code: function(stderr) {
      // Only return the last stderr lines that don't start with a space or a square bracket
      return stderr.split(nlRegexp).reduce(function(messages, message) {
        if (message.charAt(0) === ' ' || message.charAt(0) === '[') {
          return [];
        } else {
          messages.push(message);
          return messages;
        }
      }, []).join('\n');
    }
docs: Extract error message(s) from ffmpeg stderr
  
  @param {String} stderr ffmpeg stderr data
  @return {String}
  @private