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 F.746.1 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2014) SERIES F: NON-TELEPHONE TELECOMMUNICATION SERVICES Audiovisual services Requirements for low-latency interactive multimedia streaming Recommendation ITU-T F.
2、746.1 ITU-T F-SERIES RECOMMENDATIONS NON-TELEPHONE TELECOMMUNICATION SERVICES TELEGRAPH SERVICE Operating methods for the international public telegram service F.1F.19 The gentex network F.20F.29 Message switching F.30F.39 The international telemessage service F.40F.58 The international telex servic
3、e F.59F.89 Statistics and publications on international telegraph services F.90F.99 Scheduled and leased communication services F.100F.104 Phototelegraph service F.105F.109 MOBILE SERVICE Mobile services and multidestination satellite services F.110F.159 TELEMATIC SERVICES Public facsimile service F
4、.160F.199 Teletex service F.200F.299 Videotex service F.300F.349 General provisions for telematic services F.350F.399 MESSAGE HANDLING SERVICES F.400F.499 DIRECTORY SERVICES F.500F.549 DOCUMENT COMMUNICATION Document communication F.550F.579 Programming communication interfaces F.580F.599 DATA TRANS
5、MISSION SERVICES F.600F.699 AUDIOVISUAL SERVICES F.700F.799 ISDN SERVICES F.800F.849 UNIVERSAL PERSONAL TELECOMMUNICATION F.850F.899 HUMAN FACTORS F.900F.999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T F.746.1 (10/2014) i Recommendation ITU-T F.746.1 Requiremen
6、ts for low-latency interactive multimedia streaming Summary Recommendation ITU-T F.746.1 describes the major functions and their interactions for low-latency interactive multimedia streaming (LIMS). The scenarios and requirements are also identified in this Recommendation. Desktop and client-server
7、applications can be provided to users through LIMS. The desktop application software and client software of client-server applications are deployed in the LIMS platform (server) and the outputs of the applications are delivered back to users as media streams. In such a way, the traditional data stor
8、ing, computing and graphic processing tasks are offloaded from user devices to LIMS servers. Provided the interaction delay is kept low, LIMS can provide the same experience to end users with less powerful devices. The output of one instance of the application can be encoded into different audio and
9、 video formats, which can be sent to one or more user devices simultaneously. That means the application can be used continuously when the user switches from a powerful device such as a high-end computer to a less powerful device such as a mobile phone or vice versa. Since the software is no longer
10、installed in the user device, easier deployment, maintenance and upgrade of the software is possible in the centrally-managed LIMS servers are much easier than before. If needed, it is easy to provide centralized management capability to fulfil the requirements of enterprises, such as single sign-on
11、 and access control. It is very difficult to hack an application provided through LIMS. Furthermore, software reverse engineering is no longer possible, which is useful for the protection of intellectual property rights. Since the delay of interaction with the application has a major impact on the u
12、ser experience, it is critical for LIMS to keep the interaction delay in a range that the end user is willing to tolerate. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T F.746.1 2014-10-14 16 11.1002/1000/12225 Keywords Interactive multimedia streaming, low-latency, service
13、 provider. _ * 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 F.746.1 (10/2014) FOREWORD The International Telecommunication U
14、nion (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 responsible for studying technical, operating and tariff questions
15、 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 ITU-T study groups which, in turn, produce Recommendations on
16、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 collaborative basis with ISO and IEC. NOTE In this Recommendation, the e
17、xpression “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 mandatory provisions (to ensure, e.g., interoperability or appli
18、cability) 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. The use of such words does not suggest that compliance with t
19、he 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 takes no position concerning the evidence, validity or applicabi
20、lity 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 property, protected by patents, which may be required to implement
21、 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 2015 All rights reserved. No part of this publication may be reproduced, by any means
22、whatsoever, without the prior written permission of ITU. Rec. ITU-T F.746.1 (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 . 1 4 Abbreviations and acronyms 2 5 Conventions 2 6 Introduction . 3 7
23、 Scenarios for LIMS . 5 7.1 LIMS for enterprise application delivery . 5 7.2 LIMS for application delivery service 6 7.3 LIMS for family application delivery . 6 8 Requirements for LIMS 7 8.1 General requirements 7 8.2 Client-side requirements . 8 8.3 Platform-side requirements 8 8.4 Requirements fo
24、r the service provider side 9 8.5 Codec requirements 9 8.6 Security requirements . 9 Appendix I An experiment for measuring the delay tolerance level of various applications . 10 I.1 Testing environment . 10 I.2 Extra delay imposed and applications tested 10 I.3 Test solutions 11 I.4 Test results 12
25、 Bibliography. 14 Rec. ITU-T F.746.1 (10/2014) 1 Recommendation ITU-T F.746.1 Requirements for low-latency interactive multimedia streaming 1 Scope This Recommendation identifies the functions, scenarios and requirements for low-latency interactive multimedia streaming (LIMS). 2 References The follo
26、wing ITU-T Recommendations and other references contain 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 Recom
27、mendation are therefore encouraged to investigate the 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
28、give it, as a stand-alone document, the status of a Recommendation. ITU-T H.263 Recommendation ITU-T H.263 (2005), Video coding for low bit rate communication. ITU-T H.264 Recommendation ITU-T H.264 (2013), Advanced video coding for generic audiovisual services. ITU-T H.265 Recommendation ITU-T H.26
29、5 (2013), High efficiency video coding. ITU-T T.81 Recommendation ITU-T T.81 (1992), Information technology Digital compression and coding of continuous-tone still images Requirements and guidelines. ITU-T T.87 Recommendation ITU-T T.87 (1998), Information technology Lossless and near-lossless compr
30、ession of continuous-tone still images Baseline. ITU-T T.800 Recommendation ITU-T T.800 (2002) | ISO/IEC 15444-1:2004, Information technology JPEG 2000 image coding system: core coding system. ISO/IEC 14496-3 ISO/IEC 14496-3 (2009), Information technology Coding of audio-visual objects Part 3: Audio
31、. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 application server: A device composed of the server software of a client-server application as well as the hardware and software environment to support it
32、. 3.2.2 low-latency interactive multimedia streaming (LIMS): A service used to provide the applications to users as interactive media streams. 3.2.3 low-latency interactive multimedia streaming (LIMS) client: A device used to collect the user commands and send them to the LIMS server as well as disp
33、lay the media stream from the LIMS server. 2 Rec. ITU-T F.746.1 (10/2014) 3.2.4 low-latency interactive multimedia streaming (LIMS) platform communication module: A module used to receive user commands from the LIMS client and send them to the LIMS proxy service module as the input of application lo
34、gic. 3.2.5 low-latency interactive multimedia streaming (LIMS) proxy service module: A module used to provide the software environment for desktop application software or the client software of client-server application. It is also responsible for forwarding the user commands from the LIMS platform
35、communication module to the application, and sending the output of the application to the LIMS visualization and compression module. 3.2.6 low-latency interactive multimedia streaming (LIMS) server: A device composed of the LIMS platform communication module (LPC), LIMS proxy service module (LPS), L
36、IMS visualization and compression module (LVC) and LIMS stream service module (LSS). 3.2.7 low-latency interactive multimedia streaming (LIMS) stream service module: A module used to receive audio and video streams from the LIMS visualization and compression module and stream the mixed media stream
37、back to the LIMS client. 3.2.8 low-latency interactive multimedia streaming (LIMS) visualization and compression module: A module used to convert the output of application into images and audio data and encode them into video streams and audio streams. 4 Abbreviations and acronyms This Recommendatio
38、n uses the following abbreviations and acronyms: AAC Advanced Audio Coding ALS Audio Lossless Coding CPU Central Processing Unit DDoS Distributed Denial of Service GPU Graphical Processing Unit HID Human Interface Device LIMS Low-latency Interactive Multimedia Streaming LPC LIMS Platform Communicati
39、on LPS LIMS Proxy Service LSS LIMS Streaming Service LVC LIMS Visualization and Compression MPEG Motion Picture Experts Group PC Personal Computer TV Television USB Universal Serial Bus VoD Video on Demand 5 Conventions In this Recommendation the following conventions are used: “Shall“ indicates a m
40、andatory requirement. “Should“ indicates a suggested but optional course of action. Rec. ITU-T F.746.1 (10/2014) 3 “May“ indicates an optional course of action rather than a recommendation that something take place. 6 Introduction In a low-latency interactive multimedia streaming (LIMS) system, a us
41、ers experience of one application is the display of an interactive media stream customized for him/her. The various functions and modules required by a LIMS system are shown in Figure 6-1. The LIMS client collects the user inputs from devices such as a keyboard, pointing device or any other input de
42、vice and transfers them to the LIMS server as user commands. The LIMS platform communication (LPC) module of the LIMS server relays the user commands to LIMS proxy service (LPS), which are used as the input of the application software. Besides providing the input and output channels, the LPS is also
43、 responsible for providing all the necessary software environment and resources for the application software, which might be the software of desktop applications or the client software of client-server applications. Figure 6-1 Framework of a LIMS system The commands are then processed by the applica
44、tion logic, which is part of the standalone desktop program or the server software of a client-server application. The output is then processed by the display controller. Usually a graphical processing unit (GPU), of LIMS visualization and compression (LVC) module shall convert the visual informatio
45、n into images and an audio driver shall convert the audio information into audio data. The images and audio data shall be compressed by the video encoder and audio encoder respectively. The resulted audio stream and video stream shall be sent to LIMS streaming service (LSS), which delivers the mixed
46、 media stream back to the LIMS client. Finally, the LIMS client decodes the media stream and displays the audio and video contents to the user. The software including a standalone program of a desktop application and the client part of a client-server application is not installed in the user devices
47、 as before. That means a user device will not execute the application logic as well as most of the graphic processing tasks. The tasks left to the user device are collecting the user inputs/commands from the keyboard, mouse as well as other input 4 Rec. ITU-T F.746.1 (10/2014) devices and forwarding
48、 them to the LIMS server, and displaying the media streams which is the output of the application sent back from the LIMS server. The software is deployed in the LIMS servers and the output of application logic is sent to the display controller for further processing, in which case GPU rendering and
49、 audio processing might be involved. The output images from display controller might be encoded or compressed into different formats, such as lossy and lossless JPEG formats ITU-T T.81, ITU-T T.87 or JPEG 2000 format ITU-T T.800. The output images are further encoded into video sequences. Many video codec standards are available, such as ITU-T H.263, ITU-T H.264, ITU-T H.265. Both lossy digital audio compression and lossless audio compression codec standards are available, such as
