Secrets of C1/C2/PI/PO error and beta/jitter tests
| Disc Testing Methods and Software Discuss, Secrets of C1/C2/PI/PO error and beta/jitter tests at Blank Optical Media forum; Much confusion and misconception about C1/C2/PI/PO errors and jitter tests are widespread, most probably because of inadequate understanding. So I feel there are needs to discuss, among others, how the errors occur and what these tests measure. Some other aspects about such tests can be found in: "Precision, accuracy, and |
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Posted:
22-01-2006
- # 1
Much confusion and misconception about C1/C2/PI/PO errors and jitter tests are widespread, most probably because of inadequate understanding. So I feel there are needs to discuss, among others, how the errors occur and what these tests measure. Some other aspects about such tests can be found in:
"Precision, accuracy, and reliability of disc quality (PI/PO/jitter) tests"
Firstly, some terms as given by ECMA 337:
mark: A feature of the recording layer which may take the form of an amorphous domain, a pit, or any other type or form that can be sensed by the optical system. The pattern of marks and spaces represents the data on the disk.
space: A feature of the recording layer which may take the form of an crystalline, a non-pit, or any other type or form that can be sensed by the optical system. The pattern of marks and spaces represents
Channel bit: The elements by which the binary values ZERO and ONE are represented by marks and spaces on the disk.
For graphical presentations essential to a proper understanding of DVD jitter and its measurement by time interval analyzer (TIA):
http://www.yokogawa.com/tm/ta/ta320/tm-ta320_09.htm
For definitions of other terms, please refer to the following:
http://club.cdfreaks.com/showpost.php?p=1244253&postcount=1
- Today (MyCE Staff)
- Posts: 15,596
- Posted:
22-01-2006
- # 2
I agree that jitter is very misunderstood along with its relationship to cd/dvd quality. glad someone has started a thread on this. And a perfect extension of
this thread
__________________
A warrior doesn't know remorse for anything he has done, because to isolate one's acts as being mean, or ugly, or evil is to place an unwarranted importance on ourselves.The trick is in what one emphasizes. We either make ourselves miserable or we make ourselves strong. The amount of the work is the same. - Posted:
23-01-2006
- # 4
Being not an American, I don’t know who Boskin is, so I can’t tell whether you are cynical or not. If you are, then you have missed a very important point in the definitions I quoted, that is: "The pattern of marks and spaces represents the data on the disk." This statement by ECMA is sufficient to dismiss the misconception that data are not written onto the disc. In addition, I want to promote the use of terms commonly adopted by the professionals.Quote:Originally Posted by rdgrimesNice job of cutting and pasting. Reminds me of Boskin.
You may disagree, but IMHO quoting or citing reliable materials is often of great value, especially when such stuffs have not been presented before. - Posted:
24-01-2006
- # 5
Fine, but the only drives we have that report jitter are the Benq ones AFAIK, and it would be interesting to find out if what they report can be judged on the ECMA standards numbers (max 9% if I remember well), which I doubt as most Benq scans show jitter levels above that (up to 13% sometimes), with discs that don't seem to have any readability problems. 
Also I personally haven't found sound references on how to interpret the jitter variations. For example, is slightly high (10%) but stable jitter better than a lower one with wild variations? What can be considered as significant variation? 0.5%? 1%? 3%? None of these because Benq drives jitter reporting would be looney??
With CDRs, I found the jitter reporting of the Benq 1640 very useful, as I could link very high reported jitter levels with audio CDs (>20%) to real-world issues with some CDR players. But with DVDRs, up to this day I have my doubts about what the drive reports as I couldn't link it to real-world reading issues.
Sorry for adding only questions and no answers to this topic...__________________
François "Wizzu" Marchand, the artist formerly known as Francksoy
I won't reply to technical help requests by PM, but ask you question in the forum and notify me, I'll be glad to help if I can! - Posted:
24-01-2006
- # 6
... and Plextors...Quote:Originally Posted by FrancksoyFine, but the only drives we have that report jitter are the Benq ones AFAIK
Regards,
ET__________________
KTPHTT - Posted:
24-01-2006
- # 7
Quote:Originally Posted by eltranquil... and Plextors...
Why do I always forget the Plextor scanning features...
(probably because it's like another planet, considering there are so few Plextor discs scans / tests around on this board, despite the fact that these seem far more reliable and consistent...).__________________
François "Wizzu" Marchand, the artist formerly known as Francksoy
I won't reply to technical help requests by PM, but ask you question in the forum and notify me, I'll be glad to help if I can! - Posted:
24-01-2006
- # 8
The problem with Plextors is that they will but jitter on a graph, but not give you an easy-to-read % total, nor have I found anyone yet to explain how to read the jitter results on a Plextools graph. 
About all I can tell Plextor users can determine is if it's 'acceptable' or 'bad' jitter. AFAIK about general in particular, the less 'spikes' and 'humps' there are, the better, and the more 'level' the jitter looks in general is better (looking from left to right on a CD-DVD Speed graph). __________________
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Want to be better informed about good media, solving computer problems and DVD burner performance? Join CDFreaks by clicking here. - Posted:
24-01-2006
- # 9
there are a ton of Plextor scans here: http://club.cdfreaks.com/showthread.php?t=115081
there's also a thread for Plextor CD scans, just not stickied....
re: reading jitter, the graph is low to high...the beta is a bit easier to analyze since it should not exceed + or - 8% or 0.08...__________________
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Plextor PX-716A / Plextor PX-708UF / BenQ 1640 / OCZ 520ADJ PowerStream / Lian-Li V1000B - Posted:
25-01-2006
- # 10
Very interesting discussion there http://club.cdfreaks.com/showthread....07#post1254607, with great input from ftp1020.
Too bad that they haven't taken this discussion here.
__________________
François "Wizzu" Marchand, the artist formerly known as Francksoy
I won't reply to technical help requests by PM, but ask you question in the forum and notify me, I'll be glad to help if I can! - Posted:
25-01-2006
- # 11
OK, here are some things I'm still confused about, perticularly as they relate to CDSpeed's output and how closely they may or may not corespond to any ECMA standards definitions for "Data Errors".
What exactly is a PIF?
It has been my understanding that the term PIF is synonymous with the ECMA standards defined term known as "PI-uncorrectable". However it seems that some people don't exactly see it that way, so I feel a strong need to have this cleared up.
What is a PO Error?
Near as I can tell, a PO Error, is NOT synonymous with PI-uncorrectable, yet some do seem to speak of them interchangably, while others speak of them as if they are indeed two completely differnt things. Once again I feel strongly that this needs clearing up.
What is a PO Failure?
I have a vague notion of what this likely means, however my notion, assumes I understand what a "PO error" is, and that a "PO Error" is differnt then a PI-uncorrectable. So untill I know the exact deffintion of the other terms I question above, I really have no real certianty that my notion about "PO Failures" are accurate or not.
How many (if any) "PO Failures" can you have on a functional disk?
If I could clear up those questions, I most likely have other questions... but these listed above, are the ones I feel are most in need of clarification. - Posted:
25-01-2006
- # 12
Not a problem to move it here in this forum, if needed.Quote:Originally Posted by FrancksoyVery interesting discussion there http://club.cdfreaks.com/showthread....07#post1254607, with great input from ftp1020.
Too bad that they haven't taken this discussion here.__________________
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25-01-2006
- # 13
ECMA does not mention PIF. I adopt the usage according to the following post by Erik Deppe:Quote:Originally Posted by DynoMoHumOK, here are some things I'm still confused about, perticularly as they relate to CDSpeed's output and how closely they may or may not corespond to any ECMA standards definitions for "Data Errors".
What exactly is a PIF?
It has been my understanding that the term PIF is synonymous with the ECMA standards defined term known as "PI-uncorrectable". However it seems that some people don't exactly see it that way, so I feel a strong need to have this cleared up.
What is a PO Error?
Near as I can tell, a PO Error, is NOT synonymous with PI-uncorrectable, yet some do seem to speak of them interchangably, while others speak of them as if they are indeed two completely differnt things. Once again I feel strongly that this needs clearing up.
What is a PO Failure?
I have a vague notion of what this likely means, however my notion, assumes I understand what a "PO error" is, and that a "PO Error" is differnt then a PI-uncorrectable. So untill I know the exact deffintion of the other terms I question above, I really have no real certianty that my notion about "PO Failures" are accurate or not.
How many (if any) "PO Failures" can you have on a functional disk?
If I could clear up those questions, I most likely have other questions... but these listed above, are the ones I feel are most in need of clarification.
http://club.cdfreaks.com/showpost.ph...3&postcount=33
PO errors and PO failures have been explained in the thread below:
http://club.cdfreaks.com/showthread.php?t=161716
- Posted:
25-01-2006
- # 14
OK... now I'm getting somewhere... Thanks Muchin.
Let me try to sumerize... Acording to the post by Erik when using CDSpeed(presumably), the BenQ (DW1620 at least) does not accurately (by ECMA standards) report PI Error, but that it reports PI Errors minus PI-uncorrectable... Yet the LiteOn (LDW 851S at least) does give PI Error counts that is on par with the ECMA-337 standards defintion of PI Errors. Which means if nothing else... what gets reported as PIE can vary from one drive to another.
By the way, in the following post by Erik, the graphs clearly show what a big differance you can see in the output displays on the two differnt drives as a result of this differance in the way PI Errors are displayed...
http://club.cdfreaks.com/showpost.ph...0&postcount=31
Also...
The DrageMester give a very convincing opinon/statment about his understanding of PO Errors and/or Failures... and what he says is pretty much how I personaly had envisioned the description of these terms.
One thing that does concern me about what DargeMester said... He says he has seen in ECMA-337 Standard a indication that zero PO Failures are allowed... I personaly have never seen that part, and I've looked pretty throughly... It makes sense that is what it should be, but then I also have seen some CDSpeed Disk Quality scans that report multiple PO Failures and yet seemingly the disks were still readable (this on a BenQ and possibly other drives).
Quote:Originally Posted by muchinECMA does not mention PIF. I adopt the usage according to the following post by Erik Deppe:
http://club.cdfreaks.com/showpost.ph...3&postcount=33
PO errors and PO failures have been explained in the thread below:
http://club.cdfreaks.com/showthread.php?t=161716
- Posted:
25-01-2006
- # 15
It may need an article to explain jitter adequately. I shall answer your questions only briefly for the present.Quote:Originally Posted by FrancksoyFine, but the only drives we have that report jitter are the Benq ones AFAIK, and it would be interesting to find out if what they report can be judged on the ECMA standards numbers (max 9% if I remember well), which I doubt as most Benq scans show jitter levels above that (up to 13% sometimes), with discs that don't seem to have any readability problems.
Also I personally haven't found sound references on how to interpret the jitter variations. For example, is slightly high (10%) but stable jitter better than a lower one with wild variations? What can be considered as significant variation? 0.5%? 1%? 3%? None of these because Benq drives jitter reporting would be looney??
With CDRs, I found the jitter reporting of the Benq 1640 very useful, as I could link very high reported jitter levels with audio CDs (>20%) to real-world issues with some CDR players. But with DVDRs, up to this day I have my doubts about what the drive reports as I couldn't link it to real-world reading issues.
Pioneer has found that 15% is about the highest jitter for a DVD to be read without errors for sure. Of course the distribution of the time deviations at the edges is assumed to be Gaussian, which may not be always true. Above certain jitter level, PIE rate increases with jitter, though the relation is not straightforward, partly because PIE are usually counted by rows rather than bytes.
FYI, Aopen 1648 DVD-ROM drive can also report jitter. - Posted:
25-01-2006
- # 16
I have been looking for more information on jitter for quite a while, but from what I understand even using a oscilloscope testing is very inaccurate. I imagine the reason there is not more information is because sophisticated equipment is needed to accurately test jitter and even then just like with C1-C2 or PI PIF there are many influences and from what I have read there are even more variables.
I have not seen anything on Optical drives that test jitter but I cant believe they are very accurate.__________________
A warrior doesn't know remorse for anything he has done, because to isolate one's acts as being mean, or ugly, or evil is to place an unwarranted importance on ourselves.The trick is in what one emphasizes. We either make ourselves miserable or we make ourselves strong. The amount of the work is the same. - Posted:
26-01-2006
- # 17
Why not, what's you take about it? Maybe it should include Spath's input, then...Quote:Originally Posted by zeviaNot a problem to move it here in this forum, if needed.
*
@muchin: thanks - even if this is still not enough info to my taste - but as nmpaulcp mentions, it's difficult to find good sources about this whole (DVD, not CD) jitter thing. The article here about Cats scanning vs. homemade scans was the only source I found that actually helped me in being less dumb about it. Since the time I first read this article, I keep on being frustrated despite intensive googling.
If anyone has links to more readings, please post them!!
For example, muchin, where did you find this info about Pioneer's "findings"?__________________
François "Wizzu" Marchand, the artist formerly known as Francksoy
I won't reply to technical help requests by PM, but ask you question in the forum and notify me, I'll be glad to help if I can! - Posted:
26-01-2006
- # 18
@ Francksoy
I have several links concerning jitter, definitions, its causes, etc. but no specifics on acceptable levels or what is needed for accurate tests other than actual jitter testers. Interesting reading though. I will post the links when I get to my other computer.Quote:If anyone has links to more readings, please post them!! __________________
A warrior doesn't know remorse for anything he has done, because to isolate one's acts as being mean, or ugly, or evil is to place an unwarranted importance on ourselves.The trick is in what one emphasizes. We either make ourselves miserable or we make ourselves strong. The amount of the work is the same. - Posted:
26-01-2006
- # 19
Same here. I have read lots of stuff concerning jitter, what is it, its effects etc... this is easy to find, but not much about jitter testing, and about nothing concerning jitter reporting of Benq and Plextor drives except the aforementioned article @CDFreaks and some anecdotic input here from Jean-Luc and others. Still, good idea to post your links, it can't hurt, I'll post mine tooQuote:Originally Posted by nmpaulcpI have several links concerning jitter, definitions, its causes, etc. but no specifics on acceptable levels or what is needed for accurate tests other than actual jitter testers. __________________
François "Wizzu" Marchand, the artist formerly known as Francksoy
I won't reply to technical help requests by PM, but ask you question in the forum and notify me, I'll be glad to help if I can! - Posted:
26-01-2006
- # 20
I thought a good laugh would be nice...
Source: cdr-zoneQuote:"Jitter is how well balanced your recorded media stays at any given speed. "
This must be, for sure, the most accurate and comprehensive definition of jitter I ever came across __________________
François "Wizzu" Marchand, the artist formerly known as Francksoy
I won't reply to technical help requests by PM, but ask you question in the forum and notify me, I'll be glad to help if I can! - Posted:
26-01-2006
- # 21
LOL!!Quote:Originally Posted by FrancksoyI thought a good laugh would be nice...
Source: cdr-zone
This must be, for sure, the most accurate and comprehensive definition of jitter I ever came across __________________
A warrior doesn't know remorse for anything he has done, because to isolate one's acts as being mean, or ugly, or evil is to place an unwarranted importance on ourselves.The trick is in what one emphasizes. We either make ourselves miserable or we make ourselves strong. The amount of the work is the same. - Posted:
26-01-2006
- # 22
Can some 'expert' in these matters please address the following question/statement, and tell me what is correct and/or what is wrong with it...
A PI-uncorrectable is any row in a ECC block that has more then 5 erronious bytes. Since a row has 182 bytes, a PI-uncorrectable row can have between 6 and 182 erronious bytes in it.
( I beleive the above statement is entirely true, this next part is what I'm not so sure about, and would really like verification of)
Each and every erronious byte in a row, would result in what is commonly called a PO error... Thus, a single PI-uncorrectable row could yeild between 6 and 182 PO errors... - Posted:
26-01-2006
- # 23
Correct.Quote:Originally Posted by DynoMoHumA PI-uncorrectable is any row in a ECC block that has more then 5 erronious bytes. Since a row has 182 bytes, a PI-uncorrectable row can have between 6 and 182 erronious bytes in it.
No, PO correction is applied on columns, not rows.Quote:Originally Posted by DynoMoHumEach and every erronious byte in a row, would result in what is commonly called a PO error...
So any wrong byte in a column will normally give a PO error.
No, a single PI-uncorrectable row might correspond to 1 PO error.Quote:Originally Posted by DynoMoHumThus, a single PI-uncorrectable row could yeild between 6 and 182 PO errors... - Posted:
27-01-2006
- # 24
A PI-uncorrectable could also result in zero PO errors, if the erroneous bytes exist only in the 10 PI columns (at the right side of the diagram below) and not in the 172 scrambled data frames columns, at least that is how I see it.Quote:Originally Posted by spathQuote:
Originally Posted by DynoMoHum
Each and every erronious byte in a row, would result in what is commonly called a PO error...
No, PO correction is applied on columns, not rows.
So any wrong byte in a column will normally give a PO error.
Quote:
Originally Posted by DynoMoHum
Thus, a single PI-uncorrectable row could yeild between 6 and 182 PO errors...
No, a single PI-uncorrectable row might correspond to 1 PO error.
This is also suggested by the fact that I have seen POE (Burst) scans on my Plextor PX-712A with only a single POE spike, and I have seen other such scans on the net with zero POE, but I have never ever had or seen a scan with zero PIF(*). (Another explanation is that the Plextor reports something else as POE).
(*) Well I have seen such a scan, but it was not on a Plextor drive.__________________
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27-01-2006
- # 25
chas had a 0 PIF scan, but i find such dubious, at best, as well... __________________
AMD A64 Clawhammer 3200+ / TT Venus 7+ / ASUS K8V Dlx / Corsair TwinX 4000PRO (2x512)
WD360GD 2*36GB Raptor (RAID0) / WD800JB 80GB PATA / IBM Deskstar 25.4GB PATA
ASUS R9800XT / VX900 19"CRT / Boston Acoustics BA7500 4.1
Plextor PX-716A / Plextor PX-Premium / Samsung SD-816B ROM / OCZ 520ADJ PowerStream / Kingwin KT424SWM
AMD A64 Winchester 3200+ / Thermalright XP-90 / ASUS A8V Dlx r2 / OCZ PlatR2 (2x512)
WD740GD 2*74GB Raptor (RAID0) / WD2500SD/JD 2*250GB SATA / Seagate 2*160GB PATA / Maxtor OneTouchII 300GB Ext (Firewire)
ATI X800XL / Viewsonic VP201s 20.1"LCD / Creative SBAudigy2ZS Plat / Klipsch ProMedia Ultra 5.1
Plextor PX-716A / Plextor PX-708UF / BenQ 1640 / OCZ 520ADJ PowerStream / Lian-Li V1000B
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