Add excerpt to the content to be scanned by the WP SEO Video plugin

gistfile1.php

<?php
function fix_content_input( $content, $vid ) {
  $post = get_post( $vid['post_id'] );
  if ( !empty( $post->post_excerpt ) )
    $content = "\n" . $post->post_excerpt . "\n" . $content;
  return $content;
}
add_filter( 'wpseo_video_index_content', 'fix_content_input', 10, 2 );