1、 ETSI TS 126 449 V15.0.0 (2018-07) Universal Mobile Telecommunications System (UMTS); LTE; Codec for Enhanced Voice Services (EVS); Comfort Noise Generation (CNG) aspects (3GPP TS 26.449 version 15.0.0 Release 15) TECHNICAL SPECIFICATION ETSI ETSI TS 126 449 V15.0.0 (2018-07)13GPP TS 26.449 version
2、15.0.0 Release 15Reference RTS/TSGS-0426449vf00 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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15、p.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 interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provis
16、ions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TS 126 449 V15.0.0 (2018-07)33GPP TS 26.449 version 15.0.0 Release 15Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 Reference
17、s 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 EVS primary CNG operation . 7g36.2 EVS AMR-WB IO CNG operation 7g37 Computational details and bit allo
18、cation 7g3Annex A (informative): Change history . 8g3History 9g3ETSI ETSI TS 126 449 V15.0.0 (2018-07)43GPP TS 26.449 version 15.0.0 Release 15Foreword This Technical Specification has been produced by the 3rdGeneration Partnership Project (3GPP). The contents of the present document are subject to
19、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 of release date and an increase in version number as follows: Version x.y.z where: x the first digit:
20、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, i.e. technical enhancements, corrections, updates, etc. z the third digit is incremented when editor
21、ial only changes have been incorporated in the document. ETSI ETSI TS 126 449 V15.0.0 (2018-07)53GPP TS 26.449 version 15.0.0 Release 151 Scope The present document gives an overview for the requirements of the background acoustic noise evaluation, noise parameter encoding/decoding and comfort noise
22、 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 this text, constitute provisions of the present document. - References are either specific (identified
23、 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 applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific referenc
24、e 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 Voice Services (EVS); Codec Detailed Algorithmic Description“. 3 3GPP TS 26.442: “Codec for Enhanced V
25、oice 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 present document, the abbreviations given in TR 21.905 1 and the following apply. An abbreviation de
26、fined 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 based CNG LP-CNG Linear Prediction based CNG SID Silence Insertion Descriptor 4 General The present do
27、cument 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 codec during Discontinuous Transmission (DTX) operation. The present document is mandatory for implem
28、entation 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 contained in 3, the procedure defined by 3 prevails. In the case of discrepancy between the procedur
29、e 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 is transmitted together with the speech, would disappear when the transmission is cut, resulting in d
30、iscontinuities of the background noise. Since the DTX switching can take place rapidly, it has been found that this effect 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. ETSI ETSI TS 126
31、449 V15.0.0 (2018-07)63GPP TS 26.449 version 15.0.0 Release 15The present document specifies the way to overcome this problem by generating on the receive (RX) side synthetic noise similar to the transmit (TX) side background noise. The comfort noise parameters are estimated on the TX side and trans
32、mitted 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 supports two Comfort Noise Generation (CNG) schemes, a linear prediction based CNG (LP-CNG) as well as
33、 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 comfort noise are packed as a Silence Insertion Descriptor (SID) payload. The update rate of the SID payl
34、oad 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 while in the adaptive rate mode the updates are limited to 8 and 50 depending on the noise behaviour
35、. 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 relevant references to the algorithmic descriptions are provided in the following. 5 Functions on the tra
36、nsmit (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 payload should be updated, the CNG Selector enables either the LP or the FD CNG encoder depending on the
37、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 functions In 2, all TX functions are described in clause 5.6. The algorithmic description of the - SI
38、D 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 AMR-WB IO CNG operation The update rate is basically fixed to an update every 8thframe. However, when
39、 switching into DTX mode, the first and the third frame after active speech are coded by a SID frame. The CNG in the EVS 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. ETSI ETSI TS 126 449
40、 V15.0.0 (2018-07)73GPP TS 26.449 version 15.0.0 Release 156 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 bit of the SID payload determines the CNG module. The remaining bits contain the information of the
41、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 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
42、 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 mode can be found in 2, clause 6.8.4. 7 Computational details and bit allocation A computational descri
43、ption 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 modes, the SID payload consists of 48 bits. The first bit of the payload determines the CNG scheme, where
44、 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 V15.0.0 (2018-07)83GPP TS 26.449 version 15.0.0 Release 15Annex A (informative): Change history Change history Date TSG # TSG Doc. CR Rev Subject/Comment Old New 2014
45、-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 2018-06 80 Version for Release 15 15.0.0 ETSI ETSI TS 126 449 V15.0.0 (2018-07)93GPP TS 26.449 version 15.0.0 Release 15History Document history V15.0.0 July 2018 Publication
