Following an extensive trial period, Comcast said it has moved forward on the commercial launch of “Xfinity On Campus,” a multiscreen, IP-based video service that is tailored for college students and accessible on Web browsers and select tablets and smartphones. Comcast is using the authenticated service, which is powered by Comcast’s cloud-based X1 platform, to make a pay-TV connection with tech-savvy, on-the-go college students, a group that is accustomed to consuming video on mobile devices and to be among those likely to have cut the cord or have not previously subscribed to a pay-TV service.