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Question regarding offsets
Allytronic
post Feb 18 2010, 00:40
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Two years ago I downloaded an album ripped in FLAC. According to the log file, the drive used was a SONY DVD RW DRU-800A. The ripper configured EAC to use "Combined read/write offset correction : 0".

According to this page, the combined read/write offset correction for the drive should be +6, not zero.

Recently, I downloaded the same album, ripped again in 2009 by the same person. This time he used a different drive (SONY DVD RW AW-G170A), and configured EAC to use "Read offset correction : 48", which is the correct read offset for that drive, according to the Accurate Rip database.

Out of curiosity I compared the tracks from both rips with Foobar's bit-compare utility, expecting to find sample differences, but Foobar says the tracks are identical, except for the last ones.

I would understand the tracks being identical if the guy had used the correct combined offset in the first rip, but since he didn't, shouldn't ALL tracks show a sample difference? I don't get it. Is something else regarding combined read/write offsets that I'm missing here?

If anyone can enlighten me on the issue, I appreciate it. Thanks in advance.
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greynol
post Feb 18 2010, 01:20
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First, buy the disc so you don't have to worry about it.

Second, please make an effort to choose the correct forum before posting. Your topic is clearly about ripping and as such belongs in the CD Hardware/Software forum, which, if you look here, is described as "Discussion of CD-ROM/-R/-RW/DVD-hardware, copying, ripping and burning of CD media, EAC, CDex, Plextools etc." Our Terms of Service, to which you agreed upon choosing to register, specifically states that "all new threads must be started in the correct forum categories". We have an expectation that all members follow these terms. Your topic does not belong in the General Audio forum. If you had read the posts that are pinned to the top of that forum you would have seen read this one. We also have an expectation that our members read stickies before posting as well.

Now on to your question...

EAC had a bug that would, depending on certain factors, cause the log files to report a combined read/write offset correction of zero when AccurateRip was enabled. IIRC, depending on how you were ripping EAC might either use the AR-configured offset or the combined read/write offset, but in the case of standard ripping of separate tracks with gaps appended, the AR-configured offset was what was used. This perfectly explains why your tracks were identical. That the last track was not identical can be explained by the two drives having different offsets with at least one of them being configured as not being able to overread.

Unless you are using a burner with the same write offset as the drive for which you provided that link, the combined read/write offset is of no use to you whatsoever. The read offset correction is only thing that matters.

This post has been edited by greynol: Feb 18 2010, 01:24


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