EAC and C2 Error checking...

2002-02-26 01:20:49

Just thought I'd start a thread specifically on this topic, cuz I was reading another and made an interesting discovery after performing this test:

(1) I ripped a relatively scratchy CD using EAC in secure mode using C2 error information (which my drive supports).  I used "Test and Copy" to be sure everything was OK.

(2) I then did the same thing, with C2 errors turned off for the drive (causes EAC to check each sector twice instead), and saved the .WAVs in a different folder.

(3) I used a utility to compare the 8 tracks in the two different folders (byte for byte comparison)... and tracks 5 & 7 did NOT match!  BTW, those were the tracks with the most errors recorded by EAC while ripping.

If anyone's curious, the drive I used is a Toshiba SD-M1612, a *very* new and up to date DVD-ROM drive I bought less than a month ago.  It has all the latest features (C2 error detection, no caching, "accurate stream").  Testing is done with EAC 0.9pb11.

So, something different happened with C2 errors turned on and off for the same drive (other than just the ripping speed being faster with C2 error checking active). 

P.S. and followup -- I hear audible clicking in Track 7 with both copies, and it actually seems a bit worse with the copy that didn't use C2 error checking (audible in both files though... so much for "perfect" copies, bah  ).

EAC and C2 Error checking...

Reply #1 – 2002-02-26 02:16:10

After performing a new test using a different CD on a severely scratched track, I used a hex editor (Hexworks) and found 98 different (16-bit) samples between the ripped .WAV using C2 error infos, and the one  using EAC's standard "read the track twice."

Unfortunately, I can't tell on this one which is "more correct" since they both sound the same to me (no clicks are noticeable over the music). 

My conclusion (thus far) is that if C2 error checking works properly with a drive after thorough testing, it's reasonable to depend on it.  If someone wants to prove me wrong, please do (I want the best quality rips), but if C2 checking works then I don't think it's worth sacrificing the speed gain and reduced tear on the drive -- and I'm thinking the C2 info might be *more* reliable than multiple reads if implemented properly ('lower level' of error checking).

EAC and C2 Error checking...

Reply #2 – 2002-02-26 02:47:30

OK, this is my last post on the thread.  Read here:

http://www.digital-inn.de/showthread.php?threadid=7334

Extract (from the author of EAC):

"And yes, it is possible that the results with C2 are not bit-perfect, but I really assume that no one will really hear a difference... cu, Andre"

I guess that's the final word.

EAC and C2 Error checking...

Reply #3 – 2002-02-26 19:18:58

Same thing here with a Hitachi GD7500

The C2 is wrong : test and copy CRC don't match. You must check this yourself, EAC displays "copy ok" in both cases. There are usually one or two errors per CD.

The errors are inaudible, they always affect one of the least significant bit, and occur usually in silent parts (maybe an effect of the EFM setup).