Several companies are developing generative AI technology that can create videos from a short description. Runway AI is one of the firms building the AI systems, which can generate text, images and sounds, and is set to open its service to a small group of testers this week. While the new technology, which is capable of generating videos that show where the industry is headed, could speed up the work for moviemakers or be used in online misinformation, some firms including Google and Facebook are cautious as they believe it represents a risk.