1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU H.223 (07/2001) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services - Transmission mu It plexi ng and synchronization Multiplexing protocol for low bit rate multimedia communic
2、ation ITU-T Recommendation H.223 (Formerly CCITT Recommendation) ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.100-H.199 H.200-H.219 ra+misSion multi 22GH.22 Systems aspects H.230-H.239 C
3、ommunication procedures H.240-H.259 Coding of moving video H.260-H.279 Related systems aspects H.280-H.299 SYSTEMS AND TERMINAL EQUIPMENT FOR AUDIOVISUAL SERVICES H.300-H.399 SUPPLEMENTARY SERVICES FOR MULTIMEDIA H.450-H.499 For further details, please refer to the list of ITU-T Recommendations. ITU
4、-T Recommendation H.223 Multiplexing protocol for low bit rate multimedia communication Summary This Recommendation specifies a packet-oriented multiplexing protocol for low bit rate multimedia communication. This protocol can be used between two low bit rate multimedia terminals, or between a low b
5、it rate multimedia terminal and a multipoint control unit or an interworking adapter. The protocol allows the transfer of any combination of digital voice/audio, digital video/image and data information over a single communication link. This protocol provides low delay and low overhead by using segm
6、entation and reassembly and by combining information from different logical channels in a single packet. The control procedures necessary to implement this multiplexing protocol are specified in ITU-T H.245. Annexes A, B and C are multiplexing protocol extensions for low, medium and highly error-pro
7、ne channels, respectively. Annex D provides an optional Reed-Solomon code error correction which is an alternative to the RCPC coding of Annex C. Source ITU-T Recommendation H.223 was revised by ITU-T Study Group 16 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 July 2001. ITU-
8、T H.223 (07/2001) i FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and t
9、ariff 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 ITU-T study groups which, in turn, produce Reco
10、mmendations 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 collaborative basis with IS0 and EC. NOTE In this Recomme
11、ndation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use o
12、f 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 the Recommendation development process. As of the date of approval of this Recommendation, I
13、TU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. o rmr 2002 All ri
14、ghts reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. 11 ITU-T H.223 (07/2001) CONTENTS Page 1 2 3 3.1 3.2 4 5 5.1 5.2 6 6.1 6.2 6.3 6.4 6.5 6.6 7 7
15、.1 7.2 7.3 General Normative references Definitions and format conventions Definition of terms Format conventions . 3.2.1 Numbering convention 3.2.2 Order of bit transmission . 3.2.3 Field mapping convention . Abbreviations Overview . Multiplex (MX) layer overview . Adaptation layer overview Multipl
16、ex (MUX) layer specification . Primitives exchanged between the MUX layer and the AL . 6.2.1 Description of primitives . 6.2.2 Description of parameter . MUX-PDU framing 6.3.1 Flag Framework of MUX layer MUX-PDU format and coding . 6.4.1 Header 6.4.2 Information field 6.4.3 Abort Marking of MX-SDU b
17、oundaries Examples . Adaptation Layer (AL) specification Introduction . Adaptation Layer Type 1 (AL1) specification 7.2.1 Framework of AL1 7.2.2 Primitives exchanged between AL1 and AL1 user . 7.2.3 Procedures for Abort . Adaptation Layer Type 2 (AL2) specification 7.3.1 Framework of AL2 7.3.2 Primi
18、tives exchanged between AL2 and AL2 user . 7.3.3 Functions. format and coding of AL2 . ITU-T H.223 (0712001) i 1 1 1 2 2 2 3 3 4 4 5 6 6 6 6 6 6 6 7 7 9 9 10 10 12 12 12 12 13 13 14 14 14 14 . 1ll 7.4 7.3.4 Procedures for Abort . 7.3.5 Procedures for sequence numbering 7.3.6 Procedures for error con
19、trol . Adaptation Layer Type 3 (AL3) specification 7.4.1 Framework of AL3 7.4.2 Primitives exchanged between AL3 and AL3 user . 7.4.3 Functions, format and coding of AL3 . 7.4.4 Procedures for Abort . 7.4.5 Procedures for Error Control . 7.4.6 Retransmission procedure Annex A . Multiplexing protocol
20、 for low bit rate multimedia mobile communication over A.l General A.2 Multiplex (Ma) layer specification . A.2.1 MUX-PDU framing . low error-prone channels Annex B . Multiplexing protocol for low bit rate multimedia mobile communication over moderate error-prone channel . B.l General B.2 Abbreviati
21、ons B.3 Multiplex (MUX) layer specification . B.3.1 MUX-PDU framing . B.3.2 MUX-PDU format and coding/decoding B.3.3 Making of MUX-SDU boundaries . Annex C . Multiplexing protocol for low bit rate multimedia mobile communication over highly error-prone channels C.l General C.2 Acronyms Multiplex (MU
22、X) layer specification . C.3.1 Stuffing mode C.4 Adaptation Layer C.4.1 ALAM C.4.2 AL2M C.4.3 AL3M C.3 Annex D . Optional multiplexing protocol for low bit rate multimedia mobile communication over highly error-prone channels D.l General D.2 Acronyms D.3 Multiplex (MUX) layer specification . Page 15
23、 16 16 16 16 16 17 19 19 19 23 23 23 23 24 24 25 25 25 25 28 28 28 28 29 29 29 29 49 52 52 52 52 52 iv ITU-T H.223 (07/2001) Page 52 52 58 59 D.4 Adaptation layer D.4.1 AL1M D.4.2 AL2M D.4.3 AL3M Appendix I - Generator matrixes of the Systematic Extended BCH . 1.1 BCH codes 1.2 Systematic Extended B
24、CH codes . 1.3 Decoder overview . 1.4 Generator matrices for Systematic Extended BCH codes Appendix II - Binary representation for a . i ITU-T H.223 (07/2001) 59 59 59 59 60 61 V ITU-T Recommendation H.223 Multiplexing protocol for low bit rate multimedia communication 1 General This Recommendation
25、specifies the frame structure, format of fields and procedures of the packet multiplexing protocol for low bit rate multimedia communication. This protocol can be used between two low bit rate multimedia terminals, or between a low bit rate multimedia terminal and a Multipoint Control Unit (MCU) or
26、an Interworking adapter (NA). The control procedures necessary to implement this multiplexing protocol are specified in ITU-T H.245. In this Recommendation communication between different protocol layers is modelled as a set of abstract primitives, which represent a logical exchange of information.
27、The decomposition of functionality into (sub)layers, as well as the description of the primitives, do not imply a particular method of implementation. In particular, layers may exchange the contents of a logical unit (an SDU) in a “streaming“ mode where information exchange may sfart before the tran
28、sferring layer has the complete unit in its possession. 2 Normative 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 vali
29、d. All Recommendations 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
30、is regularly published. i 2 ITU-T V.42 (1996), Error-correcting procedures for DCEs using 3 4 ITU-T H.245 (2000), Control protocol for multimedia communication. asynchronous-to-synchronous conversion. ITU-T H.324 (1998), Terminal for low bit rate multimedia communication. ITU-T Q.922 (1992), ZSDN da
31、ta link layer specification forframe mode bearer services. 3 Definitions and format conventions 3.1 Definition of terms This Recommendation defines the following terms: 3.1.1 adaptation layer (AL): The upper of the two layers of the multiplexer of this Recommendation. 3.1.2 AL-PDU: An information un
32、it exchanged between peer Adaptation Layer entities. An AL-PDU is conveyed as one MUX-SDU. 3.1.3 AL-SDU: A logical information unit whose integrity is preserved in transfer from one AL user to the peer AL user. 3.1.4 AL user: A higher-layer entity which makes use of the services of the Adaptation La
33、yer. 3.1.5 control channel: A logical channel which carries H.245 control messages. ITU-T H.223 (07/2001) 1 3.1.6 header error control (HEC) field: A 3-bit CRC field in the MUX-PDU header which is used to detect errors that affect the MC field. 3.1.7 logical channel number (LCN): A unique integer be
34、tween O and 65535 assigned to a logical channel. 3.1.8 multiplex code (MC) field: A 4-bit field in the MUX-PDU header which specifies, by reference to a multiplex table entry, the logical channel to which each octet in the information field belongs. 3.1.9 multiplex (MUX) layer: The lower of the two
35、layers of the multiplexer of this Recommendation. 3.1.10 multiplex table: A table with up to 16 entries which specifies the multiplexing pattern for the information field of a MUX-PDU. 3.1.11 MUX-PDU: An information unit exchanged between peer MUX layer entities. 3.1.12 MUX-SDU: A logical informatio
36、n unit whose integrity is preserved in transfer from one Adaptation Layer to the peer Adaptation Layer. 3.1.13 non-segmentable logical channel: A logical channel whose MUX-SDUs may not be segmented. MUX-SDUs from a non-segmentable logical channel are transmitted in consecutive octets of a single MUX
37、-PDU. 3.1.14 packet marker (PM) field: A one-bit field used to mark the end of a MUX-SDU from a segmentable logical channel. 3.1.15 protocol data unit (PDU): A unit of information exchanged between peer protocol layer entities. 3.1.16 quality of service (QOS): The quality of the service that individ
38、ual information streams receive from the multiplexer, as measured by parameters such as bit rate, delay jitter, loss, etc. 3.1.17 segmentable logical channel: A logical channel whose MUX-SDUs may be segmented. Segmentation allows the temporary suspension of the transmission of a MUX-SDU in order to
39、transmit octets from another MUX-SDU. 3.1.18 service data unit (SDU): A logical unit of information whose integrity is preserved in transfer from one protocol layer entity to the peer protocol layer entity. 3.1.19 slot: A consecutive sequence of octets within a single MUX-PDU, described by a single
40、H.245 MultiplexElement structure of type 1ogicalChannelNumber. Each slot holds an integral number of octets from a single MUX-SDU. 3.2 Format conventions The numbering, field mapping and bit transmission conventions used in this Recommendation are consistent with those used in ICTU-T V.42. 3.2.1 Num
41、bering convention The basic numbering convention used in this Recommendation is illustrated in Figure 1. The bits in each information unit are grouped into octets. The bits of an octet are shown horizontally and are numbered from 1 to 8. Multiple octets are shown vertically and are numbered from 1 t
42、o n. 3.2.2 Order of bit transmission The octets are transmitted in ascending numerical order; inside an octet, bit 1 is the first bit to be transmitted. 2 ITU-T H.223 (07/2001) 3.2.3 Field mapping convention When a field is contained within a single octet, the lowest-numbered bit of the field repres
43、ents the lowest-order value (or the least significant bit). When a field spans more than one octet, the highest-numbered bit of the first octet represents the highest-order value, and the lowest-numbered bit of the last octet represents the lowest-order value. 8 76 543 2 1 Octets I n TI 520080-95 Fi
44、gure 1/H.223 - Format convention An exception to the preceding field-mapping convention is the Cyclic Redundancy Check (CRC) field. In this case, the lowest-numbered bit of the first octet is the highest-order term of the polynomial representing the CRC field; the highest-numbered bit of the last oc
45、tet is the lowest-order term of the polynomial representing the CRC field. 4 Abbreviations This Recommendation uses the following abbreviations: . AL AL1 -AL3 CRC DRTX EI HDLC HEC IWA LAPM LCN MC MUX PDU PM PT Adaptation Layer Adaptation Layer 1-3 Cyclic Redundancy Check Declined Retransmission Erro
46、r Indication High-level Data Link Control Header Error Control Interworking Adapter Link Access Procedure for Modems Logical Channel Number Multiplex Code Multiplex Protocol Data Unit Packet Marker Payload Type ITU-T H.223 (07/2001) 3 QOS Quality of Service SDU Service Data Unit SN Sequence Number S
47、REJ Selective Reject Control 5 Overview This Recommendation specifies a packet-oriented multiplexing protocol designed for the exchange of one or more information streams between higher-layer entities such as data and control protocols and audio and video codecs. In this Recommendation, each informa
48、tion stream is represented by a uni-directional logical channel which is identified by a unique Logical Channel Number (LCN), an integer between O and 65535. LCNO is a permanent logical channel assigned to the H.245 control channel. All other logical channels are dynamically opened and closed by the
49、 transmitter using the H.245 OpenLogicalChannel and CloseLogicalChannel messages. All necessary attributes of the logical channel are specified in the OpenLogicalChannel message. For applications that require a reverse channel, a procedure for opening bi-directional logical channels is also defined in ITU-T H.245. The general structure of the multiplexer is shown in Figure 2. The multiplexer consists of two distinct layers: a Multiplex (MUX) layer and an Adaptation Layer (AL). Data Audio Video Application Layer H.245 Data protocol LAPM Audio Video Coder Coder Adaptation Layer I Mul
