1、BSI Standards Publication BS ISO/IEC 29170-2:2015 Information technology Advanced image coding and evaluation Part 2: Evaluation procedure for nearly lossless codingBS ISO/IEC 29170-2:2015 BRITISH STANDARD National foreword This British Standard is the UK implementation of ISO/IEC 29170-2:2015. The
2、UK participation in its preparation was entrusted to Technical Committee IST/37, Coding of picture, audio, multimedia and hypermedia information. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the ne
3、cessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2015. Published by BSI Standards Limited 2015 ISBN 978 0 580 85940 3 ICS 35.040 Compliance with a British Standard cannot confer immunity from legal obligations. This British Standa
4、rd was published under the authority of the Standards Policy and Strategy Committee on 30 September 2015. Amendments/corrigenda issued since publication Date T e x t a f f e c t e dBS ISO/IEC 29170-2:2015 Information technology Advanced image coding and evaluation Part 2: Evaluation procedure for ne
5、arly lossless coding Technologies de linformation Codage dimage avanc et valuation Partie 2: Mode opratoire dvaluation pour codage presque sans perte INTERNATIONAL STANDARD ISO/IEC 29170-2 Reference number ISO/IEC 29170-2:2015(E) First edition 2015-08-15 ISO/IEC 2015 BS ISO/IEC 29170-2:2015ii ISO/IE
6、C 2015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2015, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or postin
7、g on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41
8、 22 749 09 47 copyrightiso.org www.iso.org ISO/IEC 29170-2:2015(E)BS ISO/IEC 29170-2:2015ISO/IEC 29170-2:2015(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Symbols and abbreviated terms . 3 5 Test methods . 3 5.1 Protocol selection . 3 5.2 Media sel
9、ection . 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
10、retry . 7 5.7 Test reporting . 7 5.8 Verification of procedure . 7 Annex A (normative) F or c ed choic e par adigm with non-flick ering images t est pr ot oc ol 8 Annex B (normative) Forced choice paradigm with interleaved images test protocol .10 Annex C (normative) Media selection and preparation
11、procedure .12 Annex D (normative) Test report procedure 15 Annex E (informative) Observer vision testing .21 Annex F (informative) S elf-t est c ertification 22 Bibliography .25 ISO/IEC 2015 All rights reserved iii Contents PageBS ISO/IEC 29170-2:2015ISO/IEC 29170-2:2015(E) Foreword ISO (the Interna
12、tional 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 establishe
13、d 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 fiel
14、d 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
15、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
16、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 thi
17、s 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 ISOs adherence to the WTO principles in the Technical Barriers t
18、o 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 th
19、e general title Information technology Advanced image coding and evaluation: Part 1: Guidelines for coding system evaluation (forthcoming) Part 2: Evaluation procedure for visually lossless codingiv ISO/IEC 2015 All rights reservedBS ISO/IEC 29170-2:2015ISO/IEC 29170-2:2015(E) Introduction This Inte
20、rnational 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 disp
21、lay 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 co
22、ding 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 perf
23、ormance 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
24、 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 m
25、emory 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 vBS ISO/IEC 29170-2:2015BS ISO/IEC 29170-2:2015Information technology Advanced image coding and eval
26、uation 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 distingu
27、ish 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 im
28、perfections 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 certific
29、ation. 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, observers age is considered a meaningful parameter
30、 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 (in
31、cluding any amendments) applies. ISO 3664, Graphic technology and photography Viewing conditions 3 T erms a nd definiti ons 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 comp
32、arison 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
33、level and the same coding method represents a second unique algorithm. 3.3 bl a n k t i me time between trials when the display shows no stimulus INTERNATIONAL ST ANDARD ISO/IEC 29170-2:2015(E) ISO/IEC 2015 All rights reserved 1BS ISO/IEC 29170-2:2015ISO/IEC 29170-2:2015(E) 3.4 b l o c k o f t r i a
34、 l s 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 ima
35、ge 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 vis
36、ion 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 observe
37、r 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 intende
38、d functionality (e.g. colour and gray scale) of the display Note 1 to entry: In a multicolour display, the smallest addressable element capable of producing the full colour range or the smallest element that is capable of generating the full functionality of the display. 3.13 reference image cropped
39、 original image displayed during a trial 3.14 session description of the full time interval in which an observer participates in the experiment on a given day Note 1 to entry: It can encompass multiple blocks of trials. A full experiment can be divided into multiple sessions. 3.15 test image cropped
40、 version of a reconstructed image after coding displayed during a trial2 ISO/IEC 2015 All rights reservedBS ISO/IEC 29170-2:2015ISO/IEC 29170-2:2015(E) 3.16 trial single unit of the experiment Note 1 to entry: A set of images will be presented on the screen for a defined viewing time. The trial is c
41、omplete only when the observer has entered a response. 3.17 viewing time number of seconds an observer views paired stimuli. The viewing time has a maximum value in all situations 3.18 visually lossless fully decoded image or multimedia sample presenting a display that is visually indistinguishable
42、from the original uncompressed data over the same spatial area and when viewed under the same conditions 4 Symbols and abbreviated terms AQL acceptable quality level PPD pixels per degree RGB red-green-blue 5 Test methods 5.1 Protocol selection The evaluator shall select the most suitable test proto
43、col from those listed in Table 1 and contained in the listed annex. The protocol selection depends on the media under test, end display usage and the target AQL. Table 1 Visually lossless testing protocol Test Protocol Comment Annex A forced choice paradigm with a non-flick- ering image sensitive te
44、sting, suitable for testing images compressed and reconstructed by light coding systems, but not as sensitive as interleaved testing Annex B forced choice paradigm with interleaved images most sensitive testing, suitable for testing images com- pressed and reconstructed by light coding systems 5.2 M
45、edia selection Media selection takes images or other media for display rendering relevant to the display type and user applications. Evaluators shall follow media selection procedures in Annex C after selecting a test protocol. 5.3 Observers 5.3.1 Observer selection The observers shall be selected f
46、rom a general population that may include both experts and non- experts. The observers for the experiment shall not include evaluators who participated in the media selection for the experiment being conducted. ISO/IEC 2015 All rights reserved 3BS ISO/IEC 29170-2:2015ISO/IEC 29170-2:2015(E) The obse
47、rver population should include variations in gender, ethnicity and age. The experiment is visual in nature and age can strongly correlate to visual acuity, therefore, participant age for this procedure favours the age range for the observer from 18 to 30 years old. An observers age shall not exceed
48、40 years. This procedure recommends evaluators recruit a suitable number of observers sufficient to include no less than 10 observers who pass visual acuity (see 5.3.2) and test reporting (see D.1.2) requirements of this Technical Specification. 5.3.2 Observer visual screening The following selectio
49、n criteria shall apply: a) Observers may wear corrective lens, either glasses or contacts that shall not have multiple focal lengths, e.g. progressive, bifocal or trifocal corrective lens. b) Observers shall demonstrate normal visual acuity verified by using a Snellen reading test chart where the observer reads at 20/20 from 50 cm. c) Participants shall demonstrate normal colour vision verified by testing with Ishihara plates or equivalent. Evaluators can refer to Annex E for tools th
