Get images from gallery post format

I’m working on a custom post type called Movie.
I enabled post format so that I can use Gallery Post Format.

Now, in my single-movie.php I need to get images uploaded in gallery in Gallery Post Format. I’m using this snip

<!-- Gallery immagini -->
<div class="live-gallery">
<?php
$gallery = get_post_gallery_images(get_the_ID());
foreach($gallery as $img) :
?>
<a href="<?php echo get_permalink(get_the_ID()); ?>">
    <img src="<?php echo $img; ?>" alt="<?php echo get_the_title(); ?>" />
</a>
<?php endforeach; ?>
</div>
<!-- fine Gallery -->

But I get only images from galleries I create inside the content, while I need images uploaded with specific field before the post content, when I select Gallery as post format.

How can I fix this?
Thanks in advance