What does your Video SEO plugin actually do?
It goes through a series of steps, as soon as you update a post that you put a video in:
It recognises the video and, depending on whether it's a self-hosted video or hosted on a site like Vimeo, determines what to do;
If it's for instance hosted on Vimeo, it'll retrieve the video details from the Vimeo API;
It'll determine which thumbnail to attach to the video and what the duration of the video is;
It then saves all this metadata so that you get a video snippet in the snippet preview AND a video XML sitemap entry is generated for the post / page.
It does all that on the fly, as soon as the plugin is activated you only have to add a video to a post and it'll automatically recognize it and go through those steps for you.