DVD:Non-return-to-zero encoding

Non-return-to-zero encoding

Data is written on the disk using a non-return-to-zero inverted (NRZI) for- mat in which a transition from pit to land represents a one and a non- transition represents a zero. The effect of this is to halve the number of transitions required to represent the bitstream. Consider the stream of ten pulses in Figure 20.9. With NRZI inverted, a change from land to pit or vice versa occurs only when a logic state of 1 is followed by a 1, or a logic zero is

followed by a logic 1 as illustrated in Figure 20.9b. Otherwise, no change takes place. The result is five pulses or transitions instead of the original ten.