WP - Wrap class around videos

CSS-responsive-video.css

.video-container {
	width: 100%;
	position: relative;
	padding-bottom: 56.25%; /* 16:9 */
	padding-top: 25px;
	height: 0;
}
.video-container iframe {
	position: absolute;
	top: 0;
	left: 0;
	width: 100%;
	height: 100%;
}

WP-wrap-video-class.php

<?php

// responsive video embed
add_filter( 'embed_oembed_html', 'custom_oembed_filter', 10, 4 );

function custom_oembed_filter( $html, $url, $attr, $post_ID ) {
	$video_wrap = '<div class="video-container">' . $html . '</div>';
	return $video_wrap;
}

?>