Authenticated online services, premium channels, on-demand and HD are all included in the extension of an agreement between ATT Uverse and Starz Entertainment. The extension, announced this week will be multi-year and cover multiple platforms such as portable devices, PCs and tablets. Both companies benefit from the extension, with AT&T being a leader in providing content that customers can access with virtually any device, and Starz Entertainment offering some of the highest quality movie content available. The entertainment company says that AT&T has done a superb job of selling its video content to subscribers. Starz boasts over 50 million subscribers to its range of premium channels, which includes HD On Demand, Encore and Movieplex. Further details of the extension agreement were not made available to the public.