pull youtube thumbnail and url out of ACF oEmbed field for use
<?php
// check if the repeater field has rows of data
if( have_rows('videos') ):
// loop through the rows of data
while ( have_rows('videos') ) : the_row();
$video_url = get_sub_field('video_item', false, false);
$video = get_sub_field( 'video_item' );
preg_match('/src="(.+?)"/', $video, $matches_url );
$src = $matches_url[1];
preg_match('/embed(.*?)?feature/', $src, $matches_id );
$id = $matches_id[1];
$id = str_replace( str_split( '?/' ), '', $id );
?>
<!--video item-->
<div class="grid-item<?php if (get_sub_field('video_size') == 'large'): ?> lg<?php else: ?><?php endif; ?>">
<a data-fancybox href="<?php echo $video_url; ?>">
<img src="http://img.youtube.com/vi/<?php echo $id; ?>/maxresdefault.jpg">
</a>
</div>
<?php endwhile;
else :
// no rows found
endif;
?>