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ECC block size of testing software - 4/29/2005 5:12:39 AM   
curlyhead2000

 

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OK, here is the deal – if the ECC block testing size needed for PIE is 8 (max 280) and PIF is 1 (max 4) then which does my quality testing software use? If it uses 8 then won’t it over-report PIF peaks? And at 1 it will under-report PIE? How do I change the settings for CD-DVD Speed Test and DVDInfoPro? Or do these programs already test both block sizes and the displays they show are correct?

If the block size is 8 then you could theoretically have a PIF of 8x4 = 32 and still fall in the safe zone (though, statistically it is unlikely to have a row of eight 4s) – is this why one is supposed to ignore high individual spikes? The reason I ask is that I have a disk with a narrow band of around 12 PIFs – if this is testing at 8 ECC, I could reasonably expect that at the 1 ECC level I would have no PIFs above 4. If the Nero CD-DVD disk speed uses 8 ECC, then surely its quality score is meaningless?

p.s. Would a test at 1 ECC take eight times longer than at 8 ECC?

p.p.s. Is all this quality testing really necessary? I have a couple of disks that show groups of high PIFs (in the late teens) but which pass CRC and copying tests with flying colours! I have a suspicion that the only meaningful failed test is a series of tests on the same disk at 16x, 8x, 4x, 2x and 1x that shows a high PIF peak in the same spot in all test. Obviously, high PIE / PIF at higher speeds will slow down transfer rates, but if a small problem area of the disk can be read in its entirety for at least one of the speeds, then the disk is readable, and any slow down will be small. What I want to know is this – if I use PIE / PIF testing to find a media type that generally has low errors, can I rely on a combination of data verification, CRC testing and careful, scratch free, disk storage to safeguard my data? The only disks I can’t read reliably are Datawrite Grey (prodisk dye) on my LG combo drive and these fail CRC check. I am a person who easily becomes a little obsessed by this kind of thing and I would really like to be able to just forget about PIE/PIF quality testing every single burn I do!

XP Pro SP2
Athlon 1.1GHz
NEC 3520AW 3.04
LG 4320B combo 1.02
512Mb RAM


< Message edited by curlyhead2000 -- 4/29/2005 5:17:31 AM >


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RE: ECC block size of testing software - 4/29/2005 9:34:40 AM   
Quikee


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At what ECC the scanning software tests depends on the drive... for example LiteOn drives report both PIE and PIF at 1 ECC.. BenQ reports PIE and PIF at 8 ECC... for Nec drives you can choose the ECC. Most scanning software then converts in case of 1 ECC for PIE to 8 ECC so then they are compatible with the specs.. in case of 8 ECC PIF you can't really convert it back to 1 ECC but aproximate how the values are at 1 ECC. So a 32 PIF at 8 ECC can be all values from 1 single 1 ECC spike of 32 PIF to 8 values of 4 PIF. High spikes are ignored because they can be a glich in scanning... however if they are real usually they don't matter much.

Scanning at 1 ECC and 8 ECC takes the same amount of time.

Well.. if a disc has high PIF they can still be corrected in PO so a high PIF doesn't mean that the disc is unreadable. However they measure the amount of errors and over time error level will sooner or later become greater.. this means that a disc with few PIF will last longer than a disc with a lot of PIF in the deterioration rate on both disc is the same.


< Message edited by Quikee -- 4/29/2005 9:35:07 AM >


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RE: ECC block size of testing software - 4/29/2005 6:20:08 PM   
emperor


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More or less, quickee answered your questions, usually the less errors a disc contains, the best chances you have, it will last longer, and of course be readable at the upcoming years

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RE: ECC block size of testing software - 5/6/2005 5:53:42 AM   
Halcyon

 

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The sampling interval is based on the chipset and the software polling the chipset:

Philips Nexperia (BenQ/Philips/NuTech): PIE rows/8ECC, PIF rows/8ECC
Mediatek (LiteOn): passive, but can be polled down to c. PIF rows/1ECC (and summed PIE rows/8ECC)
Nec (Nec): variable, rows/1-8ECC are used at least in CD-DVD Speed
ALI (AOpen/Asus some dvd-rom models): PIE/PIF rows/32ECC or rows/64ECC (depending on model)
Sanyo (Plextor/Optorite burners): PIE rows/8ECC, PIF rows/1ECC (PIE/PIF have to be scanned as separate scan runs)
Via (Toshiba/Plextor some dvd-rom models): PIE rows/8ECC, PIF c. rows/1.5ECC
Ricoh (some AOpen/Ricoh): rows/16ECC

This information comes from the author of CD-DVD speed.

As for the other questions:

quote:


Q1: "If it uses 8 then won’t it over-report PIF peaks?"


If the scanning interval is more than 1ECC block at a time, then error spikes will be underreported, because the number of errors in an 8ECC sum window are just averaged.

It is possible that a 32 PIF from 8ECC blocks (summed) comes from 6 blocks containing 3 PIF each (=18 PIF) and the rest two containing 14 PIF (32 total from all 8 blocks). Of course, the software will only report 32/8 = 4 for each, because it cannot know the distribution of those errors within the 8ECC block window.

quote:


Q2: "And at 1 it will under-report PIE?"


If the chip/drive/software reports PIE at each consecutive block (i.e. rows/1ECC), it is very easy to calculate the floating 8ECC block window from this, without any under or over-reporting.

So, only too high block sampling size is somewhat problematic, because it will hide the peaks (maxima) in each sample block.

quote:


Q3: "How do I change the settings for CD-DVD Speed Test and DVDInfoPro?


This can only be changed for drives that support it (i.e. basically Nec), through some registry hacks and I wouldn't do it, unless I knew what I was doing (really knew). It’s not worth the time, unless you really become engulfed in read error testing, imho.

quote:


Q4: "Or do these programs already test both block sizes and the displays they show are correct?"


See above listing of PIE/PIF reporting window sizes.

All in all, I wouldn't be too worried about this, because if the disc is truly bad, you will get a huge increase in PIE/PIF regardless of the sampling size.

Also, as the errors are not on the disc, but in the reading process, it is useless to measure accurate PIF/1ECC block and determine based on that whether the disc is out of spec or not. All it tells whether that particular read on that particular drive produced a read error rate within the specifications (or not).

quote:


Q5:"is this why one is supposed to ignore high individual spikes?


High spike ignoring comes from chips/drives that have glitches and occasionally over-report errors, even when they read no such errors.

For example, if PIE remains really low, but there is a huge single sample area spike in PIF, it is more than likely that the error is from the drive's reporting and that there is no problem with the disc. PIE and PIF are interrelated, PIF only happens when there is a high enough number of PIE errors (in the same block).

quote:


Q6: "The reason I ask is that I have a disk with a narrow band of around 12 PIFs – if this is testing at 8 ECC, I could reasonably expect that at the 1 ECC level I would have no PIFs above 4. If the Nero CD-DVD disk speed uses 8 ECC, then surely its quality score is meaningless?"


PIE is always graphed at 8ECC (or an average of that), PIF is always graphed at 1ECC (or an average of that).

If your PIF is already at 12 in the graph, then the maximum in all of the single blocks it AT LEAST 12 and statistically can be much higher.

To repeat: samples may be gathered at higher intervals than 1ECC (due to drives/chipset), but they are graphed at 8ECC for PIE and 1ECC for PIF (at least in CD-DVD Speed, don't know about DVDInfoPro). This means that for any drive where sample size is bigger than 1ECC, the PIF maxima will be more than the averages graphed by CD-DVD Speed.

Hence, PIF spikes are somewhat under reported, while the averages remain truthful.

quote:


Q6: "p.s. Would a test at 1 ECC take eight times longer than at 8 ECC?"


Depends on the drive, but generally no.

It's just that not all drives support reporting of read errors at 1ECC, because the drive makers didn’t see it useful to implement it.

quote:


Q7:"Is all this quality testing really necessary? I have a couple of disks that show groups of high PIFs (in the late teens) but which pass CRC and copying tests with flying colours!"


If you only make the copies for fast day-to-day use and don't need long storage life / archiving, then it's down to you to decide.

If it works for you in day-to-day use and you don’t need to store it for longer periods, never mind about the error rates

However, if you are concerned with either:

A) long time storage of your discs

or

B) maximum compatibility of your burns with other drives

Then read error (digital error) rate testing can be useful, but ONLY when done properly. Single scans from LiteOn drives (or any other drive for that matter) do not prove reliably the quality of the disc or the quality of the burn.

quote:


Q8: "I have a suspicion that the only meaningful failed test is a series of tests on the same disk at 16x, 8x, 4x, 2x and 1x that shows a high PIF peak in the same spot in all test."


That is a reasonable working theory, but unfortunately somewhat incorrect.

It would only hold true for discs, where the errors are truly encoded in bit stream on the disc (the actual bits stored on the disc are erroneous).

However, such discs only appear in specially manufactured test discs and not in ordinary burning.

The other read errors (PIE/PIF/POE/POF) are the results of focus errors, tracking errors, eccentricity, reflectivity/birefringece problems, ftracking/slicer level adjustments and the jitter that results in the analog RF signal from those errors/problems. This jitter is then translated to bit-level errors in the DA stage of the drive.

To repeat: PIE/PIF/POE/POF errors are NOT on the disc. They are the results of the reading process, when the drive is inable to properly track/read/decode the analog RF signal stored on a DVD disc.

A normal read error related PIF (not chipset glitch) will almost invariably increase when the read speed is increased. This is due to increased difficulty in controlling RF jitter when the linear velocity increases.

Sure, it can be argumented that there is a problem on that part of the disc, where the spike occurs, regardless of the read speed. However, the spike level will be mostly dependent on read speed (excluding scratch/smudge/spotty polymer layer issues for now).

quote:


Q9: "Obviously, high PIE / PIF at higher speeds will slow down transfer rates, but if a small problem area of the disk can be read in its entirety for at least one of the speeds, then the disk is readable, and any slow down will be small."


This is another unfortunate and somewhat erroneous assumption, often propagated in various forums.

I have several drive/disc combos that produce excellent speed graphs (no slow-downs). However the same discs in the same drives report very high PIE/PIF rates.

Clearly the transfer speed graphs and PIE/PIF rates do not ALWAYS correlate highly.

This means that transfer rate graphs on their own are unreliable measures of readability quality of a disc/drive combo.

It is unfortunate that many people have not really tested this themselves and continue to propagate the idea that a transfer speed graph is a reliable measure of disc quality in general.

Sure, transfer rate graphs can weed out the obviously problematic discs. However, there can be serious compatibility/quality issues long before transfer speed graphs show you that there’s anything to worry about.

So, it can be a useful tool in measuring, but it’s not reliable on it’s own.

quote:


Q: "What I want to know is this – if I use PIE / PIF testing to find a media type that generally has low errors, can I rely on a combination of data verification, CRC testing and careful, scratch free, disk storage to safeguard my data?"


On the average: yes.

However there are dependencies.

First of all, to truly/reliably find a compatible media, you would need to:

Scan the burns in VARIOUS different drives (not just one!) and ensure proper low error rates in all of them.

This means that the burn is compatible in a large number of drives (i.e. it is good as far as the burn quality is concerned).


The second problem is that for longer term archiving, it's not just the initial read error rates that matter.

You need to consider the quality of the disc ingredients (particularly dye) and the quality of construction (sputtering/bonding in particular).

Good quality discs pass these requirements (dye/sputtering/bonding is almost impossible to test reliably with home grown methods, so you need to trust 3rd party independent scientific data like that from National Institute of Science and Technology).

The third problem is that, even if you find a good disc (low error rates in various of burners and very good proven disc quality overall), then you cannot be 100% sure that all discs from all batches are as good as the ones you've measured, if you only do CRC/transfer speed tests with them.

Both CRC and transfer speed test will only show you when you have really bad disc, that is when the burn quality is already at such level that the drive reading it almost cannot read the data back 1:1 bit accurately. A disc like that is already an inch away from being thrown to the garbage can.

Transfer speed rates are of course good for discs that have low read error rates with most drives. But you never know for sure if it's a good or bad disc, just by looking at CRC/transfer speed tests.

But because testing is cumbersome and sometimes difficult, as a practise it is perhaps best to find a compatible disc that:

- burns well with your burners (no coasters, low read error rates in all drives you test)
- is compatible with all the drives you want to use the discs in (no slow-downs, no read problems)
- comes from a high quality manufacturer (TY, Maxell, Ricoh, MCM, etc.)
- isn't an obvious fake (cheap imitation costing 1/3-1/6 of the real branded discs)

Then keep on using those as long as they work. However, be also aware the dye formulations and power calibration instructions (and firmware) do change with discs/drives.

This means that a disc that used to work ok, may become less compatible in the future.

If the change is big enough, you'll probably notice it as an increase in coasters or read compatibility issues.

quote:


"The only disks I can’t read reliably are Datawrite Grey (prodisk dye) on my LG combo drive and these fail CRC check. I am a person who easily becomes a little obsessed by this kind of thing and I would really like to be able to just forget about PIE/PIF quality testing every single burn I do!"


I feel your pain.

It's not easy I can tell you, but if you want to get easy out of it, then just buy the most compatible burner recommended by cdrinfo/cdrlabs/cdfreaks (they must be in unison in their findings) and the most compatible disc (don't be cheap, quality costs) and stick to those as long as they work for you.

regards,
halcyon


< Message edited by Halcyon -- 5/7/2005 3:30:46 AM >

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RE: ECC block size of testing software - 5/10/2005 12:55:15 PM   
emperor


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as usual a big and deep explaining thread by halc

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RE: ECC block size of testing software - 5/12/2005 5:13:57 AM   
curlyhead2000

 

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Thanks, Halcyon, for your very detailed explanation - I feel I have been put right on my misunderstandings. Have started using Verbatim 8X DVD-R burned at 4X on my 3520a v3.04 for my important data, and cheap Datawrites for my day-to-day unimportant stuff. Check quality for each disk on my NEC using Nero CD-DVD Speed and then on my LG combo using DVDInfoPro. So far I am getting very good results for Verbatim and reasonable for Datawrite (as I would expect) - esp since flashing my drive to 3.04 and updating Nero to latest version.

I knew there were issues with DVD burning, but it has turned out to be more complicated than I was expecting. The (rather obvious) conclusion I have come to is this - if it is important, back it up on more expensive, well regarded disks and expect good testing results on more than one drive. After all, it isn't worth saving £10 on a tub of 50 DVDs if you find you loose all your important family pictures or other irreplacable data. It seems that companies selling cheap DVDs are preying upon people's lack of knowledge (esp when switching dyes on their disks) - I wonder how many people out there are backing up important data to cheap disks unaware that they would be much safer using expensive disks? After all, even bad burns on cheap disks can pass the data verification process! Perhaps it would be usefull if Nero burning software offered to do a quality scan as well as a verification check after burning (would want improved 'disk quality' measurement, though). I also think that companies should be obliged to put the dye they use for their disks on the outside of the box.

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RE: ECC block size of testing software - 6/25/2005 11:59:53 AM   
Clint


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quote:

ORIGINAL: emperor

as usual a big and deep explaining thread by halc

Agreed, nice little summary of DVD writing/error testing do's and don'ts.

quote:

ORIGINAL: Halcyon
I have several drive/disc combos that produce excellent speed graphs (no slow-downs). However the same discs in the same drives report very high PIE/PIF rates.

Clearly the transfer speed graphs and PIE/PIF rates do not ALWAYS correlate highly.

This means that transfer rate graphs on their own are unreliable measures of readability quality of a disc/drive combo.

It is unfortunate that many people have not really tested this themselves and continue to propagate the idea that a transfer speed graph is a reliable measure of disc quality in general.

Sure, transfer rate graphs can weed out the obviously problematic discs. However, there can be serious compatibility/quality issues long before transfer speed graphs show you that there’s anything to worry about.

So, it can be a useful tool in measuring, but it’s not reliable on it’s own.

Yes, many people often overlook the fact that different drives have very different error correction mechanisms/logic. It's asif these mentioned people believe that all drives have the same capabilities in general, and a smooth read on one unit automatically equals a smooth graph on the next. Even certain firmware revisions/drive usage amounts of vendors can attribute to the same model having difficulties, wheras, another of the same type produces a perfect 'line'.

Nice, reliable info. If everyone conducted their DVD burning with the knowledge of the above post, there would be very few discs that fail to be read, or dreaded CRC errors/pixilization/jumps in home produced recordings... Thanks for the input.


< Message edited by Clint -- 6/25/2005 12:05:33 PM >


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RE: ECC block size of testing software - 1/20/2006 5:11:49 PM   
shimman

 

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i vote it to be sticky ;)

i did not know my benq did not report pif from 8ecc blocks. it sound like scans on 1ecc block using nero drive speed + nec drive would be the fastest way to sacn. my 716a takes way too much time.

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RE: ECC block size of testing software - 2/9/2006 6:01:38 PM   
Clint


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quote:

ORIGINAL: shimman

i vote it to be sticky ;)

i did not know my benq did not report pif from 8ecc blocks. it sound like scans on 1ecc block using nero drive speed + nec drive would be the fastest way to sacn. my 716a takes way too much time.

Ok, done!

To improve your scan time on the Plextor hardware, reduce the accuracy to medium as is done for testing here, as it all adds up when you have many scans to do... You will loose precision however, at the expence of short(er) scan times.

quote:


The sampling interval is based on the chipset and the software polling the chipset:

Philips Nexperia (BenQ/Philips/NuTech): PIE rows/8ECC, PIF rows/8ECC
Mediatek (LiteOn): passive, but can be polled down to c. PIF rows/1ECC (and summed PIE rows/8ECC)
Nec (Nec): variable, rows/1-8ECC are used at least in CD-DVD Speed
ALI (AOpen/Asus some dvd-rom models): PIE/PIF rows/32ECC or rows/64ECC (depending on model)
Sanyo (Plextor/Optorite burners): PIE rows/8ECC, PIF rows/1ECC (PIE/PIF have to be scanned as separate scan runs)
Via (Toshiba/Plextor some dvd-rom models): PIE rows/8ECC, PIF c. rows/1.5ECC
Ricoh (some AOpen/Ricoh): rows/16ECC

This information comes from the author of CD-DVD speed.

The above needs to be noted by all to have an idea on how different equipment/software relates if you will. Andre's info is correct, so no discrepencies.


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