DVD HF Signal
The eight-to-sixteen (EFM+) modulation scheme used, produces eleven different possible lengths of pits and lands.
Therefore, the resulting HF consists of square waves of eleven different durations. The signal appears sinusoidal on the
‘scope because of the limited frequency response of the optics. The “eye pattern” displayed on the oscilloscope is a
superposition of many sweeps, each consisting of up to eleven different lengths. Each of the eleven pit/land lengths are
exact multiples of one fundamental length, called 1T. The eleven possible lengths of pits and lands are 3T, 4T, 5T, 6T,
7T, 8T, 9T, 10T, 12T, 13T and 14T. The waveforms generated by these pits & lands are called I
3
, I
4
, I
5
, I
6
, I
7
, I
8
, I
9
, I
10
,
I
12
,
I
13
,
and I
14
respectively. I
3
represents the shortest pit / land, and I
14
represents the longest pit or land. Generally, we
only need to look and the longest and shortest pits to get a good picture of pit geometry.
Terminology
The CD and DVD standards use different terminology to refer to the same concepts. For instance, the maximum light
level returned from the disc is called I
top
in CD terminology, but is called I
14H
in DVD terminology.
Fig. 22 - DVD HF Eye Pattern
34
DVX
Instruction
Manual
