What do Negative Deflections Mean?

vbimport

#1

Below are two PxScans of the same burned data (8 files, 178 MB of flac audio) on sequential Maxell branded Ritek CD-R’s from the same spindle, first one burned at 48X and the second one at 8X. Nero 6.6.0.14 used.

What do the negative deflections in the beta/jitter blue line mean? Why are there more in the disc burned at a much slower speed? Which disc is better?

Thanks


#2

Nothing to worry about, IMHO.

From Plextors documentation:

[I]What the Jitter Measurement Means

The data on the surface of a DVD or CD 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 have 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 PX-712 or Premium 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. The test lets you evaluate the relative amounts of jitter in different media brands, or compare the results from a specific media brand recorded on different drives.
[/I]


#3

Sidenote: PxScan uses a sample length of 1 second.

An optimal beta line is one straight line, so disc 2 is actually better in this respect, but disc 1 really doesn’t have a bad beta line. If a fully recorded disc also shows such a result, you can record them at 48x.


#4

Thanks for the replies.

Both discs played without issue but I was concerned because I had not seen those negatives waveforms on previous scans of media from the same spindle of media (or any media prior to this with my 716A). I was worried this signaled a change for the bad with the function of the drive.

Regardless, I would prefer not to have them at all.

Just received some new Taiyo Yuden CDR and hope they don’t have those nasty looking spikes!