I'd put this in the 'nice to have for custom campaigns'.
Outlook is a long way from adopting HTML5. It seems to me to be a lot of work for little return. In the mean time, it might be worth looking at animated GIFs that will be available to a larger poriton of your audience.
However, here is an example that Litmus put together: https://litmus.com/blog/how-to-code-html5-video-background-in-email