Extract an embedded video from the content

Embeds are cached in hidden post meta fields with _oembed_* keys. You could retrieve all of meta (with get_post_custom() for example) and try to get info from it.

However, from quick look at my test data it seems that duplicates are not uncommon there (might have to do with either WP version changes or embed endpoint changes).

If you are not displaying this as “normal” content at all I would consider just adding custom metabox for video and its description.