@Andre Wiethoff and who feels to have a say on offsets.

Discussion in 'Exact Audio Copy - English' started by IpseDixit, Jan 14, 2005.

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  1. IpseDixit

    IpseDixit New Member

    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.
  2. IpseDixit

    IpseDixit New Member


    :24: I still waiting for an answer.
  3. IpseDixit

    IpseDixit New Member

    What about this?

    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.
  4. Andre Wiethoff

    Andre Wiethoff <font color="#FF0000">E.A.C. Coder</font><br><img

    Then I would say : Congratulations! :11:
    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 :13:)


  5. IpseDixit

    IpseDixit New Member

    Very nice conclusion.

    Thanks for being so honest.
    Oh, pity:44:
    Again, right. :1:
  6. TheLegioneer

    TheLegioneer New Member

    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...

  7. IpseDixit

    IpseDixit New Member


  8. Andre Wiethoff

    Andre Wiethoff <font color="#FF0000">E.A.C. Coder</font><br><img

    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
  9. Aquarium

    Aquarium New Member

    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.
  10. JeanLuc

    JeanLuc Member Deluxe

    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.
  11. spare

    spare New Member


    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..."

  12. greynol

    greynol Member Deluxe

    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!
    Last edited: Nov 22, 2006
  13. IpseDixit

    IpseDixit New Member

    This is all I've got.

    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.
  14. Aquarium

    Aquarium New Member

    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.
    Last edited: Nov 20, 2006
  15. greynol

    greynol Member Deluxe


    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?
    Last edited: Nov 20, 2006
  16. Aquarium

    Aquarium New Member

    I have a good ear for music and play an instrument so I think I can gauge when something is right rather than obviously incorrect!(and Lo-Fi is a myth).I have issues with anyone that does not use proper AC line conditioning for their digital components and computers,because bluntly it makes a hell of a difference.I know how poor CD's sound compared to one burnt in my system and I am reporting here I find further improvement with the new offset.
  17. greynol

    greynol Member Deluxe

    JeanLuc is right, offsets have nothing to do with sound quality (nor does the use of null samples in CRC calculations!).

    I'm not going to discuss this with you any longer other than to say that you shouldn't be surprised when people don't take you seriously.
    Last edited: Nov 20, 2006
  18. Aquarium

    Aquarium New Member

    I heard the differences I heard is all I can say to this.I do not claim to be any sort of technical expert and would concede that to you.I tested "That's All Right Mama" from Elvis 2 just to make sure again and the improvements I noted before were all there.The new offset was better than EAC's.There is no reason why it shouldn't be so as I was getting better CD's using just line conditioning before I discovered EAC.Everything is coming together better and I hear it.In a blind test it really would not be an issue because a veil is lifted quite noticeably and more detail is present.Needless to say I will use the new offset in future.
  19. Hunter

    Hunter Guest

    re: offsets

    If you are so certain that you could head the difference in an ABX blind test, could you please try and share your results? I would be very interested to see the outcome. :)
  20. Aquarium

    Aquarium New Member

    There is a major issue here and that is one I can't do much about unfortunately.The fact that I use a dedicated AC line filter and conditioner that gives me the ability to run all my digital and computer components,AT THE ABSOLUTELY CORRECT VOLTAGE without issues that effect hardware performance.Now this means that I can't really give you a sample that would be meaningful unless your system was at least as sensitive as mine.Sound issues I know,occur just because of the lack of regulated power and it is not pretty.Now I would only advise that if you care about sound,invest in line conditioning at the audiophile level anyway-you have not heard what EAC can do until you have.Yes my CD's are the best in the world.
    Last edited: Nov 20, 2006
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