IpseDixit

I'm very sorry to bother you, I wouldn't do that if unnecesary. I've read information about offsets through all the net, including EAC, AR and the respective forums. I understand everything perfectly, but there's something that still not clear...

You mention you've determined the exact absolute offset for your Plextor once. You've discovered the quantity of samples that your drive was deviating from a sample you've considered the very first of a CD's 1st track, right?

Disc factories make discs with different "offsets" all the time (for media it's called skew, subchannel to main channel skew). They sometimes put the 1st sample of a recording in a point slightly far (+- 75 sectors skew) from the exact start of the disc (00:00.00). Wouldn't be optimal to take a disc that has no sub to main skew ("zero offset") as reference (we would have to contact mastering engineer)? Are your calculations aware of that?

In other words: does a "corrected" drive point to the 00:00.00 implicit sample of every disc, or just to the sample that seems to be the 1st for most recordings?

I think this thread may help to make my question clear to you: http://club.cdfreaks.com/showthread.php?t=111913&page=1
(you don't need to read it if you clearly saw my point).

BTW, was your offset correction a reference for PlexTools offset correction?

Thanks in advance.

Best Regards,
Charlie Hernandez.

IpseDixit

I still waiting for an answer.

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Carlos Hernandez Xpert tools - PerfectRip
Sony VAIO Digital Studio PCV-RX85M OC'd @ 2.65 GHz,
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Finally, the optical drives' OFFSET CONCLUSION.
Learn about CIRC, CRC & CD Physics.

IpseDixit

What if I tell you that I have done an experiment
with industrial CD encoders and found your
reference point is 30 samples off from
the real absolute zero?

Thanks again
for answering.

__________________
Carlos Hernandez Xpert tools - PerfectRip
Sony VAIO Digital Studio PCV-RX85M OC'd @ 2.65 GHz,
Pinnacle DC10Plus, Plextor PX-760A & PlexWriter Premium II.
Finally, the optical drives' OFFSET CONCLUSION.
Learn about CIRC, CRC & CD Physics.

Andre Wiethoff

Then I would say : Congratulations!
Just add (or substract) that number to the determnined offset and use that one instead... I had (and have) only limited instruments for measuring the real read offset. Anyway, the vast majority of CDs I measured at that time had the exact same offset (and most of them were from different studios and manufacturers!). So if around 6/10 CDs have the exact same offset, I must have come to the conclusion that this is the most valid offset. (And I did find some other offsets on CDs doing these tests...)
Therefore I never have stated that my offset is the absolute correct and only possible (zero) offset. My intention was not to find that absolute (zero) offset (but come as close to it as possible) in order to bring all drives to the same extraction results. I knew that I didn't have the tools to determine the absolute (zero) offset these days, but a partial success seemed to be better than none. Now all drives using offset correction will report the same data for a given CD (eg. very important for AccurateRip or to compare audio otherwise), so only this relative offset is really important for everyday use (at least for EAC).
That is also the reason (even though I believe you!) I will (can!) not change the offsets in EAC any more. Too many results and databases depends on the (now fixed) offset. The AccurateRip database had to be deleted completely and setup anew (and be populated) for changing the offset only by 1 sample...
So feel free to use this 30 samples moved offset within EAC, if you are perfectionist then you will probably not use EACs determined offset anymore...
For other users (that may also be perfectionists to that level), please give the direction in which the absolute offset is 30 samples away from EACs? E.g. if EACs proposed read offset was +679 would the correct read offset be +649 or +709? Thanks! (If I need to guess, I would say it is 30 samples less, this would bring some Plextor drives exactly to a +0 read offset )

Regards,

Andre

IpseDixit

Thanks.
Thanks for being so honest.
Oh, pity
Afirmative!
Again, right.

__________________
Carlos Hernandez Xpert tools - PerfectRip
Sony VAIO Digital Studio PCV-RX85M OC'd @ 2.65 GHz,
Pinnacle DC10Plus, Plextor PX-760A & PlexWriter Premium II.
Finally, the optical drives' OFFSET CONCLUSION.
Learn about CIRC, CRC & CD Physics.

TheLegioneer

So are you suggesting that for me to get an extraction as close as possible to the original pressed audio disc, I should leave my read sample offset correction at +0?

I can see in PlexTools that the audio read offset of my PX-PREMIUM is -120 bytes = -30 samples, or a +30 offset correction in EAC. Are you saying that PlexTools is wrong as well?

Just trying to wrap my head around this...

Thanks!

IpseDixit

Yes.

Yes.

__________________
Carlos Hernandez Xpert tools - PerfectRip
Sony VAIO Digital Studio PCV-RX85M OC'd @ 2.65 GHz,
Pinnacle DC10Plus, Plextor PX-760A & PlexWriter Premium II.
Finally, the optical drives' OFFSET CONCLUSION.
Learn about CIRC, CRC & CD Physics.

Andre Wiethoff

Plextools only build in the offset correction after some users asking for it (after having it seen in EAC), so they just take the offsets etc. like in EAC exactly into Plextools... Which is basically ok, as for having the same offsets in both programs in order to compare the results.

cu, Andre

Aquarium

I don't know if this is helpful but after reading this thread I compared how a rip sounded with a Lite-On drive(+6 -6 EAC).First I ripped as I would normally with the prevous settings then I adjusted the read value to -24 to account for the postulated -30 that are missing from "true zero" offset.I hear a definite improvement in sound overall(Love And Theft-Bob Dylan).The "hissing" was removed from the drum cymbals in the foreground and seemed to be accurrate.Some more percussive details,all round,better enunciated vocal-the whole CD showed general improvement.I also left "no use of null samples" unchecked following another recent thread and I think this works to improve the sound also.It seems to make everything more "analogue" sounding as they say.

JeanLuc

Excuse me ... but CD read offset correction has absolutely nothing to do with sound quality. It's just about getting a reference starting point for each track on the CD.

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spare

Good Morning !!!

Are you sure about this ??
Since you're the one with a "privileged connection to them", could we have a quote ???



What ???
I thought that the point of all of us using and liking EAC was to get a perfect copy of a CD for archival (protection against damage, and usability) purposes at least ??!!!
The advantage of you making a free piece of software is that it can and should be modified to be as good as it can be!!
So what if a lot of databases depend on whatever ??? None of those databases will cease functioning just because "we" try to improve the system !!!
If "we" can do better, we must, or as you say, should do better !!!
The old databases will still be there for anyone who wants to use them.
The mantainers only have to initialize a new one...
All the "work" of populating them is up to the users, they will decide either to do it or not !! I WANT to do it !! (newcomers, would be able/want to do it...)
But if you don't improve your software, and the Accurip mantainers don't improve theirs, then I Won't Be Able To... !!!

Because even if i have results i won't be able to compare/guarantee them !!!
(This will only open the space for someone to try clonning the databases and your software, bringing "more" anarchy to a once quieter and "nicer" world)


This brings me to my usual question:

"Is a perfect CD Copy, really possible??"

"If so, where do i find a tutorial that shows me how to do it ??"
(i find the forums very confusing)

All i can say is that:
"Although i don't understand a lot of this (and i'd like to) I'm very disapointed..."

spare

greynol

So much grief over something so trivial and inaudible, I cannot believe it!

Copying a CD not only involves reading, it involves writing as well. Whether you continue to use EAC the way you've done in the past or you've changed your offset per this new revelation (which IpseDixit has only stated here without giving any evidence to support the claim, BTW), your copies will not be any different except for the possibility that 30 non-silent samples at the beginning will be replaced by silence; but the absolute position of the audio on the copy will indeed remain the same!

EDIT: In the case of the Plextor drives that have a +30 sample read offset correction and -30 write samples offset according to the currently accepted standard, ripping and burning without a configured offset gives you back those beginning 30 samples that were previously ignored. The flip side is now the 30 samples at the end are ignored. These are the same samples some people were so proud to be able to get because the drive could overread from the lead-out. The irony to all that was it wasn't ever possible to burn those last 30 samples so they ended up being lost anyway. So if this new offset is correct, these Plextor drives would indeed be able to duplicate every calibrated sample and maintain the proper length of the last track without the need to apply any correction. An obvious consequence to this is that just about any burning software can be used except PlexTools!

IpseDixit

I've talked to Rich Wall, at DCA (Doug Carson and Associates),
THE optical disc encoder company (www.dcainc.com),
he allowed me to disclose about the offset experiment:
he prepared a DDP file (Disc Descriptor Protocol) for me
where 1st byte of 00: 02.00 was !00 and encoded it
in a MIS VIII encoder (http://www.dcainc.com/products/MIS/MIS_V8/),
then captured signal from LBR (Laser Beam Recorder) into a bitstream
in a raw reading file, discovering encoder places main channel's 1st byte
aligned into channel frame 00: 02.00, then came genial Mr. Sidney Cadot
(http://ch.tudelft.nl/~sidney/) with his FPGA audio readout system
(http://club.cdfreaks.com/showthread.php?t=111913 ), made with an
old drive which precisely returns such !00 when asked for 00:02.00,
Then I concluded when I saw such drive in Wiethoff's database having
a +30 samples offset correction.

__________________
Carlos Hernandez Xpert tools - PerfectRip
Sony VAIO Digital Studio PCV-RX85M OC'd @ 2.65 GHz,
Pinnacle DC10Plus, Plextor PX-760A & PlexWriter Premium II.
Finally, the optical drives' OFFSET CONCLUSION.
Learn about CIRC, CRC & CD Physics.

Aquarium

I know this thread is about finding the correct offset position to start to read a CD,but any contributions were invited and I feel I have discovered an important aspect of results to expect.I do use properly regulated AC power(eliminating power issues)so my CD's always sound better than most normally.All I can report is that this new setting through my sensitive system yields good audible results and this is what is looked for.Please refrain from avoiding the obvious calamity.

greynol

Aquarium,

Please realize that I mean you no disrespect, but it doesn't seem to me that you understand what an offset does to audio data.

If you don't mind me asking, were your tests sighted or blind?

IOW, did you know ahead of time what it was that you were listening to?

If yes, I recommend you use an ABX test to deteremine if you really hear a difference or if your mind is playing tricks on you. It is clear to me that the latter is true.

foobar2000 is a good player that allows you to perform ABX tests which you can use on the source files used to burn your copies.

It would also be useful for you to know that it is very easy to obtain two copies of the same CD that differ only by an offset, just like we're discussing here. Do you really think one is going to sound better than the other?