PHP Headers with DivX and Matroska

Ok, This is a simple php code to hide the video files and if this is you can block him or give him better access to the video to anyone. I always worked perfectly, The problem is that works with DivX and Matroska does not work. (I tried to change the MIME type). Thank posts on the topic.
Code:
HTML File 1
embed ... src='file2.php'>/embed

PHP File 2 (file2.php)
<?php
$filename = 'hello.mkv'; //with DivX File Work and with MKV don´t work
header('Content-Length: '. filesize($filename));
header('Content-Type: video/divx');
header('Content-Disposition: attachment; filename="'.basename($filename).'"');
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
ob_clean();
flush();
readfile($filename); // send the file
exit; // make sure no extraneous characters get appended
?>