Google’s YouTube is setting up a virtual screening room to bring the work of independent filmmakers to a global audience. Struggling filmmakers already use YouTube to kick-start viral marketing campaigns. The new feature, which debuts Wednesday, gives them an easy-to-find home — and makes them partners in drawing new ad revenue. “Hopefully as they see thousands of people watching their films, it’s going to be a very eye-opening experience,” said Sara Pollack, YouTube’s film and animation manager.