A recommended practice intended to provide a method of coding video index information in which various picture- and program-related source data can be carried in conjunction with the video signal. Note: There are three classes of video index data based on type and use of the data. Class 1 contains information that is required to know how to use the signal. Class 2 contains heritage information for better usage of the signal. Class 3 contains other information not required to know how to use the signal.