Q-Check vs. CD/DVD-Test: Different number of CU Errors

A quite strange result with all Plextor-Burners with Q-Check:

I tested a copy protected CD with Q-check and CD/DVD-Test (both 10-24x):
Q-Check: 1375 uncorrectables
CD/DVD-Test: 6228 uncorrectables (this is the same amount of errors, which is found, when extracting the CD)
How is this possible? Similiar results with all CDs with uncorrectable errors. Q-check shows always less errors…

What drive?
CD/DVD-Test is what software?
What software for extracting?
Please be more specific.

One possibility could be that “Q-Check” (Plextools) reports E23 (CU) whereas “CD/DVD-Test” reports E22 (C2) and not E23.

[quote=hwp;2125770]One possibility could be that “Q-Check” (Plextools) reports E23 (CU) whereas “CD/DVD-Test” reports E22 (C2) and not E23.[/quote] The Plextors certainly report CU=E32 with PlexTools, but I can’t think of a drive that reports C2=E22 with CDSpeed (they generally report C2=E32), so I don’t think that’s the explanation.

Perhaps the Plextor drive has better error correction then the other drive that reports more E32?

The 2 tests were performed always with the same drive! Both tests wit Plextor Premium, with 755, with 712)

It happens with all Plextor drives, I tested:
Plextor Premium, Plextor 755, Plextor 712

Extracting Software Plextools V2.36
Firmware: always the newest

Results px-755:
CD/DVD-Test: 7422 CU-errors
Q-Check: 1339
Thus a similiar result compared to Plextor Premium, esp. the high difference of the factor 5 is the same.

Plextor drives are not supported by CDSpeed for quality scans.

If you bypass the blocked scanning feature for Plextor drives by editing the registry, the Plextor drives will scan CD media, but they will not report correctly.

If I remember correctly, Plextor drives wil report [B]bytes[/B] failing C2 error correction per second instead of [B]frames[/B] failing C2 error correction per second), which would explain why the count is higher.

[QUOTE=DrageMester;2125885]Plextor drives are not supported by CDSpeed for quality scans.

If you bypass the blocked scanning feature for Plextor drives by editing the registry, the Plextor drives will scan CD media, but they will not report correctly.

If I remember correctly, Plextor drives wil report [B]bytes[/B] failing C2 error correction per second instead of [B]frames[/B] failing C2 error correction per second), which would explain why the count is higher.[/QUOTE]

This would mean, that Plextor uses two kinds for counting E32-errors in the same software (Plextools Professional).
Both tests are part of Plextools Prof, but the CD/DVD-Test can also be performed by drives, which are not Q-Check-able (e.g. the px 48/24/48), Q-Check only by Plex Premium, px712, 716, 755, and 760.

Is your theory compliable with the difference in errors of about 5 to 6 times between both test?

I just realized that you were NOT talking about using Nero CD-DVD Speed a.k.a. CDSpeed for testing, but rather talking about another test in PlexTools. So please ignore my reference above to scanning with CDSpeed. :o

The PlexTools CD/DVD Test will probably report the number of unreadable bytes (bytes that cannot be corrected by the C1/C2 error correction), while the Q-Check will report CU as the number of frames that fail C2 correction. The number of unreadable bytes will be higher than the number of uncorrectable frames.

Plextools Professional reports the number of [B]frames[/B] that have correctable BLER and C2 or uncorrectable CU errors.

As for different methods of counting: I think q-check and DAE with PTP is not really comparable when it comes to results (especially CU). Q-check just does a scan. It does not retry. DAE with Plextools has different settings for error recovery and does retries on C2. If they both were reporting CU as ‘uncorrectable’ it’d be rather astonishing that DAE would report more errors after exhausting the additional recovering options.

What testing-software do you mean with"CD/DVD-Test"?

[Edit: I see Drage figured it out :slight_smile: ]

[QUOTE=DrageMester;2125903]
The PlexTools CD/DVD Test will probably report the number of unreadable bytes (bytes that cannot be corrected by the C1/C2 error correction), while the Q-Check will report CU as the number of frames that fail C2 correction. The number of unreadable bytes will be higher than the number of uncorrectable frames.[/QUOTE]

Thanks; this seems to be a plausible explanation for the difference.

[QUOTE=hwp;2125908]Plextools Professional reports the number of [B]frames[/B] that have correctable BLER and C2 or uncorrectable CU errors.

[/QUOTE]

So does this apply to C1 errors too? If a frame has more than one error the software will only display the error count as 1?

That might explain why the error counts on Plextools are lower than with hardware error checkers like the Stagetech or Clover.

Cheers

James.

[quote=jamesp;2126729]So does this apply to C1 errors too? If a frame has more than one error the software will only display the error count as 1?[/quote] Yes, the error reporting for C1, C2, CU is frames in error (not bytes in error). This is how it’s defined in the standards, and any scanner that reports correctly will report frames in error.

That might explain why the error counts on Plextools are lower than with hardware error checkers like the Stagetech or Clover.
It’s possible that such professional equipment will also report bytes (symbols) in error, but they must report frames in error to comply with the definitions of BLER, E11, E21, E31, E12, E22 and E32.

E11: One byte/symbol in error in a C1 frame
E21: Two bytes/symbols in error in a C1 frame
E31: Three or more bytes/symbols in error in a C1 frame

E12: One byte/symbol in error in a C2 frame
E22: Two bytes/symbols in error in a C2 frame
E32: Three or more bytes/symbols in error in a C2 frame

BLER=E11+E21+E31 per second (should technically also be averaged over 10 seconds)

[QUOTE=hwp;2125908]Plextools Professional reports the number of [B]frames[/B] that have correctable BLER and C2 or uncorrectable CU errors.
[/QUOTE]

I’ve just run a test and found that Plextools XL displays C1, C2 and CU error rates of more than 75 per second which means that it can’t be reporting the number of frames with errors as there are only 75 frames per second.

In my test I had 12927 CU’s in the Q Check and 68917 in the CD Test. However, the Q Check showed errors in different places to the CD Test with CD Test ignoring small numbers of errors early in the disc.

I tend to use these test more as a guide to disc quality rather than as an absolute test of the exact number of errors.

Cheers

James.

[quote=jamesp;2126742]I’ve just run a test and found that Plextools XL displays C1, C2 and CU error rates of more than 75 per second which means that it can’t be reporting the number of frames with errors as there are only 75 frames per second.[/quote] Not that kind of frame (audio frame of 1/75 second) but rather error detection/correction frame of 24 bytes plus ecc.