1、 International Telecommunication Union ITU-T J.388TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2010) SERIES J: CABLE NETWORKS AND TRANSMISSION OF TELEVISION, SOUND PROGRAMME AND OTHER MULTIMEDIA SIGNALS Digital transmission of television signals Real-time video and audio transmission system o
2、ver IP networks Recommendation ITU-T J.388 Rec. ITU-T J.388 (08/2010) i Recommendation ITU-T J.388 Real-time video and audio transmission system over IP networks Summary Recommendation ITU-T J.388 defines a system for real-time video/audio transmission over an IP-based network. The protocol of the s
3、ystem consists of session control and media transmission. Session control is based on the session initiation protocol (SIP), and for the use of SIP this Recommendation refers to Recommendation ITU-T J.366.4. Several types of packet formats are defined for media transmission. With regard to codecs, t
4、his Recommendation provides some mandatory codecs and some optional ones. The system equipped with the protocol specified here can be used for bidirectional applications, such as video telephony, as well as unidirectional applications, such as video news gathering. Even in case of video news gatheri
5、ng, bidirectional transmission is often required for communication between a reporter in the field and the studio. In addition, the system is defined taking into account implementation complexity. Thus, a software-based embedded solution is also available, which requires less cost and a shorter deve
6、lopment period than a hardware-based one. History Edition Recommendation Approval Study Group 1.0 ITU-T J.388 2010-08-29 9 ii Rec. ITU-T J.388 (08/2010) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information a
7、nd 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 standardizing telecommunications on a worldwide b
8、asis. 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 covered by the procedure laid down in WTSA Res
9、olution 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 indicate both a telecommunication administratio
10、n 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 achieved when all of these mandatory provisions a
11、re 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 PROPERTY RIGHTS ITU draws attention to the p
12、ossibility 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 asserted by ITU members or others outside of t
13、he 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 that this may not represent the latest inf
14、ormation and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T J.388 (08/2010) iii CONTENTS Pag
15、e 1 Scope 1 2 References. 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 3 4 Abbreviations and acronyms 3 5 Conventions 4 6 System overview . 4 6.1 Architecture framework 4 6.2 Session control 6 6.3 Media transmission . 6 6.4 Example of the sequence 6 7 Se
16、ssion control 7 7.1 Authentication 7 7.2 Registration . 8 7.3 Starting a session 8 7.4 Closing a session 8 7.5 Cancelling a request . 8 8 Media transmission . 8 8.1 Profiles 8 8.2 Codecs 9 8.3 Codec profile selection in set-up UE procedures 9 8.4 Packet format 9 8.5 Transport . 10 8.6 Real-time text
17、 support (optional) 10 Rec. ITU-T J.388 (08/2010) 1 Recommendation ITU-T J.388 Real-time video and audio transmission system over IP networks 1 Scope This Recommendation defines a system for real-time video/audio transmission over an IP-based network. Three profiles are defined, for video telephony,
18、 SDTV video transmission, and HDTV video transmission. The protocol of the system consists of session control and media transmission. Session control is based on the session initiation protocol (SIP), and for the use of SIP this Recommendation refers to ITU-T J.366.4. Several types of packet formats
19、 are defined for media transmission. With regard to codecs, this Recommendation provides some mandatory codecs and some optional ones for each profile. The system equipped with the protocol specified here can be used for bidirectional applications such as video-enabled order wire as well as unidirec
20、tional applications such as electronic news gathering. 2 References The following 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 Reco
21、mmendations and other references are subject to revision; users of this Recommendation 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 regularl
22、y 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 H.222.0 Recommendation ITU-T H.222.0 (2006) | ISO/IEC 13818-1:2007, Information technology Generic coding of moving pictures and associated audio inf
23、ormation: Systems. ITU-T H.262 Recommendation ITU-T H.262 (2000) | ISO/IEC 13818-2:2000, Information technology Generic coding of moving pictures and associated audio information: Video. ITU-T H.263 Recommendation ITU-T H.263 (2005), Video coding for low bit rate communication. ITU-T H.264 Recommend
24、ation ITU-T H.264 (2010), Advanced video coding for generic audiovisual services. ITU-T J.360 Recommendation ITU-T J.360 (2006), IPCablecom2 architecture framework. ITU-T J.361 Recommendation ITU-T J.361 (2006), IPCablecom 2 codec and media. ITU-T J.366.3 Recommendation ITU-T J.366.3 (2010), IPCable
25、com2 IP Multimedia Subsystem (IMS); Stage 2 specification. ITU-T J.366.4 Recommendation ITU-T J.366.4 (2010), IPCablecom2 IP Multimedia Subsystem (IMS): Session Initiation Protocol (SIP) and Session Description Protocol (SDP) Stage 3 Specification. ITU-T J.366.7 Recommendation ITU-T J.366.7 (2010),
26、IPCablecom2 IP Multimedia Subsystem (IMS): Access security for IP-based services. ETSI EN 301 704 ETSI EN 301 704 V.7.2.1 (2000), Digital cellular telecommunications system (Phase 2+) (GSM); Adaptive Multi-Rate (AMR) speech transcoding. 2 Rec. ITU-T J.388 (08/2010) IETF RFC 2250 IETF RFC 2250 (1998)
27、, RTP Payload Format for MPEG1/MPEG2 Video. IETF RFC 2327 IETF RFC 2327 (1998), SDP: Session Description Protocol. IETF RFC 3016 IETF RFC 3016 (2000), RTP Payload Format for MPEG-4 Audio/Visual Streams. IETF RFC 3261 IETF RFC 3261 (2002), SIP: Session Initiation Protocol. IETF RFC 3267 IETF RFC 3267
28、 (2002), Real-Time Transport Protocol (RTP) Payload Format and File Storage Format for the Adaptative Multi-Rate (AMR) and Adaptative Multi-Rate Wideband (AMR-WB) Audio Codecs. IETF RFC 3550 IETF RFC 3550 (2003), RTP: A Transport Protocol for Real-Time Applications. IETF RFC 3984 IETF RFC 3984 (2005
29、), RTP Payload Format for H.264 Video. IETF RFC 4629 IETF RFC 4629 (2007), RTP Payload Format for ITU-T Rec. H.263 Video. ISO/IEC 13818-3 ISO/IEC 13818-3:1998, Information technology Generic coding of moving pictures and associated audio information Part 3: Audio. ISO/IEC 13818-7 ISO/IEC 13818-7:200
30、6, Information technology Generic coding of moving pictures and associated audio information Part 7: Advanced Audio Coding (AAC). ISO/IEC 14496-2 ISO/IEC 14496-2:2004, Information technology Coding of audio-visual objects Part 2: Visual. ISO/IEC 14496-3 ISO/IEC 14496-3:2009, Information technology C
31、oding of audio-visual objects Part 3: Audio. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 message IETF RFC 3261: Data sent between SIP elements as part of the protocol. SIP messages are either requests or responses. 3.1.2 method IETF
32、 RFC 3261: The method is the primary function that a request is meant to invoke on a server. The method is carried in the request message itself. Example methods are INVITE and BYE. 3.1.3 proxy, proxy server IETF RFC 3261: An intermediary entity that acts as both a server and a client for the purpos
33、e of making requests on behalf of other clients. A proxy server primarily plays the role of routing, which means its job is to ensure that a request is sent to another entity “closer“ to the targeted user. Proxies are also useful for enforcing policy (for example, making sure a user is allowed to ma
34、ke a call). A proxy interprets, and, if necessary, rewrites specific parts of a request message before forwarding it. 3.1.4 request IETF RFC 3261: A SIP message sent from a client to a server, for the purpose of invoking a particular operation. 3.1.5 response IETF RFC 3261: A SIP message sent from a
35、 server to a client, for indicating the status of a request sent from the client to the server. 3.1.6 server IETF RFC 3261: A server is a network element that receives requests in order to service them and sends back responses to those requests. Examples of servers are proxies, user agent servers, r
36、edirect servers, and registrars. Rec. ITU-T J.388 (08/2010) 3 3.1.7 session IETF RFC 3261: From the SDP specification: “A multimedia session is a set of multimedia senders and receivers and the data streams flowing from senders to receivers. A multimedia conference is an example of a multimedia sess
37、ion“. IETF RFC 2327 (A session as defined for SDP can comprise one or more RTP sessions.) As defined, a callee can be invited several times, by different calls, to the same session. If SDP is used, a session is defined by the concatenation of the SDP user name, session id, network type, address type
38、, and address elements in the origin field. 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 profile: A specified subset of the functionalities of the terminal defined in this Recommendation, or a specified subset of the bitstream syntax of video codecs.
39、 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: AAC Advanced Audio Coding AMR Adaptive Multi-Rate AV Audio/Video AVC Advanced Video Coding BP Baseline Profile CSCF Call Session Control Function ENG Electronic News Gathering HDTV High Definition Televi
40、sion HL High Level HP High Profile I-CSCF Interrogating-CSCF IMS IP Multimedia Subsystem IP Internet Protocol L* Level* (e.g., L0 means Level Zero) MAC Medium Access Control ML Main Level MP Main Profile NB Narrow-Band P0 Profile Zero P-CSCF Proxy-CSCF RTP Real-time Transport Protocol SBR Spectral B
41、and Replication S-CSCF Serving-CSCF SDP Session Description Protocol SDTV Standard Definition Television 4 Rec. ITU-T J.388 (08/2010) SIP Session Initiation Protocol SP Simple Profile TCP Transmission Control Protocol TS Transport Stream UDP User Datagram Protocol UE User Equipment URI Uniform Resou
42、rce Identifier VT Video Telephony (bidirectional conversational communication with video and audio) 5 Conventions None. 6 System overview 6.1 Architecture framework This Recommendation specifies protocols for session control and media transmission for real-time video/audio transmission over IP netwo
43、rks. Examples of the system architecture are shown in Figure 1, and an example protocol stack is shown in Figure 2. Rec. ITU-T J.388 (08/2010) 5 a) Unidirectional case b) Bidirectional case Figure 1 Examples of system architecture Session control (SIP) Codec Packet format UDP or TCP UDP IP MAC Physi
44、cal Figure 2 Example protocol stack of the system As shown in these examples, protocols defined in this Recommendation can be used for unidirectional applications such as video news gathering and bidirectional applications such as video telephony. 6 Rec. ITU-T J.388 (08/2010) The system contains the
45、 following components: Terminal (UE): A terminal issues SIP requests and receives SIP responses for session set-up, and transmits and receives media packets of video and audio. Registrar: A registrar provides address binding for a particular domain. S-CSCF may behave as a registrar as defined in ITU
46、-T J.360. Proxy: A proxy routes SIP messages from the UE to the I-CSCF or S-CSCF and vice versa. This is performed by the P-CSCF. Detailed descriptions of the components are given by ITU-T J.360. This Recommendation focuses on the specification of terminals. The use of registrar and proxy is optiona
47、l. A terminal defined in this Recommendation shall support communications without these servers, in other words, peer-to-peer communication. 6.2 Session control The session initiation protocol (SIP) is used for creating, modifying and terminating sessions with users in this Recommendation. This Reco
48、mmendation uses the following SIP methods, extracted from the methods defined in ITU-T J.366.4: REGISTER INVITE ACK BYE CANCEL PRACK INFO A terminal conforming to this Recommendation shall have the capability to send these requests and receive responses directly peer to peer without a proxy, as well
49、 as via a proxy. 6.3 Media transmission After a session has been established, the terminals start sending media packets using the format agreed in the SDP, which is exchanged in the INVITE request. In general, the end-to-end media packets are directly transmitted and take a path different from that of the SIP signalling messages. In this Recommendation, a terminal shall support both unidirectional transmission and bidirectional transmission. Clause 8.
