1、 ETSI TS 126 091 V14.0.0 (2017-04) Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; Mandatory Speech Codec speech processing functions; Adaptive Multi-Rate (AMR) speech codec; Error concealment of lost frames (3GPP TS 26.091 version
2、 14.0.0 Release 14) TECHNICAL SPECIFICATION ETSI ETSI TS 126 091 V14.0.0 (2017-04)13GPP TS 26.091 version 14.0.0 Release 14Reference RTS/TSGS-0426091ve00 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 Siret N 3
3、48 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice The present document can be downloaded from: http:/www.etsi.org/standards-search The present document may be made available in electronic versions and/or in print. The con
4、tent of any electronic and/or print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any existing or perceived difference in contents between such versions and/or in print, the only prevailing document is the print of the Portable Doc
5、ument Format (PDF) version kept on a specific network drive within ETSI Secretariat. Users of the present document should be aware that the document may be subject to revision or change of status. Information on the current status of this and other ETSI documents is available at https:/portal.etsi.o
6、rg/TB/ETSIDeliverableStatus.aspx If you find errors in the present document, please send your comment to one of the following services: https:/portal.etsi.org/People/CommiteeSupportStaff.aspx Copyright Notification No part may be reproduced or utilized in any form or by any means, electronic or mech
7、anical, including photocopying and microfilm except as authorized by written permission of ETSI. The content of the PDF version shall not be modified without the written authorization of ETSI. The copyright and the foregoing restriction extend to reproduction in all media. European Telecommunication
8、s Standards Institute 2017. All rights reserved. DECTTM, PLUGTESTSTM, UMTSTMand the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members. 3GPPTM and LTE are Trade Marks of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. GSM and the GSM l
9、ogo are Trade Marks registered and owned by the GSM Association. ETSI ETSI TS 126 091 V14.0.0 (2017-04)23GPP TS 26.091 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 t
10、hese essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Late
11、st updates are available on the ETSI Web server (https:/ipr.etsi.org/). Pursuant to the ETSI IPR Policy, no investigation, 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 W
12、eb 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 i
13、dentities 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“, “s
14、hall 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 provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in dir
15、ect citation. ETSI ETSI TS 126 091 V14.0.0 (2017-04)33GPP TS 26.091 version 14.0.0 Release 14Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 References 5g33 Definitions and abbreviations . 5g33.1 Definitions 5g33.2 Abbreviations . 5g34 Gen
16、eral . 6g35 Requirements 6g35.1 Error detection 6g35.2 Lost speech frames . 6g35.3 First lost SID frame 6g35.4 Subsequent lost SID frames 6g36 Example ECU/BFH Solution 1 6g36.1 State Machine . 7g36.2 Assumed Active Speech Frame Error Concealment Unit Actions . 8g36.2.1 BFI = 0, prevBFI = 0, State =
17、0 8g36.2.2 BFI = 0, prevBFI = 1, State = 0 or 5 . 8g36.2.3 BFI = 1, prevBFI = 0 or 1, State = 1.6 9g36.2.3.1 LTP-lag update 9g36.2.3.2 Innovation sequence 9g36.3 Assumed Non-Active Speech Signal Error Concealment Unit Actions . 10g36.3.1 General 10g36.3.2 Detectors. 10g36.3.2.1 Background detector .
18、 10g36.3.2.2 Voicing detector 10g36.3.3 Background ECU Actions 10g36.4 Substitution and muting of lost SID frames . 10g37 Example ECU/BFH Solution 2 11g37.1 State Machine . 11g37.2 Substitution and muting of lost speech frames . 11g37.2.1 BFI = 0, prevBFI = 0, State = 0 11g37.2.2 BFI = 0, prevBFI =
19、1, State = 0 or 5 . 11g37.2.3 BFI = 1, prevBFI = 0 or 1, State = 1.6 12g37.2.3.1 LTP-lag update 12g37.2.4 Innovation sequence . 12g37.3 Substitution and muting of lost SID frames . 12g3Annex A (informative): Change history . 13g3History 14g3ETSI ETSI TS 126 091 V14.0.0 (2017-04)43GPP TS 26.091 versi
20、on 14.0.0 Release 14Foreword This Technical Specification has been produced 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 pres
21、ent 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: 1 presented to TSG for information; 2 presented to TSG for approval; 3 or greater indicates TSG approved document under cha
22、nge 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 document. ETSI ETSI TS 126 091 V14.0.0 (2017-04)53GPP TS 26.091 version 14.0
23、.0 Release 141 Scope The present document defines an error concealment procedure, also termed frame substitution and muting procedure, which shall be used by the AMR speech codec receiving end when one or more lost speech or lost Silence Descriptor (SID) frames are received. The requirements of the
24、present document are mandatory for implementation in all networks and User Equipment (UE)s capable of supporting the AMR speech codec. It is not mandatory to follow the bit exact implementation outlined in the present document and the corresponding C source code. 2 References The following documents
25、 contain provisions which, through reference in this 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-s
26、pecific reference, the latest version applies. 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 TS 26.102: “AMR Speech Codec; Interface to Iu
27、 snd Uu“. 2 3GPP TS 26.090: “Transcoding functions“. 3 3GPP TS 26.093: “Source Controlled Rate operation“. 4 3GPP TS 26.101: “Frame Structure“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: N-point median operatio
28、n: consists of sorting the N elements belonging to the set for which the median operation is to be performed in an ascending order according to their values, and selecting the (int (N/2) + 1) -th largest value of the sorted set as the median value Further definitions of terms used in the present doc
29、ument can be found in the references. 3.2 Abbreviations For the purposes of the present document, the following abbreviations apply: AN Access Network BFH Bad Frame Handling BFI Bad Frame Indication from AN BSI_netw Bad Sub-block Indication obtained from AN interface CRC checks CRC Cyclic Redundancy
30、 Check ECU Error Concealment Unit medianN N-point median operation PDFI Potentially Degraded Frame Indication prevBFI Bad Frame Indication of previous frame ETSI ETSI TS 126 091 V14.0.0 (2017-04)63GPP TS 26.091 version 14.0.0 Release 14RX Receive SCR Source Controlled Rate (operation) SID Silence De
31、scriptor frame (Background descriptor) 4 General The purpose of the error concealment procedure is to conceal the effect of lost AMR speech frames. The purpose of muting the output in the case of several lost frames is to indicate the breakdown of the channel to the user and to avoid generating poss
32、ible annoying sounds as a result from the error concealment procedure. The network shall indicate lost speech or lost SID frames by setting the RX_TYPE values 3 to SPEECH_BAD or SID_BAD. If these flags are set, the speech decoder shall perform parameter substitution to conceal errors. The network sh
33、ould also indicate potentially degraded frames using the flag RX_TYPE value SPEECH_PROBABLY_DEGRADED. This flag may be derived from channel quality indicators. It may be used by the speech decoder selectively depending on the estimated signal type. The example solutions provided in paragraphs 6 and
34、7 apply only to bad frame handling on a complete speech frame basis. Sub-frame based error concealment may be derived using similar methods. 5 Requirements 5.1 Error detection If the most sensitive bits of the AMR speech data (class A in 4) are received in error, the network shall indicate RX_TYPE =
35、 SPEECH_BAD in which case the BFI flag is set. If a SID frame is received in error, the network shall indicate RX_TYPE = SID_BAD in which case the BFI flag is also set. The RX_TYPE = SPEECH_PROBABLY_DEGRADED flag should be set appropriately using quality information from the channel decoder, in whic
36、h case the PDFI flag is set. 5.2 Lost speech frames Normal decoding of lost speech frames would result in very unpleasant noise effects. In order to improve the subjective quality, lost speech frames shall be substituted with either a repetition or an extrapolation of the previous good speech frame(
37、s). This substitution is done so that it gradually will decrease the output level, resulting in silence at the output. Clauses 6, and 7 provide example solutions. 5.3 First lost SID frame A lost SID frame shall be substituted by using the SID information from earlier received valid SID frames and th
38、e procedure for valid SID frames be applied as described in 3. 5.4 Subsequent lost SID frames For many subsequent lost SID frames, a muting technique shall be applied to the comfort noise that will gradually decrease the output level. For subsequent lost SID frames, the muting of the output shall be
39、 maintained. Clauses 6 and 7 provide example solutions. 6 Example ECU/BFH Solution 1 The C code of the following example is embedded in the bit exact software of the codec. In the code the ECU is designed to allow subframe-by-subframe synthesis, thereby reducing the speech synthesis delay to a minim
40、um. ETSI ETSI TS 126 091 V14.0.0 (2017-04)73GPP TS 26.091 version 14.0.0 Release 146.1 State Machine This example solution for substitution and muting is based on a state machine with seven states (Figure 1). The system starts in state 0. Each time a bad frame is detected, the state counter is incre
41、mented by one and is saturated when it reaches 6. Each time a good speech frame is detected, the state counter is reset to zero, except when we are in state 6, where we set the state counter to 5. The state indicates the quality of the channel: the larger the value of the state counter, the worse th
42、e channel quality is. The control flow of the state machine can be described by the following C code (BFI = bad frame indicator, State = state variable): if(BFI != 0 ) State = State + 1; else if(State = 6) State = 5; else State = 0; if(State 6 ) State = 6; In addition to this state machine, the Bad
43、Frame Flag from the previous frame is checked (prevBFI). The processing depends on the value of the State-variable. In states 0 and 5, the processing depends also on the two flags BFI and prevBFI. ETSI ETSI TS 126 091 V14.0.0 (2017-04)83GPP TS 26.091 version 14.0.0 Release 14The procedure can be des
44、cribed as follows: Figure 1: State machine for controlling the bad frame substitution 6.2 Assumed Active Speech Frame Error Concealment Unit Actions 6.2.1 BFI = 0, prevBFI = 0, State = 0 No error is detected in the received or in the previous received speech frame. The received speech parameters are
45、 used in the normal way in the speech synthesis. The current frame of speech parameters is saved. 6.2.2 BFI = 0, prevBFI = 1, State = 0 or 5 No error is detected in the received speech frame, but the previous received speech frame was bad. The LTP gain and fixed codebook gain are limited below the v
46、alues used for the last received good subframe: (1) STATE = 0BFI = 0PrevBFI = 0 or 1STATE = 1BFI = 1PrevBFI = 0STATE = 2BFI = 1PrevBFI = 1STATE = 3BFI = 1PrevBFI = 1STATE = 5BFI = 0 or 1PrevBFI = 1STATE = 6BFI = 1PrevBFI = 0 or 1Good frame (BFI=0) Bad frame (BFI=1) STATE = 4BFI = 1PrevBFI = 1()() ()
47、gggggggppppppp=,111ETSI ETSI TS 126 091 V14.0.0 (2017-04)93GPP TS 26.091 version 14.0.0 Release 14where = current decoded LTP gain, = LTP gain used for the last good subframe (BFI = 0), and (2) where = current decoded fixed codebook gain and = fixed codebook gain used for the last good subframe (BFI
48、 = 0). The rest of the received speech parameters are used normally in the speech synthesis. The current frame of speech parameters is saved. 6.2.3 BFI = 1, prevBFI = 0 or 1, State = 1.6 An error is detected in the received speech frame and the substitution and muting procedure is started. The LTP g
49、ain and fixed codebook gain are replaced by attenuated values from the previous subframes: (3) where = current decoded LTP gain, = LTP gains used for the last n subframes, median5() = 5-point median operation, P(state) = attenuation factor (P(1) = 0.98, P(2) = 0.98, P(3) = 0.8, P(4) = 0.3, P(5) = 0.2, P(6) = 0.2), state = state number, and (4) where = current decoded fixed codebook gain, = fixed codebook gains used for the last n subframes, median5() = 5-point median operation, C(state) = attenuation factor (C(1) = 0.98, C(2) = 0.98, C(3)
