ISO/IEC 29170-2:2015

INTERNATIONAL ISO/IEC
STANDARD 29170-2
First edition
2015-08-15
Information technology — Advanced
image coding and evaluation —
Part 2:
Evaluation procedure for nearly
lossless coding
Technologies de l’information — Codage d’image avancé et
évaluation —
Partie 2: Mode opératoire d’évaluation pour codage presque sans
perte
Reference number
©
ISO/IEC 2015
© ISO/IEC 2015, Published in Switzerland
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ii © ISO/IEC 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
5 Test methods . 3
5.1 Protocol selection . 3
5.2 Media selection . 3
5.3 Observers . 3
5.3.1 Observer selection . 3
5.3.2 Observer visual screening. 4
5.3.3 Instructions to observers . 4
5.3.4 Training session . 4
5.4 Viewing conditions . 5
5.4.1 Lighting and display calibration . 5
5.4.2 Viewing distance . 5
5.4.3 Viewing position . 6
5.5 Viewing time . 7
5.6 Trial retry . 7
5.7 Test reporting . 7
5.8 Verification of procedure . 7
Annex A (normative) Forced choice paradigm with non-flickering images test protocol .8
Annex B (normative) Forced choice paradigm with interleaved images test protocol .10
Annex C (normative) Media selection and preparation procedure .12
Annex D (normative) Test report procedure .15
Annex E (informative) Observer vision testing .21
Annex F (informative) Self-test certification .22
Bibliography .25
© ISO/IEC 2015 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/IEC JTC 1, Information technology, Subcommittee
SC 29, Coding of audio, picture, multimedia and hypermedia information.
ISO/IEC 29170 consists of the following parts, under the general title Information technology —
Advanced image coding and evaluation:
— Part 1: Guidelines for coding system evaluation (forthcoming)
— Part 2: Evaluation procedure for visually lossless coding
iv © ISO/IEC 2015 – All rights reserved

Introduction
This International Standard normalizes a procedure to evaluate coding systems by subjective methods.
The procedure is particularly useful for evaluating lightly compressed coding systems used, for instance,
in display stream compression where a source compresses image data sent to a display. Examples of
display streams include but are not limited to a wired link between a set-top box unit and a television
or between a mobile host graphics processor and a display panel module in a mobile appliance. Viewers
of these displays should be unaware that a coding system is employed in the device or system. A coding
system will be considered visually lossless if the test results meet a pre-defined acceptable quality level
demonstrated by the performance criteria described in this Specification under the viewing conditions
specified and media sets provided.
Appliances that may require visually lossless performance for compressed display streams include:
computer monitor displays, televisions, mobile phone and tablet displays. Data compression for these
systems allows existing display links to carry more display data than is possible with uncompressed
image streams or to reduce system power consumption or both.
The types of coding systems tested by this procedure may have the following properties:
a) The presence of a coding system should be undetectable to a user who is viewing the display.
b) The coding system operates in real-time, with negligible latency, low complexity hardware and
minimal memory in both the encoder and the decoder.
This procedure builds on prior standardization and best practices embodied in ISO 3664, ISO 20462-2
and ISO/IEC TR 29170-1.
© ISO/IEC 2015 – All rights reserved v

INTERNATIONAL STANDARD ISO/IEC 29170-2:2015(E)
Information technology — Advanced image coding and
evaluation —
Part 2:
Evaluation procedure for nearly lossless coding
1 Scope
This Technical Specification normalizes evaluation and grading of a light coding system used for
displays and display systems, but is independent of the display technology. This procedure measures
whether an observer can distinguish between an uncompressed reference and the reconstructed image
to a pre-determined, statistically meaningful level.
The procedure compares individual images with two possible forced choice comparison test methods.
This procedure relies on subjective evaluation methods designed to discern image imperfections on
electronic colour displays of any technology or size.
Image selections for testing a specific coding system has bearing on the results this procedure will
yield, but specific images required for testing are not within scope, excluding an informative annex
describing self-test certification. Image categories may vary between end-usage products. For
example, content relevant to television manufacturers may or may not be relevant to computer display
manufacturers. Due to the nature of this procedure as a visual psychophysical test, observer’s age is
considered a meaningful parameter of the results.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3664, Graphic technology and photography — Viewing conditions
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
advance time
time a reference image or test image is displayed during an interleaved pair comparison test
3.2
algorithm
unique combination of test conditions that contribute to a unique test image, for example, the
combination of coding an image with one compression level and one coding method represents coding
with one algorithm
Note 1 to entry: Coding an image with a different compression level and the same coding method represents a
second unique algorithm.
3.3
blank time
time between trials when the display shows no stimulus
© ISO/IEC 2015 – All rights reserved 1

3.4
block of trials
long experiment is logically divided into a series of trials
Note 1 to entry: There is an expectation that the observer iteratively completes each trial presented during a
short block of time without stopping for breaks beyond those allocated by the software presentation timing.
3.5
control image
cropped test image coded to ensure defects are easily detectable in a paired comparison test
3.6
evaluator
expert in the field of image or compression artefact analysis or vision science, who prepares images,
categorizes images or instructs the observer
3.7
expert observer
observer skilled in vision science or coding technology and image artefacts
3.8
image
still representation of pixels rendered by the display
3.9
just noticeable difference
stimulus difference that would lead to a 0,75 probability of correct responses in a two-alternative
forced-choice task
3.10
non-expert observer
observer with no special skills or training in vision science or coding technology
3.11
observer
individual performing the subjective evaluation procedure by evaluating stimulus to make paired
comparison task choices
3.12
picture element
pixel
smallest element that is capable of generating the full intended functionality (e.g. colour and gray scale
...