WordPress Oembed.

gistfile1.txt

function oembed_filter( $content) {
	global $wp_embed;
	add_filter( 'embed_oembed_discover', '__return_false', 999 );
	$comment_text = $wp_embed->autoembed( $content );
	remove_filter( 'embed_oembed_discover', '__return_false', 999 );
	return $content;
}

add_filter( 'the_content', 'oembed_filter');