1、 ETSI TS 1Digital cellular telecoUniversal Mobile TelSpeech codec sAdaptive Multi-Rate - Com(3GPP TS 26.1TECHNICAL SPECIFICATION126 192 V13.0.0 (2016communications system (Phaelecommunications System (LTE; c speech processing functionWideband (AMR-WB) speecomfort noise aspects .192 version 13.0.0 Re
2、lease 1316-01) hase 2+); (UMTS); ons; ech codec; 13) ETSI ETSI TS 126 192 V13.0.0 (2016-01)13GPP TS 26.192 version 13.0.0 Release 13Reference RTS/TSGS-0426192vd00 Keywords GSM,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
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12、b server) which are, or may be, or may become, essential to the present document. Foreword This Technical Specification (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 id
13、entities or GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables. 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“, “sh
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15、ct citation. ETSI ETSI TS 126 192 V13.0.0 (2016-01)33GPP TS 26.192 version 13.0.0 Release 13Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 Normative references . 5g33 Definitions, symbols and abbreviations . 6g33.1 Definitions 6g33.2 Symb
16、ols 6g33.3 Abbreviations . 6g34 General . 7g35 Functions on the transmit (TX) side . 7g35.1 ISF evaluation 8g35.2 Frame energy calculation . 9g35.3 Analysis of the variation and stationarity of the background noise 9g35.4 Modification of the speech encoding algorithm during SID frame generation 9g35
17、.4 SID-frame encoding . 10g36 Functions on the receive (RX) side 10g36.1 Averaging and decoding of the LP and energy parameters 10g36. 2 Comfort noise generation and updating 11g37 Computational details and bit allocation 12g3Annex A (informative): Change history . 13g3History 14g3ETSI ETSI TS 126 1
18、92 V13.0.0 (2016-01)43GPP TS 26.192 version 13.0.0 Release 13Foreword This Technical Specification has been produced by the 3GPP. The present document defines the detailed requirements for the correct operation of the background acoustic noise evaluation, noise parameter encoding/decoding and comfor
19、t noise generation in the narrowband telephony speech service employing the Adaptive Multi-Rate Wideband (AMR-WB) speech coder within the 3GPP system. The contents of the present document are subject to continuing work within the TSG and may change following formal TSG approval. Should the TSG modif
20、y the contents of this TS, 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: 1 presented to TSG for information; 2 presented to TSG for approval; 3 Indicates TSG approved document under c
21、hange 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 editorial only changes have been incorporated in the specification; ETSI ETSI TS 126 192 V13.0.0 (2016-01)53GPP TS 26.192 versi
22、on 13.0.0 Release 131 Scope This document gives the detailed requirements for the correct operation of the background acoustic noise evaluation, noise parameter encoding/decoding and comfort noise generation for the AMR Wideband (AMR-WB) speech codec during Source Controlled Rate (SCR) operation. Th
23、e requirements described in this document are mandatory for implementation in all UEs capable of supporting the AMR-WB speech codec. The receiver requirements are mandatory for implementation in all networks capable of supporting the AMR-WB speech codec, the transmitter requirements only for those w
24、here downlink SCR will be used. In case of discrepancy between the requirements described in this document and the fixed point computational description of these requirements contained in 1, the description in 1 will prevail. 2 Normative references This document incorporates by dated and undated ref
25、erence, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this document only when incorporated in
26、it by amendment or revision. For undated references, the latest edition of the publication referred to applies. 1 3GPP TS 26.173 : “AMR Wideband Speech Codec; ANSI-C code“. 2 3GPP TS 26.190 : “AMR Wideband Speech Codec; Transcoding functions“. 3 3GPP TS 26.191 : “AMR Wideband Speech Codec; Error con
27、cealment of lost frames “. 4 3GPP TS 26.193 : “AMR Wideband Speech Codec; Source Controlled Rate operation “. 5 3GPP TS 26.201 : “AMR Wideband Speech Codec; Frame Structure“. ETSI ETSI TS 126 192 V13.0.0 (2016-01)63GPP TS 26.192 version 13.0.0 Release 133 Definitions, symbols and abbreviations 3.1 D
28、efinitions For the purpose of this document, the following definitions apply. Frame: Time interval of 20 ms corresponding to the time segmentation of the adaptive multi-rate wideband speech transcoder, also used as a short term for traffic frame. SID frames: Special Comfort Noise frames. It may conv
29、ey information on the acoustic background noise or inform the decoder that it should start generating background noise. Speech frame: Traffic frame that cannot be classified as a SID frame. VAD flag: Voice Activity Detection flag. TX_TYPE: Classification of the transmitted traffic frame (defined in
30、4). RX_TYPE: Classification of the received traffic frame (defined in 4). Other definitions of terms used in this document can be found in 2 and 4. The overall operation of SCR is described in 4. 3.2 Symbols For the purpose of this document, the following symbols apply. Boldface symbols are used for
31、 vector variables. 1621. fffT=f Unquantized ISF vector 1621.fffT=f Quantized ISF vector f()mUnquantized ISF vector of frame m $f()mQuantized ISF vector of frame m Averaged ISF parameter vector enlogLogarithmic frame energy enmeanlogAveraged logarithmic frame energy ISF parameter prediction residual
32、Quantized ISF parameter prediction residual 3.3 Abbreviations For the purpose of this document , the following abbreviations apply. AMR Adaptive Multi-Rate AMR-WB Adaptive Multi-Rate Wideband CN Comfort Noise fmeane$exnnab()=() ( ) ( ) ()=+xa xa xb xb11KETSI ETSI TS 126 192 V13.0.0 (2016-01)73GPP TS
33、 26.192 version 13.0.0 Release 13SCR Source Controlled Rate operation ( aka source discontinuous transmission ) UE User Equipment SID SIlence DescriptorLP Linear Prediction ISP Immittance Spectral Pair ISF Immittance Spectral Frequency RSS Radio Subsystem RX Receive TX TransmitVAD Voice Activity Det
34、ector 4 General A basic problem when using SCR is that the background acoustic noise, which is transmitted together with the speech, would disappear when the transmission is cut, resulting in discontinuities of the background noise. Since the SCR switching can take place rapidly, it has been found t
35、hat 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. This document specifies the way to overcome this problem by generating on the receive (RX) side synthetic noise similar to t
36、he transmit (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. 5 Functions on the transmit (TX) side The
37、comfort noise evaluation algorithm uses the following parameters of the AMR-WB speech encoder, defined in 2: - the unquantized Linear Prediction (LP) parameters, using the Immittance Spectral Pair (ISP) representation, where the unquantized Immittance Spectral Frequency (ISF) vector is given by 1621
38、fffT.f = ; The algorithm computes the following parameters to assist in comfort noise generation: - the weighted averaged ISF parameter vector (weighted average of the ISF parameters of the eight most recent frames); - the averaged logarithmic frame energy enmeanlog(average of the logarithmic energy
39、 of the eight most recent frames). These parameters give information on the level ( enmeanlog) and the spectrum ( ) of the background noise. The evaluated comfort noise parameters ( and enmeanlog) are encoded into a special frame, called a Silence Descriptor (SID) frame for transmission to the RX si
40、de. A hangover logic is used to enhance the quality of the silence descriptor frames. A hangover of seven frames is added to the VAD flag so that the coder waits with the switch from active to inactive mode for a period of seven frames, during that time the decoder can compute a silence descriptor f
41、rame from the quantized ISFs and the logarithmic frame energy of the decoded speech signal. Therefore, no comfort noise description is transmitted in the first SID frame after active speech. If the background noise contains transients which will cause the coder to switch to active mode and then back
42、 to inactive mode in a very short time period, no hangover is used. Instead the previously used comfort noise frames are used for comfort noise generation. The first SID frame also serves to initiate the comfort noise generation on the receive side, as a first SID frame is always sent at the end of
43、a speech burst, i.e., before the transmission is terminated. The scheduling of SID or speech frames on the network path is described in 4. fmeanfmeanfmeanETSI ETSI TS 126 192 V13.0.0 (2016-01)83GPP TS 26.192 version 13.0.0 Release 135.1 ISF evaluation The comfort noise parameters to be encoded into
44、a SID frame are calculated over N=8 consecutive frames marked with VAD=0, as follows: Prior to averaging the ISF parameters over the CN averaging period, a median replacement is performed on the set of ISF parameters to be averaged, to remove the parameters which are not characteristic of the backgr
45、ound noise on the transmit side. First, the spectral distances from each of the ISF parameter vectors ()f i to the other ISF parameter vectors ()f j , i=0,.,7, j=0,.,7, ij, within the CN averaging period are approximated according to the equation: () ()=1612kjiijkfkfR , (1) where ()fkiis the kth ISF
46、 parameter of the ISF parameter vector ()f i at frame i. To find the spectral distance Siof the ISF parameter vector ()f i to the ISF parameter vectors ()f j of all the other frames j=0,.,7, ji, within the CN averaging period, the sum of the spectral distances Rijis computed as follows: ,7,0=ijjijiR
47、S (2) for all i=0,.,7, ij. The ISF parameter vector ()f i with the smallest spectral distance Siof all the ISF parameter vectors within the CN averaging period is considered as the median ISF parameter vector fmedof the averaging period, and its spectral distance is denoted as Smed. The median ISF p
48、arameter vector is considered to contain the best representation of the short-term spectral detail of the background noise of all the ISF parameter vectors within the averaging period. If there are ISF parameter vectors ()f j within the CN averaging period with SSTHjmedmed , (3) where THmed= 225. is
49、 the median replacement threshold, then at most two of these ISF parameter vectors (the ISF parameter vectors causing THmedto be exceeded the most) are replaced by the median ISF parameter vector prior to computing the averaged ISF parameter vector fmean. The set of ISF parameter vectors obtained as a result of the median replacement are denoted as () f ni, where n is the index of the current frame, and i is the averaging period index (i=0,.,7). When the median replacement is performed at the end of the hangover
