what are CD timings?

newbiesforever · 02-03-2008, 12:33 AM

Since I installed cdck, I have been checking all my used CD-RWs with it. For this last one, cdck said
"CD timings:
Minimal = 7 usec (0.000007s)
Maximal = 4874713 usec (4.874713s)
Average = 570 usec (0.000570s)

Conclusion:
Even there is no unreadable sectors, disc is unstable!"

Obviously I should throw the disc away, but what are CD timings?

nileshgr · 02-04-2008, 06:53 AM

usually a 700 MB cd is about 70-80 mins

win32sux · 02-04-2008, 07:22 AM

Quote:

Originally Posted by nilesh.3892

usually a 700 MB cd is about 70-80 mins

If you read the description of cdck you'll see it doesn't have anything to do with capacity:

Quote:

cdck (CD/DVD check tools) is a simple console program to verify CD/DVD
quality. The known fact is that even if all files on the disc are readable,
some sectors having bad timing can easily turn into unreadable ones in the
future.

To get an idea about a disc cdck reads it sector by sector, keeping all
reading timings and then tells you its verdict. Optionally it can write the
timing table into text file usable by gnuplot(1) program, so you can draw
some graphs out of it.

I'm thinking the timings might refer to the time it takes to read a sector.

I'm not sure about this, though.

nileshgr · 02-04-2008, 09:22 PM

^ actually his question isn't clear. i thought he's asking what is the max time a CD can accomodate a continuous video. hehe

win32sux · 02-05-2008, 06:15 AM

Quote:

Originally Posted by nilesh.3892

^ actually his question isn't clear. i thought he's asking what is the max time a CD can accomodate a continuous video. hehe

The question seems pretty clear to me when you consider the cdck context it is asked in: "What are CD timings?" The word video isn't used at all in the OP, and your 70-80min response applies to audio (not video).

Anyhow, enough about that. Getting back to the topic at hand, I actually ran my Unreal Tournament CD through cdck to see what it would look like. Keep in mind this is an original CD in perfect condition. Here's the results:

Code:

win32sux@candystore:~$ cdck -i
Track list (1-1):
  1: 00:02:00 (sec: 000000) data 
170: 70:31:29 (sec: 317204) data (leadout)

Disc status: data mode 1
Multisession: 0
Audio status: no status

Try to find out what sort of CD this is...
CD-ROM with iso9660 fs
iso9660: 619 MB size, label 'UT_GOTY_CD1                     '
Creating software: 'EASY CD CREATOR 4.1 (202) COPYRIGHT (C) 1996-1999 ADAPTEC, INC.'
Publisher: 'INFOGRAMES'
Preparer: 'EPIC GAMES'
win32sux@candystore:~$ cdck
Reading sectors 1-317204
317204 ok

CD overall:
   Sectors total: 317204:
   Good sectors: 317204:
   Bad sectors (incl. with poor timing): 0
CD timings:
   Minimal = 2 usec (0.000002s)
   Maximal = 2411980 usec (2.411980s)
   Average = 774 usec (0.000774s)

Conclusion:
   Even there is no unreadable sectors, disc is unstable!
win32sux@candystore:~$

Considering the source of my CD (and the condition it is in), I must say I have serious doubts about the validity of the "disc is unstable" claim cdck makes. That said, the part I put in bold tells me that the timing is indeed about the sectors. So I would think the "CD timings" being given here mean something like "the sector which was the fastest to read took 0.000002s, while the slowest to read took 2.411980s" etc. It's kinda weird that there isn't much information about this showing-up on Google. Could it be that this cdck way of testing CDs is completely bogus? Hmmm.

newbiesforever · 02-05-2008, 03:45 PM

I hope not, because it's the only thing I've got so far.

win32sux · 02-05-2008, 05:32 PM

Quote:

Originally Posted by newbiesforever

I hope not, because it's the only thing I've got so far.

What about doing a checksum of the burnt CD and comparing it to the ISO? I do this test pretty much any time I burn a CD. If the checksum matches, I rest assured that both the CD and the burn are fine.

newbiesforever · 02-05-2008, 05:42 PM

I had in mind checking blank CD-RWs that I may or may not be about to reuse.

win32sux · 02-05-2008, 05:54 PM

Quote:

Originally Posted by newbiesforever

I had in mind checking blank CD-RWs that I may or may not be about to reuse.

OIC. Well, in that case, cdck definitely sounds like the right tool. I just wouldn't go by its "disc is unstable" output unless I knew exactly what it meant (I checked the man page but it's useless). If it's reporting zero bad sectors (such as with the example I posted), I'd hold-on to the CD.

electronpusher · 04-01-2008, 12:00 PM

I make no claim to being an expert but I have had a little experience and done some research. I think that the reason timings are important is because if it takes a long time to read a given sector then that probably means that multiple attempts were made to read the sector with out error. Errors would usually be indicated by an incorrect checksum. In deciding if a CD is good or bad I think that two things must be taken into account. First-- does the data on the CD match the data from the source ( your hard drive ). This is a rare problem but I have seen at least two cases where the data on the CD was correctly recorded ( it would pass a test like CDCK ) but didn't match what was on the hard drive. MD5Sums will answer this question. Second--- is all the data on the CD readable with out correctable errors--- CDCK should answer this question.