2Actor Joaquin Phoenix admitted this week that the process of filming his role in "I'm Still Here" made him want to leave the project.

The film, which follows Phoenix as he shocks the public by retiring from acting  to pursue a hip-hop career, was filmed as a documentary. But the truth is Phoenix was playing a role.

In fact both Phoenix and Casey Affleck, who made his directorial debut with the movie, continued to claim that the actor's behaviour was not a performance until shortly after the movie's release.

Phoenix told the press this week: "At some point, it became such a public spectacle. To be frank, we were kind of hostage to the process. There were times, honestly, where I wanted out. Even on a conventional film, I'm done after four months. But this went on and on."

Despite the pressure of maintaining his public performance, Phoenix insisted he was glad to have participated: "I wanted to make a movie with my friends and make one in a different way. I wanted to have a different experience, and I'm really happy to have done that."

The 35-year-old actor added that his now famous appearance on Late Night with David Letterman was never intended to embarrass the TV host. "I wasn't on the show to make a fool of him," Phoenix explained. "In this film, I think the only person who comes off as a real jerk is me."