, FLAC or OGG.';
            }
          }
        }
        if (message) {
          return Promise.reject(message);
        }
        return Promise.resolve();
      }
docs: Input is a standard msg.payload