Frequently Asked Questions  

Please contact Media Sciences if your questions are not answered on these pages.

Select a category for a list of frequently asked questions.

CD and DVD Glossary: More than 200 terms from 8-to-16 to Yellow Book.

Quality Issues: Answers to questions about general quality issues.

Compact Discs Answers to questions about CD discs.

CD Recordable/ReWritable Answers to questions about CD-R and CD-RW discs.

DVD Recordable Answers to questions about DVD discs.

Diskettes Answers to questions about flexible diskettes.

Helpful Topics

Home Page: What's new, quality alerts.

Quality Testing: Obtain test results for indicators that predict successful interchange.

Training Seminars: Learn fundamentals and the newest techniques from experienced instructors.

FAQs: Answers to frequently asked questions about interchangeable computer media.

How to Contact Media Sciences: by phone, fax, e-mail, Internet, or mail.

About Media Sciences: History and personnel.

Site Map: Guide to all resources on this web site.

Other Services: Personalized support, specs, reference and calibration discs, and a torque kit.

Product Certification: Vendor certification based on ISO Standards.

Publications: A Quality Tips book, papers, and a newsletter offer timely information.

ISO Standards: Listings and sources of international Standards for interchange.

Links for Professionals: Other web sites containing useful quality and technology information.

Freeware and Shareware for Computer Media: Conduct quality tests using these programs.

FREQUENTLY ASKED QUESTIONS ABOUT QUALITY

1. How are CD and DVD specs related to sound and picture quality?

2. Do we really need flawless discs? It is not practical to meet demands for perfect quality.

3. When I talk to knowledgeable quality engineers, they talk of AQL methods that require sample sizes involving hundreds of units. Media Sciences seems to use much smaller sample sizes. Does this compromise your testing?

4. How do AQL, LTPD, and SPC sampling plans differ?

5. What is the accepted value or benchmark for incoming media defects?

6. What is a test plan, and how do you define critical, major, and minor defects?

FREQUENTLY ASKED QUESTIONS ABOUT COMPACT DISCS

1. Why should I spend money to test CD-R and CD-ROM discs? They seem to work just fine in our drives.

2. Long lists of CD quality indicators do not really interest me. Which ones are really important?

3. Is it true that BLER is the best measure of CD quality?

4. Why do low BLER discs fail in some user drives?

5. Is it true that jitter is the most important measurement of CD quality?

6. What do the tests referenced in CD standards really mean?

7. CD jitter test equipment seems to be expensive. Correlation problems also seem to exist. Is jitter really important? Is there an inexpensive way to measure jitter?

8. Why do you insist that CD E22 and E32 errors must be zero? I cannot find this requirement in any of the standards. Only BLER and BURST are specified, and seem to be adequate quality indicators.

9. Standards only require CD-ROM and CD-R discs to have a BLER less than 220. Why bother with tighter limits or other tests such as E22 and E32?

10. My CD-ROM discs unpredictably fail in the field. Some show E22 and E32 errors that do not always reproduce when the disc is retested. What is wrong with the data on these discs?

11. What is CD unbalance? Why do I keep hearing about it?

12. Why do CD discs fail in some drives but are readable in others?

13. CD discs work great in our test drive. Why do they fail in some 40X and higher speed drives?

14. Fragile CD discs are causing user problems. They crack or even shatter in high speed drives. What causes this? Discs appear to satisfy the standards.

15. My CD-ROM discs sometimes contain milky areas when viewed from the readout side. When I call this to the attention of their manufacturer, I am told that the effect is only cosmetic. Sometimes I cannot read such discs. Is it possible that my quality problems are related to this unusual appearance?

16. ISO, ECMA, and ANSI Standards for diskettes designate PTB Reference Material. CD-ROM Standards do not. Why?

17. I do not obtain the same CD test results using test equipment from various vendors or even with different testers from the same manufacturer. Why cannot these CD test equipment manufacturers achieve correlation?

18. I thought compact discs were bulletproof. Why do I hear that careful handling is required?

19. Are CD and DVD discs reliable? I keep hearing about "CD Rot" and "Techno Rot" that imply media is unstable.

20. Are CDs damaged by irradiation of U.S. mail?

21. CD discs that arrive in cardboard sleeves seem to work o.k. Why do a few suppliers continue to use expensive jewel cases?

22. What is the best way to clean a dirty CD-ROM or CD-R disc or to repair a scratched disc?

23. Some DVD drives read my CD-R or CD-RW discs while others do not. What is wrong with the discs?

24. What is the meaning of ISO 9660, Joliet, and other options in my pre-mastering software?

FREQUENTLY ASKED QUESTIONS ABOUT CD-R AND CD-RW DISCS

1. Who makes good CD-R and CD-RW discs? How can I be certain they will work in my writer?

2. Are green CD-R discs better than gold or blue ones?

3. Do gold CD-R discs have better longevity than green discs?

4. Rumors state that silver CD-R discs can damage the lasers in drives. Do blue CD-R discs with silver metallization have the same quality as gold?

5. I am told by some suppliers that all CD-R discs are the same. Others tell me that gold discs are the best, another states that blue discs are of the highest quality, and some say that silver is unacceptable. What discs are best?

6. How are Grade A, Grade B, and Grade C CD-R discs defined? Are they all usable?

7. What are "audio" rated CD-R discs? Are they of higher quality?

8. The manufacturer of my 48X CD-R writer states that media used in the writer must be 48X certified. Is this just an attempt to control my choices of media?

9. I always buy high capacity, 74 minute CD-R discs. Why would anyone use discs with only 63 minute capacities?

10. Where can I find the new 90 minute CD-R discs? Why were they previously unavailable?

11. Tests of blank floppy disks can assure quality. Why not do the same for blank CD-R discs?

12. Why does my recording software indicate different capacities for CD-R discs from various manufacturers?

13. Why do I hear so much about CD-R problems? Isn't CD-R the same as CD-ROM, a trouble-free product?

14. What level of cleanliness is required to write high quality CD-R discs? How can it be achieved?

15. Even after a successful recording, a CD-R disc may not be readable. The drive does not recognize it. Does this indicate a defective unrecorded disc?

16. Recorded CD-R discs work fine in my CD-R drive but fail in some CD-ROM drives. Do I have format problems?

17. Why do I have problems reading CD-R discs recorded at high speeds, especially in my car player?

18. Sometimes CD-R writing aborts, and the recorded disc is not readable? What is wrong with my discs?

19. I do not have any coasters, and my recorded discs are perfectly readable. Why should I be concerned about CD-R quality?

20. Is it safe to use marking pens on CD-R discs?

21. When should multisession recording be used?

22. Why are ISO Mode 2 image files that I create not properly recorded to the disc?

23. My latest CD-R software has CD-ROM/XA Mode 2 as the default format for multisession. I am told that this is best if recorded discs are to be playable in all drives. Is this correct?

24. My recording software erroneously places two-second gaps between tracks when I do multi-track recording. Why don't engineers fix their bad software?

25. What are the most important requirements of CD-R discs used for mastering?

26. Some new CD recorders offer "running OPC" that is advertised as a necessary feature. If this is true, how did older recorders work without it?

27. My CD recording program suddenly gives strange error messages such as I/O errors. What is wrong with my hardware?

28. Does 1X recording result in better CD-R quality than high speed recording provides?

29. Why do my CD-R audio discs work in my computer but not in my car or home audio player?

FREQUENTLY ASKED QUESTIONS ABOUT DVD DISCS

1. I hear of many different DVD recordable or rewritable discs. Are they all acronyms for a single format? Which one is best?

2. Why do low PIE discs fail in some user drives?

3. Is UDF required for all DVD discs?

FREQUENTLY ASKED QUESTIONS ABOUT FLEXIBLE DISKS

1. Why bother with diskette quality certification? I understand that floppies will be obsolete in a few months.

2. What is the accepted value or benchmark for error rates in duplication and interchange?

3. I agree with your comments about high clip diskettes, but many say that high clip is essential to long term, archival storage quality. Does clip level deteriorate with time?

4. Some diskette manufacturers are replacing traditional 3.5" stainless steel shutters with other materials such as plastic or coated aluminum shutters. Are there potential problems with permanent deformation of aluminum due to its low elasticity? Can plastic shutters develop static charge that attracts dust?

5. What selection criteria and pitfalls are important when selecting liner material for diskettes?

6. Why must diskettes be erased before duplication?

7. What is asymmetry and why is it an important duplication quality issue?

8. My diskette vendor tells me that his diskettes are better because they have low peak shift and therefore fewer read errors. Is this correct?

9. We duplicate diskettes that must have files written to them by the user, so write protection is not possible. How can we avoid boot sector and FAT corruption by the user?

10. Why do disks jam in autoloaders? Their manufacturers claim that they meet all specifications.