Kids' movie about a boy who films movies in his room and befriends a ghost, figu...

I'm trying to identify a movie. What I remember:

• It was a kids' movie.
• A kid likes to make movies/films in his room?
• A ghost finds this kid, and they become friends.
• They figure out together who killed him and what happened.
• I remember a scene where the ghost gets hit by a car, or a car goes through him (I think).