You could try something like this (please note that this will work only for newly imported videos). Enter the code below in your theme functions.php file:
/**
* Filter the post content on new video insert
*/
function twentythirteen_cbc_video_content( $post_content, $video, $theme_import ){
// check if importing in theme
if( !$theme_import ){
return $post_content;
}
// we want to add the video link to post content at the beginning
$video_url = 'http://www.youtube.com/watch?v='.$video['video_id'];
return $video_url."\n (more…)