function videotube_add_video_schema(){
    if( is_singular( 'video' ) ){
        ?>
        <meta itemprop="video" itemscope itemtype="http://schema.org/VideoObject">
        <meta itemprop="name" content="<?php echo esc_attr( get_the_title() ); ?>">
        <meta itemprop="description" content="<?php echo esc_attr( wp_kses(get_the_excerpt(), array()) ); ?>">
        <meta itemprop="embedUrl" content="<?php echo get_post_embed_url( get_the_ID() );?>">
        <meta itemprop="thumbnailUrl" content="<?php echo esc_url( get_the_post_thumbnail_url( get_the_ID(), 'large' ) ); ?>">
        <meta itemprop="uploadDate" content="<?php echo esc_attr( get_the_date( 'Y-m-d H:i:s', get_the_ID() ) ); ?>">
        <?php
    }
}
add_action( 'wp_head', 'videotube_add_video_schema', 1 );