Studying the impact of movies on real-life gun violence is "overdue", veteran director Robert Redford said, suggesting a possible link between guns and box office takings. Redford was asked about the gun debate triggered by last month's school massacre in Newtown, Connecticut, at the start of the annual Sundance Film Festival, which he founded. "I'm thinking back when we started Sundance, back in 1980, and I remember, (President Ronald) Reagan was shot at that same year. I remember there was talk about gun control coming up then," he said on Thursday. "Now it's 30 years later. I think it's absolutely not only appropriate but overdue to have a dialogue. And the dialogue is now going on between the parties that it should be," he said. President Barack Obama launched an urgent review of how to curb gun violence -- including the impact of movies, video games and other media -- following the Newtown massacre, which killed 26 people including 20 young children. Vice President Joe Biden met movie industry leaders as part of consultations on a package of proposals, unveiled this week, that include reviving an assault weapons ban and universal background checks for gun buyers. Redford, co-star of "Butch Cassidy and the Sundance Kid", recalled driving down a street in Los Angeles recently and seeing two billboards advertising the latest blockbusters, both featuring guns. "One of the billboards just had a young couple, very pleasant-looking, young, happy looking. And they both had guns. "My thought was, does my industry think that guns will help sell tickets? I don't know ... It seems like a question worth asking my own industry. And maybe there's a reason, maybe yes. I don't know, but it seems fair." He added: "I've noticed how often guns are used in ads, as though there's something that translates in a positive way. I just don't know. But I think it's worth asking that question." The Sundance film festival, the top showcase of independent US cinema held in the snowy mountains of Utah, opened Thursday and runs through January 27.