In Magna’s latest effort to move advertisers’ money out of traditional TV, the media-buying arm of Interpublic Group struck a deal with Roku to help clients reach audiences who have shifted their TV viewing to over-the-top devices.

As linear TV ratings continue to decline, with people watching content on a delayed basis and a variety of devices, David Cohen, president-North America, Magna, said he is constantly looking for other ad outlets beyond linear TV.

Through the deal, Magna clients, who include Coca-Cola, BMW and MillerCoors, will be able to more precisely target audiences on the platform using custom data segments created by Magna, Mr. Cohen said. This is the first time Roku will allow an agency to use custom data segments to execute a buy, he said, rather than relying on third-party data.

Magna will also gain access to Roku data to help better understand the OTT marketplace while planning media buys. And Roku will allow Magna to tag all campaigns with Nielsen Digital Ad Ratings (DAR) to then combine viewing on TV and Roku for a more holistic picture, Mr. Cohen said.