This is pretty old, but what I do is have the user add only the video’s ID to a text field in Metabox, then on the page, use a code block like this:
<?php
$value = rwmb_meta( 'dvids_id' );
?>
<iframe src="https://www.website.net/video/embed/<?php echo $value; ?>" width="1280" height="735" frameborder="0" allowtransparency allowfullscreen style="background: black"></iframe>
You could do the same thing with a text area in Metabox and just use this code to output the iFrame code in a code block.