TiVo Chairman and CEO Michael Ramsay said Wednesday he is stepping down as chief executive of the digital video recorder maker he helped launch in 1997.

Mr. Ramsay will stay on as chairman of the Alviso, Calif.-based company, and will continue as CEO until a successor is identified. The company has hired executive search firm Howard Fischer Associates to find Mr. Ramsay’s replacement.

Saying that the “time is right” to step down, Mr. Ramsay said, “It is a natural evolution of any company to have a transition of leadership as the company grows and matures.”

The departure of Mr. Ramsay comes at a delicate time for TiVo. The company, whose shares are down nearly 50 percent from a year ago, is in the throes of transforming itself from simply a DVR maker into a technology company developing tools to promote interactive television and to make recorded video content portable.

TiVo shares traded up more than 2 percent to $4.29 in midday trading Wednesday.

The moves are necessary for TiVo. Despite its strong brand recognition, the company’s growth so far has been fueled predominantly by its partnership with satellite operator DirecTV Group, with 75 percent of the company’s fiscal fourth-quarter growth coming from DirecTV customers.

But that alliance isn’t long for this world. Now under the control of Rupert Murdoch’s News Corp., DirecTV is starting to deploy DVR-equipped set-top boxes that use technology from NDS Group, a TiVo rival controlled by News Corp.

On top of that, TiVo is facing limited success at selling its wares to cable customers, as major cable operators roll out their own set-top boxes. But the company believes it has an opportunity in going after analog cable customers, since the cable operators are focused on delivering DVR technology to digital subscribers.