ITU-T G.726-1990 40、32、24、16 kbit/s自适应差分脉冲编码调制(ADPCM) 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) (Study Group XV) 60 pp

pdf标准 ITU-T G.726-1990 40、32、24、16 kbit/s自适应差分脉冲编码调制(ADPCM) 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) (Study Group XV) 60 pp

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ITU-T G.726-1990 40、32、24、16 kbit/s自适应差分脉冲编码调制(ADPCM) 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) (Study Group XV) 60 pp 第 1 页 ITU-T G.726-1990 40、32、24、16 kbit/s自适应差分脉冲编码调制(ADPCM) 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) (Study Group XV) 60 pp 第 2 页 ITU-T G.726-1990 40、32、24、16 kbit/s自适应差分脉冲编码调制(ADPCM) 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) (Study Group XV) 60 pp 第 3 页 ITU-T G.726-1990 40、32、24、16 kbit/s自适应差分脉冲编码调制(ADPCM) 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) (Study Group XV) 60 pp 第 4 页 ITU-T G.726-1990 40、32、24、16 kbit/s自适应差分脉冲编码调制(ADPCM) 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) (Study Group XV) 60 pp 第 5 页
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国外分类,ITU,ITU-T(电信标准分局),itu,kbit,适应,差分,脉冲,编码,调制,adpcm,kbit,adaptive,differential,pulse,code,modulation,adpcm,study,group,xv,pp

INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE GENERAL ASPECTS OF DIGITAL TRANSMISSION SYSTEMS; TERMINAL EQUIPMENTS 40, 32, 24, 16 kbit/s ADAPTIVE DIFFERENTIAL PULSE CODE MODULATION (ADPCM) Recommendation G.726 Geneva, 1990 G.726 FOREWORD The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCITT 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 Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT between Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988). Recommendation G.726 was prepared by Study Group XV and was approved under the Resolution No. 2 procedure on the 14 of December 1990. ___________________ CCITT NOTE In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency. © ITU 1990 All rights 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 the ITU. Recommendation G.726 Recommendation G.726 40, 32, 24, 16 kbit/s ADAPTIVE DIFFERENTIAL PULSE CODE MODULATION (ADPCM)1) 1 General The characteristics below are recommended for the conversion of a 64 kbit/s A-law or µ-law pulse code modulation (PCM) channel to and from a 40, 32, 24 or 16 kbit/s channel. The conversion is applied to the PCM bit stream using an ADPCM transcoding technique. The relationship between the voice frequency signals and the PCM encoding/decoding laws is fully specified in Recommendation G.711. The principal application of 24 and 16 kbit/s channels is for overload channels carrying voice in Digital Circuit Multiplication Equipment (DCME). The principal application of 40 kbit/s channels is to carry data modem signals in DCME, especially for modems operating at greater than 4800 kbit/s. Sections 1.1 and 1.2 of this Recommendation provide an outline description of the ADPCM transcoding algorithm, §§ 2 and 3 provide the principles and functional descriptions of the ADPCM encoding and decoding algorithms respectively, whilst § 4 is the precise specification for the algorithm computations. Networking aspects and digital test sequences are addressed in Appendices I and II, respectively, to this Recommendation. Simplified block diagrams of both the ADPCM encoder and decoder are shown in Figure 1/G.726. In § 4, each sub-block in the encoder and decoder is precisely defined using one particular logical sequence. If other methods of computation are used, extreme care should be taken to ensure that they yield exactly the same value for the output processing variables. Any further departures from the processes detailed in § 4 will incur performance penalties which may be severe. Note 1 – Prior to the definition of this Recommendation, other ADPCM algorithms of performance similar to the 40 kbit/s algorithm specified here have been incorporated in DCME designs and used in telecommunications networks. These algorithms may be considered by bilateral agreement for limited DCME applications under certain circumstances. Technical descriptions providing information on two such algorithm approaches can be found in COM XVIII No. 101 and COM XVIII No. 102 of the 1984-1988 Study Period. Note 2 – The assignment of 16, 24, 32 and 40 kbit/s DCME channels and the associated selection of coding rates are beyond the scope of this Recommendation; see, for example, Recommendation G.763 (revised, 1990). Note 3 – Signalling and multiplexing considerations are beyond the scope of this Recommendation; see, for example, Recommendations G.761 and G.763 (revised, 1990). _______________ 1) This Recommendation completely replaces the text of Recommendations G.721 and G.723 published in Volume III.4 of the Blue Book. It should be noted that systems designed in accordance with the present Recommendation will be compatible with systems designed in accordance with the Blue Book version. Recommendation G.726 1 64 kbit/s PCM input Convert to uniform PCM Input signal + Difference signal Adaptative quantizer – ADPCM output Signal estimate Reconstructed signal Adaptive predictor + ADPCM Input Quantized difference signal Reconstructed signal + Inverse adaptive quantizer Quantized difference signal A %NCODER Inver

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