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CD Data Coding

I'm new to this site, and have been reading everyones raves on EAC.  The main reason being the attention to detail it takes, reading every frame at least twice in secure mode, ensuring perfect copies.  I came across this site, http://www.disctronics.co.uk/technology/cd...s/cd_frames.htm , and am wondering, if audio cds have an error correction system built in to them, why the need of such extensive reading of discs while ripping?

CD Data Coding

Reply #1
In theory the 2nd layer of error detection/correction (C2) should be able to detect 99.9xxx % of errors that can't be corrected.

EAC secure mode, C2 activated, uses this - and starts re-reading if a non-matching C2 (= uncorrectable error using C2) is reported by the drive. With CDs in good condition this will be faster (here 8.5x vs. 6x speed) than without C2 (= reading everything at least twice). So far so good, but ...

Even most drives that are able to detect and report (detectable) C2 errors, are not 100% reliable in this. So if you trust C2 flags reported by a drive you'll run into undetected errors sooner or later.

It's reported that recent Plextor drives with Plextools, that uses C2 for error detection/correction produce results equal to EAC secure mode, in some cases even better.

There's a lot of valuable information on this board about this topic, also in recent threads. I guess the FAQ could be a good starting point. If you do a forum search for "EAC" in combination with the username "Pio2001" you'll find a test to determine your drive's C2 accuracy.

If you want to use C2 information in secure mode anyway you could use EAC's Test & Copy feature and check CRCs after extraction to "add" C2 detection and reading twice security.
Let's suppose that rain washes out a picnic. Who is feeling negative? The rain? Or YOU? What's causing the negative feeling? The rain or your reaction? - Anthony De Mello

CD Data Coding

Reply #2
The reason for using EAC is that the error correction on audio CDs is barely enough to ensure a perfect reading under perfect conditions. The Red Book specifications envisages error correction failures, and says that in this case, the audio should be interpolated.

Reading an audio CD in a CD ROM drive, two factors can push the reading out of spec.
1- The reading speed, that is much faster than specified in the Red Book, thus likely to cause more errors than envisaged. It is itself at the limit of error correction. In order to get the fastest reading possible, drive manufacturers allow the drive to spin as fast as possible without errors on a perfect CD. Any less-than-perfect CD will thus have errors. The drive should then decrease the reading speed until no errors are got. But all this happens at the edge of the error correction ability, and some can pass through.
2- The CD state. If there are little scratches, or fingerprints, some parts can't be error corrected. Some CDs can also be defective to begin with. Many burned CDRs of poor quality can't be read without errors, etc.

The test for C2 accuracy had nothing to do with me. It's a program by Andre Wiethoff, available under the DAEquality section of the http://www.exactaudiocopy.de website.
What I did was using it to perform extended C2 tests. This is in a specific webpage : http://perso.numericable.fr/laguill2/dae/dae.htm

CD Data Coding

Reply #3
Quote
... The test for C2 accuracy had nothing to do with me. ...

I know, but you mentioned this several times here, so a search containing your nick would have been a good way to find it. You posting the link is a better way of course.
Let's suppose that rain washes out a picnic. Who is feeling negative? The rain? Or YOU? What's causing the negative feeling? The rain or your reaction? - Anthony De Mello

CD Data Coding

Reply #4
I see how the increased speed could really negate the fact that audio cds have a type of error correction built-in.  the other thing I was wondering, if an error occurs on say, just one frame...could it really be heard?  If so, what does it sound like?

CD Data Coding

Reply #5
It depends if the drive interpolates them. I've tested four drives (Memeorex DVDMaxx 1648, Yamaha CRW3200, Sony DDU1621, and Teac e540), and they all interpolate. It seems older drive did not always interpolates.

Here's an example of very light errors remaining after EasyCD-DA error correction on a track :



...from the EasyCD-DA test.

Each spike is a cluster of several wrong samples. They are inaudible, because their height varies with the music level. It takes a lot of errors to be audible. Actually, audible errors come rather from bugs in the firmware, skipping, or strong isolated scratches on the CD, than error correction failures under normal conditions.

CD Data Coding

Reply #6
So, using WMP9 to rip cd's to WMA is going to give me, near perfect copies (in respect to the way they sound, not if I were to analyze them.)?  WMP9 intergrates so well on the new OS'es (I'm running Server 2003) and is very speedy (seconds a song on my machine).

CD Data Coding

Reply #7
Quote
So, using WMP9 to rip cd's to WMA is going to give me, near perfect copies (in respect to the way they sound, not if I were to analyze them.)?  WMP9 intergrates so well on the new OS'es (I'm running Server 2003) and is very speedy (seconds a song on my machine).

man, you are so naive.
"You have the right to remain silent. Anything you say will be misquoted, then used against you."

 
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