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 G.1091 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2014) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Multimedia Quality of Service and performance Generic and user-related aspects Quality
2、of Experience requirements for telepresence services Recommendation ITU-T G.1091 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION
3、 SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHON
4、Y AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.10
5、00G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.1091 (10/2014) i Recommendation ITU-T
6、 G.1091 Quality of Experience requirements for telepresence services Summary Telepresence is an interactive audio-visual communications experience between remote locations, where users enjoy a strong sense of realism and presence between participants by optimizing a variety of attributes such as aud
7、io and video quality, eye contact, gaze awareness, body language, spatial audio, coordinated environments and natural image size. In this regard, delivering a high-level of quality of experience (QoE) is an important factor. Recommendation ITU-T G.1091 provides guidelines for achieving high QoE in t
8、elepresence services. First, a high-level description of a telepresence system is described, with an overview of important use cases. Then, specific audio and visual parameters, and other characteristics that are important from a QoE perspective are defined. Where possible, specific values for the p
9、arameters necessary to achieve high QoE are recommended, along with references to associated test methodologies. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.1091 2014-10-29 12 11.1002/1000/12310 Keywords QoE, telepresence. _ * To access the Recommendation, type the URL
10、 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 G.1091 (10/2014) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the
11、 field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standa
12、rdizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is cov
13、ered 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 collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indi
14、cate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achiev
15、ed 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. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL P
16、ROPERTY 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 takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asse
17、rted 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 property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned
18、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 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. R
19、ec. ITU-T G.1091 (10/2014) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 2 5.1 Requirement terminology . 2 5.2 Icons used . 2 6 High-level QoE considerati
20、ons for telepresence services 3 6.1 Telepresence system description 4 6.2 Use cases 4 7 Audio characteristics 5 7.1 Send and receive loudness ratings 5 7.2 Send and receive side frequency responses 5 7.3 Send and receive side distortion . 6 7.4 Send and receive side noise 6 7.5 Directionality of aud
21、io (spatial characteristics) 6 7.6 Acoustic echo/double talk 6 7.7 Intelligibility of audio . 6 8 Video characteristics . 6 8.1 Actual size 6 8.2 Resolution (definition) 6 8.3 Image quality 6 8.4 Eye gaze 7 8.5 Spatial considerations for video . 7 9 Display characteristics 7 9.1 Screen size 7 9.2 As
22、pect ratios . 7 9.3 Continuity across borders . 7 9.4 Colour space (4:2:2, 4:2:0, 4:4:4) . 7 9.5 Colour fidelity 7 9.6 Mirrored image . 7 10 Audiovisual characteristics . 7 10.1 Absolute delay of audio and video streams 8 10.2 Lip sync 8 11 Room characteristics . 8 iv Rec. ITU-T G.1091 (10/2014) Pag
23、e 11.1 Background noise . 8 11.2 Reverberation . 8 11.3 Lighting 8 11.4 Sound uniformity 8 11.5 Impact of seating arrangements 8 11.6 Temperature 8 11.7 Humidity . 8 11.8 Audibility in local room . 8 12 Other characteristics . 9 12.1 Ease of use 9 Bibliography. 10 Rec. ITU-T G.1091 (10/2014) 1 Recom
24、mendation ITU-T G.1091 Quality of Experience requirements for telepresence services 1 Scope This Recommendation provides guidelines for achieving high quality of experience (QoE) in telepresence services. First, a high-level description of a telepresence system is described, with an overview of impo
25、rtant use cases. Then, specific audio and visual parameters, and other characteristics that are important from a QoE perspective are defined. Where possible, specific values for the parameters necessary to achieve high QoE are recommended, along with references to associated test methodologies. The
26、list of parameters and requirements is not to be considered as an exhaustive list, and it is expected that this Recommendation will be updated as more experience is gained with telepresence systems. 2 References The following ITU-T Recommendations and other references contain provisions which, throu
27、gh 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 the possibility of applying t
28、he 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 Recommendation. ITU-T F.734
29、 Recommendation ITU-T F.734 (2014), Definitions, requirements and use cases for telepresence systems. ITU-T G.131 Recommendation ITU-T G.131 (2003), Talker echo and its control. ITU-T H.420 Recommendation ITU-T H.420 (2014), Telepresence system architecture. ITU-T P.300 Recommendation ITU-T P.300 (2
30、001), Transmission performance of group audio terminals (GATs). 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 actual size ITU-T F.734: A rendered figure in a display is the same size as if the person is in the room. 3.1.2 gaze awarene
31、ss ITU-T F.734: Awareness of gaze direction of persons by watching their eyes, head and body position. There is awareness of both direct gaze and averted gaze. Direct gaze is the perception of persons looking at each other directly and simultaneously. Averted gaze is the perception that other person
32、s are looking at someone/something else in the environment. 3.1.3 gaze direction ITU-T F.734: The vector positioned along the visual axis, pointing from the fovea of the looker through the centre of the pupil to the gazed-at spot. 3.1.4 eye contact ITU-T F.734: Technically equivalent to a mutual dir
33、ect-gaze between two persons communicating. 3.1.5 render b-IETF RFC 7262: The process of generating a representation from a media, such as displayed motion video or sound emitted from loudspeakers. 2 Rec. ITU-T G.1091 (10/2014) 3.1.6 telepresence ITU-T F.734: An interactive audio-visual communicatio
34、ns experience between remote locations, where the users enjoy a strong sense of realism and presence between participants by optimizing a variety of attributes such as audio and video quality, eye contact, gaze awareness, body language, spatial audio, coordinated environments and natural image size.
35、 3.1.7 telepresence system ITU-T H.420: A set of functions, devices and network elements which are able to capture, deliver, manage and render multiple high quality interactive audio and video signals in a telepresence conference. An appropriate number of devices (e.g., cameras, screens, loudspeaker
36、s, microphones, codecs, multipoint control units, PCs) and environmental characteristics are used to establish telepresence. 3.2 Terms defined in this Recommendation None. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: CRC Call and Resource Controller
37、 GW Gateway IP Internet Protocol MCU Multipoint Control Unit PC Personal Computer PLMN Public Land Mobile Network QoE Quality of Experience 5 Conventions 5.1 Requirement terminology In this Recommendation the following conventions are used: “Shall“ indicates a mandatory requirement. “Should“ indicat
38、es a suggested but optional course of action. “May“ indicates an optional course of action rather than a recommendation that something take place. 5.2 Icons used Figure 1 shows the meaning of icons used in this Recommendation. Rec. ITU-T G.1091 (10/2014) 3 Figure 1 Icons used in this Recommendation
39、6 High-level QoE considerations for telepresence services This clause provides a high-level description of telepresence systems. Some scenarios and use cases are also provided to provide a context for assessing the important factors from the point of view of QoE. 4 Rec. ITU-T G.1091 (10/2014) 6.1 Te
40、lepresence system description The term “telepresence systems“ is used to refer to conferencing systems that provide high definition and high quality audio/video, enabling a “being-there“ experience. A telepresence system includes endpoints (both telepresence and legacy), multipoint control unit (MCU
41、), call and resource controller (CRC), gateway (GW), management system, etc., as shown in Figure 2. ITU-T H.420, “Telepresence System Architecture“, provides a detailed description of a telepresence system. Figure 2 High-level telepresence architecture network model 6.2 Use cases Clause 6 of ITU-T F
42、.734, “Definitions, requirements, and use cases for telepresence systems“, presents a set of use cases describing typical scenarios. The most common and basic use cases are introduced and illustrated in detail, which are described from the viewpoint of the users. 6.2.1 Use case 1: Symmetric point-to
43、-point meeting In this use case, each of the two sites has an identical number of screens, with cameras having fixed fields of view, and one camera for each screen. The number of screens or cameras is not relevant as long as both sites have the same number. The sound type is the same at each end. Fi
44、gure 3 illustrates the use case. Figure 3 Use case 1: Symmetric point-to-point meeting For further information, see clause 3.1 of b-IETF RFC 7205. Rec. ITU-T G.1091 (10/2014) 5 6.2.2 Use case 2: Multipoint meeting In this use case of a multipoint telepresence conference, there are more than two site
45、s participating. Figure 4 illustrates the use case. The number of screens or cameras can be different or the same. Each site can have different audio/video characteristics. For further information, see clause 3.3 of b-IETF RFC 7205. Figure 4 Use case 2: Multipoint meeting 7 Audio characteristics Thi
46、s clause describes the audio characteristics related to QoE of telepresence services in more detail. 7.1 Send and receive loudness ratings Telepresence systems shall send audio to other telepresence systems with a SendLoudnessRating of (+ 13 Fs) dB, measured in accordance with ITU-T P.300. In order
47、to take into account the difference between the reference test positioning and the actual microphone-talker operating distance (ds), for which the terminal is adjusted, the following correction factor Fs is defined: (ds in metres) Telepresence systems shall receive audio from other telepresence syst
48、ems with a nominal Receive Loudness Rating of (+ 5 Fr) dB, measured in accordance with ITU-T P.300. In order to take into account the difference between the reference test positioning and the actual loudspeaker-listener operating distance (dr) for which the terminal is adjusted, the following correc
49、tion factor Fr is defined: (dr in metres) 7.2 Send and receive side frequency responses Telepresence systems shall provide audio with send and receive side frequency responses from 100 Hz to 20 kHz. 5.0dL o g20dBF ss 0 .5dL o g20dBF rr6 Rec. ITU-T G.1091 (10/2014) 7.3 Send and receive side distortion Telepresence systems shall provide audio with send and receive side distortion less than 3%. Note, different specifications exist for send and recei
