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Writing Quality v2.0 article finally up! - 1/13/2003 2:03:19 AM   
john

 

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The "old" article is now splitted at 4 major articles:

a) Writing Quality (contains all the technical stuff)
b) Testing Media Quality (contains all the testing software)
c) Testing C2 Error information (the titles says it all)
d) Jitter Tests (probably the most interesting...)

There will be some changes in the upcoming days, adding more Jitter tests.

PS. There is a *special* PDF version over here available that contains all the above articles (self extract WinRAR v3.0, 2.7mb sized)
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RE: Writing Quality v2.0 article finally up! - 1/13/2003 3:49:03 AM   
Clint


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The Jitter Tests article is amoung the most interesting, since it compares Plextor, Yamaha & Teac's jitter reducing methods (VariRec, Advanced AudioMaster Quality Recording & Boost technologies). Plus, the results of low-speed recording VS high-speed recording quality, which drive/media produces the best quality... It's all there!!!

The results are quite surprising in some areas, however you must read to know what I'm talking about..



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RE: Writing Quality v2.0 article finally up! - 1/13/2003 5:16:49 AM   
valnar

 

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Excellent article. However, I would love to see how "normal" CDR drives did against the special features of the Plextor and Yamaha. For instance, the new 52x LiteOn seems to be a real winner with data and C1/C2. How does it do with audio jitter at 4x or 8x?

Robert

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RE: Writing Quality v2.0 article finally up! - 1/13/2003 11:06:43 AM   
Clint


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quote:
Originally posted by valnar

Excellent article. However, I would love to see how "normal" CDR drives did against the special features of the Plextor and Yamaha. For instance, the new 52x LiteOn seems to be a real winner with data and C1/C2. How does it do with audio jitter at 4x or 8x?

Robert



Yes, great question. I'm sure such tests can also be added... 3T pit & land jitter results with a LTR-52246S based recorder (and ASUS CRW-5224A) VS. AAMQR and/or VeriRec and/or Boost at 1X~8X times nominal speed would be interesting - is that what you're proposing [?]

We however have 3T pit and land jitter value measurements for those drives at max speed. Also maybe a few extra different types of media could possibly be added



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RE: Writing Quality v2.0 article finally up! - 1/13/2003 11:23:12 AM   
Dolphinius_Rex


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yes, I would like to other media tested! especially since I am in the process of testing the Ritek media used, myself (literally, I'm burning it RIGHT now LOL!). I'd like to see how it stands up to Mitsui, or Taiyo Yuden's.


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RE: Writing Quality v2.0 article finally up! - 1/13/2003 12:17:50 PM   
john

 

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Thanks for your comments, we were sure that the results would be interesting, since as it seems C1/C2 scans with normal un-modified drives are at least not compareable...People who have d/l the pdf version check out pages 106-113 to see what i am talking about. The web version will come soon at the site. The Jitter tests are performed according to the standards, so we have very high accuracy

As for the near future, LiteOn LTR-52246S 4X-48X are coming. We may add more tests results with more media. Stay tuned!


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RE: Writing Quality v2.0 article finally up! - 1/13/2003 3:19:11 PM   
valnar

 

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Yes John, that was my idea. I use a 52x LiteOn but rarely every burn above 24x anyway. Seeing how audio works with good media, like Taiyo or Mitsui, at 4x and 8x would be beneficial for many users. If there isn't good reason to augment my LiteOn with a Plextor or Yamaha for music recording, I'd like to know!

Robert

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RE: Writing Quality v2.0 article finally up! - 1/29/2003 1:57:11 PM   
Halcyon

 

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John,

thank you for an excellent article.

It contains a wealth of information, but is in many parts very difficult to understand 100% unambigiously (for important parts).

The parts I did not understand:

1) How can you prove/measure which software if the best in determining C2 accuracy? Why were EAC and Nero CD speed chosen?

2) C2 pointers vs C1/C2 measurement. I really did not understand that paragraph at all. I read it seven times (p. 91).

3) As I understand it, the EAC test CD (if you make one according the tips from EAC author) can be overly scratched or too scratched and the test data from DAE Accuracy test will be skewed due to this. How can one avoid doing too or too little scratched test disc?

4) CD Speed C2 testing results (p. 105). What does the number of 'C2 errors reported' imply? Higher number could mean bad servo/optical tracking OR it could mean higher accuracy in finding C2 errors. Like you correctly state, rereading the same disc in one reader several times may produce different results (EAC author strongly agrees on this).

In short, does this mean that LTR_32123S is the best (in tracking / servo) or that LTR-52246S is the best?

Also, were the results of 'C2 errors reported' and 'C2 errors missed' averaged over several times or with just one test? Would the results vary, if the test was done several times and results averaged?

5) Comparing drives (p. 107 onwards). What do the 'C1 average' and 'C2 average' results imply? The one with the lowest number of errors is the best drive (IF and ONLY if it is 100% accurate in reporting C1/C2 errors)? Or something else? I'm confused. Sorry :(


6) Will you test with CD-Check also? It's listed on the page (106), but not to be found in the PDF test data. I know, I don't want to harass you on this, as you've already done a HUGE amount of work. But if you've already done the tests, but they were just somehow forgotten from the report...

7) CDR writing accuracy (p. 134 onwards). Do you have access to a professional calibrated C1/C2/EFM/etc measurement drive? It'd be interesting to find out not ONLY the jitter data of each drive, but also how well they write in regards to error rate at higher speeds.

I'm very skeptical about any writer writing comfortably below the CD specification tolerances at 52x, but I haven't found any good data on this? I know Digit-Life authors have access to a professional tester. Maybe you could team up?

8) Do you have any more information where JVC K2 tech will be used? Only XRCD CD pressing or cd-burners as well? If you have any additional information, I'm dying to know :)

Also, can you tell us where can one obtain Abex (Almedio) test CDs in Europe? The distributor has not answered my e-mails.

Please do NOT by any means understand these as a criticism. Your wealth of knowledge and amount of work on the issue is staggering.

I just want to make sure I understand what you are saying (or writing, to be more exact).

And once more. Thank you for an excellent article. If you need any help with proof reading or such, I'd be happy to help (you should have my e-mail as I've already e-mailed you via the functionality of
this board).

Best regards,
Halcyon


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RE: Writing Quality v2.0 article finally up! - 1/29/2003 3:30:25 PM   
john

 

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thank you for an excellent article.

Thanks for your comments! The article contains all the information we gathered around the Internet among with our personnal research. We will try to keep up the subject updated...

> 1) How can you prove/measure which software if the best in determining C2 accuracy? Why were EAC and Nero CD speed chosen?

I cannot prove anything, there are only 2 utilities that can measure C2 % Accuracy, if any other util comes out we may also test it. Remember that both utilities base their test results according to the reported errors from the drives that comply to the MMC standard. Many other drives may support *perfect* but with unknown commands to the software authors so are un-usable for us!

> 2) C2 pointers vs C1/C2 measurement. I really did not understand that paragraph at all. I read it seven times (p. 91).

The whole meaning of this paragrath was to explain that ALL drives can report C1/C2 errors (!) but not all drives have the same C2% accuracy. Can you see the difference?

> 3) How can one avoid doing too or too little scratched test disc?

Hmm..We made several attempts to create the disc. I cannot show you how to do it, but just try to be gentle with the scratches!

> 4) What does the number of 'C2 errors reported' imply

The number of C2 errors reported from the drive and measured from the CDSpeed software. As you may seen, the total number of C2 errors is not the same with all drives as someone may expected. Users should expect some variations if they read the same disc many times, but not above +/- 5-10%. The differences between drives can be explained to different optics/chipsets.

I would say that if you also look later on, the C1/C2 errors reported from various LiteOn drives, the LiteOn LTR-52246S series seems to be the best for reading C1/C2 errors. Of course someone may argue with this, meaning using the drive that returns the lower error rate, instead of using the drive that returns the worst error rates (that disc would be un-readable in that reader)...

> 'C2 errors reported' and 'C2 errors missed' averaged

No the test results were posted only after tested one time. You are right that we should have done the tests several times and averaged, we hope to update the article soon, free time is very limited as you may understand

> What do the 'C1 average' and 'C2 average' results imply?

The numbers taken as the CD Doctor software measured (and reported from the drive).

> one with the lowest number of errors is the best drive or something else? I'm confused. Sorry :(

It depends...Lets pass to the next question

> 6) Will you test with CD-Check also?

CD-Check? I don't understand

> 7) CDR writing accuracy (p. 134 onwards).

Yes we decided to use for now on, only Jitter test results. The main reason is that 3T Jitter measures the writing quality absolute, while C1/C2 errors may affected from surface problems (dust etc..)

> Maybe you could team up?

I don't know, this would be difficult, we are not close [:I]

> Do you have any more information where JVC K2 tech will be used?

Will be used in future pressed "protected" Audio discs. If you read the information, it speaks about improvement during the mastering process. We won't see that such technology in personal recorders i imagine

>can you tell us where can one obtain Abex (Almedio) test CDs in Europe

Try this company, its their European distributor

Hansa Contec GmbH, Schopenstehl 22, D - 20095 Hamburg, Germany
Tel : ++49 (0)40/ 333 956 22
Fax : ++49 (0)40/ 333 956 56

> Please do NOT by any means understand these as a criticism.

No problem, keep asking


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RE: Writing Quality v2.0 article finally up! - 1/29/2003 6:30:39 PM   
Halcyon

 

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quote:
Originally posted by john
I cannot prove anything, there are only 2 utilities that can measure C2 % Accuracy.



Ok.

I think it is still possible that a drive:

1. Reads an error from the disc (physical or data level)
2. Does not report (via MMC) C1/C2 error as having happened
3. Does not correct C1/C2 error data
4. Conceals the error in the corresponding audio file

Or is this kind of scenario implausible in your opinion?

I had a Hitachi GD-7500 dvd-rom drive that couldn't give
C2 error flags via the MMC command set and the concealment
sometimes worked (although mostly not :)

quote:

errors from the drives that comply to the MMC standard. Many other drives may support *perfect* but with unknown commands to the software authors so are un-usable for us!



I understand. I think it's the manufacturer's loss if they do not
provide information on their special commands.

The software used by people in the future will be free and non-propietary anyway, so no-one will trust manufacturer X, even if they claim (but can't achieve under the MMC command set) a 100% C2 accuracy.

Nobody will believe drives that need special programs to perform well and the superiority of which nobody can verify for themselves :)

I'm glad you are making this thing clear.

quote:

The whole meaning of this paragrath was to explain that ALL drives can report C1/C2 errors (!) but not all drives have the same C2% accuracy. Can you see the difference?



Yes, I get it now, but I think the paragraph is a little difficult to understand :)

--

Do you have a test disc for which you KNOW (ie. have the manufacturer's specs) that how many C1 errors and C2 errors it has?

These would have to be data level (not physical layer) errors on the disc.

It would be easy to test the drives then to find out if they can spot all C1 and C2 errors and report them back accurately.

The problem with physical level errors (scratches), which can lead to C1/C2 errors is, that they are hugely dependent on many factors such as servo, laser, amplification, sensor, etc performance. And the results can vary (AFAIK) from one reading to another (using the same disc and the same drive).

Hence, it becomes very difficult to measure which drive reports all C2 errors accurately, unless we know how many errors there are on the disc, right?

quote:

Hmm..We made several attempts to create the disc. I cannot show you how to do it, but just try to be gentle with the scratches!



Ok, thanks. Will do.

However, I'm not sure I'm convinced that the EAC DAE quality test with the hand made test is the best approach to determining C2 accuracy... More like servo/pickup performance :)

quote:

I would say that if you also look later on, the C1/C2 errors reported from various LiteOn drives, the LiteOn LTR-52246S series seems to be the best for reading C1/C2 errors. Of course someone may argue with this, meaning using the drive that returns the lower error rate, instead of using the drive that returns the worst error rates (that disc would be un-readable in that reader)...



This was exactly my point ("someone may argue...").

With a test disc that has errors on the physical level of the disc (data is encoded/pressed/burned on the disc error free, but the disc has physical scratches/smudges/dirt/markings), a perfect reader should fulfill FOUR conditions:

A) report back as few errors as possible, which would imply superior reading of the disc and error free reading of the data, even under difficult conditions (this only applies if condition B is met also). In CD Speed test, as low count of C2 errors flagged by the drive as possible (zero).

B) report back ALL errors that it encounters (i.e. effects of physical level problems that the reading mechanism cannot circumvent, resulting in corrupted data, which may or may not be corrected by C2). In CD speed test this should be as high C2 accuracy as possible (100%)

C) Correct as many bits of contiguous lost data as possible (according to my reference books, the C2 error correction performance of all drive is not similar. Hence not all can correct E31 errors that some drives can).

D) Do all of the above while maintaining the highest possible reading speed (i.e. 38x or somesuch).

In fact, this is initially what I thought your test from page 99 onwards did, but I don't know what kind of a test disc (Abex TCD-721R) is: are errors on data layer, physical layer or both?

Also, I don't know how to actually test the C2 error correction capability of the drive's internal circuits, unless one uses a data layer error test disc, which has progressively difficult errors on the data level (one such contiguous error per track). This disc would have to be ripped one track at a time and see how far (how many bits of contiguous data) the internal C2 implementation can correct.

Do you know if anybody makes such a test disc?

BTW, If the test disc you've used has errors on the physical layer, then how can the program calculate the amount of C2 errors missed and C2 accuracy, when the amount of C2 errors read is dependent on the a) chance, b) phase of the moon, d) quantum probability, and e) the pickup/servo of the drive?

That is, a drive may flag and report X or Y number of C2 errors on a disc that has scratches.

How many C2 errors did it miss, if it reported X in total? How many did it miss, if it reported Y total?

I don't understand. Sorry :(


quote:

No the test results were posted only after tested one time. You are right that we should have done the tests several times and averaged, we hope to update the article soon, free time is very limited as you
may understand



Please don't take it as a criticism. I was just asking how you did it. You're efforts are REALLY appreciated. I would have done this myself, if I knew how :) YOu have taught me so much new things. And I know personally how time consuming testing can be (I've done testing for several dvd-rom drives with EAC and the CD-Check test disc myself).

quote:

The numbers taken as the CD Doctor software measured (and reported from the drive).



Yes, but I don't understand if a high or low is better and why :(

quote:

CD-Check? I don't understand



Comparing drives / Procedure (on page 106):

"The Total number of the test discs was eight (8):

...

CD-Check"

Does that mean the 'Cd-Check' test disc by Digital Recordings?

I've used that myself as a crude physical level error test disc with DAE testing myself (don't have Abex discs, yet).

quote:

Yes we decided to use for now on, only Jitter test results. The main reason is that 3T Jitter measures the writing quality absolute, while C1/C2 errors may affected from surface problems (dust etc..)



Very good point. I don't exactly know what variables may change from burner to burner (with same media). If it's just land/pit jitter, then that's truly the ultimate measure.

quote:

I don't know, this would be difficult, we are not close [:I]



I know :) But there's always the postal service that can carry a test packet of 8 burned CDs quite cheaply <hint> :)

quote:
Will be used in future pressed "protected" Audio discs. If you read the information, it speaks about improvement during the mastering process. We won't see that such technology in personal recorders i imagine



Actually even a burner is a 'mastering' device in a sense.

It gets PCM data, encodes it according to CD standard and then tries to control the servos and the laser as well as possible to ensure a proper 'master' (I'm using the word 'master' in quotation marks as the word is usually reserved to glass masters for CD pressing. Still, the basic principle are the same sans).

But I digress, yes... it looks like a combination of a copy control technology and 'improved audio' marketing device :)

Thanks for the Almedio link as well. I just got a reply today.

Best regards,
Halcyon

PS I noticed several minor technical inaccuracies and some proof reading stuff in the report. I could offer to help you on those, if you want

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RE: Writing Quality v2.0 article finally up! - 1/30/2003 1:20:35 AM   
john

 

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> Or is this kind of scenario implausible in your opinion?

When a drive reads data from a disc, it won't report C1/C2 errors using the normal Drag&Drop procedure. Instead you will notice a read error , meaning there was an un-correctable error. The consealment circuit is there and will work with AudioCDs, as for the Data discs there is the 3rd Layer correction, that is explained in the pdf partially. The current information for CIRC is still not 100% clear/correct, perhaps some manufacturers could clarify this in future

> I'm glad you are making this thing clear.

Some manufacturers already got that point...

> Do you have a test disc for which you KNOW (ie. have the manufacturer's specs) that how many C1 errors and C2 errors it has?

Yes there are such discs, Philips sells them, check out the PDF pages at the end. I don't know exactly if the discs have for example 0.8 C1 average or give the upper limit of C1/C2 errors. We will have to ask and see if we can find more about this...

It would be easy to test the drives then to find out if they can spot all C1 and C2 errors and report them back accurately.

Yes that would be true, even PRO testing equipement WON"T give the same results even using the same media, there will be differences, even big between them! That's why there is a lot of talking about the reability of each testing equipement manufacturer.

Hence, it becomes very difficult to measure which drive reports all C2 errors accurately, unless we know how many errors there are on the disc, right?

That is not 100% correct, we mainly test how accurate a drive can report C2 errors according to the MMC standard, but none can tell 100% how many C2 errors (as an absolute number) are on a disc. Remember that usually the C2 errors are not physical BUT are produced when playback the disc.

(Abex TCD-721R) is: are errors on data layer, physical layer or both?

Check out the article that explains the Test media, under Articles!

How many C2 errors did it miss, if it reported X in total? How many did it miss, if it reported Y total?

As taken from the article: The Nero CD Speed software compares on-the-fly, byte-to-byte, and the extracted data of the test disc with an image. The software measures three types of C2 errors:

C2 Errors is the amount of errors reported by the drive.
Compare Errors are the differences between the original image file and the data on the test disc.
C2 Missed are present when the drive did not report an error while there was a difference between the image file and the test disc (i.e. comparison bit to bit).

According to how many C2 errors are reported/missed each drive gets a % accuracy score.

>Yes, but I don't understand if a high or low is better and why :(

Actually a low C1 error rate, indicates better servo, optics mechanism. Of course i understand why you are confused, since you are wondering if a disc with low C1 errors from LTR-52246S would be readable at an older CD-ROM drive...I am afraid i cannot answer that question (and be accurate).

> Does that mean the 'Cd-Check' test disc by Digital Recordings?

Oh yes you are correct, we forgot to add those results, dunno why [:I]

If it's just land/pit jitter, then that's truly the ultimate measure.

Yes that what we also believe!

>Thanks for the Almedio link as well. I just got a reply today.

, maybe we should ask for a % from their increased sales

> PS I noticed several minor technical inaccuracies and some proof reading stuff

You are welcomed to help, email me for more info!


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