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Topic: Different CRCs in EAC with and without C2 (Read 19718 times) previous topic - next topic
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Different CRCs in EAC with and without C2

Hello again.

I am going through a big (in my opinion) ripping project of about 75 cds. I only have access to one drive, so I figured that the most secure/borderline-paranoid way to do it is to rip each CD twice securely, once with C2 on and once with C2 off, then compare the CRCs and see that they match. One of the CDs that I came across consistently reports a different CRC when it is ripped with C2 than when it is ripped without, though EAC reports an error free rip each time. The other 72 all had matching CRCs when C2 was used and when it was not used.

Some information about the CD: It is pretty old, probably about ten years (probably purchased around 2000, and manufactured circa 1998) It doesn't appear to be too scratched, except for one point in the disc where there seems to be a deeper chip. It is pretty obscure, as are all the CDs in this project, and thus not available in the AccurateRip DB, though it is a pressed CD, not burnt.

So, I am wondering if anyone has come across this problem before, and if anyone can advise me how to correct the situation. I sincerely doubt that it is a copy-protection mechanism, given the age and source of the cd, but I won't rule anything out. It would be really nice to get an accurate rip, if possible.

If you have any additional questions I will attempt to provide answers to the best of my knowledge.

Thanks in advance.
Adam

Different CRCs in EAC with and without C2

Reply #1
If you tell EAC that your drive correctly reports C2 errors when it doesn't, then there could be read errors that EAC ignores because no C2 error was reported.

If you are not positive that your drive correctly reports C2 errors then it is safer to leave this unchecked.

Different CRCs in EAC with and without C2

Reply #2
I am pretty confident that my drive implements C2 correctly, since the other ~70 rips that had matching CRCs when C2 was used and not, but it is possible that it was just because those discs were in better shape and had fewer scratches. When I run the tests for C2, they always inform me that my drive does support it.

Can C2 stop working properly on a drive after time? Perhaps this is the case... I will go and retest it and see if it still reports C2 as working correctly.

Edit: I rechecked the drive using EAC's tools and it still reported my drive as being capable of reading C2 error information.

Different CRCs in EAC with and without C2

Reply #3
but it is possible that it was just because those discs were in better shape and had fewer scratches.
Bingo! EDIT: I wasn't fully aware of the situation when I made this remark.

Can C2 stop working properly on a drive after time? Perhaps this is the case...
It's doubtful that this is the case.

Edit: I rechecked the drive using EAC's tools and it still reported my drive as being capable of reading C2 error information.
pdq is right (EDIT: but I no longer think this is what's going on here).  Please read the wiki.

In general I think ripping with C2 pointers and then without will be able to identify more potential problems since it will cause the drive to seek different points on the disc (every 24 frames with C2 vs. every 27 frames without).  With this in mind, it's possible to get a good rip with C2, but not without C2 even when the drive cannot provide reliable C2 information.  The same can be said about the converse.  I've seen it happen but don't believe these instances to be very common.

What is the make and model of your drive?

Different CRCs in EAC with and without C2

Reply #4
What is the make and model of your drive?
My drive is a TOSHIBA CDRW/DVD SDR2102, which is the original drive that came with my Dell Latitude notebook (the computer I am using for my audio extraction.)

I perused the wiki, and the best advice I could take away was that you should never use C2! If you do decide to use C2, you can try test and copy, but that in no way guarantees a perfect rip, such as in this case in which I repeatedly used C2 and I consistently arrived at the same (wrong?) CRC. Edit: I was a little overzealous when I wrote this, operating under the impression that the C2 rip was the wrong one. Now I'm actually think that the C2 rip was the accurate one!

But is the C2 CRC the wrong one or the right one? Which rip is accurate, if either? I just re-ripped the CD in burst mode and got the same CRC as the C2 version, so I am thinking that the C2 rip just missed some errors that the no C2 rip was able to re-read and correct, and that the no C2 rip is thus the accurate one. Am I on the right track?

Thanks again for your help so far.

Adam

Different CRCs in EAC with and without C2

Reply #5
I perused the wiki, and the best advice I could take away was that you should never use C2!
I think this is a little extreme.  It says not to use it if you are uncertain, but you said you perused it, so maybe with this intense reading you saw something that I missed.

I repeatedly used C2 and I consistently arrived at the same (wrong?) CRC.
Let me get this straight, ripping with C2 pointers always gave you the same CRC and ripping without C2 pointers always gave you the same CRC but a different one than with C2 pointers?  Please include a log file showing the results with and without C2 pointers for the rip in question.

Is AccurateRip able to verify that one of them is correct?

Different CRCs in EAC with and without C2

Reply #6
I repeatedly used C2 and I consistently arrived at the same (wrong?) CRC.
Let me get this straight, ripping with C2 pointers always gave you the same CRC and ripping without C2 pointers always gave you the same CRC but a different one than with C2 pointers?  Please include a log file showing the results with and without C2 pointers for the rip in question.
Yes, so far I have ripped the CD approximately seven times (probably more). Every time I rip it with C2 I arrive at one CRC, every time I rip it without C2 I arrive at a different CRC. I also ripped it once in burst mode and got the same CRC as the C2 rips.
Burst Mode
Code: [Select]
Exact Audio Copy V0.99 prebeta 3 from 28. July 2007

EAC extraction logfile from 4. January 2008, 14:43

Artist / Album

Used drive  : TOSHIBA CDRW/DVD SDR2102  Adapter: 2  ID: 0

Read mode : Burst

Read offset correction                      : 708
Overread into Lead-In and Lead-Out          : No
Fill up missing offset samples with silence : Yes
Delete leading and trailing silent blocks  : No
Null samples used in CRC calculations      : Yes
Used interface                              : Installed external ASPI interface

Used output format : Internal WAV Routines
Sample format      : 44.100 Hz; 16 Bit; Stereo


TOC of the extracted CD

    Track |  Start  |  Length  | Start sector | End sector
    ---------------------------------------------------------
        1  |  0:00.00 | 25:02.74 |        0    |  112723 
        2  | 25:02.74 | 24:06.70 |    112724    |  221243 


Range status and errors

Selected range

    Filename C:\Artist - Album.wav

    Peak level 100.0 %
    Copy CRC 5D76F412
    Copy OK

No errors occurred

End of status report
C2 Test And Copy
Code: [Select]
Exact Audio Copy V0.99 prebeta 3 from 28. July 2007

EAC extraction logfile from 3. January 2008, 22:09

Artist / Album

Used drive  : TOSHIBA CDRW/DVD SDR2102  Adapter: 2  ID: 0

Read mode              : Secure
Utilize accurate stream : Yes
Defeat audio cache      : No
Make use of C2 pointers : Yes

Read offset correction                      : 708
Overread into Lead-In and Lead-Out          : No
Fill up missing offset samples with silence : Yes
Delete leading and trailing silent blocks  : No
Null samples used in CRC calculations      : Yes
Used interface                              : Installed external ASPI interface

Used output format : Internal WAV Routines
Sample format      : 44.100 Hz; 16 Bit; Stereo


TOC of the extracted CD

    Track |  Start  |  Length  | Start sector | End sector
    ---------------------------------------------------------
        1  |  0:00.00 | 25:02.74 |        0    |  112723 
        2  | 25:02.74 | 24:06.70 |    112724    |  221243 


Range status and errors

Selected range

    Filename C:\Artist - Album.wav

    Peak level 100.0 %
    Range quality 100.0 %
    Test CRC 5D76F412
    Copy CRC 5D76F412
    Copy OK

No errors occurred

End of status report
No C2 Test And Copy
Code: [Select]
Exact Audio Copy V0.99 prebeta 3 from 28. July 2007

EAC extraction logfile from 3. January 2008, 21:58

Artist / Album

Used drive  : TOSHIBA CDRW/DVD SDR2102  Adapter: 2  ID: 0

Read mode              : Secure
Utilize accurate stream : Yes
Defeat audio cache      : No
Make use of C2 pointers : No

Read offset correction                      : 708
Overread into Lead-In and Lead-Out          : No
Fill up missing offset samples with silence : Yes
Delete leading and trailing silent blocks  : No
Null samples used in CRC calculations      : Yes
Used interface                              : Installed external ASPI interface

Used output format : Internal WAV Routines
Sample format      : 44.100 Hz; 16 Bit; Stereo


TOC of the extracted CD

    Track |  Start  |  Length  | Start sector | End sector
    ---------------------------------------------------------
        1  |  0:00.00 | 25:02.74 |        0    |  112723 
        2  | 25:02.74 | 24:06.70 |    112724    |  221243 


Range status and errors

Selected range

    Filename C:\Artist - Album.wav

    Peak level 100.0 %
    Range quality 100.0 %
    Test CRC 610A4BA1
    Copy CRC 610A4BA1
    Copy OK

No errors occurred

End of status report
Is AccurateRip able to verify that one of them is correct?
Unfortunately, none of the CDs I am working with are in the AccurateRip DB - so this option is not going to work for me.

Different CRCs in EAC with and without C2

Reply #7
I couldn't tell from your original post that this was the case.  Seems like a bit of a conundrum.

Maybe perform a comparison of the two different files, identify where the differences exist and check to see if one of them has an audible error.  I would typically load both files into Audition, subtract one from the other and view the originals in the areas where they differ using the spectral view to look for signs of discontinuity and/or interpolation.

This is an excellent example of a consistent error for those who are skeptical.  Thank you so much for sharing!

Different CRCs in EAC with and without C2

Reply #8
I guess the best thing to do is: get another drive and see if you can get the same CRC from the Toshiba-drive.
Can't wait for a HD-AAC encoder :P


Different CRCs in EAC with and without C2

Reply #10
Yes, indeed you are right about the title. Someone was thoughtful enough to add it to freedb, but apparently not enough people have Accurate-ripped it for it to appear in the Accuraterip database. Also, this is a really old pressing, if it does emerge in the database, likely people will be submitting values for newer pressings (assuming something has changed between pressings, eg offsets).

here is a logfile with AccurateRip enabled.
Code: [Select]
Exact Audio Copy V0.99 prebeta 3 from 28. July 2007

EAC extraction logfile from 5. January 2008, 9:41

Artist / Album

Used drive  : TOSHIBA CDRW/DVD SDR2102  Adapter: 1  ID: 0

Read mode              : Secure
Utilize accurate stream : Yes
Defeat audio cache      : No
Make use of C2 pointers : Yes

Read offset correction                      : 708
Overread into Lead-In and Lead-Out          : No
Fill up missing offset samples with silence : Yes
Delete leading and trailing silent blocks  : No
Null samples used in CRC calculations      : Yes
Used interface                              : Native Win32 interface for Win NT & 2000

Used output format : Internal WAV Routines
Sample format      : 44.100 Hz; 16 Bit; Stereo


TOC of the extracted CD

    Track |  Start  |  Length  | Start sector | End sector
    ---------------------------------------------------------
        1  |  0:00.00 | 25:02.74 |        0    |  112723 
        2  | 25:02.74 | 24:06.70 |    112724    |  221243 


Range status and errors

Selected range

    Filename C:\Artist - Album.wav

    Peak level 100.0 %
    Range quality 100.0 %
    Copy CRC 5D76F412
    Copy OK

No errors occurred

 
AccurateRip summary
 
Track  1  not present in database
Track  2  not present in database
 
None of the tracks are present in the AccurateRip database

End of status report

I compared the two WAVE files, and it seems that the only difference between them is in the last 5 seconds of the album, which is a fadeout and then silence. I could hear no audible difference between these two tracks, yet the data was not exactly the same. (As the compare program I used, WinDiff, stated, and the different CRCs implied).

I usually use the "use null samples in CRC calculations" in options, so I toggled it to see if I would get consistent CRCs between the two methods. I did not - I still arrived at a different CRC for the C2 rip and the non-C2 rip (Different from the original ones as well, since a different method was being used to calculate it.) I can post these logs, too, if they will help.

So basically I'm still lost. I am thinking that the difference is really negligible, but I am still confused as to why different data is being written at the end of the file between the two methods. Perhaps with a little more experimenting/research enlightenment will come.

Thanks,
Adam

Different CRCs in EAC with and without C2

Reply #11
A shot in the dark here .. are the two files exactly the same size?

edit: What does EAC compare wavs report?
daefeatures.co.uk

Different CRCs in EAC with and without C2

Reply #12
Uh, i've experienced this problem before. I don't think it's about consistent errors, but more likely the drive fails to read lead-out correctly.
Can't wait for a HD-AAC encoder :P

Different CRCs in EAC with and without C2

Reply #13
Is the disc a Hemi-Sync Meta Music disc titled Transformation?

Now this really tickles my interest.
How did you know which disc was causing problems - and what is the implication regarding this specific disc?
Creature of habit.

Different CRCs in EAC with and without C2

Reply #14
A shot in the dark here .. are the two files exactly the same size?
Yes, the two files are exactly the same size: 520,365,932 bytes.
edit: What does EAC compare wavs report?
I tried the wav compare, and EAC reported that  there are 1176 repeated samples at 0:49:09.804, right at the end of the cd. If I am reading this correctly, the error is on the WAV that was done with no C2. (The error report is listed under that Wav file)

Uh, i've experienced this problem before. I don't think it's about consistent errors, but more likely the drive fails to read lead-out correctly.
Maybe, but I never enable Overread Lead-In and Lead-Out... and the error only occurs when the drive is configured one way, when C2 is not used (I think...) and (so far) only on this particular CD. I didn't have the problem with any of the other CDs. If you can remember, can you tell me how was the drive configured when you had the error?

Is the disc a Hemi-Sync Meta Music disc titled Transformation?
Now this really tickles my interest.
How did you know which disc was causing problems - and what is the implication regarding this specific disc?
I imagine that he did a search in FreeDB. I searched the database and found that it was listed there in much the same manner. I'm not sure what he was implying, but am also eager to hear what he might have had in mind!

Thank you for your questions, each ones providing a little more insight into this problem.

-Adam

Different CRCs in EAC with and without C2

Reply #15
I compared the two WAVE files, and it seems that the only difference between them is in the last 5 seconds of the album, which is a fadeout and then silence. I could hear no audible difference between these two tracks, yet the data was not exactly the same. (As the compare program I used, WinDiff, stated, and the different CRCs implied).
Look at that  area in a wave editor and zoom in to see if one of the rips had part of the fade-out replaced by silence.

I usually use the "use null samples in CRC calculations" in options, so I toggled it to see if I would get consistent CRCs between the two methods. I did not - I still arrived at a different CRC for the C2 rip and the non-C2 rip (Different from the original ones as well, since a different method was being used to calculate it.) I can post these logs, too, if they will help.
No, this won't be necessary as it won't reveal anything.  If the CRCs are the same with null samples included they will absolutely be the same with null samples not included.

So basically I'm still lost. I am thinking that the difference is really negligible, but I am still confused as to why different data is being written at the end of the file between the two methods. Perhaps with a little more experimenting/research enlightenment will come.
I'm pretty sure the drive is having a problem addressing the data in one of the two modes.  This is related to what I said earlier about 24 (or 25?) frames read at a time with C2 vs. 27 without C2.  I am inclined to believe the C2 rip is correct (the one that matches the burst rip) whereas the non-C2 rip is not.

Uh, i've experienced this problem before. I don't think it's about consistent errors, but more likely the drive fails to read lead-out correctly.
Sorry, but no...
Overread into Lead-In and Lead-Out          : No
Tell me, if you get two different but matching pairs of CRCs, how can this not indicate that at least one pair represents a rip with consistent errors?

Is the disc a Hemi-Sync Meta Music disc titled Transformation?

Now this really tickles my interest.
How did you know which disc was causing problems - and what is the implication regarding this specific disc?
I don't think there's any implication about  the disc; I simply looked it up based on the TOC information that was given.

edit: What does EAC compare wavs report?
I tried the wav compare, and EAC reported that  there are 1176 repeated samples at 0:49:09.804, right at the end of the cd. If I am reading this correctly, the error is on the WAV that was done with no C2. (The error report is listed under that Wav file)
That seems about right and 1176 samples = 2 frames.

Different CRCs in EAC with and without C2

Reply #16
I tried the wav compare, and EAC reported that  there are 1176 repeated samples at 0:49:09.804, right at the end of the cd. If I am reading this correctly, the error is on the WAV that was done with no C2. (The error report is listed under that Wav file)

EAC doesn't know which is the correct file, surely. The error report must be dictated by which wav you select first. It would be interesting to see what happens with this disc and another drive as odyssey suggested.
daefeatures.co.uk

Different CRCs in EAC with and without C2

Reply #17
Very true about a wave compare not being able to tell which is wrong, but it's also clear that the one with the repeated samples is probably the one with the error.

A fade out that has been replaced by silence is a likely scenario that would result in samples that appear to be repeated.

(I've seen this situation before, BTW )


Different CRCs in EAC with and without C2

Reply #19
Adam should verify my suspicion to make sure I'm not blowing smoke.

Like you guys are saying, results with another drive might prove very useful.  Hopefully the fade out is finished before the end of the disc as not to create discrepancies caused by offset differences.

Different CRCs in EAC with and without C2

Reply #20
A fade out that has been replaced by silence is a likely scenario that would result in samples that appear to be repeated.

I loaded the wav into Audacity, but in order to see the slight difference, I had to amplify the sample quite a bit. Here is the final moments in a png.

If you look closely, the waveforms are exactly the same until the final moments, at which point they appear to be different. It doesn't seem like one Waveform has all the information in it, but that each one has a slightly different amount of the original information. Of course, the intention on the CD could be silence, and extra samples have been repeated where they should not be. Without extreme amplification this section is completely inaudible. I performed a quick subtraction operation and got the following mix:

It seems to show a mix of some of what was originally on the C2 rip and some of what was on the no C2 rip. Neither one of the waveforms seems to completely include all that is in the other - not at exactly the same timing, anyway.

Like you guys are saying, results with another drive might prove very useful.

I have ordered another drive for my laptop about a week ago... But shipping seems to be taking a little while. When it does arrive I can do another rip, and see if the problem persists, but I would really love to find out what is going wrong with this drive in the first place, especially to know if I can trust the other rips I have made with it as secure.

-Adam

Different CRCs in EAC with and without C2

Reply #21
It seems to show a mix of some of what was originally on the C2 rip and some of what was on the no C2 rip. Neither one of the waveforms seems to completely include all that is in the other - not at exactly the same timing, anyway.

Could you upload lossless files of the last moments of each version?  Half-a-second or less should do the trick.  I'd like to look at them myself as I prefer the zooming capabilities of Audition over Audacity.

Different CRCs in EAC with and without C2

Reply #22
Could you upload lossless files of the last moments of each version?  Half-a-second or less should do the trick.  I'd like to look at them myself as I prefer the zooming capabilities of Audition over Audacity.


Here is an upload of approximately the final second of the last two files.

First is the version with No C2 in FLAC format: link

This is the second version, with C2, also in FLAC format. link

You will likely need to amplify or zoom into these samples quite a bit, as they will probably both initially appear as silence.

Thank you for all your help with this greynol. It's nice to hear that someone has else has experienced this problem before!

-Adam

Different CRCs in EAC with and without C2

Reply #23
Thank you.

I was able to determine that the 2 frames of repeated samples had a value of 1 in the right channel and were silent in the left channel.  The result was that the end was pushed out by 2 frames in the non-C2 version, assuming they were repeated.  It's also possible that they were omitted in the C2 version.  The rest of the fade-out after the repeated (or omitted) samples is identical in either case.

Which is the correct rip, I haven't a clue.  A different make and model of drive might help out.

PS:  You could have placed those files to the upload forum here at HA.  The site you chose seems a bit dodgy.

Different CRCs in EAC with and without C2

Reply #24
Which is the correct rip, I haven't a clue.  A different make and model of drive might help out.
As I mentioned, I have ordered another drive that should be arriving shortly. When it finally arrives I will try another rip and post the results here. (But don't hold your breath, shipping time here is very whimsical!)

PS:  You could have placed those files to the upload forum here at HA.
I really didn't want to start another topic for a problem whose interest seems limited only to a couple of people here.
The site you chose seems a bit dodgy.
Those were my sentiments, too, yet it was the first site that showed up with a Google search on file hosting, so it's probably pretty safe - or a least has a very large fanbase.

-Adam