If i i'm correct you can use MP4
just change the .jpg format to MP4 code is already pasted below. But you must put a mp4 file at the same resolution send me a mp4 file and i will edit it for you to fit the web. but i can't test it myself since i no longer work with mu.
Just change the .jpg to .mp4 and put a file called
fondo6.mp4 in images folder
Code:
<?php if ($page_check_id == register) {?>
<div align="left">
<video style="width: auto; height: auto; margin-center: 100px; center: 100000000000px;background:url(template/<?=$core['config']['template'] ?>/images/fondo6.mp4);background-repeat:no-repeat;background-size:cover;" loop="loop" poster="template/<?=$core['config']['template'] ?>/images/fondo6.mp4" autoplay>
<?php
if ($bgMovie == 1)
{
?>
</div>