I read on the Coaster Factory a while back about EAC's offset correction value. From the guide, I was informed that EAC uses a correction value rather than a typical offset value: you tell it how to correct your drive's offset, essentially entering the value that is the opposit of your drive's offset value. So if my drive has a +12 offset, I enter -12 in the "EAC Offset Correction" field under Drive Options. Here's a mirror of the guide for clarification. The specific paragraph I refer to is:

My question is, is my logic correct? I am in doubt because I spoke with Chris Myden (owner of *****) who has told me that he and one of his operators at ***** believe that the field in EAC is for entering your drive's actual offset. His operator's response on the matter:


I think the main confusion lies in the statement, "EAC 0.9 prebeta 8 the read offset in EAC has the more correct read samples offset correction value name." I interpret this to mean that EAC fixed the name of the field; it now states in the options that it is a "correction value," but it could also be interpret to say that they changed the field itself.

Who is right in this matter?

Thanks,
CyberInferno


MOD.: no links to or names of sharing groups, thank you.

You are both correct. The value EAC gives you should go unmodified to the settings. But the value that EAC gives you are the offset correction value. NOT the real offset. FYI I have never seen a program that reports the real offset. They write the offset correction value.

What about PlexTools? I think the values it give are the "actual" drive offsets, not corrections. But it's still confusing. I have a PX-W2410A, and I created an offset test CD using EAC 0.95pb5, and checked my drive using the disc. EAC reports a correction value of +92 for read offset. But, according to PlexTools (latest 2.11 version), my drive's audio read offset is -392.

I have +92 as the read sample offset correction value in EAC, but I don't see the logic behind the values...

Am I right using +92 for read offset in EAC?

So if I know that my drive has a +12 actual offset (determined by Accurip and other offset databases), this line from my log reflects the correct setting?:
"Read offset correction : -12"

EAC reports the drive's read offset correction which is the negated read offset value.

The write offset in EAC's dialog box is the real write offset.

Plextools do report the real offsets - for reading and writing.

If that's true, why does PlexTools report my drive has a "real" read offset of -392, but the offset correction in EAC is only +92? Am I misunderstanding something, it seems that if my drive's real read offset is -392, then the offset correction should be +392? Still confused...

ah .. Plextools report the byte offset whereas eac reports sample offsets ... 1 sample = 4 bytes

AccurateRip should give the same read offset value as EAC. the correction value.

Aha... that is making more sense. Why then the difference, as 92 x 4 is 368, not 392?

If I am not mistaken you can only find the combined offset using a test cd created by EAC.

I'm not concerned with combined offset, I don't burn audio CD's using EAC. Unless I'm wrong, combined offset is only needed when reading and burning CD's. I'm only reading CD's with EAC, so I'm only concerned with the read offset.

Unless I'm confused?

exactly. that is why the offset you found with EAC using a test cd created by EAC is useless. you need to find the offset with the EAC cd database or accuraterip database or plextools.

So, you're essentially saying that the EAC test CD is useless for determining the read offset? I thought that was the whole purpose of the test CD...

So, I know my drive's offset is -392 using PlexTools, is my correct read offset supposed to be +98 (392 / 4)?

the EAC test cd is used to find the combined offset so that you can calculate the write offset when you have the read offset.

Are you sure about that? I just ran the test again using the EAC offset test CD, and it specifically says the result is the read offset (only), it does not say it's the combined read/write offset. It recognizes the CD as the EAC offset test CD.

The function is labeled "detect read offset sample correction", which also tells me it's only for determining read offset. So either the functions in EAC are mislabeled, or I have grossly misunderstood something. Can you clarify this?

The offset is 98, bzw ... not 92

Yes I am sure. the boxes to set the combined and read offset in EAC does the same. there are just 2 so that you can switch. Since you burned the cd yourself without using write offset you will get the combined offset when reading the offset from the test cd.

EAC will give you two possible choices:

1. burn the test offset cd with the correct write offset

that way, you can use your cd to determine any drive's read offset correction

2. burn the test offset cd with a write offset of 0

that way, you can determine your combined read/write offset

OK, looks I should be using +98 instead of +92 for my read offset. Since I've been using +92 for ripping quite a few CD's, is it likely I will hear the difference of 6 samples?

no ... absolutely not ... most tracks start with silence anyway

And if I'm correct in my calculations, the 6 samples equals only .08 seconds. Correct? Not likely to be noticeable except on maybe a few tracks, like ones that start with a cymbal crash, etc...

6 samples equal 0,000136 seconds from my calc. since 44100 samples per second are being transferred in CDDA pcm ;-)

Once again, don't forget that commercial CDs are ofsetted too. Correcting offset doesn't give you a more accurate rip, since the factory can perfectly make the CD with an offset of +1500, for example.
Correcting offset gives you a calibrated ripping system that allows to compare CRCs between your drives, joining tracks read by different drives, using AccurateRip (= comparing CRCs with other people), ripping accurately CDRs burned by people using write offset correction....

So, I click "Detect read sample offset correction...", then it finds for example +12, I click "Apply", and in the "read sample offset correction value" it puts +12, not -12, is it correct or is it buggy? Should I leave +12 there or change it to -12?

EDIT: And what about write sample offset? If I calculated it's -6, should I enter -6 or +6?

You should enter the value "Detect read sample offset correction..." finds and not change it. You find the offset correction value and that is what eac wants in that box.


if you calculate the write offset like this:
write offset = [combined read/write offset correction] - [read offset correction]

you get the actual write offset and that is what EAC wants in the write offset setting.

Well that's bad news for me. I thought the Accurip value I got (+12) was an actual offset value and thus set EAC to use -12. Back to the ripping mills it is.

At least I learned the real offset of my drive: -12 samples / -3 bytes

It's actually -48 bytes

Thanks for the correction.

Thanks to everyone who replied. This was very informative. I'm glad this came at a time when I can at least contribute to the Accurip database (via EAC 0.95pb5).