Hello, Dear Etienne Dega!

If you want to put the video, we recommend for you to use the animation gif images in the breadcrumbs.

In this case, please click WP Dashboard => Appearance => Customize => Additional CSS and put the following code.

.page_breadcrumbs {
background-image: url(http://www.zenbushidomitsu.fr/youko/wp-content/themes/youko/img/parallax/breadcrumbs.gif) !important;
}

On this way, you need put own image with name of breadcrumbs.gif with permission 1920x300 

\wp-content\themes\youko\img\parallax

Also, we send for you the articles with recommendations how to use this function:

https://giphy.com/create/gifmaker

https://biteable.com/blog/tips/make-gif-video/

We hope that our instructions will help you.

Best Regards!