Measuring the three attributes that most impact awareness--ad likeability, ad relevance, and brand consideration--30-second pre-roll ads came out on top in the study, which included surveying and concept testing of 1,422 online video users.

Some analysts, however, did not buy the idea that consumers would respond more favorably to longer ads.

"That makes no sense to me," said one analyst from a rival ad association who asked not to be named. "The reason God invented TiVo was to spare us of all this."

Said Forrester analyst Peter Kim: "It makes sense because the OPA isn't factoring in the 'annoying factor.' When you assume that people have gotten past the fact that any pre-roll is annoying, a longer ad is powerful because it gives you time to engage the consumer and deliver a stronger message."

Using a variety of ads--featuring everything from consumer packaged goods and financial services to airlines and pharmaceuticals--and four ad attributes, OPA tested how 96 combinations impact key ad and brand metrics. The four ad attributes were: 15-second versus 30-second; pre-roll versus post-roll; ads with and without accompanying banner ads; and original online ads versus repurposed TV ads.

The study--conducted in partnership with the Online Testing exchange, a consumer research and consulting firm--confirmed that consumers respond more favorably to ads featuring brands with which they have some existing affinity. Indeed, if respondents had a prior brand affinity toward an advertised brand--and also liked the adjacent video content--brand consideration jumped 61%.

If the consumer's initial attitude toward the brand was neutral or negative, but they liked the video content, brand consideration still rose 21%.

Video advertising also appears to be fulfilling its promise as a highly actionable format, according to the study. Of the 80% of viewers who watched a video ad online, 52% took some sort of action, whether checking out a Web site (31%), searching for more info (22%), going into a store (15%), or actually making a purchase (12%).

Notably, visitors to media sites--magazine, newspaper, cable, broadcast and pure-play-- were more inclined to take action upon viewing video ads than visitors to portals and user-generated content sites.

Also, despite the current hype surrounding funny video, a greater percentage of viewers (14%) watch news and current events on a daily basis than comedy clips (9%).

The study also reinforces the growing importance of the Web in driving all commerce. Of consumers who made a purchase in the previous month, 48% said the Internet drove initial awareness, 57% said they learned more using the Internet, 55% used the Internet to decide where to buy, and 56% made the final purchase decision using the Internet.

Word-of-mouth, which clearly has strong Web components, was second in importance, but the Internet outpaced all others by at least 50%.

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