Kantar, the wholly-owned media research and analytics subsidiary of WPP, has agreed to acquire Civolution's Nextracker audience measurement and second screen audio watermarking business.France-based Nextracker is focused on audio watermarking technology, which allows second screen devices, such as tablets and smartphones, to automatically sync to TV content through watermark detection."The acquisition will build on Kantar Media's significant global presence and activities in digital audience measurement across all media in over 60 countries," WPP said."The Nextracker audio watermarking technology identifies viewing of content across TV, tablet and mobile screens, enriching Kantar Media's existing techniques to meet the digital measurement needs of advertisers and broadcasters."FTSE 100 listed WPP, which is led by Martin Sorrell, has seen its share price fall by almost a fifth in the year-to-date.