From ReelSEO: "...crawling, digesting, analyzing, and indexing video content is a tough job for a search engine crawler, for many reasons: variations in publishing methods, inadequate recognition technologies, etc…
Google launched video sitemaps in late 2007 as a way to overcome these challenges, by having video content publishers provide information to assist Google in locating and indexing video assets.
...However, it’s always the desire of a search engine to be able to discover content on it’s own and not necessarily rely upon sitemaps to index content.
While video is more difficult to discover, over the past year or so, I’ve seen clear indication that Google (in particular) is getting much better at indexing videos without sitemaps, and that’s the goal.
Enter Schema Markup & VideoObject:
Now that Google is getting good at identifying video assets through a crawl, they’re encouraging video publishers to implement a standard schema markup (VideoObject) for video pages to further assist Google in understanding what the video content is about.
...the good news is that for many who dont need to provide additional information, getting your videos indexed is going to become easier and easier, especially if you start marking up your video content with schema markup as it’s a clear indication to Google that you have video on a given page."
Here's how to do it: http://www.reelseo.com/schema-markup-video/
Via Robin Good