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DAEMON mounted image -> EAC OR Straight CD -> EAC?
Roy
post May 26 2005, 03:12
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Hello everyone!

Although this is my first post, I have been a long time reader here on this forum. This place has been a great help to me and is the source for most of my audio encoding knowledge. So thanks to you all. biggrin.gif

Now for my question:

I have been randomly converting some of my CD collection to MP3 and there are two methods I have been doing it by. Basically all I want to know is which ripping method of mine is better and why.

:::METHOD ONE:::
1) Insert Audio CD into DVDrom drive
2) Rip directly from DVDrom drive to wav files with EAC using all the best settings.

:::METHOD TWO:::
1) Insert Audio CD into DVDrom drive
2) Create an Image with any burning program (I use Alcohol)
3) Mount the image to a virtual drive with DAEMON Tools
4) Rip from virtual drive to wav files with EAC using all the best settings.

Can anyone shed some light on which method of mine is better? Or are they exactly the same and therefore produce the same results?

All I know is that with method two it seems to run alot smoother since it is reading from the hard drive instead of the CD. But i'm not sure is thats a good thing, bad thing, or doesn't make any difference... wink.gif
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Cosmo
post May 26 2005, 04:04
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Method two is not secure. Once the image has been ripped with Alcohol (which does no error checking), there's no way to detect/correct any errors. If you want to benefit from EAC's secure ripping features, it has to rip directly from the CD drive. http://www.hydrogenaudio.org/forums/index....showtopic=33727

This post has been edited by Cosmo: May 26 2005, 04:06
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Jebus
post May 26 2005, 07:34
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uhm, what's the point? Once you have the disc imaged on your drive you don't have to "rip" again with EAC... EAC's job is already done (poorly - by Alcohol). The conversion from disc image to wave is not the problematic part, its the reading of the image OFF the physical media that is a problem because of the inherent lack of error correction in CD-audio. Once you have a good image, you could mount with daemon tools and rip with freaking Windows Media Player if you want - hard to screw up at that point!

This post has been edited by Jebus: May 26 2005, 07:38
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westgroveg
post May 26 2005, 08:11
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I don't think CD-Audio has worse error tolerance than than any other CD format just that software/hardware implementation are poor & mostly not even present.
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guruboolez
post May 26 2005, 09:18
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QUOTE (westgroveg @ May 26 2005, 08:11 AM)
I don't think CD-Audio has worse error tolerance than than any other CD format just that software/hardware implementation are poor & mostly not even present.
*

The error correction mode of Audio CD is very limited. It's a well-known weakness of RedBook format, and it have nothing to do with software or hardware readers. Otherwise, software like EAC Secure Mode, CD Paranoia routine or Test & Copy mode would be totally useless (i.e. explorer should be enough to rip unprotected audio tracks).
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westgroveg
post May 26 2005, 09:47
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QUOTE (guruboolez @ May 26 2005, 08:18 PM)
QUOTE (westgroveg @ May 26 2005, 08:11 AM)
I don't think CD-Audio has worse error tolerance than than any other CD format just that software/hardware implementation are poor & mostly not even present.
*

The error correction mode of Audio CD is very limited. It's a well-known weakness of RedBook format, and it have nothing to do with software or hardware readers. Otherwise, software like EAC Secure Mode, CD Paranoia routine or Test & Copy mode would be totally useless (i.e. explorer should be enough to rip unprotected audio tracks).
*


The reason explorer doesn't detect errors is because it doesn't perform CIRC processing if it did like say PlexTools it could tell you exactly where an error occurred, that's my point.
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guruboolez
post May 26 2005, 10:00
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If I'm not wrong, RedBook uses ~20 bytes per sector to insure data correction. CD-Rom uses more than ~200 bytes per sector (i.e. 15% of total block size) to do it. I suppose that people who choose to increase the total amunt of space dedicated to error correction didn't have in mind to waste space, and therefore that RedBook is clearly less robust than ISO9660 PlexTools or not.

But I'm maybe wrong. We should ask to Pio2001, which is a real specialist smile.gif
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Zurman
post May 26 2005, 10:04
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QUOTE (guruboolez @ May 26 2005, 01:00 AM)
If I'm not wrong, RedBook uses ~20 bytes per sector to insure data correction. CD-Rom uses more than ~200 bytes per sector (i.e. 15% of total block size) to do it. I suppose that people who choose to increase the total amunt of space dedicated to error correction didn't have in mind to waste space, and therefore that RedBook is clearly less robust than ISO9660 PlexTools or not.

But I'm maybe wrong. We should ask to Pio2001, which is a real specialist smile.gif
*

You are not wrong and you know that very well tongue.gif
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westgroveg
post May 26 2005, 10:22
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QUOTE (guruboolez @ May 26 2005, 09:00 PM)
If I'm not wrong, RedBook uses ~20 bytes per sector to insure data correction. CD-Rom uses more than ~200 bytes per sector (i.e. 15% of total block size) to do it. I suppose that people who choose to increase the total amunt of space dedicated to error correction didn't have in mind to waste space, and therefore that RedBook is clearly less robust than ISO9660 PlexTools or not.

But I'm maybe wrong. We should ask to Pio2001, which is a real specialist smile.gif
*

But even with 20 bytes don't you agree that errors should be noticable?

My understanding is that CD-Audio data is encoded using Cross Interleaved Reed-Solomon Code, to perform error processing you need to decode this data in the correct fashion either by hardware or software then output to the user or application the status.

I would like to hear from Spoon or another developer who really understands how this works.

This post has been edited by westgroveg: May 26 2005, 10:23
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kjoonlee
post May 26 2005, 10:37
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QUOTE (Jebus @ May 26 2005, 03:34 PM)
its the reading of the image OFF the physical media that is a problem because of the inherent lack of error correction in CD-audio.
*

I have to disagree. To say that CD audio lacks error detection or correction is plain wrong.

If you think it's not adequate, just look at how well EAC is able to deal with most scratched CDs.


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guruboolez
post May 26 2005, 10:44
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QUOTE (kjoonlee @ May 26 2005, 10:37 AM)
If you think it's not adequate, just look at how well EAC is able to deal with most scratched CDs.
*

EAC Secure and scratched CD is not necessary a good thing. Many users have noticed it. Extraction takes hours, and audible glitches could be more annoying that a simple burst extraction. I've also noticed it, with various drives.
Even when scratchs are not excessive, EAC let audible glitches. I have various damaged CD-Rom (even CD-R) and my datas are all readable (and quickly readble), without corruption.

In short:
scratched CD-Rom -> fast extraction and no corruption
scratched CD-A -> slow extraction and damaged audio data.

I suppose that a better error correction of data CD could easily explain that. No?
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kjoonlee
post May 26 2005, 11:41
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I agree that error detection and correction is better with CD-ROMs rather than with CDDA discs. No doubt about it.

Still, I have only one CD out of 130 or so that fails audibly with EAC. It works well enough for me, I guess.


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spoon
post May 26 2005, 14:26
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20 bytes error correction per sector and 2352 bytes of audio data per sector.

Each of those bytes of error correction corressponds with over 100 bytes of audio data...

Put another way, even if you had 2352 bytes of error correction (for example an exact duplicate of the audio data), it is still possible for the exact error to be present on the two (audio data and correction), although this possiblilty will be tiny.

When people are testing cds, some will scratch or drill holes (or scratch off the data foil), the scratches will be harder for the cd drive to spot rather than holes as it is obvious when a hole is there there is no error correction.


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Jebus
post May 26 2005, 17:35
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The issue is, CD-audio discs weren't designed to be bit-perfect on an error, they were designed so that the error could be smoothed-over (made inaudible). That of course wouldn't work for data, where every bit is vital, so thats why CD-ROM has more (of a different kind of) error correcting code.

Don't forget that CD-audio is far older than computers with CD players, so the idea of a "bit-perfect rip" was't realy on the agenda at the time. And also because of that, this "smoothing-over" type of error-correction is also performed by most CD-ROM drives before they even let the system see the result! So that is why bit-perfect rips are difficult.

This post has been edited by Jebus: May 26 2005, 17:37
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oilshocked
post May 26 2005, 18:22
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The CD-ROM (data) spec is governed by Yellow Book and is actually an extension to the Red Book standard for CD-Audio. The extension, among other things, covers additional ECC space that Jebus and Guruboolez mention. As far as extracting to an image and then using EAC, you have lost your ability to extract using a secure process from an unsecure medium (ie. Red Book).

In essence, to get a secure rip, you must perform the secure extraction from the actual CD-Audio disc, not from an unsecure, possibly not bit-perfect image of the disc. Red Book media + Secure Extraction = Secure Rip.

The following link clarifies the differences between Red Book and Yellow Book nicely...

http://www.samsungodd.com/eng/Information/...&no=8&type_no=3

Edit: typo

This post has been edited by oilshocked: May 26 2005, 18:23
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