2.3.5 Recording quality as a constitutive factor of life expectancy of recordable optical discs

Recordable optical discs (CD-Rs, DVD-Rs, BD-Rs) have become very popular media for audio, video, and data recording. As with many other digital carriers, their reliability depends on a sophisticated error correction system that permits the full reconstruction of the information even if small parts of the medium have become unreadable because of damage or deterioration by ageing. The correction capability is limited and, therefore, the quality of the recording becomes an important factor of life expectancy. A perfect, almost error free recording leaves more correction capacity to compensate for handling and ageing effects and, therefore, enhances the life expectancy. If, however, optical discs start their life with a high error rate, then there is little capacity left to compensate for further errors. The life of such discs will be shorter. Consequently, IASA has defined recommendations for maximal acceptable errors for optical discs in order to maximize their life expectancy, whatever it may be (IASA-TC 04, 8.1.9).

A major problem in burning recordable optical discs is the interaction between blanks (unrecorded discs) and writers. There are no standards defined, and the processes of automated adjustment do not always work sufficiently well. Tests have shown that randomly chosen blank/writer combinations produce 50% acceptable, and 50% unfavourable results. Consequently, to reliably burn recordable optical discs would need extensive testing of writer/blank combinations, control of each single disc produced, and further checking at regular intervals. As testing is labour intensive and test equipment is expensive, more reliable and, ultimately, more cost effective storage systems than recordable optical discs are used for professional data storage.15

15. J.-M. Fontaine, 2000.