1、 International Telecommunication Union ITU-T G.711.1TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (09/2012) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital terminal equipments Coding of voice and audio signals Wideband embedded extension for ITU-T G.711 pulse code mo
2、dulation Recommendation ITU-T G.711.1 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 SYSTEMS G.200G.299 INDIVIDUAL CHARACTERIST
3、ICS 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 RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSIO
4、N MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 General G.700G.709 Coding of voice and audio signals G.710G.729Principal characteristics of primary multiplex equipment G.730G.739 Principal characteristics of second order multiplex equipment G.740G.749 Pr
5、incipal characteristics of higher order multiplex equipment G.750G.759 Principal 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
6、for the synchronous digital hierarchy G.780G.789 Other terminal equipment G.790G.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.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.
7、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.711.1 (09/2012) i Recommendation ITU-T G.711.1 Wideband embedded extension for ITU-T G.71
8、1 pulse code modulation Summary Recommendation ITU-T G.711.1 describes an ITU-T G.711 embedded wideband speech and audio coding algorithm operating at 64, 80 and 96 kbit/s. The encoder input and decoder outputs are sampled at 16 kHz by default, but 8-kHz sampling is also supported. When sampled at 1
9、6 kHz, the output of the ITU-T G.711.1 coder can encode signals with a bandwidth of 50-7000 Hz at 80 and 96 kbit/s, and for 8-kHz sampling the output may produce signals with a bandwidth ranging from 50 up to 4000 Hz, operating at 64 and 80 kbit/s (the bandwidth of the narrowband signal output from
10、the decoder is characterized by the built-in split-band filterbank which has a frequency cut-offs at 4000 Hz). At 64 kbit/s, Recommendation ITU-T G.711.1 is compatible with Recommendation ITU-T G.711; hence an efficient deployment in existing ITU-T G.711-based voice over IP (VoIP) infrastructures is
11、 foreseen. The coder operates on 5 ms frames, has a maximum algorithmic delay of 11.875 ms, and has a worst-case computational complexity of 8.70 weighted million operations per second (WMOPS). The encoder produces an embedded bitstream structured in three layers corresponding to three available bit
12、 rates: 64, 80 and 96 kbit/s. The bitstream can be truncated at the decoder side or by any component of the communication system to adjust the bit rate to the desired value, but since it does not contain any information on which layers are contained, an implementation would require outband signallin
13、g on which layers are available. The underlying algorithm has a three-layer coding structure: log companded pulse code modulation (PCM) of the lower band including noise feedback, embedded PCM extension with adaptive bit allocation for enhancing the quality of the base layer in the lower band, and w
14、eighted vector quantization coding of the higher band based on modified discrete cosine transformation (MDCT). Annex A defines an alternative implementation of the ITU-T G.711.1 algorithm using floating-point arithmetic to facilitate its use on hardware optimized for floating-point operations. The a
15、ccompanying floating-point C-code is fully interoperable with the fixed-point C-code and provides equivalent quality. Annex B contains the RTP payload format, capability identifiers and parameters for signalling of ITU-T G.711.1 capabilities using Recommendation ITU-T H.245. The packet format is ful
16、ly compatible with the corresponding ITU-T G.711.1 RTP definitions to allow seamless interoperability. Annex C describes an algorithm applying ITU-T G.711.0 lossless compression algorithm to ITU-T G.711.1. As Recommendation ITU-T G.711.0 is more efficient when applied to large frame sizes, to achiev
17、e efficient compression rate as many ITU-T G.711.1 frames as possibly supported by ITU-T G.711.0 are encoded together. The use of this extension introduces no quality degradation when compared to Recommendation ITU-T G.711.1, as it is a lossless encoding of the ITU-T G.711 portion of the ITU-T G.711
18、.1 bitstream. Furthermore, there is no additional algorithmic delay; the delay will be the same as the one of ITU-T G.711.1, plus the selected size of the packet minus five milliseconds. It keeps the same robustness against packet losses as Recommendation ITU-T G.711.1 and no error propagation in ca
19、se of frame errors. The proposed scheme can easily be transcoded to ITU-T G.711.1 or ITU-T G.711.0 at minimum complexity. ii Rec. ITU-T G.711.1 (09/2012) Annex D describes a scalable superwideband (SWB, 50-14000 Hz) speech and audio coding algorithm operating from 96 to 112 kbit/s for ITU-T G.711.1
20、80 kbit/s core, and operating from 112 to 128 kbit/s for ITU-T G.711.1 96 kbit/s core. The ITU-T G.711.1 superwideband extension codec is interoperable with both ITU-T G.711 and ITU-T G.711.1. The output of the ITU-T G.711.1 SWB coder has a bandwidth of 50-14000 Hz. The coder operates with 5 ms fram
21、es, has an algorithmic delay of 12.8125 ms and a worst case complexity of 21.498 MOPS. By default, the encoder input and decoder output are sampled at 32 kHz. The superwideband encoder produces an embedded bitstream structured in two layers corresponding to two available bit rates from 96 to 112 kbi
22、t/s or from 112 to 128 kbit/s with a step size of 16 kbit/s depending on the chosen ITU-T G.711.1 core. The bitstream can be truncated at the decoder side or by any component of the communication system to instantaneously adjust the bit rate to the desired value with no need for out-of-band signalli
23、ng. At ITU-T G.711.1 80 kbit/s mode or 96 kbit/s mode, ITU-T G.711.1 SWB is fully interoperable with ITU-T G.711.1. The underlying algorithm includes three main parts: higher band enhancements, bandwidth extension (BWE) and transform coding in modified discrete cosine transform (MDCT) domain based o
24、n algebraic vector quantization (AVQ). Annex E describes a proposed draft of an alternative implementation of ITU-T G.711.1 Annex D based on floating-point arithmetic. While Annex D provides a bit-exact, fixed-point specification with the fixed-point C-source code available from the ITU-T, alternati
25、ve floating implementation is useful for platforms equipped with floating-point processors. This alternative floating-point arithmetic was found to be fully interoperable with Annex D in all configurations including the cross configurations. Annex F describes a stereo extension of the wideband codec
26、 ITU-T G.711.1 and its superwideband extension, ITU-T G.711.1 Annex D. It is optimized for the transmission of stereo signals with limited additional bitrate, while keeping full compatibility with both codecs. Annex F operates from 96 to 160 kbit/s: five superwideband stereo bitrates from 112 to 160
27、 kbit/s and two wideband stereo bitrates at 96 and 128 kbit/s. The wideband stereo modes are backward compatible with legacy ITU-T G.711 and ITU-T G.711.1, while the superwideband modes offer the backward compatibility with mono narrowband ITU-T G.711, mono wideband ITU-T G.711.1 and superwideband I
28、TU-T G.711.1 Annex D. The stereo codec operates on 5 ms frames with an algorithmic delay of 18.125 ms for wideband stereo and 19.0625 ms for superwideband stereo. The encoder input and decoder output are sampled at 16 kHz and 32 kHz for wideband and superwideband operating modes respectively. The un
29、derlying algorithm includes three main parts: stereo parameter analysis and down-mix at the encoder and stereo synthesis at the decoder. The first stereo extension layer is a 16 kbit/s layer comprising the basic stereo parameters, the whole wideband inter-channel time difference/inter-channel phase
30、difference/inter-channel coherence, sub-band inter-channel level differences and the low frequency sub-band inter-channel phase differences. The second stereo layer is a 16 kbit/s layer. In this last layer, the inter-channel phase differences of a larger bandwidth are transmitted, which allow to fur
31、ther improve the stereo image. The bitstream can be truncated by the decoder, or by any components of the communication system, to instantaneously adjust the bitrate to the desired value, including narrowband ITU-T G.711, wideband ITU-T G.711.1 and superwideband ITU-T G.711.1 Annex D bitrates, with
32、no need for out-of-band signalling. Appendix I describes a supplementary postfilter for use in the decoder. This postfilter enhances the quality of the decoded signal when a legacy ITU-T G.711 or only the basic log companded PCM part of the ITU-T G.711.1 bitstream are available. It is intended for e
33、nd-user terminals and usage in tandem scenarios should be avoided (such as in a signal mixer or bitstream translators). Appendices II and III provide information on frame size selection and on decoding of the ITU-T G.711.0 bitstream part of ITU-T G.711.1 LLC bitstreams, respectively. Rec. ITU-T G.71
34、1.1 (09/2012) iii Appendix IV to ITU-T G.711.1 defines a coding scheme for mid-side (MS) stereo using ITU-T G.711.1 Annex D (ITU-T G.711.1-SWB). By introducing the mid-side stereo coding into stereo terminals, interoperability with the monaural devices could be obtained in very low complexity. The b
35、asic coding scheme is as follows: two channels of the left-right (LR) stereo are converted to those of the MS stereo and then the signals of each channel are independently encoded using ITU-T G.711.1-SWB; and at the decoder side, the MS channels of the bitstream from the encoder are decoded respecti
36、vely and then the decoded signals of the MS channels are reversed to those of the LR channels. The LR-MS conversion and its inverse are conducted in a conventional way. On the encoder side, additional two arithmetic operations per sample are required for the LR-MS conversion and one operator for the
37、 MS-LR conversion in the decoder. In an STL2009, see Recommendation ITU-T G.191 (2010) basic operator implementation, the conversion complexity amounts to about 0.2 WMOPS in total. The coding algorithm for each channel is identical to the one in ITU-T G.711.1 Annex D. ANSI C source code is provided
38、for the algorithms specified in the main body of this Recommendation and in Annexes A, C, D, E and F. These ANSI C source codes are an integral part of this Recommendation. A non-exhaustive set of test signals for use with these ANSI C source codes is also provided as an electronic attachment to thi
39、s Recommendation. It should be noted that some of the text vectors are too voluminous for distribution with the source code, in particular for Annex F. The test vectors can be downloaded for free from the ITU web site at: http:/itu.int/net/itu-t/sigdb/speaudio/Gseries.htm#G.711.1. History Edition Re
40、commendation Approval Study Group 1.0 ITU-T G.711.1 2008-03-15 16 1.1 ITU-T G.711.1 (2008) Amd. 1 2008-11-13 16 1.2 ITU-T G.711.1 (2008) Amd. 2 2009-03-16 16 1.3 ITU-T G.711.1 (2008) Amd. 3 2010-10-14 16 1.4 ITU-T G.711.1 (2008) Amd. 4 2010-11-13 16 1.5 ITU-T G.711.1 (2008) Amd. 5 2011-03-25 16 2.0
41、ITU-T G.711.1 2012-09-13 16 Keywords Embedded coding, ITU-T G.711, ITU-T G.711.1, lossless compression, stereo coding, superwideband. iv Rec. ITU-T G.711.1 (09/2012) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications,
42、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 standardizing telecommunications on
43、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 covered by the procedure laid dow
44、n 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 indicate both a telecommunication
45、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 achieved when all of these mandatory
46、 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 PROPERTY RIGHTS ITU draws atten
47、tion 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 asserted by ITU members or others
48、 outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had 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 l
49、atest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2013 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 G.711.1 (09/2012) v Table of Contents Page 1 Scope . 1 2 References 1 3 Definitions . 2 4 Abbreviations and acronyms . 2 5 Conventions . 3 6 General description of the coder 8 6.1 Encoder 8 6.2 Decoder 9 6.3 Coder modes 10 6.4 Bit allocation . 10 6.5 Algorithmic delay 11 6.6 Computat
