Movie star Jake Gyllenhaal can't wait for the DVD release of his new war film JARHEAD because it will feature his video diaries.

Director Sam Mendes gave Gyllenhaal and his castmates video cameras at the start of shooting and invited them all to film journals of their "military lives" and Gyllenhaal took the task very seriously.

He reveals, "We all talked, like, a diary into the camera and shot whatever we wanted to shoot around set, each other or at home.

"I remember when I got my head shaved - and they shaved it right down - it was the most horrible haircut. It was pretty mundane. I filmed that.

"Then I filmed me honing the haircut because I wanted it to look perfect. I remember it just coming all off and there was a ceremony afterwards. I filmed that."