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Dedicated to Quality
Media Sciences, Inc. is an internationally recognized independent testing laboratory, training center, and research facility for the data storage industry. Media Sciences provides clients with professional, third party support of their quality programs. Test data and analytical reports can establish confidence in media interchange and longevity and strengthen the link between vendor and customer. Knowledge gained from our seminars enables vendors and customers to efficiently and effectively manage their quality programs.
QUALITY ALERTS: Current quality issues affecting media interchange.
Timely quality issues that affect interchange and longevity of media for mass storage.
IMPROVED DRIVES: Some newer models might read otherwise unreadable discs. These drives incorporate Partial Response Maximum Likelihood (PRML) decoding that is commonly used for hard drives and is required for Blu-ray. PRML operates prior to conventional error correction, and can significantly reduce high bit error rates caused by closely packed channel bits. PRML cannot compensate for errors from large defects that cause burst errors and disturb read drive servos. Read Drive Quality Evaluation provides useful tools.
QUESTIONABLE LONGEVITY CLAIMS: Longevity Testing by Media Sciences has shown that disc lifetimes printed on labels or in marketing literature are often misleading, or even incorrect. Longevity depends on media and recording drive quality, storage, handling, and read drive quality. Media quality depends on many indicators contained in disc interchange standards. Some life tests utilize only DVD PISum8 or CD BLER indicators that are insufficient quality indicators. Request comprehensive data from the manufacturer if archival life is important, or use our independent laboratory for accurate, objective evaluations.
BAD CD-AUDIO DISCS: CD-R discs may play in CD-ROM drives but not in car or home audio players. Problems are more frequent when discs have been recorded at 1X or at speeds above 12X. See our FAQ for additional information on this subject.
FRAGILE CDs: Some discs develop cracks near the center at high speeds. Others shatter when flexed, or metal and protective layers delaminate. High quality, stress free polycarbonate substrates do not exhibit such characteristics. Discs with high internal stress or other materials may, even though they satisfy color book requirements. High quality discs should always elastically return to their initial shape when flexed, and should have low internal stress, as indicated by low birefringence.
80 AND 90 MINUTE DISCS: Illegal high capacities are achieved using values for scanning velocity and track pitch that are slightly out of spec. Disc manufacturers correctly warn that 80 min. discs may not be recordable in all drives or with all recording software, and that recorded discs may not be readable in all drives. Higher capacity 90 and 99 minute discs present even greater risks. See our FAQ for additional information on this subject.
DEFECTIVE CD-ROM DISCS: Discs that fail for low radial tracking (push-pull) or high jitter are becoming common. Poor quality control at mastering or molding is the cause. Such discs will read in some drives but fail in others. Conduct CD TESTING to verify that your discs will be readable in all drives.
INVALID CD FORMATS: Forbidden switching between XA and CD-ROM sectors, incorrect post-gap formats, erroneous volume descriptors, and missing L path tables have been recently observed. Defective pre-mastering software causes these problems that forgiving systems may ignore. Every replica will contain the same defects, and some will unexpectedly fail. SOFTWARE supports format testing by users that understand sector structures. Or use our reliable CD TESTING service.
UNUSUAL CD SHAPES: Standards allow only round 120 mm and 80 mm diameter discs. "Business Card" or other irregular shapes may result in unpredictable interchange. Discs that work in some drives can fail in others. CD TESTING of all important physical and optical quality requirements must be conducted to verify that discs will be readable in all drives.
CD RADIAL ACCELERATION: Sudden radial jumps in track location are causing unpredictable field failures. This serious problem can result from either mastering or molding flaws, but it has appeared more frequently as molding cycle times have decreased. Although a specification for radial acceleration has existed since 1980, test equipment manufacturers are just now offering a radial acceleration capability. CD TESTING is available from Media Sciences that can aid in troubleshooting field failures or in evaluating vendors.
CD-R BRANDS: Both interchange and longevity can be compromised without careful media selection. An in-depth MEDIA SURVEY of 41 discs from 13 manufacturers showed that 17 discs passed, 13 were marginal, and 11 discs failed.
JEWEL CASES: CD-ROM samples have been received loose in some jewel cases that appear to be thinner than normal. Many discs have been scratched or otherwise physically damaged during shipment. Such discs often contain uncorrectable errors. Check for proper clamping in jewel cases used to ship discs.
CD-R INTERCHANGE: Severe defects caused by recording systems such as absent or short postgaps, high jitter, and severe E32 errors originate from flaws in recording software or in the CD-R drives themselves. Discs recorded by these systems may be readable in some drives but will fail in others. CD-R TESTING will identify such defects and support corrective action before field failures occur.
