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  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
I have a problem  .

EAC seems to have a problem reading cds with errors on 'em (that is 'errors' as in: "Step right up folks, *tap tap tap* come see the errors, an error for the fine lady Sir? You can never go wrong with an error my good lady, an error for every season and taste, an error a day keeps the sanity away is what I say"..., i.e. generic errors of any kind).

Just. So.

And how, then, can I be certain I've read the CD correctly? Notice the word 'certain', by the way. Sadly, few people seem to grasp the abstract meaning of the word, much the same way that the concepts 'accurate', 'precise', and 'reliable' seem to escape them.

So I throw my meager wits upon the mercy of the minds in this forum, in my pitifull plea for an injection of intelligible truth into my chaotic existence (ok, maybe the 'corny'-factor could be turned down a little,  , but my verbosity is great because my plight is in blight. Or something. ).

  • _Shorty
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The ONLY way to be guaranteed correct ripping?
Reply #1
www.accuraterip.com providing that two other people have already ripped that CD and had agreement in the results, if your results match those two people, pretty safe to say you ripped it 100% correctly without error.  It would be nice to have a combination of this and EAC's routines to make it easier to rip a problem disc, but with a disc that's in decent shape then EAC's method is unnecessary when you can verify your results against others'.
  • Last Edit: 29 April, 2003, 04:45:16 PM by _Shorty

  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
Reply #2
Excellent, could be exactly what I am looking for!

Thanks a bunch!

  • Halcyon
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The ONLY way to be guaranteed correct ripping?
Reply #3
There is no known way to be sure that you have 100% accurately got the data from the CD correctly, especially if the CD is scratched.

There are several reasons for this and I'm sure Pio2001 will chime in later, but I'll just list some of the most fundamental reasons here:

1) CD Audio Reading is not a 100% repeatable process with identical results from one rip to another

2) If you have scratches that are beyond the error correction mechanism of CD-readers, then you are out of luck

3) Copy protected CDs add another layer of problem: is the original data on the master before the copy protection was applied (which destroyed some original data as it was applied) what you are after? Or is the copy protected, non-original (in terms of the studio master) data with erroneus C2 data, what you are after?

4) AccurateRip can only give you information that another people got the same result. It is statistically a good approach against random errors (such as scratches), but is not perhaps the optimal tool for copy protected discs. Why? Two erroneus rips will be the same if neither of them was able to circumvent the copy protection and there were no scratches. Now, if your rip matches this erroneus rip with AccurateRip, are you happy? Surely not. You got a rip with clicks/pops/mute points on the audio, which is different from the pre-copy protection cd master and different from what a normal hifi rack cd player would output (which would probably use higher order interpolation to fill in the erroneus parts induced by the copy protection).

regards,
Halcyon

  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #4
Quote
I have a problem   .

EAC seems to have a problem reading cds with errors on 'em (that is 'errors' as in: ............. )

What exacty do you mean by "EAC has problems reading CDs with errors". Does it say "there were errors" after extraction finished?
I assume your answer will be "yes", since EAC is very accurate at reporting errors, but it often can't actually correct them).
( BTW, If your answer is No, EAC claims to have a good rip, but I hear pops", then you have probably misconfigured EAC, or using it badly )

Yes? well, there are a few things you can do:

1. throw the CD out of the window
2. clean the CD. If this doesn't help, 'restore' the CD (brasso/toothpaste/... have a search on the forum, there were some good threads about it). From my own experience I must say restoring can do wonders.
3. forget EAC and 1:1 copies, and use a less secure ripper. Feurio is your best choice (by far...)
(4. if you have a digital soundcard input, and a digital CD player output, you could also use these to get your CD copy...)
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  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
Reply #5
Quote
There is no known way to be sure that you have 100% accurately got the data from the CD correctly, especially if the CD is scratched.


I've read up on this a bit now, and I disagree with the above claim.

*) If you have a drive that reports C2 errors with a 100% reliability (oh please God, make it exist!)
*) And you get no C2 errors when reading the CD
*) GOTO ::ReadGoodCD

Quote
1) CD Audio Reading is not a 100% repeatable process with identical results from one rip to another


Why not, exactly? Is it not digital information?

Quote
2) If you have scratches that are beyond the error correction mechanism of CD-readers, then you are out of luck


If you do not have scratches that are beyond Outofluckia, you not bad CD have read can.

Quote
3) Copy protected CDs add another layer of problem: is the original data on the master before the copy protection was applied (which destroyed some original data as it was applied) what you are after? Or is the copy protected, non-original (in terms of the studio master) data with erroneus C2 data, what you are after?


Now why would anybody want to rip a copy-protected CD? Isn't there enough music in the world? And why, pray tell, would one want to rip it on a CD-ROM (as opposed to a real good audio cd player with SPDIF)?

Quote
4) AccurateRip can only give you information that another people got the same result.


Yes... well, damn the Bell-Curve, I say, damn it! 

  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
Reply #6
Quote
What exacty do you mean by "EAC has problems reading CDs with errors". Does it say "there were errors" after extraction finished?


No. It happily rips two different copies of the same CD. With a plextor w1210A firmware 1.10 at 14-32x CAV, mind. Haven't tried at 8x CLV yet... but maybe I should.

Quote
...since EAC is very accurate at reporting errors, but it often can't actually correct them


Isn't it the DRIVE's responsibility to report C2 errors? Hummmm? 

Quote
( BTW, If your answer is No, EAC claims to have a good rip, but I hear pops", then you have probably misconfigured EAC, or using it badly )


Methinks not.

Quote
... well, there are a few things you can do:
Yes, well I think I'll try 2 and 4... in time.
Thanks!

  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #7
Quote
4) AccurateRip can only give you information that another people got the same result. It is statistically a good approach against random errors (such as scratches), but is not perhaps the optimal tool for copy protected discs. Why? Two erroneus rips will be the same if neither of them was able to circumvent the copy protection and there were no scratches

Is that true?
(I am not so familiar with copy-protections...)
The example you might have in mind, is (deliberately inserted)clicks/pops in the tracks when read by a CD-ROM drive, right?


Then, @ DrDoogie: it depends on how you define 'guaranteed correct'... 100% sure you'll never be, but yes we can come pretty close

For the rest: This seems to be thestory of the glass of beer.. . Is it half-full, or is it half-empty?
  • Last Edit: 02 May, 2003, 11:16:00 AM by liekloo
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  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
Reply #8
Quote
Then, @ DrDoogie: it depends on how you define 'guaranteed correct'... 100% sure you'll never be, but yes we can come pretty close

For the rest: This seems to be thestory of the glass of beer.. . Is it half-full, or is it half-empty?


I define "guaranteed correct" as in: 100% sure.

Whether one can be 100% sure or not may well be a philosophical question, but if there are no errors it is a reasonable assumption that one has read correctly, provided that one can be certain any possible errors would have been detected.

Hence the C2-error reporting has to be correct, or one might as well use SPDIF (digital audio out).

The glass of beer is an analog example though.

  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #9
Quote
No. It happily rips two different copies of the same CD. With a plextor w1210A firmware 1.10 at 14-32x CAV, mind. Haven't tried at 8x CLV yet... but maybe I should.

Ripping in Test&Copy mode and getting a CRC mismatch, or WAV compare, are good (secure) ways to be sure of that. Assuming you have done something similar, my guess is the EAC drive options are not correctly set. This can be easily verified: Go to:  EAC > Drive Options and set your drive's settings 'safe', i.e.:
    * Accurate stream: No
    * Caching: Yes
    * C2: No
Now rip again & see if you get 2 identical rips...

Quote
Quote

...since EAC is very accurate at reporting errors, but it often can't actually correct them

Isn't it the DRIVE's responsibility to report C2 errors? Hummmm? 

Yep, but we don't have to bother about that. More relevant is when the drive can't correct an error, and it reports so to EAC. If EAC can't solve things, it will warn you: "there were errors"! Moreover, the drive sometimes overlooks errors, which EAC will pick up most of the time. If the drive reported all errors, we'd be using Audiograbber instead of EAC
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  • mrosscook
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The ONLY way to be guaranteed correct ripping?
Reply #10
DrDoogie,

Your flag says you are based in Iraq, and ripping a perfect CD is your biggest problem?

DUCK!  For God's sake, DUCK!

  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #11
*ROFL*
The other day on this forum, I came across another so-called "Iraqi" who spoke better english than any native Englishman/American - so to speak   
And it wasn't just plain English, it was juicy British English!
  • Last Edit: 02 May, 2003, 11:47:54 AM by liekloo
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  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
Reply #12
Quote
Ripping in Test&Copy mode and getting a CRC mismatch, or WAV compare, are good (secure) ways to be sure of that. Assuming you have done something similar, my guess is the EAC drive options are not correctly set. This can be easily verified: Go to:  EAC > Drive Options and set your drive's settings 'safe', i.e.:
    * Accurate stream: No
    * Caching: Yes
    * C2: No
Now rip again & see if you get 2 identical rips...


Okay, maybe I am using the wrong settings after all... but why are they wrong (accurate stream, C2)?
Aren't you, with these settings, DISABLING ALL (C2) ERROR CHECKS?

That would... reduce the question of accuracy to a statistical chance that the drive returned a different audio stream (with error hiding in it), each time, would it not? Which is less probable the worse the error hiding is, right?

My original question was not whether my CD-ROM drive knew best how to mess up the sound, oh no, it was: "How do I make sure that the sound is correct?"

I daresay it is you who are using the wrong settings, my good man...

  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
Reply #13
Quote
DrDoogie,

Your flag says you are based in Iraq, and ripping a perfect CD is your biggest problem?

DUCK!  For God's sake, DUCK!



Well, I have to use all the US grants for something, and there's a limit to how many chemical weapons they are willing to sell me, after all.


[span style='font-size:8pt;line-height:100%']Edit : fixing quotes[/span]
  • Last Edit: 03 May, 2003, 09:58:21 AM by Pio2001

  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #14
Quote
I daresay it is you who are using the wrong settings, my good man...


hehe 

I am not claiming your settings are wrong... Wether they are wrong is something we need to find out. And if you use my advice, you'll know soon.  Actually, you'd better hope they are wrong, cuz then your problem is solved.

(@everyone:Don't panic if you are using different settings!). The settings I posted are the safest ones: they are 100% secure, but extraction will be very slow.
Depending on the drive type, you can change some of these settings, which will result in a higher extraction speed, while the rip will still be perfect. The configuration wizard usually tells correctly which settings can be 'adapted' safely. If you change settings that shouldn't be changed, you'll get bad rips)


Quote
Aren't you, with these settings, DISABLING ALL (C2) ERROR CHECKS?

No, EAC is software, not firmware. It can't change your drive's working at all. Disabling C2 means: EAC will always read twice, even if your drive says it is not needed (C2 info says 'data ok')


note: i have to go now. i'll track the thread


[span style='font-size:8pt;line-height:100%']Edit : fixing quotes[/span]
  • Last Edit: 03 May, 2003, 09:59:01 AM by Pio2001
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  • DrDoogie
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The ONLY way to be guaranteed correct ripping?
Reply #15
Forgive my slowness, but...

Quote
Quote
Aren't you, with these settings, DISABLING ALL (C2) ERROR CHECKS?

No, EAC is software, not firmware. It can't change your drive's working at all. Disabling C2 means: EAC will always read twice, even if your drive says it is not needed (C2 info says 'data ok')


So it reads twice. Allrigh-tee-then.

And reading an audio stream twice... does what exactly?

Does it guarantee you an error free rip? I cannot see that it does, given that there is the chance that the stream will be "wrong" both times.

Does it increase the probability that you have read the stream correctly? I don't see that it does, given that if there is an unrecoverable (C2) error, for all I know the drive may well choose to hide that error in an identical way each time it is encountered.

But perhaps I need to be brought to justice. 



[span style='font-size:8pt;line-height:100%']Edit : fixing quotes[/span]
  • Last Edit: 03 May, 2003, 10:00:46 AM by Pio2001

The ONLY way to be guaranteed correct ripping?
Reply #16
After reading twice
1. Drive report a C1 error n any of the reads - see 3.
2. The copies will match - proceed further
3. The copies don't match -  try rereading until 8 identical results
(with High error correction quality)
  • Last Edit: 02 May, 2003, 02:28:57 PM by AstralStorm
ruxvilti'a

  • tigre
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The ONLY way to be guaranteed correct ripping?
Reply #17
Quote
Quote
There is no known way to be sure that you have 100% accurately got the data from the CD correctly, especially if the CD is scratched.


I've read up on this a bit now, and I disagree with the above claim.

*) If you have a drive that reports C2 errors with a 100% reliability (oh please God, make it exist!)
*) And you get no C2 errors when reading the CD
*) GOTO ::ReadGoodCD
...

[nitpicking mode]

I disagree with the above claim. 

If you find errors in the following estimation feel free to correct me
For each chunk of audio data containing 24 bytes there's 4 bytes of C1 and 4 bytes of C2.
IIRC C1 as well as C2 information is capable of locating+correcting 1 error (not only of detecting if the chunk is unchanged or not), so there's redundancy in C1/C2 of at least 50% (maybe I'm wrong with this as I'm not very familiar with the mathematics of error detection/correction algorithms).

So there are (at most)
2^(2*4*8*50%) = 2^32 possible C1/C2 combinations that have to cover
2^(24*8)=2^192 possible data chunks.
So each C1/C2 combination gives correct checking results for 2^(192-32)=2^160 data chunks.
If you change a 24 byte chunk randomly, the probability to get correct C1/C2 checking results is ~1/1^32

Not taking into account all the mistakes made so far, to get a probability of 0.5 = 50% of getting an undetectable C1/C2 error you need on average N randomly changed 24 byte data chunks with (1-1/2^32)^N=0.5, so N=2977044471 which is 112.5 hours of audio if every 24 byte chunk is randomly changed. This is not 100% security, even with a drive that reports all detectable C2 errors (and corrects all correctable C1 errors)!!!  But it's enough security for me to be satisfied with this faulty calculation. For you maybe ripping two copies of the same CD and comparing the results might give enough security.
[/nitpicking mode]


About the reading twice vs. use C2 information issue:
Usually, if an error that the drive can't correct using C1 info occurs there'll be
- maaaany more errors nearby and
- a random behaviour in extraction results of those errors.

So in 99.9xxx % of dirty/scratched/... CDs erroreous positions will be noticed by reading twice and comparing the results. This has been tested and is result of the experience of many EAC users.

If you believe testing yourself is better than trusting you can do it like this: Take a brand-new CD with perfect surface and ripp it - C2 on test & copy or use whatever method you trust most ATM (or a CD that you have burned yourself - make sure that you have the original .wav files stored at a safe place), Than scratch it, paint some lines on it with a thin marker, eat a hot dog and wipe your fingers on the data side afterwards, ... whatever you want. Then rip with EAC secure mode
A. C2 enabled, Test & Copy
B. C2 disabled, "Drive caches ..." checked, Test & Copy,
check if T & C CRCs match and compare the results to the original with some sound editor's wave substraction or EAC's wave compare.
If the result for a track is "no errors occured" and CRCs match there should be no differences compared to the original. If there are differences and/or CRCs don't match you know that you can't trust the settings you tested.
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

  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #18
Quote
So it reads twice. Allrigh-tee-then.
And reading an audio stream twice... does what exactly?
Does it guarantee you an error free rip? I cannot see that it does, given that there is the chance that the stream will be "wrong" both times. Does it increase the probability that you have read the stream correctly? I don't see that it does, given that if there is an unrecoverable (C2) error

Reading twice is exactly the thing that makes EAC so good!

If there is an uncorrectable error, one of the following situations will occur :

1. the drive reports the uncorrected error, and EAC tries to correct (by rereading untill it gets 8/16 identical results etc...)

2. the drive 'hides' the error (as you call it), anyhow, let's say EAC doesn't know there the data is wrong. Well, actually errors 'always' (99.99...%) return different data for every new read. This is what is so typical for an error (this has to do with cicumventing the CD's correction codes), and EAC takes advantage from it: By reading every sector twice, EAC is 'sure' that the rip is a 1:1 copy.

And this is the point where we meet the 'danger' of C2:
C2 is used anyhow in your drive, but you can ADDITIONALLY set EAC to read only once (instead of twice) if C2 says the data is 'ok'. So what you do is telling to EAC: 'close your eyes & trust on C2'[/b]. This will of course increase speed, but can decrease quality (because C2 is bad for many drives, and if C2 skips an error, EAC will not notice).

ADDON (to be complete): This notorious C2 has an advantage though: In theory C2 can spot errors in the very rare case where EAC would fail (but I haven't heard of a single example so far. But in Plextools it works more accurately)
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  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #19
Hope you find this info useful, DroDoogie

More important: does EAC work perfectly now, do you get matching copies? Is your problem solved?
  • Last Edit: 03 May, 2003, 09:10:38 AM by liekloo
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  • spoon
  • [*][*][*][*][*]
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The ONLY way to be guaranteed correct ripping?
Reply #20
Quote
Well, actually errors 'always' (99.99...%) return different data for every new read.


How do you know that? it might be 60%, or 10%, because it cannot detect when the data is the same you cannot put a % on it. When AccurateRip makes its way onto EAC then you could put a percentage on it.

The ONLY way to be guaranteed correct ripping?
Reply #21
EAC presents such a number: (number of frames / number of wrong frames) * 100%
EDIT: and additionally decreases 0,01% for each reread.
It won't give 100% if there was even a single reread.
  • Last Edit: 03 May, 2003, 06:50:01 AM by AstralStorm
ruxvilti'a

  • liekloo
  • [*][*][*][*]
The ONLY way to be guaranteed correct ripping?
Reply #22
Quote
Quote
Well, actually errors 'always' (99.99...%) return different data for every new read.

How do you know that? it might be 60%, or 10%, because it cannot detect when the data is the same you cannot put a % on it. When AccurateRip makes its way onto EAC then you could put a percentage on it.

In theory you are right (cuz there is no reference), but in practise.... we can tell a lot. Quite a lot is known about EAC meanwhile !    If you say '10' or '60%', do you realize what that would mean? It would mean EAC gives very bad results anytime (CDs contain a huge lot of errors). Well that conclusion is not conform our findings: We just know that EAC is a secure ripper. If I would say 'EAC sucks', everyone would just laugh at me

You are right that it is impossible to determine an exact %, or to know for SURE a rip is a perfect copy. But an en eductated guess can already be pretty accurate/credible : e.g. if I rip 10 CDs with different drives and perform a WAV compare afterwards, I am pretty confident the WAVs will be identical (on condition EAC is used as well as it gets). Using a different good ripper (e.g. Plextools) will generally not result in deviant rips either. In times of doubt a WAV editor can also give an indication, to see if the extracted WAV is 'credible' to be a 1:1 copy. These are serious indications that EAC is secure. Are we 100% sure? No.

Finally, AccurateRip can increase the secureness of your %, but doesn't change anything fundamentally to this (same method: comparing WAVs from different drives!).
  • Last Edit: 03 May, 2003, 09:27:03 AM by liekloo
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  • Pio2001
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The ONLY way to be guaranteed correct ripping?
Reply #23
Testing procedure by Tigre and further discussion split here : http://www.hydrogenaudio.org/forums/index....ST&f=20&t=9049&

In order to draw attention on the real topic of the discussion.
  • Last Edit: 04 May, 2003, 02:53:38 PM by Pio2001

  • liekloo
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The ONLY way to be guaranteed correct ripping?
Reply #24
Well... no more news from Dr.Doogie? 
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