Definitions

Definitions

BLER:
Stands for BLock Error Rate, a measure of the average number of raw channel errors when reading or writing CD type media. BLER is a measure of the number of data blocks per second that contain detectable errors at the input of the C1 decoder.

CD-R:
Stands for Compact Disc – Recordable. An extension of the CD format allowing data to be recorded once on a disc by using dye sublimation technology. Defined by part II of the Orange Book standard. Orange Book is the set of specifications created by Philips and Sony to define the optical signal characteristics, physical arrangement, writing methods and testing conditions for CD-R (Orange Book Part II) and CD-RW (Orange Book Part III) discs.

DVD-R*:
Stands for Digital Versatile Disc – Recordable. A format of DVD which uses dye sublimation recording technology, and conforms with ISO/IEC DIS 23912: Information technology - 80 mm (1.46 Gbytes per side) and 120 mm (4.70 Gbytes per side) DVD Recordable Disk (DVD-R). On DVD-R, data can be written to once and read many times.

DVD+R**:
Stands for Digital Versatile Disc + Recordable. A format of a recordable DVD which uses dye sublimation recording technology, and conforms with ISO/IEC 17344:2005: Information technology -- Data interchange on 120 mm and 80 mm Optical Disk using +R format -- Capacity: 4.7 and 1.46 Gbytes per side. On DVD+R, data can be written to once and read many times.

DVD-RW*:
Stands for DVD-ReWritable. A format of a re-writable DVD disc, which uses phase change recording technology, and conforms with ISO/IEC 17342:2004: Information technology -- 80 mm (1.46 Gbytes per side) and 120 mm (4.70 Gbytes per side) DVD re-recordable disk (DVD-RW). On DVD-RW, data can be written to several hundred times and read many times.

DVD+RW**:
Stands for DVD+ReWritable. A format of a re-writable DVD disc, which uses phase change recording technology, and conforms with ISO/IEC 17341:2005: Information technology -- Data interchange on 120 mm and 80 mm optical disk using +RW format -- Capacity: 4.70 Gbytes and 1.46 Gbytes per side. On DVD+RW, data can be written to several hundred times and read many times.

E32:
Stands for Error 32. In a CD system, there are two stages or levels of error correction codec. Each stage of the codec can correct two bad symbols in a block. The first number in an "E" error always references the number of errors and the second number always references the codec level. For example, the error type E11 means one bad symbol was corrected in the first stage (C1) or level 1; E21 means two bad symbols were corrected in the C1 stage; E31 means that there were three or more bad symbols at the C1 stage. This block is uncorrectable at the C1 stage, and is passed to the C2 stage. E12 means one bad symbol was corrected in the C2 stage and E22 means two bad symbols were corrected in the C2 stage. E32 means that there were three or more bad symbols in one block at the C2 stage, and therefore this error in not correctable.

ECC:
Stands for Error Correction Code, additional information added to data to allow errors to be detected and possibly corrected.

EOL:
Stands for End of Life. The state of the disc when the level of correctable errors is such that the onset of uncorrectable errors is imminent. For CD type media, this means when BLER reaches 220 and for DVD type media, this means when PIE reaches 280. Also may be used to describe the point at which uncorrectable errors actually occur.

Group:
A collection of specimens that are aged under the same accelerated aging condition.

Incubation Cycle:
A complete single incubation cycle includes the initial ramping to stress conditions, the maintenance at that stress condition and ramping back to ambient conditions. This is described in section 4 of this paper.

Life expectancy:
The length of time (usually measured in years), up to which, a disc is expected to provide access to data stored on it with no uncorrectable errors. For this study, and in general for optical media, it is the length of time before the level of correctable errors is such that the onset of uncorrectable errors is imminent. For CD type media, this means the length of time before BLER reaches 220 and for DVD type media, this means the length of time before PIE reaches 280.

PI and PO :
Stands for Parity Inner and Parity Outer. Reed-Solomon Product Code (RS-PC) is a method of error correction employing several (usually two) groups of Reed-Solomon parity bytes computed from rows, columns, or diagonals of a rectangular data array. DVD uses two-group method of RS-PC for error correction. The redundant codes of rows and columns are called Parity of the Inner code (PI) and of the Outer code ( PO ) respectively. DVD discs correct small read errors using PI, that operates on rows, and corrects large read errors using PO , that operates on columns of the data array.

PIE:
Stands for Parity Inner Error. The number of error corrections made on incoming rows of data in the first pass of the decoder using the inner parity correction code. A row of an ECC Block that has at least 1 byte in error constitutes a PI error. PIE is measured over 8 ECC blocks. In any 8 consecutive ECC Blocks the total number of PI errors before correction shall not exceed 280, also called as PI Sum 8.

POE:
Stands for Parity Outer Errors. Parity outer fails. The decoder was unable to correct the data using the outer parity codes. It is measured over 1 ECC block.

Shelf life:
The length of time, up to which, a blank disc is expected to be suitable for recording.

Specimen:
An individual disc as used in this aging study.

Stress:
A condition of elevated temperature and relative humidity used to accelerate the aging process for optical media in this study.

Time to failure:
From the point of view of this study, the time to failure is the time taken, in hours, for a specimen to reach the EOL.

* 'dash' media uses a low frequency track ‘wobble' to ensure the writing laser remains on track, and uses ‘pre-pits' for addressing during recording.
** 'plus' media uses a high frequency track ‘wobble' to ensure writing laser remains on track and phase modulation within that wobble for write addressing.