1、 ETSI TS 1Digital cellular telecoUniversal Mobile TelGeneral audio codEnhanced aaEnhanSpectral Ba(3GPP TS 26.4TECHNICAL SPECIFICATION126 404 V13.0.0 (2016communications system (Phaelecommunications System (LTE; odec audio processing functiaacPlus general audio codec;anced aacPlus encoder Band Replic
2、ation (SBR) part .404 version 13.0.0 Release 1316-01) hase 2+); (UMTS); ctions; c; 13) ETSI ETSI TS 126 404 V13.0.0 (2016-01)13GPP TS 26.404 version 13.0.0 Release 13Reference RTS/TSGS-0426404vd00 Keywords GSM,LTE,UMTS ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 9
3、2 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 7803/88 Important notice The present document can be downloaded from: http:/www.etsi.org/standards-search The present document may be made available in e
4、lectronic versions and/or in print. The content 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 prevailin
5、g document is the print of the Portable Document 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 doc
6、uments is available at http:/portal.etsi.org/tb/status/status.asp 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
7、 by any means, electronic or mechanical, 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
8、media. European Telecommunications Standards Institute 2016. 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 Organizat
9、ional Partners. GSM and the GSM logo are Trade Marks registered and owned by the GSM Association. ETSI ETSI TS 126 404 V13.0.0 (2016-01)23GPP TS 26.404 version 13.0.0 Release 13Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI
10、. The information pertaining to these 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 availabl
11、e from the ETSI Secretariat. Latest 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
12、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 Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports us
13、ing their 3GPP identities, UMTS identities 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
14、 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 provisions). “must“ and “must not“ are NOT allowed in ETSI del
15、iverables except when used in direct citation. ETSI ETSI TS 126 404 V13.0.0 (2016-01)33GPP TS 26.404 version 13.0.0 Release 13Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 Normative references . 5g33 Definitions, symbols and abbreviation
16、s . 5g33.1 Definitions 5g33.2 Symbols 6g33.3 Abbreviations . 7g34 Outline description . 7g35 SBR encoder description 7g35.1 SBR tools overview 7g35.1.1 Enhanced aacPlus sdynchronization without parametric stereo 8g35.1.2 Enhanced aacPlus synchronisation with parametric stereo . 9g35.1.3 SBR encoder
17、modules overview . 10g35.2 Analysis filterbank . 12g35.3 Frequency band tables 15g35.4 Time / frequency grid generation . 15g35.4.1 Transient detector . 15g35.4.2 Frame splitter 16g35.4.3 Frame generator 17g35.5 Envelope estimation . 21g35.6 Additional control parameters 22g35.6.1 Introduction. 22g3
18、5.6.2 Tonality estimation . 23g35.6.3 Noise-floor estimation 24g35.6.4 Inverse filtering estimation . 25g35.6.5 Additional sines estimation . 26g35.7 Data quantization 29g35.8 Envelope and noise floor coding 30g36 Bitstream 32g3Annex A (informative): Change history . 34g3History 35g3ETSI ETSI TS 126
19、 404 V13.0.0 (2016-01)43GPP TS 26.404 version 13.0.0 Release 13Foreword The present document describes the detailed mapping of the general audio service employing the aacPlus general audio codec within the 3GPP system. The contents of the present document are subject to continuing work within the TS
20、G and may change following formal TSG approval. Should the TSG modify 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 pres
21、ented to TSG for approval; 3 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 editorial only changes have been incorporated in the specif
22、ication; ETSI ETSI TS 126 404 V13.0.0 (2016-01)53GPP TS 26.404 version 13.0.0 Release 131 Scope This Telecommunication Standard (TS) describes the SBR encoder part of the Enhanced aacPlus general audio codec 3. 2 Normative references This TS incorporates by dated and undated reference, provisions fr
23、om other publications. These normative references are cited in 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 TS only when incorporated in it by amendment or revision
24、. For undated references, the latest edition of the publication referred to applies. 1 ISO/IEC 14496-3:2001/Amd.1:2003, Bandwidth Extension. 2 ISO/IEC 14496-3:2001/Amd.1:2003/DCOR1. 3 3GPP TS 26.401 : Enhanced aacPlus general audio codec; General Description 3 Definitions, symbols and abbreviations
25、3.1 Definitions For the purposes of this TS, the following definitions apply: band: (as in limiter band, noise floor band, etc.) a group of consecutive QMF subbands chirp factor: the bandwidth expansion factor of the formants described by a LPC polynomial Down Sampled SBR: the SBR Tool with a modifi
26、ed synthesis filterbank resulting in a down sampled output signal with the same sample rate as the input signal to the SBR Tool. May be used whenever a lower sample rate output is desired. envelope scalefactor: an element representing the averaged energy of a signal over a region described by a freq
27、uency band and a time segment frequency band: interval in frequency, group of consecutive QMF subbands frequency border: frequency band delimiter, expressed as a specific QMF subband noise floor: a vector of noise floor scalefactors noise floor scalefactor: an element associated with a region descri
28、bed by a frequency band and a time segment, representing the ratio between the energy of the noise to be added to the envelope adjusted HF generated signal and the energy of the same patch: a number of adjoining QMF subbands moved to a different frequency location SBR envelope: a vector of envelope
29、scalefactors SBR frame: time segment associated with one SBR extension data element SBR range: the frequency range of the signal generated by the SBR algorithm subband: a frequency range represented by one row in a QMF matrix, carrying a subsampled signal time border: time segment delimiter, express
30、ed as a specific time slot time segment: interval in time, group of consecutive time slots ETSI ETSI TS 126 404 V13.0.0 (2016-01)63GPP TS 26.404 version 13.0.0 Release 13time / frequency grid: a description of SBR envelope time segments and associated frequency resolution tables as well as descripti
31、on of noise floor time segments time slot: finest resolution in time for SBR envelopes and noise floors. One time slot equals two subsamples in the QMF domain 3.2 Symbols For the purposes of this TS, the following symbols apply: Description of variables defined in one sub clause and used in other su
32、bclasses. ch is the current channel, and when used as index in vectors left channel is represented by ch= 0 and right channel is represented ch= 1. EOrighas LEcolumns where each column is of length NLowor NHighdepending on the frequency resolution for each SBR envelope. The elements in EOrigcontains
33、 the envelope scalefactors of the original signal. has two column vectors containing the frequency border tables for low and high frequency resolution. internal sampling frequency of the SBR Tool, twice the sampling frequency of the core coder (after sampling frequency mapping, Table 4.55). The samp
34、ling frequency of the SBR enhanced output signal is equal to the internal sampling frequency of the SBR Tool, unless the SBR Tool is operated in downsampled mode. If the SBR Tool is operated in downsampled mode, the output sampling frequency is equal to the sampling frequency of the core coder. fMas
35、teris of length NMaster+1 and contains QMF master frequency grouping information. fTableHighis of length NHigh+1 and contains frequency borders for high frequency resolution SBR envelopes. fTableLowis of length NLow+1 and contains frequency borders for low frequency resolution SBR envelopes. fTableN
36、oiseis of length NQ+1 and contains frequency borders used by noise floors. kxthe first QMF subband in the SBR range. k0the first QMF subband in the fMastertable. LEnumber of SBR envelopes. LQnumber of noise floors. M number of QMF subbands in the SBR range. middleBorder points to a specific time bor
37、der. NLnumber of limiter bands. NMasternumber of frequency bands in the master frequency resolution table. NQnumber of noise floor bands. number of frequency bands for low and high frequency resolution. numPatches a variable indicating the number of patches in the SBR range. numTimeSlots number of S
38、BR envelope time slots that exist within an AAC frame, 16 for a 1024 AAC frame . offset-values for the SBR envelope and noise floor data, when using coupled channels. ,TableLow TableHigh=Ff fSBRFs, Low HighNN=n24,12=panOffsetETSI ETSI TS 126 404 V13.0.0 (2016-01)73GPP TS 26.404 version 13.0.0 Releas
39、e 13patchBorders a vector containing the frequency borders of the patches. patchNumSubbands a vector holding the number of subbands in every patch. QOrighas LQcolumns where each column is of length NQand contains the noise floor scalefactors. frequency resolution for all SBR envelopes in the current
40、 SBR frame, zero for low resolution, one for high resolution. reset a variable in the encoder and the decoder set to one if certain bitstream elements have changed from the previous SBR frame, otherwise set to zero. tEis of length LE+1 and contains start and stop time borders for all SBR envelopes i
41、n the current SBR frame. tHFAdjoffset for the envelope adjuster module. tHFGenoffset for the HF-generation module. tQis of length LQ+1 and contains start and stop time borders for all noise floors in the current SBR frame. 3.3 Abbreviations For the purposes of this TS, the following abbreviations ap
42、ply. NA Not Applicable aacPlus Combination of MPEG-4 AAC and MPEG-4 Bandwidth extension (SBR) Enhanced aacPlus Combination of MPEG-4 AAC, MPEG-4 Bandwidth extension (SBR) and MPEG-4 Parametric Stereo QMF Quadrature Mirror Filter SBR Spectral Band Replication 4 Outline description This TS is structur
43、ed as follows: Section 5.1 gives an encoder overview description. Section 5.2 gives a detailed description of the filterbanks used in the encoder. Section 5.3 gives a specification of the used frequency band tables. Section 5.4 gives a detailed description of the time grid calculation and the transi
44、ent detection. Section 5.5 gives a detailed description of the envelope estimation. Section 5.6 gives a detailed description of the estimation of the additional control parameters. Section 5.7 gives detailed description of the data quantisation. Section 5.8 gives a detailed description of the envelo
45、pe coding. 5 SBR encoder description 5.1 SBR tools overview The encoder part of the SBR tool estimates several parameters used by the high frequency reconstruction method on the decoder side. In order to synchronise the SBR bitstream data with the AAC codec, the two different modes of operation have
46、 to be considered; normal aacPlus operation and aacPlus parametric stereo operation. In the normal case, the AAC encoder is responsible for downsampling of the input PCM signal, while the SBR encoder works in parallel on twice the sampling frequency compared to the downsampled signal. When using par
47、ametric stereo aacPlus, the SBR tool is also 0 1 ,., Lr r=rETSI ETSI TS 126 404 V13.0.0 (2016-01)83GPP TS 26.404 version 13.0.0 Release 13responsible for downsampling of the AAC coder signal. The two modes are outlined in the following sections and illustrated in Figure 1 and Figure 2. Figure 1 aacP
48、lus block diagram Figure 2 Parametric stereo aacPlus block diagram 5.1.1 Enhanced aacPlus sdynchronization without parametric stereo The time domain input PCM signal is assumed to be stored in a buffer x, where 2048 new samples are added to the end of the buffer every frame. Before adding new sample
49、s, all samples in the buffer must be left-shifted 2048 samples. The buffersize amounts to 576 + 2048 + tinputDelaysamples, where tinputDelayequals the total AAC delay, i.e. the delay for the entire encoder decoder chain, plus the SBR decoder buffer delay minus the SBR encoder buffer delay. All delays are expressed in the SBR input sampling rate: The PCM buffer x is fed to the analysis QMF bank, where subband filtering is performed. The window stride of the QMF bank is illustrated in Figure 3a, which shows that the first window is applied from sample 0 to
