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]

http://www.digital-inn.de/exact-audio-copy...se-offsets.html
http://www.digital-inn.de/exact-audio-copy...ay-offsets.html
http://www.hydrogenaudio.org/forums/index....showtopic=50301
http://club.myce.com/f61/offsets-handling-...channel-111913/

There are a few links relevant to the topic. I am not sure if any of them explicitly states that the differences between these two references (which I will readily admit I do not understand in the first place) prevents extraction of the same files that were burned to the CD, but that was how I interpreted it.

The bottom line, as far as I can tell, seems to be that it is hard to tell where the actual data on the CD starts. (I have previously shared with greynol that this strikes me as unintuitive, as I feel that the CD drive should have no problem recognising where the little pits on the surface of the disc start and where they end - but that is an aside.)

Again, my problem is that I have a hard time understanding how this is consistent with the fact that my own experiments showed me that I could indeed get the same files back from a CD that I burned to it.

Another, albeit related, thing that confuses me, is how I were able to accomplish this despite my drive consistently reading 30 samples prior to where it 'should' be reading. I suspect the answer lies in basic math, but nonetheless, I would be glad if someone could clarify.