BS ISO 9642:2020 PDF

What is  ISO 9642 - Time and control code for 24, 25, and 30 frames per second motion-picture film systems about?

ISO 9642 specifies digital code formats and modulation methods for the motion-picture film to be used for timing, control, editing, and synchronization purposes. ISO 9642 also specifies the relationship of the codes to the motion picture frame. The modulation method in ISO 9642 is such that a transition occurs at the beginning of every bit period. "One" is represented by a second transition half a bit period after the start of the bit. "Zero" is represented when there is no transition within the bit period.