public function get_duration($convert = false)
	{
		if ($this->duration !== null)
		{
			if ($convert)
			{
				$time = SimplePie_Misc::time_hms($this->duration);
				return $time;
			}
			else
			{
				return $this->duration;
			}
		}
		else
		{
			return null;
		}
	}