YouTube, part of Google (NSDQ: GOOG), has done a rare acquisition: it has bought online video tools firm Omnisio, for an undisclosed sum. The small Atherton, CA-based startup has mashups, video annotation, video presentations and other tools to allow video sharing users to better express themselves…the thought is that these will be integrated within YouTube as well. For these mashups, the service could ingest video in from YouTube, Google Video and Blip.tv, though it may be that it discontinues Blip if it is integrated into YouTube. TC says the deal is all cash and is in the $15 million range.

More on Youtube blog and Omnisio blog. The company was incubated out of Ycombinator, and launched earlier this year.