sub pre_process {
	threads->detach();
	my ( $file_name, $desc,  $dirpath ) = @_;
	my ( $file1,  $file2, $file3 )   = ( getTempFile(), getTempFile(), getTempFile() );
	my $metadata = i_PreProcessor->new(
		FILENAME      => $file_name,
		SEARCHXMLFILE => $file1,
		DESCRIPTION   => $desc,
		MAPXMLFILE    => $file2,
		TAGXMLFILE    => $file3,
		DIRNAME       => $dirpath
	);
	$metadata->build2();

	#delete temp files.
	my @files = ( $file1, $file2, $file3 );
	unlink(@files);
	threads->exit();
}