Audience-measurement giant Nielsen said it would acquire the digital-media monitor DoubleVerify in an all-cash transaction that takes place as more media companies and advertisers are putting the company under new scrutiny as they seek to unify tabulation of linear and digital viewership of media. Nielsen will take DoubleVerify private for a price estimated at approximately $2.15 billion, or $13.60 per share. Hollywood’s recent streaming wars, however, have cast all kinds of doubts on the value of such totals. In recent years, Nielsen has also had to contend with a number of would-be upstarts hoping to make inroads into its business with media buying agencies and TV companies. DoubleVerify will become a private unit of Nielsen upon the completion of the deal.