Jitter test wierdness with Plextools Pro

vbimport

#1

I’ve noticed a few things about the jitter/beta test with Plextools Pro and my 712 drive. When changing the range (.05, -.05, .1,-.1 etc) the readings do not stay consistent. For example in the .05 range a cd may read -.03 on average, but when I change the scale to .1 it now reads -.06 on average and when I change the scale again to .5,-.5 and do another test it reads -.3ish (thats ten times the original number).

Also I’ve noticed during the test if the reading is starting to move below the current scale the entire reading will suddenly change and bump itself up so the it remains on the visual graph -however the scale does not change to reflect that. So a test that starts at -.04 and then dips below the bottom of the scale (-.05) will suddenly change itself so the entire reading starts at -.03.

Can anyone explain this -it seems completely useless to me.

One final question -the directions say that the beta is best to read closest to 0. What is best with jitter -I assume the lower negative number is best. If that’s the case, why are there numbers above 0?

Ok, I cheated, on more question which is way off the original title. I downloaded the latest Nero 7 in order to try the CD/DVD speed test instead of plext pro, however for some reason as soon as I start to run the comprehensive test for jitter/c1 etc the jitter greys out and does not get tested? I tried this with my Plextor 712 drive as well as the Yamaha CRF-1 (both USB). Any suggestions?


#2

Which version of PT are you using? Up to some point the older versions had a bug showing wrong values in the Beta-scale-labelling (by a factor of 10). Also no testing twice of a single media will produce the exact same result (because the scan setup is not calibrated in any way). Some variance is thus totally normal.

Notice that the red beta-scale-labelling is only for the red beta line and not for the blue jitter results.

Plextools does NOT give you absolute values for jitter results in %. It shows the relative change in Jitter, whether the absolute value it gets bigger or smaller. Nevertheless the visual presentation of the graph has to start somewhere and if the Jitter happens to be very high at the beginning and drops later on the graph needs to be ‘scrolled’ so it can be seen entirely. This is normal behaviour for Plextools.

There is no 0 in the graph for Jitter because Plextools does not give absolute values. As for interpreting the changes in jitter that PT reports it is “better” if the graph stays level and does, for example, not raise towards the outside of the disc.

CD/DVD-speed (could but to avoid legal discussions with Plextor) does not support the scanning functions of Plextor drives.


#3

HWP, thanks for your detailed response. I’m using PT 2.12. Based on your response I take it that PT might not be able to do what I’m looking for -comparing different types of burning methods (vari rec settings, media etc) in order to be able to create the lowest jittery cd. From what you’re telling me, PT tracks the CHANGE in jitter across the cd but not absolute values.

I’m going to start a different thread around this since it’s a bit in a different direction.


#4

PT 2.12? That must be several years old


#5

2.32a is the most recent one. Get the update at www.plextools.com

You still can. But it requires a different testing methology, the key word being multisession. Just burn a sessions per different settings you want to compare to the same disc and then do a scan of the whole disc. This method let’s you even compare different drives. Here are some examples:

http://club.cdfreaks.com/showpost.php?p=988175&postcount=68
http://club.cdfreaks.com/showpost.php?p=988177&postcount=69
http://club.cdfreaks.com/showpost.php?p=1259834&postcount=146
http://club.cdfreaks.com/showpost.php?p=1259835&postcount=147
http://club.cdfreaks.com/showpost.php?p=1260774&postcount=148

Plextor Japan has a nice example online on their Q-Check explanation page: http://plextor.jp/support/faq/ptp_01.html (the scan about 2/3rds down the page)


#6

hwp has suggested one way of comparing jitter between different burning speeds and/or drives.

Although I haven’t used this method yet, it seems very elegant to me, but there’s usually more than one way of accomplishing something, so here’s another way.

By using PxScan/PxView for jitter scans, you get jitter scans with “absolute” jitter numbers reported by your drive. These jitter numbers are not percentages, but because you get “absolute” numbers instead of just a floating scale, it’s possible to compare jitter scans of separate discs!

You can’t compare the “absolute” jitter numbers you get from one scanning drive to the “absolute” jitter numbers you get from another scanning drive, however. That’s why I use quotes for the term “absolute” numbers.