Cable industry veterans Michael S. Willner and Sidney R. Knafel, who co-founded Insight Communications and served respectively as CEO and chairman for nearly three decades, are reuniting to invest in and lead a new media venture, Penthera Partners. Willner will be Penthera's CEO, and Knafel will be its vice chairman.Penthera Partners is a privately held software firm that has developed a patented software engine to move HD video between the cloud and smartphones, tablets and IP-enabled set-top boxes. One product, Ribit, is a cloud-based video sharing service that's available in the Apple Store. Another product, Virtuoso, delivers HD video to a smartphone/tablet for later playout.