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.)

[2Bdecided]

There's subcode, HTOA, offsets, pregaps etc which you'll have varying degrees of success reading, depending on your drive and method - but apart from these, you can get the exact audio data back, and you are getting the exact audio data that was pressed.

Some audiophools don't believe this is the case, but some mastering engineers check exactly that: that the audio data from the pressed CD matches what they sent off. Sometimes it doesn't, but that's because another stage of unwanted signal manipulation was added to the chain by someone down the line - and that's exactly why they check it.

There's a study somewhere investigating the supposedly different "sound" of CDs glass mastered + pressed at different factories. They looked at the issue of the CDs (and master tape) being bit-identical very carefully.

Cheers,
David.