SIST ISO 18921:2011

INTERNATIONAL ISO
STANDARD 18921
Second edition
2008-10-15
Imaging materials — Compact discs
(CD-ROM) — Method for estimating
the life expectancy based on the effects
of temperature and relative humidity
Matériaux pour l'image — Disques compacts (CD-ROM) — Méthode
d'estimation de l'espérance de vie basée sur les effets de la
température et de l'humidité relative

Reference number
©
ISO 2008
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ii © ISO 2008 – All rights reserved

Contents Page
Foreword .iv
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Purpose and assumptions.3
4.1 Purpose .3
4.2 Assumptions.3
5 Measurements .3
5.1 Block error rate (BLER).3
5.2 Test equipment .3
5.3 Test specimen.4
6 Accelerated stress test plan.4
6.1 General .4
6.2 Stress conditions .5
6.3 Accelerated test cell specimen population.7
6.4 Time intervals .8
6.5 Test plan.8
6.6 Measurement conditions .8
7 Data evaluation .8
7.1 Eyring acceleration model.8
7.2 Failure distribution model .9
7.3 Acceleration factors .9
7.4 Survivor analysis.10
8 Disclaimer .10
Annex A (informative) Step analysis outline .11
Annex B (informative) Example of test plan and data analysis.12
Bibliography.19

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 18921 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18921:2002), of which it constitutes a minor
revision.
The following changes have been made to the first edition:
⎯ modification of definition 3.8 (life expectancy);
⎯ modification of 5.1 on block error rate;
⎯ correction of Equations (1) and (2) in 7.1;
⎯ updating of normative and bibliographical references;
⎯ removal of the original Annex A.

iv © ISO 2008 – All rights reserved

INTERNATIONAL STANDARD ISO 18921:2008(E)

Imaging materials — Compact discs (CD-ROM) — Method
for estimating the life expectancy based on the effects
of temperature and relative humidity
1 Scope
This International Standard specifies a test method for estimating the life expectancy (LE) of information
stored on compact disc (CD-ROM) media, including CD audio, but excluding recordable media. Only the
effects of temperature and relative humidity on the media are considered.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
1)
ISO/IEC 10149 , Information technology — Data interchange on read-only 120 mm optical data disks
(CD-ROM)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
cumulative distribution function
F(t)
probability that a random unit drawn from the population fails by time t, or the fraction of all units in the
population which fails by time t
3.2
survivor function
R(t)
probability that a unit drawn from the population will survive at least time t, or the fraction of units in the
population that will survive at least time t
NOTE R()tF=−1 (t) .
3.3
baseline
condition representing the disc at time of manufacture
NOTE This is customarily the initial parameter measurement taken prior to any application of stress. The designation
is usually t = 0 for a stress time equal to zero hours.

1) Equivalent to ECMA 130.
3.4
block error rate
BLER
ratio of erroneous blocks to total blocks measured at the input of the first (C1) decoder (before any error
correction is applied)
NOTE The more commonly reported value for BLER is the number of erroneous blocks per second measured at the
input of the C1-decoder during playback at the standard (1X) data rate.
[IEC 60908:1999]
3.5
CD-ROM
compact disc-read only medium
3.6
end-of-life
occurrence of any loss of information
3.7
information
signal or image recorded using the system
3.8
life expectancy
LE
length of time that information is predicted to be retrieved in a system at 23 °C and 50 % relative humidity
(RH)
3.8.1
standard life expectancy
SLE
minimum life span, predicted with 95 % confidence, of 95 % of the product stored at a temperature not
exceeding 25 °C and a relative humidity (RH) not exceeding 50 % RH
3.9
retrievability
ability to access information as recorded
3.10
stress
experimental variable to which the specimen is exposed for the duration of the test interval
NOTE In this International Standard, the stress variables are confined to temperature and relative humidity.
3.11
system
combination of recording medium, hardware, software and documentation necessary to retrieve information
3.12
test cell
device that controls the stress to which the specimen is exposed
3.13
test pattern
distribution of the characters l and 0 within a block and the block-to-block variation
2 © ISO 2008 – All rights reserved

4 Purpose and assumptions
4.1 Purpose
The purpose of this International Standard is to establish a methodology for estimating the life expectancy of
information stored on CD-ROMs. This methodology provides a technically and statistically sound procedure
for obtaining and evaluating accelerated test data.
4.2 Assumptions
The validity of the procedure defined by this International Standard relies on three assumptions:
⎯ the dominant failure mechanism acting at the usage condition is the same as at the accelerated
conditions;
⎯ the dominant failure mechanism is appropriately modelled by an Eyring acceleration model;
⎯ life expectancy is appropriately modelled by the two parameter Weibull distribution (see [1] in the
Bibliography). The shape parameter of the Weibull distribution is assumed to be independent of the stress
level.
5 Measurements
5.1 Block error rate (BLER)
The objective of measuring the block error rate (BLER) is to establish a practical estimation of the system's
ability to read the pre-recorded bits using a standard drive. This International Standard considers BLER to be
a high level estimate of the performance of the system. A change in BLER in response to the time at an
elevated temperature and humidity is the principal quality parameter.
–2
IEC 60908 states that the BLER averaged over any 10 s shall be less than 3 × 10 . At the standard (1X) data
rate, the total number of blocks per second entering the C1-decoder is 7 350. Thus, an equivalent limit on
BLER is 220 blocks per second.
For the purposes of this International Standard, recorded data are considered to have reached end-of-life
when the BLER, measured as erroneous blocks per second, exceeds 220 anywhere on the disc, i.e. when the
maximum BLER exceeds 220. It is recognized that the correlation between actual loss of information and
maximum BLER is very system dependent. A BLER of 220 is an arbitrary level chosen as a predictor of the
onset of uncorrectable errors and thereby end-of-life.
5.2 Test equipment
5.2.1 Compact disc test system
Any compact disc test system (tester) that is in accordance with ISO/IEC 10149 may be used. The make,
model and version of the test equipment (including software) shall be reported with the test results.
5.2.2 Calibration and repeatability
Calibration according to the tester manufacturer's procedure shall be performed prior to any measurement
data being collected. A calibration disc shall be available from the tester manufacturer.
In addition to the calibration disc, one control disc shall be maintained at ambient conditions and its maximum
BLER measured before and after each data collection interval. A control chart shall be maintained for this
control disc with ± 3 σ action limits. The mean and standard deviation of the control disc shall be established
by collecting at least five measurements. Should any individual maximum BLER reading exceed the action
limit, the problem shall be corrected and all data collected since the last valid control point shall be
remeasured.
If it becomes necessary to replace the tester, a method shall be followed for correlating tester outputs (see [2]
in the Bibliography).
5.3 Test specimen
A test specimen is any disc that meets ISO/IEC
...