Quality Scan vs Transfer Rate Test

semp · 24-12-2007

Well this was pretty strange and a real surprise.

I had accidentally left my IDE channel set on PIO mode for something else I was doing before I did a burn. As a result, I got a horrible transfer rate test and a horrible quality scan even when switched back to DMA and was about to chuck the disc when I decided to try it out in the most picky DVD player I know, the GameCube. I thought for sure it would not work as usually the slightest imperfections cause skipping or stopping, but it plays flawlessly. I scanned more discs to make sure the scan was working correctly and it was.

Maybe neither test is reliable...

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semp · 24-12-2007

...the crazy thing is, even though it plays perfectly, I still find my self wanting to throw it away, just because of the tests.

In this case ignorance would have been bliss.

*DrageMester* · 24-12-2007

I'd still reburn that disc.

A good disc IMO should be playable AND have a good TRT AND have a good quality scan. 2 out of 3 isn't enough for me (except sometimes with backups on DL media).

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semp · 24-12-2007

Into the trash it goes then!

I was just reminiscing about the good ole days before I knew scanning even existed...in those days, every burn was a good burn.

lol

*cd pirate* · 25-12-2007

Semp what drive are you using to scan that disc there??? I never seen it before, is it a liteon based drive? Is it new?

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MediumRare · 25-12-2007

Looking at the firmware version and permuting the ID a bit, it looks like a LiteOn 1633S. It'd be worthwhile crossflashing to a 1653S with fw CS0T in that case.

G

semp · 26-12-2007

Yep, it's a 1633S rebadge. Usually I run 1653S CS0T on it. I was just testing with the above firmware on the RITEKF1 - results were about the same as CS0T though (when not in PIO mode).

SeanW · 05-05-2008

I've taken up the habit of scanning my discs. I rely primarily on the ScanDisc test, with Read Testing, which checks the data for integrity.

It tells me in straight terms whether my disc is good, is shaky and should be replaced, or has failed. On the advice of these tests, I've thrown out about 20 CDs recently (most of them CMC MAG

never again) and one MBI DVD+R which had failed.

The yellow blocks under read testing, I think, generally mean that the "subchannel" data is out of order, e.g. that there are a lot of failed bits (but within the margins of what the redundency bits allow for).

The ScanDisc read test also does a crude TRT, in that if you're watching the test unfold, you should see the scanning speed climbing continuously. If you happen to see that it falls off (even if the resulting blocks are green), a full TRT/QS is required.

Quality Scanning doesn't tell me much, many of the results I get from that particular activity just don't make sense, e.g. verifiably good discs getting a QS score of 0 for no credible reason other than an alleged error/failure spike, and sometimes damaged discs get a postivie Quality Score, which is complete rubbish. I have also seen discs that read, get similar QS graphs to discs that don't read, for example, I had a Verbie MCC004 that got a TRT rate of 2x towards the end of the burn, and while it had a lot of PIFs, the number and rate was similar to damaged discs that didn't read at all.

In simple terms, a QS must be done on the assumption that the disc is readable since it will not tell you that.

*Wizzu* · 05-05-2008

Quote:

Originally Posted by SeanW

In simple terms, a QS must be done on the assumption that the disc is readable since it will not tell you that.

Well put.

Those who don't accept this simple concept are those who use exclusively premium media with very low failures, thus they are under the impression that a good QScan is a warrant of actual readability. Man are they wrong, and it's been demonstrated over and over and over, but some people always prefer to deny facts than to abandon a comfortable belief.

(Who's afraid of cognitive dissonance?)

Just a hint for you: a TRT will IMO give you the at least the same info as a "Scandisc" test.
Substantial slowdown = Yellow = one or several re-reads
Fail = Red = abort after several reading passes (don't know how many, though).
At least that's what I came to understand by comparing tests. I can be wrong.

Don't forget that a disc showing a perfect test in a given drive can still read so-so (or fail) in another drive. Just for the record.

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*DrageMester* · 05-05-2008

For the record, I have yet to find a CD that is unreadable in a true Plextor drive and that completes a quality scan in the same Plextor drive without showing CU, and I also have yet to find a DVD that is unreadable in a true Plextor drive and that completes a quality scan without showing POF. So in my experience a successful quality scan in a true Plextor drive also means the disc is redable in the same drive.

But for other drives I agree, that a successful quality scan does not necessarily mean that the disc is readable in the same drive (e.g. POF reporting in BenQ drives is not reliable).

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Last edited by DrageMester; 05-05-2008 at 19:48. Reason: too many nots

SeanW · 05-05-2008

At the end of the day, what will prompt me to bin a disc is when a ScanDisc test shows unexplainable non-green sectors, or when a disc performs badly in a Trasfer Rate Test.

None of my drives are capable of reporting CU/PO Failures or jitter during a QS. Obviously if they did, that would make Quality Scanning more useful in bad-case scenarios particularly.

Oh and BTW, I have had discs that read at full speed in a ScanDisc test but show yellow blocks. It is for that reason that I assume the sector is easily readable, but that failures of individual bits leaves very little redundency margin for more loss before the data itself is gone. At least that's what I think it means anway. I'm more likely to toss a disc based on this - or a slow TRT - than what I consider to be rather arbitrary PI/C reports in a Quality Scan.

*CJ2* · 06-05-2008

Even my everyday discs are good quality so i don't really bother scanning them. I do QS of random MCC (Verbatim) discs to check variation even if there's hardly anything to notice. I used the same scanner for several years and it does the job i recuire it to do. Since i have had no reading problems with my good discs i perform TRT even more rare than QS.
To be honest i mostly test discs when i get a new burner.... Which definately happens now and then. Anyway i change writer more often than discs and discs seem to be slightly more consistant imo

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Quality Scan vs Transfer Rate Test

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