Plextor PX-712, Installation And User Manual

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Section 5. Advanced Features and PlexTools Professional
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PX-712 Installation and Users Manual
What the Jitter Measurement Means
The data on the surface of a CD or DVD disc is expressed by “pits”
burned into the recording dye, and by unburned areas, or “lands,” which
represent the “0” and “1” binary bits of the computer data. The CD book
standards prescribe these 0 and 1 pits and lands as a series of 3 to 11
pieces in sequence (described as 3T to 11T). The millions of 3T data
segments on the recorded media actually contain minute variations in
length, with practically no individual 3T segment matching another.
This variation distribution is called the “jitter ratio,” and is a
measurement of the variation of the prescribed length of the 3T segment
against what is actually written on the disc. A lower jitter value indicates
better uniformity of 3T data, which means the recording is of a higher
quality. The book standard regulates jitter value at no more than 35
nanoseconds.
Using PlexTools Professional and the Plextor drive, you can use the Q-
Check Beta/Jitter Test to determine the quality of writing on a disc. The
test graph displays an average rate for jitter occurring between 3T and
11T. When you select the sample length, you actually specify a range of
addresses that represent anywhere from 15 seconds to 5 minutes on the
disc. This test lets you check for the relative amounts of jitter in
different media brands, or compare a specific media brand recorded on
different drives.
What the Beta Measurement Means
Beta is a representation of the balance between pit and land. If the laser
power is too high, the pit becomes too pronounced. If power is too low,
the land becomes too pronounced. In either case, data will not be
accurately reproduced.
In the Beta/Jitter Test window, the beta measurement is displayed as a
red line on the graph, and also reported as an absolute value.
When the Plextor PX-712 controls its write strategy using VariRec, the
resulting strategy will be the best balance of the lowest jitter and the
appropriate laser power for a quality recording.