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EAC C2 error correction, Use it or not?
RiskyP
post May 29 2003, 22:56
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My drive supports C2 error correction and I have been using it always since it gives the fastest rips for me, while still no errors are reported and all track qualities are above 99.5%. Using this option, I get rip speeds of 18x and I was wondering whether C2 error correction is really that reliable? I mean, I never get error messages, the track quality is always reported to be over 99.5% and I cannot hear any audible difference. Is there any incentive NOT to rip at 18x under these conditions?! Btw, my drive is a LiteOn 48x CDRW (I can't remember the model name off the top of my head)
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Pio2001
post Jun 1 2003, 01:25
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QUOTE (atici @ Jun 1 2003 - 01:03 AM)
I trust "No C2" because (implicitly assuming "an error, in most of the cases, do not occur the same way, and is random by nature") my CRCs are reproducable. Wheras on the tracks I have a mismatch with the CRC of "C2 on" and "C2 off", the "C2 on" could not produce the same CRC repeatedly.


Wow, this is getting complicated...

You are right, getting different CRC with C2 and same without C2 means that no C2 detects, and corrects errors that C2 doesn't. On the other hand, I just realized that permanent errors, that can only be detected by C2, can never be corrected anyway, because EAC corrects by rereading. It will even not report any of them at the end.

Say that we've got 1000 light errors on a CD.

a) 990 not consistent and detected by C2.
B) 5 consistent and detected by C2,
c) 5 not consistent and not detected by C2.

Reading with C2 : the 990 a) errors are detected and corrected
The 5 B) errors are detected, but not corrected, though EAC believes they are
The 5 c) errors are not detected.
Result : 10 errors, zero reported.
Reading again, same thing, but different CRC because of the 5 c) errors.

Now reading without C2, we get the 990 a) errors detected and corrected
The 5 B) errors are not detected at all.
The 5 c) errors are detected and corrected.
Result : 5 errors, zero reported
Reading again, same thing, same CRC, because the 5 errors are consistent.

But in fact, the extra errors detected with C2 might or might not be corrected (they can repeat twice by chance).
In conclusion, it is very probable if we consider that the C2 undetection is not related to the repeataibility of the error, that the extra errors detected without C2 will be corrected, if we assume that we are ripping a CD with correctable errors, while this is not sure at all for extra errors detected with C2, since they repeat themselves to begin with.

QUOTE (atici @ Jun 1 2003 - 01:03 AM)
How does a drive realize it made a mistake if there's no error detection mechanism in audio CDs?


There is an error detection, and correction, mechanism in audio CDs : http://www.ee.washington.edu/conselec/CE/k...audio2/95x7.htm
There are even two of them : the C1 for random errors, and the C2 for burst errors.

QUOTE (atici @ Jun 1 2003 - 01:03 AM)
In the same manner I'm sure there're other errors in some of my CDs, which C2 system could not realize because there's no indication that the byte has a flaw


This goes back to the question : are errors undetected because of CIRC or because of buggy drives ? (question originally debated here : http://www.digital-inn.de/showthread.php?t...?threadid=15921 )
The most recent opinion I made about it is that I think that relaxing the C2 accuracy allows to correct much more errors than enforcing an exhaustive detection. Explanation on a CD Freaks thread (sorry but CD Freaks is offline for the time being).

QUOTE (atici @ Jun 1 2003 - 01:03 AM)
But if there were a real time deglitch system built in EAC, maybe we could correct those errors. Was the experimental switch related to "C2 error correction" that is removed from newest prebetas coded for that purpose?


Yes it was. It turned out not very efficient, and completely unuseful since most drives do deglitch errors themselves (interpolating C2 detected errors).
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Posts in this topic
- RiskyP   EAC C2 error correction   May 29 2003, 22:56
- - atici   Compare the CRCs of your reads with and without C2...   May 29 2003, 23:01
- - Pio2001   This CRC method only works for tracks with errors ...   May 30 2003, 00:26
- - RiskyP   I could not find info on cdrinfo.com but thanks fo...   May 30 2003, 16:17
- - RiskyP   This is a bit off topic, but how much do you think...   May 30 2003, 17:13
- - liekloo   QUOTE (Pio2001 @ May 30 2003 - 12:26 AM)This ...   May 30 2003, 18:21
- - atici   You may want to check this thread about the setti...   May 30 2003, 18:24
- - Pio2001   I meant that if you turn C2 on, then test and copy...   May 30 2003, 19:35
- - atici   Yes, you're right! I knew that. But that...   May 30 2003, 19:52
- - Pio2001   I don't know, I still must verify Tigre's ...   May 30 2003, 19:56
- - atici   But wasn't it you who said when you unset ...   May 30 2003, 20:49
- - Pio2001   When C2 is unset, the drive doesn't take C2 in...   May 31 2003, 01:09
- - liekloo   QUOTE (Pio2001 @ May 30 2003 - 07:35 PM)I mea...   May 31 2003, 21:36
- - atici   @liekloo : I think you're too much of a stickl...   May 31 2003, 23:03
- - Pio2001   QUOTE (atici @ Jun 1 2003 - 01:03 AM)I trust ...   Jun 1 2003, 01:25
- - atici   QUOTE a) 990 not repeatable and detected by C2. b...   Jun 1 2003, 06:22
- - westgroveg   If someone was to test the C2 info of their CD-ROM...   Jun 1 2003, 06:48
- - liekloo   QUOTE (atici @ May 31 2003 - 11:03 PM)the kin...   Jun 1 2003, 16:32
- - Pio2001   QUOTE (atici @ Jun 1 2003 - 08:22 AM)I think ...   Jun 1 2003, 18:41
- - moikboy   If i rip with c2, i rip the data twice, and compar...   Feb 6 2008, 21:52
- - greynol   Whoa, resurrection of a 4.5 year old thread! ...   Feb 6 2008, 22:08
- - Shamray   Hello! "CD ROMs are like audio CD with ...   Mar 30 2011, 07:36
|- - pdq   QUOTE (Shamray @ Mar 30 2011, 02:36) Hell...   Mar 30 2011, 13:53
- - JunkieXL   Sheesh... what's with the random resurrection ...   Mar 30 2011, 21:13
|- - mjb2006   The first revival of the thread was on topic and m...   Mar 30 2011, 22:35
- - greynol   My last post was a bit difficult to follow if take...   Mar 30 2011, 22:55


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