1、 ETSI TS 126 449 V14.0.0 (2017-04) Universal Mobile Telecommunications System (UMTS); LTE; Codec for Enhanced Voice Services (EVS); Comfort Noise Generation (CNG) aspects (3GPP TS 26.449 version 14.0.0 Release 14) TECHNICAL SPECIFICATION ETSI ETSI TS 126 449 V14.0.0 (2017-04)13GPP TS 26.449 version
2、14.0.0 Release 14Reference RTS/TSGS-0426449ve00 Keywords LTE,UMTS ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/8
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9、S 26.449 version 14.0.0 Release 14Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI
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11、vestigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This Technical Spe
12、cification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM identities. These should be interpreted as being references to the corresponding ETSI deliver
13、ables. The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under http:/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “shall“, “shall not“, “should“, “should not“, “may“, “need not“, “will“, “will not“, “can“ and “cannot“ are to be interpr
14、eted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TS 126 449 V14.0.0 (2017-04)33GPP TS 26.449 version 14.0.0 Release 14Contents Intellec
15、tual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 References 5g33 Abbreviations . 5g34 General . 5g35 Functions on the transmit (TX) side . 6g35.1 EVS primary CNG operation . 6g35.2 EVS AMR-WB IO CNG operation 6g36 Functions on the receive (RX) side 7g36.1 E
16、VS primary CNG operation . 7g36.2 EVS AMR-WB IO CNG operation 7g37 Computational details and bit allocation 7g3Annex A (informative): Change history . 8g3History 9g3ETSI ETSI TS 126 449 V14.0.0 (2017-04)43GPP TS 26.449 version 14.0.0 Release 14Foreword This Technical Specification has been produced
17、by the 3rdGeneration Partnership Project (3GPP). The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change o
18、f release date and an increase in version number as follows: Version x.y.z where: x the first digit: 1 presented to TSG for information; 2 presented to TSG for approval; 3 or greater indicates TSG approved document under change control. y the second digit is incremented for all changes of substance,
19、 i.e. technical enhancements, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporated in the document. ETSI ETSI TS 126 449 V14.0.0 (2017-04)53GPP TS 26.449 version 14.0.0 Release 141 Scope The present document gives an overview for the requirem
20、ents of the background acoustic noise evaluation, noise parameter encoding/decoding and comfort noise generation for the Enhanced Voice Services (EVS) speech codec during Discontinuous Transmission (DTX) operation. 2 References The following documents contain provisions which, through reference in t
21、his text, constitute provisions of the present document. - References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. - For a specific reference, subsequent revisions do not apply. - For a non-specific reference, the latest version appli
22、es. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document. 1 3GPP TR 21.905: “Vocabulary for 3GPP Specifications“. 2 3GPP TS 26.445: “Codec for Enhanced V
23、oice Services (EVS); Codec Detailed Algorithmic Description“. 3 3GPP TS 26.442: “Codec for Enhanced Voice Services (EVS); EVS Codec ANSI C code (fixed-point)“. 4 3GPP TS 26.443: “Codec for Enhanced Voice Services (EVS); EVS Codec ANSI C code (floating-point)“. 3 Abbreviations For the purposes of the
24、 present document, the abbreviations given in TR 21.905 1 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905 1. CNG Comfort Noise Generation EVS Enhanced Voice Services FD-CNG Frequency Domain b
25、ased CNG LP-CNG Linear Prediction based CNG SID Silence Insertion Descriptor 4 General The present document gives an overview for the requirements of the background acoustic noise evaluation, noise parameter encoding/decoding and comfort noise generation for the Enhanced Voice Services (EVS) speech
26、codec during Discontinuous Transmission (DTX) operation. The present document is mandatory for implementation in all network entities and UEs supporting the EVS codec. In the case of discrepancy between the EVS comfort noise aspects described in the present document and its ANSI-C code specification
27、 contained in 3, the procedure defined by 3 prevails. In the case of discrepancy between the procedure described in the present document and its ANSI-C code specification contained in 4, the procedure defined by 4 prevails. A basic problem when using DTX is that the background acoustic noise, which
28、is transmitted together with the speech, would disappear when the transmission is cut, resulting in discontinuities of the background noise. Since the DTX ETSI ETSI TS 126 449 V14.0.0 (2017-04)63GPP TS 26.449 version 14.0.0 Release 14switching can take place rapidly, it has been found that this effe
29、ct can be very annoying for the listener - especially in a car environment with high background noise levels. In bad cases, the speech may be hardly intelligible. The present document specifies the way to overcome this problem by generating on the receive (RX) side synthetic noise similar to the tra
30、nsmit (TX) side background noise. The comfort noise parameters are estimated on the TX side and transmitted to the RX side at a regular rate when speech is not present. This allows the comfort noise to adapt to the changes of the noise on the TX side. The Enhanced Voice Services (EVS) speech codec s
31、upports two Comfort Noise Generation (CNG) schemes, a linear prediction based CNG (LP-CNG) as well as a frequency domain based scheme (FD-CNG). The selection of the one of the two schemes is performed within the transmit side functions on an input signal bases. The parameters for generating the comf
32、ort noise are packed as a Silence Insertion Descriptor (SID) payload. The update rate of the SID payload can be configured to a fixed number or to a mode where the update rate is adaptively modified according to the background noise. The fixed rate mode is limited to updates between 1 and 100 frames
33、 while in the adaptive rate mode the updates are limited to 8 and 50 depending on the noise behaviour. As the functions of the CNG processing are highly integrated into the speech codec and make use of other coding parameters, The present document only provides an overview of the functions. The rele
34、vant references to the algorithmic descriptions are provided in the following. 5 Functions on the transmit (TX) side 5.1 EVS primary CNG operation The CNG operation on the transmit side is described in figure 1. In DTX operation, the SID updater decides if any SID update is required. If the SID payl
35、oad should be updated, the CNG Selector enables either the LP or the FD CNG encoder depending on the signal characteristic of the background noise. The selected CNG encoder calculates the noise generation parameter and creates the related SID payload. Figure 1: Transmit side Comfort Noise Generator
36、functions In 2, all TX functions are described in clause 5.6. The algorithmic description of the - SID Update mechanism can be found in sub-clause 5.6.1.1 and 5.6.1.2 - CNG Selector can be found in sub-clause 5.6.1.3 - LP-CNG encoder in sub-clause 5.6.2 - FD-CNG encoder in sub-clause 5.6.3. 5.2 EVS
37、AMR-WB IO CNG operation The update rate is basically fixed to an update every 8thframe. However, when switching into DTX mode, the first and the third frame after active speech are coded by a SID frame. ETSI ETSI TS 126 449 V14.0.0 (2017-04)73GPP TS 26.449 version 14.0.0 Release 14The CNG in the EVS
38、 AMR-WB interoperable modes is based the LP-CNG coding scheme only. The complete CNG TX description of the EVS AMR-WB IO mode can be found in 2, clause 5.7.12. 6 Functions on the receive (RX) side 6.1 EVS primary CNG operation The CNG operation on the receiver side is depicted in Figure 2. The first
39、 bit of the SID payload determines the CNG module. The remaining bits contain the information of the noise generator parameters to render the signal. Figure 2: Receive side Comfort Noise Generator functions The RX CNG operation is described in clause 6.7. The synthesis of the LP-CNG is described in
40、sub-clause 6.7.2 and the synthesis of FD-CNG is described in clause 6.7.3 in 2. 6.2 EVS AMR-WB IO CNG operation The CNG in the EVS AMR-WB interoperable modes use only the LP-CNG decoding scheme for rendering the AMR-WB compatible CN parameters. The complete CNG RX description of the EVS AMR-WB IO mo
41、de can be found in 2, clause 6.8.4. 7 Computational details and bit allocation A computational description of comfort noise encoding and generation in form of an ANSI-C source code is given in 3 for the fix point implementation and in 4 for the floating point implementation. For the EVS primary mode
42、s, the SID payload consists of 48 bits. The first bit of the payload determines the CNG scheme, where 0 stands for the LP-CNG and 1 for the FD-CNG. For the EVS AMR-WB IO modes, the SID payload consists of 35 bits. ETSI ETSI TS 126 449 V14.0.0 (2017-04)83GPP TS 26.449 version 14.0.0 Release 14Annex A
43、 (informative): Change history Change history Date TSG # TSG Doc. CR Rev Subject/Comment Old New 2014-09 65 SP-140464 Presented at TSG SA#65 for approval 1.0.0 2014-09 65 Approved at TSG SA#65 1.0.0 12.0.0 2015-12 70 Version for Release 13 12.0.0 13.0.0 Change history Date Meeting TDoc CR Rev Cat Subject/Comment New version 2017-03 75 Version for Release 14 14.0.0 ETSI ETSI TS 126 449 V14.0.0 (2017-04)93GPP TS 26.449 version 14.0.0 Release 14History Document history V14.0.0 April 2017 Publication
