public function bitrate($var, $type = 'audio')
    {
        // Value must be numeric
        if (!is_numeric($var)) 
        {
            return false;
        }

        switch ($type) 
        {
            case 'audio':
                array_push($this->parameters, '-b:a '.$var.'k');
                return $this;
                break;

            case 'video':
                array_push($this->parameters, '-b:v '.$var.'k');
                return $this;
                break;

            default:
                return false;
                break;
        }
    }