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EAC T&C without C2. Overkill?
liekloo
post Nov 20 2002, 16:51
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If you rely on C2 info when using EAC, using 'test&copy' is better than just 'copy'.

What if you don't use C2? EAC reads each sector twice and, as a result, has the oportunity to calculate CRC twice, and compare them.


Is that correct? and is the opportunity actually used? (that would mean test&copy is overkill if you disable C2)


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Pio2001
post Nov 27 2002, 15:01
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QUOTE (Volcano @ Nov 27 2002 - 12:16 PM)
" On scratched CDs, I found it impossible to get matching CRCs with this drive - although there were no errors reported for each rip.


Liekloo is right. A minor scratch usually produce an enormous amount of errors. One of them is always detected. However, there are two cases in which CRC can mismatch without a bad rip reported :

1 - the scratch is light enough for all errors to be corrected in less than 80 rereads. Then EAC displays "no errors occured". But as thousands of errors were corrected, it is highly possible that one of them gave more than 8/16 times a wrong value, that was taken for right.

2 - A bad drive combined with a bad media. For example the Hitachi GD-7500, that always finds one or two errors on brand new CDs, reading a Memorex black CDR, will find tenths of isolated errors, all of them corrected in one row. With this combination, on most of the tracks, CRC mismatch while "no errors occured".

QUOTE (user @ Nov 27 2002 - 12:16 PM)
Has somebody ever heard a bad tune in a song, when eac did not use t&c and reported no errors occurred ?!


Yes, in Halcyon's test http://www.digital-inn.de/showthread.php?t...or&pagenumber=2
12th message in the link above :

Sony CRX140E
C2: OFF (not available)
Accurate Stream: ON
Disable Audio cache: ON

Copy OK status (from EAC log):
track 3: OK

Track audible quality (listening test):
track 3: Two loud pops 6 seconds from the start of the track

CRC (from EAC test & copy):
track 3: B601AA2C <> EA0EA86C


QUOTE (user @ Nov 27 2002 - 12:16 PM)
If the scratch reflects the light in other ways, then eac (and any other program) will even think, that these wrong data is the correct one, because the programs read again and again the SAME values (...) The safety of reading twice (without test, NO c2) for error detection is high, it is not like 50% (would be very unsafe), as eac compares sectors, which contain a lot data, I think, the safety is around 1:10.000 or so ?


The safety of C2 is very high in theory. From BobHere's documentation http://www.digital-inn.de/showthread.php?t...15&pagenumber=5

QUOTE
The much quoted figures for the 1st generation players (Philips CD100) with their much simpler CIRC implementations are:

sample interpolation rate:
one sample every 10 hours at 10exp-4 BER (Bite error rate)
1000 samples per minute at 10exp-3 BER.

Undetected error samples (clicks) less than 1 every 750 hours at BER 10exp-3, negligible at BER 10exp-4


Reading twice safety is impossible to evaluate. It must be between 1/8 (jitter errors - E32 chipset) and 1/1,099,511,627,776 (damaged CD, E52 chipset). (quoting myself). Explanations in the same link.

This post has been edited by Pio2001: Nov 27 2002, 15:03
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Posts in this topic
- liekloo   EAC T&C without C2. Overkill?   Nov 20 2002, 16:51
- - cmyden   What if you don't use C2? EAC reads each secto...   Nov 20 2002, 17:05
- - Annuka   EAC is not exact at all, if your CD-ROM drive is o...   Nov 20 2002, 17:25
- - liekloo   Thanks for your replies To cMyden: (Yes, I s...   Nov 20 2002, 18:16
- - Pio2001   QUOTE (liekloo @ Nov 20 2002 - 06:51 PM)If yo...   Nov 20 2002, 21:48
- - spoon   If I can hijack this thread - I am currently tac...   Nov 20 2002, 23:46
- - liekloo   Could anyone please explain why accurate stream is...   Nov 21 2002, 15:56
- - Case   QUOTE (liekloo @ Nov 21 2002 - 04:56 PM)Could...   Nov 21 2002, 17:15
- - liekloo   I am sorry, I apparently didn't put my questio...   Nov 21 2002, 17:20
- - Case   QUOTE (liekloo @ Nov 21 2002 - 06:20 PM)When ...   Nov 21 2002, 17:24
- - liekloo   So, to conclude: in secure mode, with a properly c...   Nov 25 2002, 19:38
- - liekloo   But what in this situation: A scratched CD... if ...   Nov 25 2002, 19:53
- - liekloo   Of course, if sectors are big enough this is not a...   Nov 25 2002, 20:20
- - Pio2001   The "sectors" re-read by EAC are in fact...   Nov 25 2002, 23:53
- - liekloo   Thank you very much, this is not too bad B) Hyd...   Nov 26 2002, 15:12
- - Volcano   Just my 0.02: Test & Copy without C2 is cert...   Nov 26 2002, 22:42
- - liekloo   If Volcano's EAC is correctly configured (cach...   Nov 27 2002, 09:38
- - liekloo   QUOTE I found it impossible to get matching CRCs w...   Nov 27 2002, 09:43
- - user   " On scratched CDs, I found it impossible to ...   Nov 27 2002, 10:16
- - Pio2001   QUOTE (Volcano @ Nov 27 2002 - 12:16 PM)...   Nov 27 2002, 15:01
- - Pio2001   By the way, this thread is interesting : (http://w...   Nov 27 2002, 15:10
- - Pio2001   I forgot : http://www.digital-inn.de/showthread.ph...   Nov 27 2002, 15:48
- - user   For all these reasons and uncertainty, checking in...   Nov 27 2002, 15:56
- - Volcano   user: QUOTE QUOTE On scratched CDs, I found it im...   Nov 27 2002, 16:51
- - user   " But even with my crappy Acer CD writer I co...   Nov 27 2002, 17:07
- - Pio2001   QUOTE (user @ Nov 27 2002 - 07:07 PM)hmm, Hal...   Nov 27 2002, 22:28
- - Volcano   Pio2001: QUOTE QUOTE which leaves more room for m...   Nov 28 2002, 16:23
- - liekloo   QUOTE VOLCANO: My question is, is that theory righ...   Nov 28 2002, 17:18
- - liekloo   In fact Pio2001 already answered the question: In...   Nov 30 2002, 12:18
- - spoon   Here is what I have found on ripping audio CDs - ...   Nov 30 2002, 22:47
- - liekloo   T&C should also help to verify whether your dr...   Dec 4 2002, 09:33
- - Pio2001   QUOTE (liekloo @ Dec 4 2002 - 11:33 AM)***Abo...   Dec 4 2002, 12:39
- - liekloo   QUOTE (Pio2001 @ Dec4 12:39)So it's not 1...   Dec 5 2002, 10:12
- - liekloo   Tests have been done meanwhile, and a conclusion i...   Apr 23 2003, 20:49


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