Sitemaps are intended to list the individual pages of your blog, not every way something might view those pages, eg. <a href="http://webmasters.stackexchange.com/questions/22411/sitemap-to-display-hash-tag-links-or-not">via anchors</a>. The video extension tags follow the same pattern: they're for listing what (whole) videos are on a given page. If the separate videos were accessible in some way, and then aggregated into your viewer with a playlist function, *then* it'd be appropriate to list them separately. But as you're describing right now, the multiple URLs would likely get ignored.