In the midst of trying to fend off Microsoft's $44.6 billion takeover bid, Yahoo on Tuesday said it has acquired Maven Networks for $160 million, boosting the Web portal's position in the emerging online video advertising market.

Maven's technology delivers content and ads to more than 30 media companies, including Fox News, Gannett, The Financial Times, Hearst, E.W. Scripps and CBS Sports. Maven doesn't sell ads, but is heavily involved in testing new ad formats that go beyond the typical clip that runs before the video.

The acquisition lifts Yahoo in the online video market by taking it closer to more media companies, some of which are already Yahoo partners. Hearst and Scripps, for example, are members of Yahoo's classified advertising network of newspapers. Yahoo says it has video advertising relationships today with more than three-quarters of the "top TV advertisers," and also has partnerships with a number of "premium publishers," including eBay, Comcast, Newspaper Consortium, and Forbes.com.

Yahoo said it intends to offer publishers the option of letting Yahoo handle ad sales as part of Maven's offerings. For advertisers, Yahoo plans to also offer search and display ads.

"Video is projected to be the fastest growing segment of the online ad market, and Maven will significantly help advance Yahoo's strategy, expanding the video opportunity for publishers and increasing the efficiency and effectiveness for advertisers," Hilary Schneider, executive VP for global partner solutions at Yahoo, said in a statement.

Yahoo's failure to date to compete effectively with Google in the online ad market has been a major contributor to its low stock price, which led to the recent takeover bid by Microsoft. Last year, Yahoo bought online advertising exchange Right Media for $680 million in response to Google's plans to buy Internet advertising company DoubleClick.

In December, nearly 141 million U.S. Internet users watched more than 10 billion videos, according to ComScore. Video lovers watched an average of 3.4 hours of video during the month, representing a 34% gain since the beginning of 2007. The average online video lasted 2.8 minutes, and the average viewer watched 72 videos.