"Some discs have no progressive_frame flag set on any pictures on the disc, and don’t use repeat_first_field. They just dump the film transfer with its inherent 3-2 pulldown onto the disc without any special flags, as though it was video. When this is done, 2 out of every 5 frames on the disc contain fields from two different frames of film (see the third MPEG flags table at the top of the article for a diagram). Again, a player that uses the flags exclusively will treat this material as video, and you lose the special film mode deinterlacing that makes a progressive player look so good. In the worst case, the player will combine fields that are stored in one MPEG frame, but came from two different film frames, causing combing."
"Some discs have no progressive_frame flag set on any pictures on the disc, and don’t use repeat_first_field. They just dump the film transfer with its inherent 3-2 pulldown onto the disc without any special flags, as though it was video. When this is done, 2 out of every 5 frames on the disc contain fields from two different frames of film (see the third MPEG flags table at the top of the article for a diagram). Again, a player that uses the flags exclusively will treat this material as video, and you lose the special film mode deinterlacing that makes a progressive player look so good. In the worst case, the player will combine fields that are stored in one MPEG frame, but came from two different film frames, causing combing."