Customers of Cablevision will soon be able to stream online video, photos, e-mail and other data to their living room televisions through the company’s new “PC to TV Media Relay” service that was unveiled on Wednesday. Dubbed a “first of its kind” service by Cablevision, the service would only require a software download that would permit subscribers to display content showing on their PC screens on their TV sets via a dedicated cable channel. As the quality and quantity of Internet video offerings continue to grow, experts predict that Cablevision’s service may provide cable operators with a key weapon in their fight to keep customers who may otherwise cancel their cable subscriptions in favor of web-based video services. Cablevision, which serves more than three million subscribers in New York, said it would launch the service on a trial basis starting in June. Although rates for the trial service were not disclosed, Cablevision said the service will be offered only to customers that purchase both a cable and a broadband Internet subscription. Aside from the required software, customers will not need to obtain any additional equipment, as online content will be streamed directly to television sets through Cablevision’s network lines. The company also hopes to expand the service to handheld and other consumer devices. Observing that the new service “will make it easy for our television customers to take broadband services including Internet video, as well as family photos or anything else displayed on a computer screen and move it to the television with the click of a mouse,” Cablevision CEO Tom Rutledge declared, “we are putting an end to the need for families to huddle around their laptops or PCs to watch content together.”