ATT Inc and the Chernin Group are close to buying a majority slice of Fullscreen, in a deal that will value the popular YouTube video network at $200 million to $300 million, tech blog Re/code cited sources familiar with the target company as saying. Otter Media, a joint venture between the telecom carrier and the media investment group, is finalizing a deal with Fullscreen, which has been courted by prospective buyers in past months, the blog reported on Wednesday. Under the deal now being hammered out, Fullscreen CEO George Strompolos, the ex-YouTube executive who started the company, will continue to run the video network and will retain a stake in the company, it said.