Why can't you extract all the data on a factory-pressed CD when it Options

[guest0190]

In the past when I have burned a CD with EAC (with read and write offset correction values consistent with Andre Wiethoff's reference), I have been able to rip files from it identical to the source files.

Based on what I could gather from this forum, I used to be of the conviction that with a drive capable of overreading and overwriting, the exact same files that were burned to a CD can be extracted from it again, and that the only disadvantage of using a drive not capable of overreading was that a few samples at the beginning or end of the first or last audio file would be replaced with silence, regardless of what the samples originally contained.

Recently, however, it has come to my understanding that it is very hard (or even impossible) to extract the original files that were burned to it from a mass-produced CD.

My question is simple: How is it that I can rip files identical to the source files from a CD I have burned myself, but not from one that is factory-pressed? And, perhaps more importantly, how is it that I managed to achieve this using 'incorrect' offset values?

I apologise in advance for any difficulty I might have understanding any mathematical arguments you put forth. I fear I am slightly dyscalculic.

(I have decided, henceforth, to rip using the 'ideal scenario' reference which is 30 samples before that established by Mr Wiethoff, but I am not sure if it is relevant.)

[guest0190]

Thank you all for your answers.

So if I understand this correctly, any uncertainty in the situation stems from the fact that in order to extract the unaltered files that were written to it from any given CD, one would need to know the write offset of the drive that wrote it (or, in the case of commercial CDs, the write offset of the drive that wrote the master CD)? I can certainly understand how that is not a feasible scenario!

My drive has an AccurateRip-configured read offset correction of +6. Does that mean it should be changed to -24, should I wish to follow the newer reference?

[Porcus]

in order to extract the unaltered files that were written to it from any given CD, one would need to know the write offset of the drive that wrote it (or, in the case of commercial CDs, the write offset of the drive that wrote the master CD)?

Yes. So the +30 or -30 won't matter much, and you can rather stick to the EAC suggestion.

Unless you know the write offset used by the master plant / writer,
- your files will be offset by an unknown number
- if you take care of the offset when burning, you will still get the same audio as on the pressed CD
- ... which is also offset by an unknown number.

Your files and the CD will differ by 30, and two wrongs don't make a right, but I wouldn't (and I don't) worry.

This post has been edited by Porcus: Sep 7 2012, 19:44