/**
 * Get thumbnails of video
 *
 * @since   1.0
 * @param   integer $post_id
 *
 * @return  array
 */
function rtmedia_transcoding_get_video_thumbs($post_id)
{
    return maybe_unserialize(get_post_meta($post_id, rtmedia_transcoding_get_video_thumb_meta_key(), true));
}
 /**
  * Save thumbnails of media from transcoding server
  *
  * @since   1.0
  */
 public function save_media_thumbnails($post_id, $thumbs)
 {
     // those thumbs may be in serialize form
     $thumbs = maybe_unserialize($thumbs);
     if (!empty($thumbs) && is_array($thumbs)) {
         $post_thumbs = array();
         // loop through each thumb and save them
         foreach ($thumbs as $single_thumb) {
             // get thumb from remote
             $remote_thumb = wp_remote_get($single_thumb);
             $thumb_body = wp_remote_retrieve_body($remote_thumb);
             // generate thumb file name
             $thumb_info = pathinfo($single_thumb);
             $thumb_file_name = basename(urldecode($thumb_info['basename']));
             // upload thumb file
             $thumb_upload_info = wp_upload_bits($thumb_file_name, null, $thumb_body);
             $post_thumbs[] = $thumb_upload_info['url'];
         }
         // save media thumb details into post meta
         update_post_meta($post_id, rtmedia_transcoding_get_video_thumb_meta_key(), $post_thumbs);
     }
 }