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"DVD Rot" /
    DVD Longevity and Reliability  (9/2003)

    by Douglas Dixon

The Issues
Pressed Discs: "Disc Rot"
Care and Handling
Longevity of Recordable Discs
Recordable DVD Compatibility Test
DVD-ROM Compatibility Test
Choosing Discs
References

What is going on with DVDs? The industry states that discs should last 50 to 100 years, but on-line reports claim significant problems with both pressed and recordable discs. Can movie discs wear out and fail from "DVD rot?" Is recordable DVD a trustworthy archival media, or is there evidence that discs can wear out from extended play? And what is the situation with the compatibility of recordable media? Is there a way to guarantee reasonable compatibility, some magic combination of formats and brands, software and burners, content and players?

       

DVD was supposed to be the answer: reliable and compatible, from movies on the set-top to digital video on the desktop. Instead, it just seems to get more confusing and frustrating.

Longevity and compatibility were among the issues explored at the DVD 2003 International Conference, held in June in Gaithersburg, Maryland. This is the annual conference of the DVD Association (DVDA, www.dvda.org), an independent organization of DVD professionals, and co-sponsored by the National Institute of Standards and Technology (NIST, www.nist.gov), an agency of the U.S. Department of Commerce involved in developing and promote technology, measurement, and standards, from atomic clocks and automated teller machines to mammograms and semiconductors.

The conference included sessions on "Preserving Digital Assets on DVD" and "DVD Quality, Longevity, and Compatibility," and did promise some answers from independent testing of DVD characteristics.

The Issues

Before getting to the conference, let's first understand the issues, what all the fuss is about on the Internet.

The first issue is "DVD rot," a term derived from problems with laser discs and now applied to problems with pressed discs when Hollywood movie DVDs become unplayable, either as the video starts to break up during playback due to corrosion in the disc, or the disc itself even begins to physically split apart due to delamination of the bonded layers.

Beyond the online discussion groups, this issue was highlighted by The Sydney (Australia) Morning Herald, in a widely linked article from February 1, 2003 (www.smh.com.au/articles/2003/01/31/1043804519345.html). The Herald reported that some DVD movies "are already starting to rot while others are falling apart." The article states that "unofficial estimates put the number of affected discs at between one and 10 per cent." It then characterizes the industry response by reporting that "some of the largest distributors for Hollywood Studios are accused of refusing to accept the problem exists and replace faulty products."

Web sites now collect lists of Hollywood movie titles reportedly known to have problems. Other frequently-linked sites carry photographs of cloudy regions that have grown along the edges of discs, and even electron microscope images of "spots" that appear to be associated with playback failures across the layer break of dual-layer DVD-9 discs. The DVD industry has clearly not responded effectively to these reorts and concerns.

The second issue is the reliability of recordable DVD discs as an archival media, either for write-once recordable (R) or rewritable (RW) formats. Can we really trust that we can save our digital files for decades on DVD discs? Or, if we use them constantly in applications like kiosk displays, is it possible for them to effectively burn out from constantly being read by a laser beam?

The final issue is the compatibility of recordable discs. We all have seen cases where discs that we burnt did not work as expected on a DVD player. Consumer and even professional discussion lists repeatedly carry plaintive queries and speciation about which brands of DVD media are reliable.

The industry seems to require that consumers depend on folklore and anecdotal reports for finding reliable and compatible media. Web pages and discussion lists spread confusion about possible problems, and even suggestions of shady behavior by manufacturers of DVD media.

Some posts suggest that different batches of media from the same manufacturer can have significantly different reliability, so that each batch should be spot-checked before acceptance. Others suggest sticking with media from the same brand as the manufacturer of the DVD burner. And recently there have been reports of counterfeit discs with name-brand labeling, and suggestions of gray-market discs from lower-quality manufacturing batches.

What is the poor consumer supposed to do with this mess? The sessions and studies presented at the DVD 2003 Conference can help provide some answers.

Pressed Discs: "Disc Rot"

First up is the issue of "disc rot," movies on DVD that become unplayable after some period of time.

The replicator/duplicator perspective was presented at the conference by Melodie Gee, Vice President and General Manager, Content Delivery Solutions, with Metatec International in Columbus, Ohio (www.metatec.com). Gee described several causes of induced manufacturing problems from inappropriate materials that could result in lower-quality discs. These included poor adhesives that could cause the layers to split, impure metal, poor resin (recycled or lower grade polycarbonate, or even the rumored use of acrylic), inks that are not formulated for low shrinkage, and even misalignment of the center hole. As a manufacturer, Gee stressed the importance of proper premastering and the use of DVD test equipment to verify the discs.

Gee also elaborated problems that could be caused by inappropriate packaging, including hub damage from standard (CD) jewel boxes, warping from shrink-wrap or flimsy mailers, and even damage from improper gluing in the packaging.

Beyond these kinds of manufacturing issues, the industry needs to do more to educate consumers that DVDs are not indestructible, and therefore should be handled with some care. It is not obvious that DVDs can warp and cause playback problems if stored horizontally, or that the disc hub can be damaged by forcing discs in and out of holders (DVDs should rotate freely in a holder; CD jewel cases have a tighter hub that is not appropriate for DVDs). Similarly, while the technology is tolerant of errors from some scratches and fingerprints, the smudge from a greasy finger not only covers a large area, but the laser actually needs to make a round trip to read through it, both to penetrate down through the surface to reach the data, and then to reflect back up to the detector.

Subutai Ahmad of the Optical Storage Technology Association (OSTA, www.osta.org) also reports that "we have seen quite a few problems with paper labels. The problem is that if the labels are not centered correctly, or if they peel off even a little bit, they can cause the disc to wobble slightly while spinning. This causes read problems for the drive."

Care and Handling

The range of these kinds of handling issues that can effect DVD playability is described by Andy Parsons, Senior Vice President, Product Development and Technical Support, Pioneer Electronics (www.pioneerelectronics.com):

"If a customer claims that they have a non-playable disc that "used to work fine", we typically ask many questions. First, what is the condition of the disc in question? Any fingerprints or obvious contamination on the surface? Any scratches (particularly tangential ones)? Has the disc been left in a player with the power on for days or weeks at a time (flatness is important for reliable playback)? How about the environment where the disc is stored? Has it been left out in the open where dust can collect on the playable surface? How about the player? How old is it? How many hours has it been used? Is there a layer of dust all over the player? What is the temperature where the player is operating? And so on. In my experience (since 1980), one of these questions almost always reveals something that helps explain the change in performance."

Consumers have gotten used to handling CDs, and do seem to realize that DVDs should be treated with some care. For example, a recent study by 321 Studios (supporting the use of its products to back up commercial DVDs) listed consumer-reported causes of damage to commercial DVDs, including accidents (21%), normal wear and tear (10%), loss (10%), and extreme weather conditions (2%), in addition to "DVD rot" (8%).

One source for educating consumers is the "Care and Handling Guide for the Preservation of CDs and DVDs" published by NIST, along with an accompanying "Quick One-Page Reference" (www.itl.nist.gov/div895/carefordisc). These guidelines stress the importance of handling and storing discs with care, avoiding warping and adhesive labels, and not exposing discs to extremes of temperature and humidity.

But the bottom line is still that we should be able to expect commercial DVDs to be long-lasting. According to Parsons, well-made DVDs should last "for many, many decades as long as they have been stored in a hospitable environment and handled with care."

And we should be able to expect that such discs are well-made. Adds Parsons, "DVD's are a well-known product, and making them is not a mystery to a competent replicator. Any company that knows what it's doing with respect to raw material procurement and process control can make high quality product."

Longevity of Recordable Discs

The same applies to recordable discs. We should be able to expect that discs are well made, and need to take some care in handling and storing them. But are at least some recordable discs archival quality, or do they burn out? And how can we tell which are which?

At the DVD 2003 Conference, several speakers from the NIST Digital Preservation Program presented early results from evaluating the stability and longevity of optical discs as a continuation of its work with CDs (www.itl.nist.gov/div895/isis/datastorage.html).

NIST is performing accelerated lifetime testing in environmental chambers, and also evaluating the effect of exposure to light on recordable discs, for example by simulating exposure to mid-August noon sunlight. Preliminary results with a few samples show wide variation between different products, with some surviving over 2500 hours, and others failing after 500 to 1000 hours. This ongoing work is intended to lead to the development of standards for archival-grade discs.

For recordable discs, NIST currently recommends avoiding prolonged exposure to sunlight or other sources of UV light. For long-term storage or archival purposes, NIST recommends using discs that have a gold metal reflective layer.

Recordable DVD Compatibility Test

The other pressing issue for recordable discs is compatibility, and especially whether we can burn discs that play reliably on set-top players. The first strong answers came from Ralph LaBarge's DVD Compatibility Test, reported in DV Magazine, July 2002 (www.dvdtoday.com/Recordable_DVD_Test.htm). This stunning effort involved over 2400 unique tests of the playback performance of over 35 different brands of media on over 70 set-top players from some 22 manufacturers.

Not surprisingly, the results showed differences in compatibility between professional DVD-R for Authoring, write-once recordable (R), and rewritable (RW) formats, since we are used to RW discs being less compatible from the experience with CDs. But instead of providing ammunition to use in the ongoing dash vs. plus format war, the key results showed stunning variation in the performance within each individual format, and across different media and players. For example, for DVD-R for General format, the compatibility ratings between the best and worst brands ranged from 80 to 40 percent!

LaBarge's conclusions stressed that to achieve higher compatibility, customers need to be careful selecting products, paying attention to both the disc media brand and player make and model. The results did show that the situation was improving, and that newer players (since 2001) had dramatically improved results.

At the DVD 2003 conference, LaBarge reported on phase 2 of the DV Magazine Recordable DVD Compatibility Test. The test still focused on consumer DVD-Video players, using a test matrix of 70 different formats and brands of recordable DVD media, and over 30 late model players. Testing with newer players, the results showed some improvement, with some consumer formats up to 97% compatibility. Again, the differences between formats were less important than the variation within each format, typically around 10 to 15 percentage points. Unfortunately, the industry still seems to not have matured enough to achieve consistent and reliable manufacturing.

DVD-ROM Compatibility Test

In addition to LaBarge's tests of the compatibility of recordable DVDs on consumer set-top players, a second group is examining compatibility with computer DVD-ROM drives. Also at the DVD 2003 Conference, Subutai Ahmad of the DVD Compatibility committee reported on this joint effort by three groups, the Optical Storage Technology Association (OSTA), NIST, and the DVD Association.

Ahmad is Vice President of Software Engineering with YesVideo, which provides a mail-in tape to DVD transfer service for consumers and professional videographers (www.yesvideo.com). Clearly, YesVideo would be out of business if it could not deliver highly-compatible DVDs for consumer players. For this reason, YesVideo had been using DVD-R for Authoring format, but is now converting to consumer recordable discs.

The Phase 1 effort of this group, with a target date of September 2003, include creating test plans, performing correlations between compatibility and physical measurements, and feeding detailed data back to individual manufacturers. The testing includes 40 discs from 19 manufacturers, tested on 14 DVD-ROM drives from 7 manufacturers.

The preliminary results found no significant compatibility difference between write once and rewritable media! They also showed steadily improving compatibility of discs manufactured from 1999 to 2002. The 2002 media in particular showed much better performance, without even intermittent problems.

The discs also were physically tested to attempt to correlate the compatibility results with physical measurements. The testing found that maximum inner parity error was a good predictor of compatibility. This suggests that there is a class of marginal discs that may seem to burn successfully, but will be prone to future problems.

Again, this testing found significant variation between different drives and discs, and even between the same disc formats.

Choosing Discs

The goal for DVD reliability and compatibility is clear. "Consumers should expect the same level of compatibility as they get with recordable VHS tapes, i.e. 100%," says Subutai Ahmad, of OSTA and YesVideo. "There is no technical reason why this cannot be achieved."

The DVD industry works through associations such as the DVD Forum (www.dvdforum.com) and the DVD+RW Alliance (www.dvdrw.com) to establish operating parameters and provide verification labs for media manufacturers. For example, Kerwyn Ballinger of Hewlett-Packard, speaking for the DVD+RW Alliance, says "the alliance members work with disc manufactures to ensure media production meets or exceeds specifications. Strict operating parameters and standards must be met prior to a media manufacture being allowed to use the DVD+R/RW license/logo and considered a qualified manufacture of media."

Yet both consumer experience and the testing results reported at the DVD 2003 Conference show that the DVD industry is still maturing, and that there is, in fact, significant variability in the quality of discs from different manufacturers.

"This is a really important issue for YesVideo," says Ahmad. "We put our media through a rigorous test process. We have sourced and tested media from over 10 sources. Before we purchase, we visit the company's manufacturing facilities, verify their QA process, do in-house proprietary physical testing, and compatibility testing with a large set of DVD players. We also sample discs from every batch shipped to us and return the batch if the discs don't meet our standards."

As a result, for the best chance of good reliability and compatibility, it's best to stick with name-brand products from reputable manufacturers. While consumers seem to understand the risk of using cheaper and possibly off-brand media from gray-market resellers, the allure of a bargain can be very tempting. Warns Andy Parsons of Pioneer, "Don't succumb to the temptation to save a few dollars by buying very cheap product from an unknown supplier. The old adage "you get what you pay for" is true with most any product, and recordable DVD is no exception."

And once you buy your discs, treat them with a little care, as described in the NIST Guide. Avoiding extremes in temperature and humidity, as well as exposure to direct sunlight. Store discs upright to avoid bending, and take care in removing them from carriers to avoid scratches and fingerprints. Clean them carefully, by wiping with a clean cotton fabric in a straight line from the center of the disc toward the outer edge (not with a circular motion).

With continued pressure from educated consumers, and independent testing from the likes of LaBarge and NIST, we should be able to expect that DVDs can achieve the reliability and compatibility we have come to expect from CD discs.

References

DVD Association (DVDA)
    www.dvda.org

National Institute of Standards and Technology (NIST)
    www.nist.gov

NIST Digital Preservation Program
    www.itl.nist.gov/div895/isis/datastorage.html

DVD Forum
    www.dvdforum.com

DVD+RW Alliance
    www.dvdrw.com

Optical Storage Technology Association - OSTA
    www.osta.org

Metatec International - Replicator/Duplicator
    www.metatec.com

Pioneer Electronics
    www.pioneerelectronics.com

YesVideo
    www.yesvideo.com

DVD Compatibility Test
    Ralph LaBarge, AlphaDVD
    DV Magazine, July 2002
    www.dvdtoday.com/Recordable_DVD_Test.htm

Care and Handling Guide for the Preservation of CDs and DVDs
    National Institute of Standards and Technology (NIST)
    CLIR and NIST joint project
    NIST Special Publication 500-252, May 2003
    PDF - 52 pages (1.55 MB file)
    www.itl.nist.gov/div895/carefordisc

A bad case of DVD rot eats into movie collections
            By Sue Lowe
            Sydney Morning Herald
            February 1, 2003
            www.smh.com.au/articles/2003/01/31/1043804519345.html