Please help me add_filter function!

Hello,
I have a function for encrypt the content:

function rewrite_text( $article, $case_sensitive=false ) {

	$workwith=$article;
	......
	$codul='<script type="text/javascript">
document.write(String.fromCharCode('.$numbers.'));
</script>';
		$workwith=$codul;
		}
	return $workwith;
}
add_filter('the_content', 'rewrite_text', 100);

But i want to using function rewrite_text to encrypt this function:

function dp_video($post_id, $autoplay = false) {
                .....
		$video = "<div class=\"video-wrap\"><embed src=\"http://www.youtube.com/v/".$youtube_id."?modestbranding=1&version=3&hl=vi_VN&rel=0&autoplay=1&showsearch=0&iv_load_policy=3&theme=light\" type=\"application/x-shockwave-flash\" allowFullScreen=\"true\" allowScriptAccess=\"always\" width=\"100%\" height=\"100%\"/></div>";
		echo $video;

Please help me add add_filter to this code:
add_filter('the_content', 'rewrite_text', 100);
I’m using:
add_filter('dp_video', 'rewrite_text', 100);
It’s not working.
Sorry, my English is bad! 🙁