Does it really matter?

vbimport

#1

For some weeks I have been reading about PI errors, PI Failures and so on.
Like most everyone else I reached the conclusion that some media were better than others and that “better” results could be obtain by burning at either higher or lower speeds, depending upon the media, firmware and so on.

This evening a backed up a movie for a friend using what I thought was a fairly poor DVD. Sure enough when I scanned the results looked poor.

The I watched the movie and as far as I could tell there were no problems on video or sound.

So my question really is - how bad does a burn have to be before it is no good ? and secondly does it really matter if a scan shows 50 PI failures , 500 PI failures or even 5,000 PI failures - if it plays ok

It seems to me that although scan results can tell use whether one dvd is “better” than another what we really need to know is the practical levels that apply.

John


#2

Are we supposed to guess? :slight_smile:


#3

The disc looks good to me. The PIE total is a bit higher than I like at 203,656 (I prefer it to be below 100,000) but this is not bad, particularly since the PIE’s only peak to a maximum of 45).

The PIF total is also a bit higher than I like at 3739 (I prefer it to be below 2,000), but again it’s not enough to worry about - particularly since it only peaks to 10 (this needs to be below 16 on the BenQ 1620 for a safe burn). Also, it’s good that this PIF peak of 10 occurs early on in the burn where the disc will be read slower and more easily, rather than toward the end of the burn, which is typically the most difficult area to both read and write.

Jitter average is below 10%, which is also good.

All in all it looks like a good burn to me. I suggest you consider scanning it at 8X next time - but only to save yourself some time. It might scan a bit dirtier at this higher speed, but probably not enough to worry about.

Based on the PIF peak early on at 10, CDSpeed rates your burn at 94%, which is quite acceptable.

How bad can it get before you need to worry? There’s really no way to tell for sure, since different players will read with more/less errors - often by a factor of 3 or maybe even more. It’s sort of like asking: “How much food poisoning can we tolerate before we get sick?”? It’s different for different people, and it’s usually best not to find out…


#4

As a software developer and engineer, this kind of question interests me greatly.

As a matter of fact, if you had 150,000 PIF, 5 million PIE, it wouldn’t matter much if there are no PO failures during the playback on the device of your choice, or if it’s data, if the data is read back.

What might be of some use, and perhaps little use at that, is to see that a disk with fewer PIF will probably survive scratches and scuffs a little better than others, but I have no data on that notion.

Some years ago, I worked on applications for manufacturing, and among them was a subject called “statistical process control”, or “SPC”. It’s part of a quality control strategy, and the Nero scan would be a tool that qualifies as a quality test.

The goal of SPC is NOT to test the particular sample. If a sample is out of spec, be it a bracket or a DVD burn, that’s one problem. What SPC seeks to monitor, though, is the stability of the process that makes the object. If that process is stable, you can reliably predict the failure rate, and know what to expect from production (be it one or two a day, or a million per hour).

When the results drift out of spec, experience will help you know why. In the case of the burn process, it might be the media quality, or it might be the burner.

In my view, Nero scans are best relegated to this position, rather than a quality assesment of each particular burn. We might use it to judge the “drift” of quality within a brand, the relative quality between brands, the stability of our drive to produce burns, or to alert us when a change in configuration has actually caused a change in results.

I agree with your central point; it doesn’t tell us if the movie will work or not, or the data will read or not. When used as part of a routine of observance, it can, at best, indicate that our system of burning the discs has remained stable or not.


#5

Jvene, that’s probably one of the better descriptions of PI/PO testing i’ve read. thanks for your input.


#6

Thanks for all your replies.

Yes Spartane - I guess when compared with other scans the one I picked is not too bad. Its just that some many posts have become obsessed with getting PIE and PIF figures as low as possible - almost like it is a “mine’s bigger than yours contest”.

I have checked my records and have numerous scans on poor disks, burned too quickly or too slowly on less than perfect drives and yet they ALL still play.

Is it possible that “better” results will mean that a disk still plays 20 years from now ?

Thanks JVene - there is nothing I can add to your post or disagree with


#7

i don’t disagree with you that a certain portion of ppl view it as a “mine’s bigger than yours contest” but that’s a very broad generalization.

keep in mind you’re seeing all these posts of PI/PO scans because that’s the focus of this site…it has no indication of how many discs are NOT scanned for errors and those discs most likely far outnumber the discs that are scanned.

you’re lucky that you don’t have a picky players, but many people do not have such tolerant players and need to be confident that their backups/data etc is in good shape.

disc errors have a strong correlation to longevity of a disc so yes, with “better” results you can have more confidence in the quality of your discs over a longer period of time.

if the discs work fine in all your drives/players there’s not much to worry about and you’re overanalyzing things (but don’t complain if your discs don’t play correctly after some use/abuse).

happy burning.


#8

>disc errors have a strong correlation to longevity of a disc so yes, >with “better” results you can have more confidence in the quality of your >discs over a longer period of time.

Thanks - that’s what I had assumed. All of my disks play now but my real concern is to write them so that they still play in years to come. With disks being so cheap now I,ve started to make several backups using different media and or different burners - if they all fail perhaps they will fail at different points - allowing me to reconstruct


#9

I can confirm what JVene has stated. When I installed my new 1620, I scanned a few of my existing DVDs that I had backed up. I was quite surprised that some of my CMC MAG disks had PIEs well into the thousands! (These were burned with an HP DVD200i, which is really a Ricoh MP-5125A). I even had a DVD that had PIE values greater than 3000! Dispite these “bad burns” the DVDs play fine in my Denon DVD-1600 player, and also play fine in all three of my computers. Also, the DVDs work OK in my new 1620 as well.

The DVDs that I burn in my new drive have much much better looking results in the Disk Quality tests, but I can see no difference between them and the ones that have PIEs in the thousands when playing them back.


#10

I think the really important thing here is the PIF levels, rather than the PIE levels. I’ve seen discs with a relatively low PIE max (below 75) count up PO Failures. But the PIF’s spiked up to 42 near the end of that burn, clearly showing the problem.


#11

i agree, PIFs are much more indicative of quality than PIEs…


#12

Error scanning is very limited and subjective. As has been already stated, it can’t tell you the quality of a burn or if it will play back or not. It may indicate some consistency level at best like JVene said. Too many people are obsessed with having “pretty looking scans”. They want the lowest PIEs and lowest PIFs with the highest quality score possible. There’s even a new thread in this BenQ forum dedicated to displaying such scans: http://club.cdfreaks.com/showthread.php?t=123453

Look at the name of that thread - it’s called the “burn quality” hall of fame. I don’t think these scans show us burn quality as per the words posted above. Many of the “pretty looking” scans can be deceptive. They sometimes have bad sectors on them which show up in surface scan tests or transfer rate tests. They aren’t truly examples of “burn quality”. I like JVene’s opinion on error scanning and think it’s more realistic than what many others around here are calling their scans. Anyhow, this is a very interesting topic.


#13

I decided to watch an old movie this evening but before I did I ran a scan
(number 1).
From memory the movie was backed up using DVD shrink on a Liteon 811 ?
Anyway the movie ran without any noticable problems.
I then decided to use DVD Dycrpter to make a new copy. I only used this program inorder to check that the dvd could be read properly. Dycrpter reported no read errors.

So now I have a second copy which shows a much prettier picture. I think its a better copy but still have my doubts - how can a copy be better than the original ?

As DVD’s are so cheap I’m considering going back through my collection and making further copies. I wonder if I should submit scan number 1 to the “burn qaulity” hall of shame ?


#14

i agree with socrates007 here, but i must add that PIFs ARE indicative of the quality of a burn as they are more directly linked to PO failures and you can see this with Read transfer rates, playback, AND beta/jitter.


#15

Well, since the original could be read without errors, it was in a way a ‘perfect’ copy, that just showed a lot of non-critical errors (which could make it unwatchable on certain standalones). Now you have created just as perfect a copy, that shows less non-critical errors.
For important data, it is always a good idea to have 2 copies, just in case one of them deteriorates to a point where it cannot be read successfully.


#16

@HarrySmiith
Daxon, CMC, Sony, and many others are greatly improved with firmware T9. And, there have been some serious improvements to Daxon. For instance, now you can overspeed it and its playback is not “choppy” as before when oversped.

The scan matters (usually). But, the importance of it is media-dependent.
One may have a scan the holds 250 or so PIErrors completely across the chart with the occaisional visit up to 350. One may also have many PIFailures ranging upwards into the 20’s. One may have 0 POFailures. That is about the limit of specifications. DVD is an analog media cut with a laser. Otherwise it does not differ from a vinyl record. It is then converted to digital, whereby a 0/off is 1/3 or less, and a 1/on is 2/3 or more.
Should errors occupy “areas” above the 1/3 tolerance mark, then the disc is said to be a coaster, or incapable of storing digital information. Movies on such a disc may still play, but you can expect the occaisional ski-sk-ski-sk-skip or “macroblock” or freeze from a set-top player.

While the amount of the PIErrors failures does not matter, their extent does. That should be less than 350 when scanned on a BenQ at 8x, less than 250 when scanned at 4x, less than 700 when scanned at 16x.

PIfailures matter in both their amount and their extent as seen on the chart. They should be skinny spikes and limited to 20 when scanned at 4x, skinny spikes and limited to 30 when scanned at 8x. If you see short, fat PIfailures completely across the chart (in addition to the normal spike pattern), it means that you probably have a communications failure between the writer drive and the motherboard. Lite-on did this to many of their customers by packaging a BenQ 1620 generic in the same box as an obsolete 40 wire cable. So, customers that have noisy computers got coasters.

PO failures should always be zero. Any amount other than zero means that the disc is incapable of storing digital information. Each PO failure will cause a freeze in a set top player.

That’s my view on DVD specs as seen through the looking glass of a BenQ drive using CD/DVDspeed’s QC test.
This popular scanning method views the disc.
It does not put the information seen on the scan to use.
CD/DVDspeed’s Scandisc test puts the disc to work for a “real life” test. However DVDDecryptor in all-file mode with “ignore errors=off” is a faster, but less graphic real-life test. DVDShrink’s “quicky” fast scan when you perform the “open disc” procedure is far faster than anything else, but not as effective. It is a popular timesaver with CMC customers who need to scan every disc.

Someday, I hope we will have a scan that reports the disc’s specs (as in Disc Quality Test) and then reports the data file integrity (as in Scandisc) in just one single pass.

Today, getting all of the necessary quality control information takes two, time-consuming, passes.
Some medias get out-of sync between Disc Quality and Scandisc. With these medias, one of the scanning methods. . .really is meaningless.
While this does not relate to T9 firmware (problems have been fixed), let’s take a look at Daxon AZ2 and CMC E01 when burned with P9 firmware.
The CMC media will always make a beautiful scan while frequently flunking the scandisc. It usually has good playback in a set-top player. I usually do not use the Disc Quality Test with this media because it usually burns in-spec. I always do a Scandisc or copy-back test of this media because of the nearly 10% data integrity failure rate.
The Daxon media will make some of the most frightening, nearly out-of-spec scans you’ve ever seen while always passing the scandisc test. With P9, it will often play back choppy unless burned at 4x (T9 is good to 12x). I usually do not verify or “Scandisc” this media, but I do use the Disc Quality Test because this media has trouble burning in-spec.

P.S. For discs that are great until the last few hundred megabytes, it is possible to reduce the target disc size in writing software. For instance, Ricohjpn R01 has ideal longevity, scans, data integrity, and playability. . .until the 4320 mark where it goes out-of-spec for PIF, then the rest may/may not be garbage. I set DVDShrink to a custom target disc size of 4320. Now the “entire” (smaller) disc it is now in-spec for excellent, repeatable results.

P.P.S. Whenever we see a beautiful scan posted on-line, and there is no scandisc test to go with it, we are looking at important, but incomplete information. Anyway, that’s my view on it.


#17

I have found the most useful “quick” scan of playability is to run the disc through DVDShrink’s initial open process. This only take a minute or two and has often found problems which have always been confirmed through more intensive quality scanning in Kprobe or CDSpeed. Conversly, whenever I see a bad scan with errors into the 300-400 ( or above) range I find DVDShrink also hesitates or fails when reading. Many of these “problem” discs would play OK on some players and yet not on others.

My feeling is that quality scans are rarely if ever wrong if they show a great burn. They are also rarely wrong when they indicate a bad burn. Usually some problem will surface with some player sooner or later. The burns in the middle are where it is hard to say what you’ve got.