Google said the test would help participants "learn the easiest and most scalable way to deliver ads to online video content ... Publishers will be able to insert high-quality, relevant ads that enhance the video content while maintaining a positive user experience."
As is currently the case with AdSense, Google said ad revenue will be split between publishers and Google, but the share was not revealed.
The videos will play on publishers' Flash players, not via Google Video or Google's YouTube--both of which have been reported to be testing their own in-stream video ad technology.
Publishers can select in which videos ads run, and where the ads appear within the videos. They can also track ad performance.
The creatives, limited to no more than 30 seconds, can be made skippable for users.
Writing in the "Inside AdSense" blog, Product Marketing Manager Christine Lee was careful to distinguish the new service from click-to-play video ads on Google's content network and from AdSense's video distribution and sponsorship service. The latter, which has been tested twice, would allow publishers to choose video channels consisting of short-form videos bundled with video ads.
Publishers using AdSense for Video should also be helped by Google's upcoming Universal Search, announced last week, which will integrate video results into all searches.