if( ! function_exists('saturn_do_video_responsive' ) ){
    /**
     * @param html $html
     * @return html
     */
    function saturn_do_video_responsive( $html ) {
        return '<div class="embed-responsive embed-responsive-16by9">' . $html . '</div>';
    }
    add_filter( 'embed_oembed_html', 'saturn_do_video_responsive', 10, 3 );
    add_filter( 'video_embed_html', 'saturn_do_video_responsive' );
}