You will find video background in index-video.html file. For banner video background the code is give below
<header class="header main header\_video th-fullpage" data-vide-bg="video/ocean">
<div class="section">
<div class="container">
<div class="row">
<button id="trigger-overlay" class="th-nav-btn" type="button"><i class="tf-ion-android-menu"></i></button>
<div class="col-md-12">
<h1 class="text-center">We’re Creative <br>
We Ensure Quality Design</h1>
</div>
</div><!– /.row End –>
</div>
</div>
</header>
video file for background is located in video folder.
Change the data-vide-bg url for change the background.
And Change contents from h1 tag.