ECMA Publishes New Standard for Testing CD/DVD Disc Longevity
Even if you have never heard of ECMA International before, you are probably familiar with the results of their work. When a manufacturer of blank DVD media advertises that their discs will last for “up to 100 years,” they can make that claim because of work done by ECMA.
But wait a minute! How do we really know that their discs will last for one hundred years? Discs haven’t been around that long! Well, that part is true. However, media manufacturers can make very accurate guesses as to how long a disc will last based on laboratory testing. ECMA International is the organization which develops the standards by which optical discs are tested.
The original standard was called ECMA-379 and was first published in April of 2008. This document established a method for testing the lifespan of recordable DVD media. The standard was revised four times, and updated most recently in 2010. While it proved valuable to researchers and disc manufacturers, there were a few problems with ECMA-379.
First, it only had provisions for testing DVD-R media. The testing criteria did not include CD-R, Blu-ray discs, or other media such as dual-layer DVD discs. This is inconvenient because people often use these other types of discs in addition to DVD-R media for storing their pictures, video, and information.
Second, the older ECMA standard only tested the longevity of optical media under extreme conditions. A typical test consisted of storing a sample of 90 discs at temperatures between 65 degrees C and 85 degrees C for a period of 9 months, with a relative humidity of between 70% to 85%. This test did not account for discs stored under normal, climate-controlled conditions.
Thus, we have the new standard: ECMA-396. Unlike the old standard, ECMA-396 includes provisions for testing all types of optical discs such as DVD-R/RW/RAM, DVD+R/+RW and CD-R/RW. This makes it a much more comprehensive test for all the various types of media in use today.
Additionally, the new standard includes a climate-controlled storage test, with temperatures of 25 degrees C and relative humidity of approximately 50% with full-time air conditioning. This additional test accounts for the conditions under which most optical media is stored, as opposed to long-term tests in greenhouse-like environments.
The published document for ECMA-396 explains in detail the conditions under which optical discs must be tested to predict their longevity. By doing an intense stress test for a period of time and recording the number of discs which fail, researchers can use mathematics to calculate the total life span of the discs. This process is called Accelerated Life Testing, or ALT.
There are two methods the ECMA recommends for calculating the lifespan of a disc. The first is called the Arrhenius method, which uses linear regression to figure out how long it will be before the discs fail. The second method is the Eyring Method, which uses multiple linear regression. Both of these mathematical formulas are models for predicting aging based on temperature and on temperature and relative humidity.
The significance of the ECMA’s new document means that in a few months, we may start seeing new or revised claims from media manufacturers about the lifespan of their blank CD and DVD discs. Will media manufacturers still boast 100-year lifespan claims for their discs with these new testing criteria? Only time will tell.