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Why can't you extract all the data on a factory-pressed CD when it
guest0190
post Sep 5 2012, 21:28
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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.)
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AndyH-ha
post Sep 5 2012, 22:19
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Do the offsets have anything to so with anything except timing? The audio data will be identical when extracted correctly, regardless of whether or not you pay any attention to the offsets. If the extracted tracks are not exact duplicates, bit for bit, of the source from which the CD was created, it is because something on the CD can't be read correctly, and this will differ due to offsets.

I think the majority of "mass produced CDs are still pressed, not written with laser on CD-R media. The read error rates are generally significantly higher on pressed CDs than on good computer written CD-Rs, but generally well within the range where perfect, bit for bit playback happens. I've never heard about any difficult with perfect extraction either. However, without the original source file to compare to your extraction from the CD, you have no way to know if your extraction is indeed identical.

I suppose these on-line databases that you can use to verify your extraction are based on other people's extractions. The assumption is that if everyone's work shows the same thing result, it is indeed correct. I would say that is a good assumption and worrying about it beyond that is not really different than worrying about stepping on sidewalk cracks.
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Posts in this topic
- guest0190   Why can't you extract all the data on a factory-pressed CD when it   Sep 5 2012, 21:28
- - AndyH-ha   Do the offsets have anything to so with anything e...   Sep 5 2012, 22:19
- - pisymbol   Is this the TAO (track at once) vs DAO/SAO (disc a...   Sep 5 2012, 22:59
- - 2Bdecided   There's subcode, HTOA, offsets, pregaps etc wh...   Sep 6 2012, 10:31
- - Rollin   If your drive has positive offset correction value...   Sep 6 2012, 14:09
|- - pisymbol   QUOTE (Rollin @ Sep 6 2012, 09:09) If you...   Sep 6 2012, 16:49
- - greynol   You need to take into account the offset of the bu...   Sep 6 2012, 15:11
- - greynol   Countless discussions on this forum, digital-inn, ...   Sep 6 2012, 17:31
|- - pisymbol   QUOTE (greynol @ Sep 6 2012, 12:31) Count...   Sep 6 2012, 20:15
- - Manlord   QUOTE (Rollin @ Sep 6 2012, 15:09) If you...   Sep 6 2012, 18:30
- - greynol   The greatest number of samples that can be replica...   Sep 6 2012, 18:55
- - guest0190   http://www.digital-inn.de/exact-audio-copy...se-of...   Sep 6 2012, 20:22
|- - db1989   QUOTE (guest0190 @ Sep 6 2012, 20:22) The...   Sep 6 2012, 21:24
- - greynol   Didn't we just have another discussion saying ...   Sep 7 2012, 01:51
- - hyman   QUOTE (greynol @ Sep 7 2012, 00:51) Didn...   Sep 7 2012, 08:12
|- - greynol   QUOTE (hyman @ Sep 7 2012, 00:12) From my...   Sep 7 2012, 12:30
- - guest0190   Thank you all for your answers. So if I understan...   Sep 7 2012, 16:15
|- - Porcus   QUOTE (guest0190 @ Sep 7 2012, 17:15) in ...   Sep 7 2012, 19:35
- - Manlord   QUOTE (guest0190 @ Sep 7 2012, 17:15) My ...   Sep 7 2012, 17:05
- - greynol   You won't be able to use CT to check titles ri...   Sep 7 2012, 17:10
- - guest0190   QUOTE You won't be able to use CT to check tit...   Sep 7 2012, 22:47
- - korth   Lack of programming to do cross-pressing verificat...   Sep 7 2012, 23:05


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