When a CAV laserdisc is placed in the still frame mode, it continuously plays back two adjacent fields of information. There are no rules in the NTSC system stating that a complete video picture has to start on field 1 or field 2. Most of the video in this program is field 1 dominant, the picture starts on field 1. There are two sections of the disc that are field 2 dominant. In the case of film translated to video, the start of a complete film picture changes from field 1 to field 2 about 6 times a second. There is a code in the vertical interval of the disc that tells the player on which field it can start displaying each of disc's still frames.