1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T G.726TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Annex B(07/2003) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital terminal equipments Coding of analogue signals by methods other than PCM 40, 32, 24, 16 kbit/s Adaptive Di
2、fferential Pulse Code Modulation (ADPCM) Annex B: Packet format, capability identifier and capability parameters for H.245 signalling ITU-T Recommendation G.726 Annex B ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND
3、 CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION 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 SATELLIT
4、E LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TESTING EQUIPMENTS G.500G.599 TRANSMISSION MEDIA CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 General G.700G.709 Coding of analogue signals by pulse code modul
5、ation G.710G.719 Coding of analogue signals by methods other than PCM G.720G.729 Principal characteristics of primary multiplex equipment G.730G.739 Principal characteristics of second order multiplex equipment G.740G.749 Principal characteristics of higher order multiplex equipment G.750G.759 Princ
6、ipal characteristics of transcoder and digital multiplication equipment G.760G.769 Operations, administration and maintenance features of transmission equipment G.770G.779 Principal characteristics of multiplexing equipment for the synchronous digital hierarchy G.780G.789 Other terminal equipment G.
7、790G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE - GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DIGITAL TERMINAL EQUIPMENTS G.7000G.7999 DIGITAL NETWORKS G.8000G.8999 For furth
8、er details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.726/Annex B (07/2003) i ITU-T Recommendation G.726 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) Annex B Packet format, capability identifier and capability parameters for H.245 signalling Summary
9、 This annex specifies the packet structure for the carriage of G.726 audio, along with the capability identifier and parameters for H.245, in order to use G.726 between multimedia communication systems that utilize H.245. Source Annex B to ITU-T Recommendation G.726 was approved by ITU-T Study Group
10、 16 (2001-2004) under the ITU-T Recommendation A.8 procedure on 14 July 2003. ii ITU-T Rec. G.726/Annex B (07/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (
11、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 basis. The World Telecommunication Standardization Assembly (WTSA), which meets every fou
12、r 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 Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the
13、 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 administration and a recognized operating agency. Compliance with this Recommendation is voluntary. H
14、owever, 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 are met. The words “shall“ or some other obligatory language such as “must“ and the negativ
15、e 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 possibility that the practice or implementation of this Recommendation may involve the use
16、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 the Recommendation development process. As of the date of approval of this Recommendation,
17、ITU had not 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. ITU 2003 All
18、 rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. G.726/Annex B (07/2003) iii CONTENTS Page Annex B Packet format, capability identifier and capability parameters for H.245 signalling 1 B.1 References 1 B
19、.2 Packet structure for G.726 frames 1 B.3 Codec reset . 1 B.4 Capability identifier and parameters for use with ITU-T Rec. H.245 1 ITU-T Rec. G.726/Annex B (07/2003) 1 ITU-T Recommendation G.726 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) Annex B Packet format, capabil
20、ity identifier and capability parameters for H.245 signalling B.1 References 1 ITU-T Recommendation H.225.0 (2003), Call signalling protocols and media stream packetization for packet-based multimedia communication systems. 2 IETF RFC 3551, RTP Profile for Audio and Video Conferences with Minimal Co
21、ntrol. 3 ITU-T Recommendation I.366.2 (2000), AAL type 2 service specific convergence sublayer for narrow-band services. B.2 Packet structure for G.726 frames The G.726 ADPCM representation consists of a series of codewords with a one-to-one correspondence to the samples in the PCM stream. The G.726
22、 data rates of 40, 32, 24, and 16 kbit/s have codewords of 5, 4, 3 and 2 bits respectively. Applications using this annex shall determine the encoding type of packed codewords from the RTP payload identifier. There are two ways that a stream of G.726 codewords may be packed into octets; one defined
23、by RFC 3551 for IP transport and the other by Annex E/I.366.2 for ATM AAL 2 transport. The bitOrder parameter is provided to signal which packetization is supported, and which is in use on an audio channel. B.3 Codec reset G.726 codecs shall be reset upon the start of any talk-spurt. If not explicit
24、ly signalled, talk-spurt starts may be detected by observation of time-stamps, sequence numbers or jitter-buffer status. B.4 Capability identifier and parameters for use with ITU-T Rec. H.245 The GenericCapability is used in H.245 for the G.726 capability exchange. Table B.1/G.726 H.245 capability i
25、dentifier for G.726 Capability name ITU-T Recommendation G.726 Capability class Audio Capability identifier type Standard Capability identifier value itu-t(0) recommendation(0) g(7) 726 generic-capabilities(1) version2003(0) MaxBitRate In capabilities, this parameter shall not be used. In an OpenLog
26、icalChannel, this field shall be set to a value of 400, 320, 240 or 160 representing operation of G.726 at 40, 32, 24 or 16 kbit/s. NonCollapsingRaw This field is not used Transport This field is not used 2 ITU-T Rec. G.726/Annex B (07/2003) B.4.1 maxSamplesPerPacket parameter Table B.2/G.726 Maximu
27、m number of samples allowed in an RTP packet Parameter name maxSamplesPerPacket Parameter description This is a Collapsing GenericParameter. The value of maxSamplesPerPacket specifies the maximum number of encoded G.726 samples that may be included in a single RTP packet Parameter identifier value 1
28、 Parameter status Mandatory Parameter type unsignedMin Supercedes This field is not used B.4.2 bitOrder parameter Table B.3/G.726 Bit order Parameter name bitOrder Parameter description This is a collapsing GenericParameter. This parameter is a Boolean array. If bit 7 is 1, this indicates support of
29、 the bit order specified in RFC 3551. If bit 8 (least significant bit) is 1, this indicates support of the bit order specified in Annex E/I.366.2. All other bits are reserved and shall be set to 0. In a capability, for each bit set to 1, this means that the device supports the indicated bit order(s)
30、. In an OpenLogicalChannel message, only 1 bit shall be set, corresponding to the bit order used on the channel. Parameter identifier value 2 Parameter status Mandatory Parameter type BooleanArray Supercedes This field is not used Terminals operating on ATM networks should encode in the order given
31、in ITU-T Rec. I.366.2. Terminals operating on IP networks should encode in the order given in RFC 3551. All terminals should be capable of decoding either format. Gateways may transcode the bit-order format. Printed in Switzerland Geneva, 2003 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of
32、 the work of ITU-T Series B Means of expression: definitions, symbols, classification Series C General telecommunication statistics Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecommunication s
33、ervices Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia signals Series K Protection against inte
34、rference Series L Construction, installation and protection of cables and other elements of outside plant Series M TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Series N Maintenance: international sound programme and te
35、levision transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone installations, local line networks Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for
36、telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks and open system communications Series Y Global information infrastructure and Internet protocol aspects Series Z Languages and general software aspects for telecommunication systems
