Disk test accuracy

[durkinjt]

Br7,
Thanks for the reply, my question was not how long the disk will remain good, but what exactly can DQ measure ?

[NightTran]

a person with cancer, will show in the scan ( what ever it is), on the other hand he/she lives fine talk fine like a normal person. how would you know when she/he will be gone if she/he is not getting a treatment?

[Chewy]

but what exactly can DQ measure ?

that's a good question

dvd's are based on error correction, the nature of the beast is such that a dvd is an accident waiting to happen.

the top graph(PIE) is the smallest level of measurement, errors are fine if they can be corrected, the bottom graph shows where correction starts to fail. As these failures increase in intensity and density the POF's start, here error correction totally breaks down. The disk still reads or plays, but barely.

The QS is a poor predictor as it's based on just the maximum value that PIF shows, one small glitch(easily handled by a player) or even an anomaly in the scan/read and you get a zero value.

[Vaios]

Recently I was, too, a little troubled for the accuracy of the scans. The same dvd in one scan gave 98 score and if tried it again after some minutes it gave 93. The same disc at one scan it had a glitch and 0 score and the other day in another scan it was ok. But I also found some specific problems that were reproducible in two scans. So I think DQ scans give a general picture of the disc that could be useful.
(Verbatim says about a life time warranty. If that is true I think they would like me to show them some Verbatims 4x dvd+r bought 4$ each 2 -3 years ago, perhaps never played ,without a visible scratch and not playing now...)
I have a Sony Vaio that has a burner (sony Q58 something) that is actually a Liteon. I tried some Verbatims 16x made in Japan (TY T03). The scans start with high PIE, 300 or 400 max and lower progressively and at around 250 mb they stay at a normal stable number for the rest of the disc. The PIFs are very low, 2 or 3 max and rare.
In my desktop I have a Nec 3550 . I doesn`t do the high PIE start like the laptop but it makes some high PIFs spikes, max 6 or 10, especially at 250 - 500 mb. (same blanks).
The final quality score is about the same but the error curves are very different as I described. So which burner should I prefer ?

[Chewy]

take the best burns from each burner and compare by scanning with the other drive, I would expect the nec to burn better, the sony/liteon gives a lower pif because of the scan interval, a 2 is the same as an 8 or 9 with the nec

make sure you are comparing burns done at 8x

figure the nec to outlast the laptop drive by a factor of 2 or 3 times as many burns

neither drive is very good at scanning, nec is especially hard to figure out how fast to scan with

[Vaios]

I made scans with both drives and the general picture is about the same. What I find strange is why the laptop drive makes such high PIEs at the first 250 mb and why the Nec gives some PIFs spikes at around 250 - 500 mb.( With every dvd I tried) . I use Verbatims mcc004 printables and some Verbatims spindle made in Japan.
I noticed that the laptop at first minute it writes at 2,4x and then it goes at 4x. (if you want 8x, after the 50% it goes at 6x). And there is a visible difference of colour at the centre of the disc.
Another example I could mention about CD-DVD speed is this. I made a backup of family photos on Verbatims cds. I scanned the first cd , it was ok. I scan the second, it was running ok like the first, at about the middle suddenly it makes a very high PIF spike (3 digit number). I tried it again and it was showing the same problem. The pc was reading the files with no problems but I was afraid because family photos are important so I made another backup and I tossed the problematic one. Perhaps at the future would be unreadable.

PS
About the drives, I can`t decide which makes the best burns (or the least worse) , but for reading , I know for sure that with some very scratched dvds the Nec gives unreadable sectors, but the Sony - Liteon reads them.

[Chewy]

for scanning cd's, nec's are good, benq's ok, sony liteon's not at all