This integrates the videos unobtrusively into the rest of the content on the sites, unlike traditional banner ads or pre-roll ads, which are often ignored.

FORBES: Sharethrough's Sponsored Videos Bringing Branded Content To Websites, Apps

Pre-roll ads will be viewable on large-format displays.

FORBES: CES Highlight #1: Smart TVs

The idea is that the campaigns will not be intrusive, like pre-roll video ads, but will be in-game virtual goods and features that users actually like and want to engage with.

FORBES: Zynga Says No To Ads, Yes To In-Game Promotions

Its software allows video creators to embed instructions for the player to show several kinds of advertising in videos, including pre-roll video ads, text ticker ads that run along the bottom of the image, and small clips displayed in the corner of a video.

FORBES: Adobe Adds A Video Player

Mr. Karp: The video ads that we're hit with are always in the form of pre-roll, the video reel you get at the front of an online video.

WSJ: Can Tumblr Turn a Profit?