Trying times make for interesting bedfellows.

Advertisers that met with Turner, Fox and Viacom on Friday said the competitors' new collaborative offering seems like a real step toward buying targeted audiences on TV in a big way.

That could be a big deal as traditional TV audiences continue to fall way, making it harder for the country's biggest marketers to reach large crowds of consumers all at once. Networks have responded by pitching advertisers on data-driven buys that theoretically make TV advertising more efficient. But assembling targets of, say, households with a car lease soon to expire, has been hard to do in big numbers when advertisers had to buy from one company at a time.

Turner, Fox and Viacom's new OpenAP product is designed to fix that by letting marketers buy identical targets across the companies' portfolios, which span networks including TNT, TBS, Fox, FX, Nickelodeon and Comedy Central.

"All in all we continue to be very encouraged that competitive entities are working collaboratively for the good of the industry," said David Cohen, president-North America, Magna. "While there are still some unanswered questions, I do believe when all is said and done we will have an easier, more consistent way to buy custom audiences -- and that's a win for marketers and agencies."

Buying specific audiences outside of Nielsen's traditional age and sex demographics has been not only laborious but complicated, inconsistent and lacking any third-party aduting.

Donna Speciale, president-ad sales, Turner, told a room of agencies, marketers and press on Friday that OpenAP is meant to solve those problems.

OpenAP will let marketers create consistent audience targets that can be used for all TV nework groups participating in OpenAP. Agencies and advertisers that have already spent time and money defining audiences can use them in OpenAP.

The product also helps clear up audience forecasting, the arduous process of defining targets and figuring out segments to go after. "It would take months to figure out the segment and only then you would realize the network could only reach 50 people in that segment," said Mike Law, director-national activation, Dentsu Aegis.

"This will give us a better sense of the scale," he added.

Once campaigns run, agencies and clients can see how many impressions in the target they reached. And campaigns will be measured by an outside party, even if it is employed by the networks: The consortium has tapped Accenture to build the platform and serve as an auditor.

The truth is, timing for OpenAP couldn't be better, as advertisers are increasingly worried about making sure their messages run within trustworthy content. Ms. Speciale emphasized that OpenAP allows marketers to buy ad inventory in the more-targeted fashion that resembles digital, but with trusted brands, premium content and the safe environment of traditional media.

"We have to hit upon it, trust," said Sean Moran, head of ad sales, Viacom. "It seems like it has become a new topic, but it's the foundation from which we are built on."

While the first step is using OpenAP for live, linear TV, Joe Marchese, president-advanced ad products, Fox Networks Group, said the network groups are looking to eventually expand it into video-on-demand and digital.

The basics of OpenAP:

• OpenAP will let clients create consistent audience targets that can be used for all participating TV network groups. Agencies and advertisers that have already made investments in defining audiences can use those audience targets.
• It is not a buying platform. Advertisers won't be able to purchase inventory through OpenAP. Deals will be negotiated individually between agencies and clients and publishers as they do today.
• OpenAP will be accessible via a website where agencies and clients can login.
• Accenture has been tapped to build the platform and serve as auditor.
• The platform is data agnostic, meaning it will support the data sets that advertisers and agencies create.
• Data from both Nielsen and ComScore will be integrated into the platform at the start.
• Data will be secure, according to OpenAP's founders. The system will require advertisers' permission before TV networks can see their targets. None of the network groups will see buyers' first-party data.
• Post-campaign reports will show all impressions delivered and reach from all participating publishers.