such thing as disc data disappearing? how long do DVDs last?

[dcassidy]

OK...I think I got it....

I decided it must be the ability of the laser to pick up and recognise the data...so I popped a CD cleaning disk into to Sony...ran it a few times.

I can now see all the disks.....I guess there must have been enough grime on the laser to stop me reading DVD+RW and DVD+R but OK not enough to stop it reading commercial disks.

Is replacing the laser (assuming it is grimy) a DIY job or best left to the professionals. ??

Thanks for the direction and help BJ_M ...I feel a right prat now...

Cheers,

Dezzz.

[gmatov]

OK, here's a ? for you.

You run NERO CD Speed, or DVDInfoPro or any other check program, and it says "All's well", just what does that mean?

That a 0 is here and a 1 is there?

What is there to say the disk is an exact copy of the file burnt from? Where is the "Compare" function?

I don't see anywhere that DVDInfoPro searches your HDD to find the file you just burnt from, particularly if you do a check the next day, after a shut down/reboot..

It may see a "reflect", "refract", or a "nothing", so bad bit, so bad burn, but if the "reflect" or "refract" is not a 0 or 1, whichever it should be, right there, but if it does not know what belongs in that area, how can you say it is a good burn/bad burn.

GIGO. It reads bad data, but it IS reflect, refract, not a nothing, so good burn.

Does this make sense?

Cheers,

George

[BJ_M]

OK...I think I got it....

I decided it must be the ability of the laser to pick up and recognise the data...so I popped a CD cleaning disk into to Sony...ran it a few times.

I can now see all the disks.....I guess there must have been enough grime on the laser to stop me reading DVD+RW and DVD+R but OK not enough to stop it reading commercial disks.

Is replacing the laser (assuming it is grimy) a DIY job or best left to the professionals. ??

Thanks for the direction and help BJ_M ...I feel a right prat now...

Cheers,

Dezzz.

cant replace a laser on your own --

[BJ_M]

ussually not worth replacing anyway -- as other parts will be or are worn also ...

[nerys]

"There is no "silver coating" on a DVD-R. The foil and dye is sandwiched between a plastic upper and plastic lower. What you claim happened is physically impossible. "

Like hell I hav SEVERAL where the silver layer is RIGHT underneath the labeling and I HAVE PEELED them

that is why I test all media with a screw driver I put a nice gouge into the top of the disc. if I see nothing on the other side I buy lots of it

Chris Taylor
http://www.zodiacreview.com/

[lordsmurf]

Believe what you want, but the facts are not on your side. There IS a plastic upper layer. A screw driver probably went through both layers. There is no "label" on the media, maybe a silkscreen or other thermal/inkjet layer on the plastic.

[Skith]

Straight from the horses mouth:

http://www.dvdrw.com/information/white-papers.htm

Look at the PDF "DVD+R - A Write Once System for video and data applications" on the above site, you will see this diagram:




Some links to the DVD-R Forum:

http://www.dvdforum.org/forum.shtml

http://www.dvdforum.org/gen-discbond.htm

[nerys]

sorry man does not matter. the physical disc I can hold in my hands trumps any diagrahm if that is dvd spec this just means whoever made this disc did not follow spec cause I am sorry you can not "slice" through polycarb that easy and you can not "peel" polycarb as if its mylar. I might still have it I will try to find it. I THINK (not sure) it was some old comp usa brand 1x/2x discs.I removed the silkscreen or whatever it is AND a super thin film like shiny metallic silver layer. when I got it all off (came on in peices not one peices too thin to get it all at once I tried I was left with a CLEAR poly disc (like the dummies you find in soindles) and a rainbowy color effect (assuming thats the dye

yes by label I meant whatever it was that they use to put there logo on top of the disc

I have also had discs with DISTINCT layers of polycarb that I was able to split and seperate into 2 halves I stay away from them too ie if I can visibly "see" the line between the 2 poly layers I stay away.

Chris Taylor
http://www.zodiacreview.com/

[BJ_M]

i actually saw a couple of these weird disks also -- they had no top polycarb layer .. and were real flexible .. this was a few years back and never saw them again ..

i found out when i tried to pull off a printed label on one I recall, becuase the customeer put it on crooked and the disk would not play right .. and i killed it ..

[Zisguy1]

I have also had discs with DISTINCT layers of polycarb that I was able to split and seperate into 2 halves I stay away from them too ie if I can visibly "see" the line between the 2 poly layers I stay away.

I've got a spool of 50 Ritek 4x DVD+R's like this, seems to be two halves visibly sandwiched together (or so it appears from looking at the edge, haven't tried pulling any apart).

Is there a particular reason (other than speculation) why you stay away from discs like this? Fwiw, many of my commercial DVD's also have this "sandwiched" appearance.

[Skith]

Is there a particular reason (other than speculation) why you stay away from discs like this? Fwiw, many of my commercial DVD's also have this "sandwiched" appearance.

These "sandwiched" discs are the ones that you want! These types of discs are in the DVD manufacturing specification. The purpose of the top "plastic" half of the dvd is to protect the data layer.

[joeg04]

Simple experiment to predict "data disappearing" for a certain DVD-R disk:

I just made an experiment, that is easy to replicate. You just need a ruler, a hair dryer, and less then 1 minute of time.

1) Take a DVD-R, that is suspicious for future "data disappearing", for example Princo.
2) Check the top side with a ruler, whether it's flat.
3) Heat up the bottom side of the disk. Use a hair dryer (about 1800 W) for 10 to 15 seconds, from a distance of 1 inch.
4) Check again the top side with a ruler, whether it's still flat or significantly warped.
5) If the disk is flat before AND after heating up, then "data disappearing" will not happen, else it can happen.

The heating simulates the higher temperature in a DVD player.

I carried out this experiment with several disks.

The following disks were flat before, but warped by 1mm immediately after heating up:
- Princo (white top, not printable),
- LONGTEN001 (white top, printable)*,
- A disk with paper label applied*.

The following disks were flat before and after heating up:
- RiData (white top printable),
- Philips (silver-top).

* Those disks are no longer playable on the outer side in a Pioneer DV-454, but were completely playable shortly after burning, 1 year ago. The others have no playability problem. I think the Princo may have problems in other players (There are many reports about bad Princo disks).

The three disks, that showed warping after heating up, have all one thing in common: They have an extra white layer on top, that might expand/shrink differently with temperature changes than the rest of the disk, and thereby warping the disk.

Experience shows, that "data disappearing" is a PROVEN FACT.
I agree with Lordsmurf, that the problem is not the DYE. I conclude from the experiment, that the problem is WARPING. The disk is either already warped (production error) or warps itself, caused by temperature changes and under influence of humidity. Warping may lead to focussing problems in the laser optics.

[lordsmurf]

I would still not lump that into a "data disappearing" category, but that is indeed an excellent addition to this post. Most time, warping is a cause of improper storage. Discs that are warped or imbalanced refuse to burn to begin with.

Having a DVD player that heats up bad, and discs that are made from comparatively more flimsy platters, is subject to death. Much like scratches. Although I will have to say that a hair dryer is SIGNIFICANTLY more heat than a typical electronics component. For these same reasons, never leaves discs in the sun, in the car, etc. Dye can be altered at a certain degrees, but I don't remember when that is. It's hot. Oven hot.

[joeg04]

I would still not lump that into a "data disappearing" category

Therefore I wrote "data disappearing" in quotes. For the user it makes no difference, if the data (for example the family videos) is still in the dye, but no longer accessable, or if it disappeared.
The material properties regarding warping (expansion temperature coefficient) may change slightly over time under influence of humidity.

[rgs_uk]

DAT storage and other tape store methods are dicy at best (specially 4mm) , 1/2" seems to fair better.

I would not consider VHS an archive format - D5 , d-beta, beta sp = yes .. at least for mid term (10+ years) , problem is, are the machines going to be around...

Disregarding the question of equipment being around... VHS uses ferric oxide tape of the kind that has been around since the 1950's (for sound and video recording). Archives reckon modern ferric oxide tape has a life of at least 50 years.

When Sony launched Hi8 in the 1990's they talked about it having a life of 10-15 years, as it is metal based, much the same as Beta SP and the current digital formats...

I have had lots of drop out problems with Hi8 over the years and very few problems with VHS. I have about 50 Hi8 tapes and more than 1800 VHS tapes of all brands, stored under constant cool conditions. I was viewing some VHS tonight from 1980 and 1984 and they are as good as the day they were recorded.

It suprises me the problems people have with VHS. It comes down to bad storage and care and the same is probably true of the CDs and DVDs that stop working. I think, in the last seven years, I have had a couple of CDs that didn't work when I went back to them, probably because I didn't check them after burning. Oh and I had one that I dropped and rolled my chair over

[Marvingj]

Heat can kill disc. Especially the Sun......

[joeg04]

I think the heat in the experiment, I described above, will not kill the disk, because I limited the heating up to 10 - 15 seconds only. So the disk gets warm, but not really very hot.

With this experiment I observe a difference between good and bad media. With the high temperature I wanted to warp the disk so much (1mm), that I can easily see the warping with help of a ruler. I think fosussing problems may already occur with much lesser warping.

[lordsmurf]

A blow dryer gets SUPER HOT in a matter of seconds. In fact, you can often burn skin or scorch hair. Hair dryers are really bad to use. Even for hair.

[joeg04]

Try it out yourself with a hair dryer and a DVD-R. If you touch the DVD-R immediately after that 10 to 15 seconds, you will observe that it is warm but not super hot.
While heating up I move the dryer slowly a little bit, so that not all heat is concentrated only on one point of the disk. The whole bottom area of the disk should heat up uniformly.

[joeg04]

In ISOBuster 1.7 version history I found the following new feature:

- Ability to wait a number of seconds before a read is retried to be able to automate reading bad discs on certain older drives that need to cool down from time to time. (Set via options menu)

Source:
https://www.videohelp.com/tools?changelog=97

I think cooling down in older drives will help to reduce temperature dependent warping of some bad disks.

[joeg04]

A blow dryer gets SUPER HOT in a matter of seconds. In fact, you can often burn skin or scorch hair. Hair dryers are really bad to use. Even for hair.

I think the discussion can be made more productive, if vague expressions like warm, hot, super hot... are replaced by a temperature value. Therefore I just repeated one experiment in a modified way:

1) I used again the white printable LONGTEN001 DVD-R as before.
2) I checked the top side with a ruler, it was flat.
3) I heated up the bottom side of the disk, until the temperature was 40°C (=104 °F) by using a hair dryer.
I verified the temperature of the disk with an infrared clinical thermometer.
I think in a normal DVD player such a temperature can be reached easily.
4) I checked again the top side with a ruler, it was now warped by about 0.5 mm. That leads to an AVERAGE tilt angle of about 0.5°. The tilt angle on the outer side of the warped disk is then much bigger than this average value and much bigger than the maximum tilt value of 0.8°/2, allowed by the DVD specification (see below).

Additional information:

Tilt: A measure of warping or dishing of an optical disc. Tilt is of particular importance for DVD discs and must be kept within strict limits.

Source:
http://www.disctronics.co.uk/technology/glossary/glossary_tz.htm

2.2.3 Tilt specification

The disc tilt limit is 0.8in the radial direction, and 0.3in the tangential direction. The specification for the radial direction is larger in consideration of the fact that it's easy for the disc to curve into a bowl shape.

Note that the tilt angle defined by the specification is not just the physical angle of inclination, but rather the angle between incident and reflected light (), measured optically.

Source:
http://www.pioneer.co.jp/crdl/tech/dvd/2-2-e.html

However, a problem arises when the disc is inclined, or tilted, with respect to the light source. A tilted disc surface cause an optical degradation known as coma aberration, which causes the light spot to be distorted and interferes with correct playback.

Source:
http://www.pioneer.co.jp/crdl/tech/dvd/2-e.html

Measuring warping: Lay the disk upside down on a ruler. The sides of the disk touch the ruler, the middle of the disk not. Look at the gap between the middle of the disk and the ruler.

[lordsmurf]

The "cooling down" you refer to in ISOBuster is being taken out of context. Not the same thing.

If you want to measure temperatures, then do a thorough test. Measure the heat of the disc, as played in 2-3 separate players, going in intervals of 1-6 hours, at each hour.

I still think the hair dryer is too much, too fast, and too hot. It's skewing the results. You also have to insure your measurement device (a ruler) is perfectly flat, as any bending in it will skew the other plane too. You'll likely need to rig up a safe measurement stand, not just "wing it" by handholding.

I'd like to see this test, but I think at this point in time you're hastily jumping to conclusions. Nobody is in a rush here, so take some time to do a thorough test. It will take some time to do.

[joeg04]

then do a thorough test.

Unfortunately, that's impossible for me with my limited equipment.
1. My infrared clinical thermometer displays only tempertures between 34°C (=93.2 °F) and 42.2 °C (=108 °F). Below 34°C it shows only "LO" and above 42.2 °C it shows only "HI".
2. Temperatures in DVD players can also be below and above this range. Even with only a slight temperature increase, temperature dependent warping may already be enough for getting playback problems, because there are many other contributions to the overall tilt. For example mechanical tolerances of the drive. So I don't know how much ADDITIONAL tilt is required for seeing playback problems.

I think from the currents experiments, from the EXISTING experience of "data disappearing", AND from your good arguments that it's not the dye, some save conclusions can be drawn:

I think it's no coincidence, that only the questionable or not properly playing DVD-Rs warped after heating up, but not the good disks. Regarding problems with some cheap disks I get more and more the impression, that the influence of dye quality is often overestimated and the influence of warping underestimated.

The material properties regarding warping (expansion temperature coefficient) may change slightly OVER TIME under influence of humidity. That may explain, why in some cases playability was first good and later bad or even not possible, at the same temperature increase in the drive. Maybe even, that by collecting moisture, a disk (with different material on top and bottom side) warps itself permanently over time, so that it's no longer playable, even at room temperature.

I think you can no longer deny the FACT, that at least some people reporting "data disappearing" did test their disks immediately after burning and stored them properly.

[joeg04]

I opened my Pioneer DV-454 for further investigation. I could not measure the temperatures in the DVD drive because I don't have an adequate thermometer. If I touch parts in the drive, they seem to be not very hot, including the top side of the disk. Perhaps only a few degrees above room temperature, if the chassis is open. What I still don't know is, how much warping of the disk is required to cause playback problems.

I saw another interesting effect: At the silver-top Philips DVD-R, the laser beam was shining bright through the disk (see photo below).
Could it be, that a white top labelling layer would reflect the laser beam strong enough to cause interference with playback?

Caution: I advise others not to repeat this experiment, to avoid exposure to a laser beam.

[lordsmurf]

Well, then maybe somebody else will read all this and have the time for such a thorough test. Until then, zero conclusions can be drawn. Far too premature. You've provided a good hypothesis, but it needs lots of testing to confirm or deny. My feeling is that it'll be totally denied, but the test need be done by somebody someday.

[joeg04]

zero conclusions can be drawn.

I agree. My current feeling is not, that it'll be totally denied. Maybe, as I mentioned before, that by collecting moisture, a disks (with different material on top and bottom side) warps ifself permanently over time, so that it's no longer playable, even at room temperature. Both, paper and inkjet printable material are designed to collect moiture, because they have to be able to hold ink. Such permanent warping may add to temperature dependent warping. Anyway, all this is only speculation up to now. I think, this problem is very complicated, and a thorough analysis will be very difficult.

[lordsmurf]

I think, this problem is very complicated, and a thorough analysis will be very difficult.

Yeah, I know how that goes. Most of the studies I do take months at minimum. Rarely do reviews, studies, etc., go very fast. If you have time, start it now, and maybe you'll be done by the fall or winter. Or maybe somebody else reading this will decide they can perform such a test.

But you do have a good thought. I would not disbelieve the heat issue as a whole, just that my initial thoughts and years of using DVD tech suggests that such heat cannot be generated under average use in a DVD player or DVD burner, not unless it's just entirely defective and is heating up due to poor ventilation (which a few of those do exist right now!).

There are too many people out there that perform one quick sloppy test on their sole piece of equipment and make a hasty judgment call, then defend it to the end, often against fact or even common sense. I'm glad you're not doing that, and that you see it as speculation (or rather, a HYPOTHESIS to work from, like science class in grade school). But, again, it's a good hypothesis, one I'd like to see a study of. Congrats for identifying it.

[ana_costa_brazil]

The ability for DYE to break down at a "fast" rate (months, few years) has been shown over and over to be pretty much impossible. It will, in many decades, start to deteriorate at earliest. The chemical reaction cycle won't happen in months or even a few years. "Fast" corruption of dye would happen in seconds if exposed to oxygen, so those rumors of glues decaying as air "slowly" permeates the materials is myth. That would cause insta-coaster, not take months.

OK.. so I bought 11 VCDs from an Ebay seller. When they arrived I noticed they had a small label on the face, BERKLEY & JENSEN. I live in Brazil so I never heard of B&J. Anyways... I played them on my DVD player. OK... all played. Then one week later I wanted to show disk # 1 to a friend and the disk wouldn't play anymore ! I tested the other ones and they are STILL playing. So I searched the web and I downloaded every software I could find that would be able to fix the errors that disk 1 were having. NONE was able to. THANK God I had copyed each VCD to my HD before I played them. Something told me I should be careful.

Looking carefully at the 11 discs I can't see any defaults. None. They seem to be perfect. So I run the DVDinfo Pro to see the media's real ID and it gave me this: CMC Magnetics Corporation. The seller of course told me the media he would use was wonderful.

What I mean to say is that its seems pretty pbvious to me that bad media (or bad recordings) can make the media non playable all of a sudden. I keep my disks away form the sun, in room temp. I don't leave them out of their cases and never put my fingers on them. I have old DVDs and CDs that continue to play normally. but it seems there are media that "erase" or damage after a while.

[lordsmurf]

CD-R is different. The discs were not tested after they were burned. They are crap media. And the details on "every software" to fix them are a bit sketchy. Definitely not an "open and closed" case, far too many unknowns and not a thorough examination from burner to supposed time of death.

[macrovision]

I wanna add my 2 cents being a tech.....Dye based media is simular to polaroid camera film with the exception that it "burns" using frequency instead of oxygen. Theoretically if you expose a fresh unburned disc to the proper frequency using a laser you will burn it even if your not transfering data(kinda like carrier wave frequency) so my guess is if you store disc next to the T.V. you may compromise its reliability simply because televisions emit high frequencies from the flyback(step-up transformer) and other electronic equipment emit high frequencies as well (like storing cassette tapes near your speakers...even if they're magnetically shielded you risk data loss...My 2 cents!