1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T P.916 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2016) SERIES P: TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Audiovisual quality in multimedia services Information and guidelines for assessing and min
2、imizing visual discomfort and visual fatigue from 3D video Recommendation ITU-T P.916 ITU-T P-SERIES RECOMMENDATIONS TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Vocabulary and effects of transmission parameters on customer opinion of transmission quality Series P.10 Voice terminal char
3、acteristics Series P.30 P.300 Reference systems Series P.40 Objective measuring apparatus Series P.50 P.500 Objective electro-acoustical measurements Series P.60 Measurements related to speech loudness Series P.70 Methods for objective and subjective assessment of speech quality Series P.80 P.800 Au
4、diovisual quality in multimedia services Series P.900 Transmission performance and QoS aspects of IP end-points Series P.1000 Communications involving vehicles Series P.1100 Models and tools for quality assessment of streamed media Series P.1200 Telemeeting assessment Series P.1300 Statistical analy
5、sis, evaluation and reporting guidelines of quality measurements Series P.1400 Methods for objective and subjective assessment of quality of services other than voice services Series P.1500 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T P.916 (03/2016) i Recommend
6、ation ITU-T P.916 Information and guidelines for assessing and minimizing visual discomfort and visual fatigue from 3D video Summary Recommendation ITU-T P.916 addresses issues related to assessing and minimizing visual discomfort and visual fatigue from 3D video. Issues addressed include 3D video c
7、haracteristics that cause visual discomfort; symptoms of visual fatigue; relationships among the camera positions, the captured content and the viewers perception; footage guidelines; viewer guidelines; information on the 3D; and viewing environment considerations. History Edition Recommendation App
8、roval Study Group Unique ID* 1.0 ITU-T P.916 2016-03-15 9 11.1002/1000/12778 * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T
9、P.916 (03/2016) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is resp
10、onsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the
11、ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborat
12、ive basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain ma
13、ndatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements.
14、 The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU ta
15、kes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual prop
16、erty, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2016 All rights reserved
17、. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T P.916 (03/2016) iii Table of Contents Page 1 Scope . 1 1.1 Limitations 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommen
18、dation . 1 4 Abbreviations and acronyms 3 5 Conventions 3 6 Technological issues for 3D displaying 3 6.1 Accommodation-vergence conflict 3 6.2 3D geometric distortions 4 6.3 Visual comfort zone or comfortable viewing zone 6 7 Binocular disparity relationship in capturing, storing and rendering . 7 7
19、.1 Conversion equations . 7 7.2 Conversion of pixel disparities to a perceptual space 8 7.3 Typical constraints for displays 11 8 3D video content guidelines . 14 8.1 Introduction 14 8.2 Disparity constraints . 14 8.3 View asymmetries 16 8.4 Scene cuts . 17 8.5 Excessive disparity/parallax . 17 9 3D
20、 viewer guidelines 17 9.1 The influence of stereopsis and abnormal binocular vision (ABV) . 17 9.2 Warnings for subjects . 18 9.3 Symptoms of 3D visual fatigue 18 10 3D viewing environment and playback guidelines . 18 10.1 Relationship between viewer and 3D monitor . 19 10.2 Viewing time and visual
21、fatigue . 20 11 Assessment methods for symptoms of visual fatigue . 20 11.1 Questionnaire to assess symptoms of visual fatigue 20 11.2 Pair comparison (PC) subjective test to visual discomfort . 20 Appendix I Open questions . 22 Appendix II Visual fatigue questionnaire . 23 Bibliography. 25 iv Rec.
22、ITU-T P.916 (03/2016) Introduction Three dimensional television (3DTV) systems are based on binocular disparity. Compared to the real world scenario, the reproduction of depth in 3DTV systems is limited by the camera position, number of cameras, source content and the technical limitations of the di
23、splay technique. These include resolution, frame rate and view separation conditions. Current display technologies may also induce a conflict between accommodation (eyes focusing on the screen) and the convergence (eyes converging to a point in front of or behind the screen). These limitations can c
24、ause visual discomfort and visual fatigue. Rec. ITU-T P.916 (03/2016) 1 Recommendation ITU-T P.916 Information and guidelines for assessing and minimizing visual discomfort and visual fatigue from 3D video 1 Scope This Recommendation includes information and guidelines for assessing and avoiding vis
25、ual discomfort and visual fatigue from 3D video. It describes potential causes of visual discomfort and symptoms of 3D visual fatigue, including problems caused by watching stereoscopic and autostereoscopic television. This information is primarily intended to be used for the design and conduct of s
26、ubjective assessment of the video or audiovisual quality of 3D video. This information is also appropriate for all 3D viewing experiences. 1.1 Limitations This Recommendation includes guidance on recognizing visual fatigue symptoms and identifying 3D programming clip characteristics that may cause v
27、isual fatigue. This Recommendation excludes objective assessment methods of 3D visual fatigue, because these are not computational algorithms but rather correspond to a medical diagnostic process performed by medical doctors. 2 References The following ITU-T Recommendations and other references cont
28、ain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate th
29、e possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a
30、Recommendation. ITU-T P.913 Recommendation ITU-T P.913 (2016), Methods for the subjective assessment of video quality, audio quality and audiovisual quality of Internet video and distribution quality television in any environment. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in
31、this Recommendation This Recommendation defines the following terms: 3.2.1 accommodation-vergence conflict: Accommodation (eyes focussing on an object) and convergence (eyes pointing toward the object) are normally linked. Accommodation-vergence conflict is a conflict between accommodation (eyes foc
32、using on the screen) and the convergence (eyes converging to a point in front of or behind the screen). Current 3D display technologies may induce accommodation-vergence conflict. 3.2.2 binocular disparity: The two eyes view an object from two different positions and angels. Due to the paralax, the
33、object is projected at different positions on the retina of each eye. The 2 Rec. ITU-T P.916 (03/2016) differences of the position between these two projections is the binocular disparity. This can be the strongest depth cue for close objects. 3.2.3 binocular depth cues: Binocular depth cues stem fr
34、om binocular disparity and the state of the oculomotor system. 3.2.4 cardboard effect: The cardboard effect occurs when the imaging and display conditions reduce the reproduction magnification ratio of depth directions and distort the perception of objects with visually imperceptible thickness. The
35、3-D positions of stereoscopic objects are perceived stereoscopically but they appear unnaturally thin. 3.2.5 depth cues: Visual indicators of the relative distances between the observer and viewed objects. There are binocular and monocular depth cues. 3.2.6 depth distortion: Depth distortion is the
36、discrepancy between the displayed depth reconstruction and real world. The cardboard effect is one example of a depth distortion. 3.2.7 depth motion: Objects moving in depth (e.g., toward the viewer). 3.2.8 depth resolution: spatial resolution in depth direction. 3.2.9 frame effect: 3D pictures appe
37、ar highly unnatural when objects positioned in front of the screen approach the screen frame. This unnatural effect is called “the frame effect“. The effect is generally reduced with a larger screen, because observers are less conscious of the existence of the frame when the screen is larger. 3.2.10
38、 medical signs: Medical signs are physiological reactions that are measured and interpreted within a controlled procedure. 3.2.11 medical symptoms: Medical symptoms are expressed by the observer and constitute an indication of his or her perceived mental or physical state. 3.2.12 planar motion: Moti
39、on with constant depth (i.e., within a plane perpendicular to the observer). 3.2.13 puppet theatre effect: This is an example of size distortion. The reproduction magnification ratio of an object at the shooting distance (the perceived size) varies with the imaging and display conditions. The result
40、ing distortion in size may make an object be perceived as unnaturally small. 3.2.14 size distortion: Distortions in the 3D geometry may occur due to inconsistencies between the capturing situation (notably the camera settings) and the reproduction (notably the display settings). The puppet theatre e
41、ffect is an example. 3.2.15 monocular depth cues: Monocular depth cues can be perceived from a single eyes view. They include occlusion (objects hidden behind other objects), relative sizes of known objects, vanishing point perception, blur from the focus, motion parallax, light, shade, texture grad
42、ient, aerial perspective, height in the visual field, kinetic depth and others. 3.2.16 visual comfort zone: Visual comfort zone is defined as the depth interval which allows for 3D viewing without the introduction of visual discomfort. 3.2.17 visual discomfort: Visual discomfort is a negative sensat
43、ion that is subjectively reported. Visual discomfort may be triggered by the perception of 3D presentations. Visual discomfort is usually a transient state that disappears quickly after the person stops watching the problematic stimuli. The amount and duration of visual discomfort is highly individu
44、al. Visual discomfort may have other causes, such as visual flicker. 3.2.18 visual fatigue: Visual fatigue is generally caused by the repetition of excessive visual effort and can build up as these efforts are repeated. It disappears after sufficient rest. Visual fatigue is a medical state that may
45、be objectively diagnosed by the presence of objective indications Rec. ITU-T P.916 (03/2016) 3 (medical signs) and subjective indications (medical symptoms). Visual fatigue can only be diagnosed by a medical doctor. 3.2.19 window violation: Window violation occurs when an object that is in front of
46、the display overlaps the border of the screen. The 3D screen is often perceived as a window and in the real world objects can only be cropped when they lie behind the window. However, objects with crossed disparity are also cropped. When this occurs, the part of the object within the screen appears
47、to be in front of the screen, while the cropping conflicts with this perception, by implying that the object should be at the depth of the screen or behind the screen. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: 3DTV Three Dimensional Television AB
48、V Abnormal Binocular Vision HD High Definition HRC Hypothetical Reference Circuit HUD Head-up Display PC Pair Comparison SD Standard Definition 5 Conventions “3D“ in this Recommendation refers to a technology that projects dedicated views for each eye. The ultimate goal is that these views depict th
49、e same situation as would be seen in reality (e.g., horizontally shifted). The technology as a whole can include more than two views, as per a multi-view autostereoscopic display. This can be noted as S3D for stereoscopic TV, or 3DMV for multiview. 6 Technological issues for 3D displaying This clause describes background information required to understand technological issues for displaying 3D content, including constraints of camera capture, transmission, display and the human visual system. 6.1 Accommodation-vergence conflict Accommodation (eyes focussing on
