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TS 26.446
Codec for Enhanced Voice Services (EVS) –
AMR-WB Backward Compatible Functions

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V16.0.0 (PDF)  2019/03  10 p.
V15.0.0  2018/06  10 p.
V14.0.0  2017/03  10 p.
V13.0.0  2015/12  10 p.
V12.0.0  2014/09  10 p.
Rapporteur:
Mr. Ragot, StephaneOrange

Content for  TS 26.446  Word version:   16.0.0

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1  ScopeWord‑p. 5
The present document specifies the AMR-WB backward compatible functions of the EVS codec.
The present document is a high level overview of the functionality with reference to the Codec Detailed Algorithmic Description where the functionality is specified in detail.

2  References

The following documents 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-specific 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]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 26.445: "Codec for Enhanced Voice Services (EVS); Codec Detailed Algorithmic Description".
[3]
TS 26.442: " Codec for Enhanced Voice Services (EVS); ANSI C code (fixed-point)".
[4]
TS 26.443: " Codec for Enhanced Voice Services (EVS); ANSI C code (floating-point)".
[5]
TS 26.444: " Codec for Enhanced Voice Services (EVS); Test Sequences".
[6]
TS 26.447: " Codec for Enhanced Voice Services (EVS); Error Concealment of Lost Packets".
[7]
TS 26.448: " Codec for Enhanced Voice Services (EVS); Jitter Buffer Management".
[8]
TS 26.449: " Codec for Enhanced Voice Services (EVS); Comfort Noise Generation (CNG) Aspects".
[9]
TS 26.450: " Codec for Enhanced Voice Services (EVS); Discontinuous Transmission (DTX)".
[10]
TS 26.451: " Codec for Enhanced Voice Services (EVS); Voice Activity Detection (VAD)".
[11]
TS 26.171: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; General description".
[12]
TS 26.173: "ANSI-C code for Adaptive Multi-Rate - Wideband (AMR-WB) speech codec".
[13]
TS 26.190: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Transcoding functions".
[14]
TS 26.191: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Error concealment of erroneous or lost frames".
[15]
TS 26.192: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Comfort noise aspects ".
[16]
TS 26.193: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Source controlled rate operation".
[17]
TS 26.194: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Voice Activity Detector (VAD)".
[18]
TS 26.201: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Frame structure".
[19]
TS 26.202: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Interface to Iu, Uu, and Nb".
[20]
TS 26.204: "Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; ANSI-C code".
[21]
RFC 4867:  "RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs".
[22]
TS 26.452: "Codec for Enhanced Voice Services (EVS); ANSI C code; Alternative fixed-point using updated basic operators".
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3  AbbreviationsWord‑p. 6
For the purposes of the present document, the abbreviations given in TR 21.905 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.
AMR-WB
Adaptive Multi Rate Wideband (codec)
CNG
Comfort Noise Generator
DTX
Discontinuous Transmission
EVS
Enhanced Voice Services
FB
Fullband
IO
Interoperable
JBM
Jitter Buffer Management
NB
Narrowband
SID
Silence Insertion Descriptor
SWB
Super Wideband
VAD
Voice Activity Detection
WB
Wideband
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4  General

The EVS coder provides enhanced AMR-WB backward compatible operation over all nine source bit rates from 6.6 kbit/s to 23,85 kbit/s, including AMR-WB backward compatible DTX operation. This backward compatible operation is referred to AMR-WB interoperable (AMR-WB IO).
Frames generated by an EVS AMR-WB IO encoder can be decoded by an AMR-WB decoder, without the need for transcoding. Correspondingly, frames generated by an AMR-WB encoder can be decoded by an EVS AMR-WB IO decoder, without the need for transcoding.
In addition to encoder and decoder enhancements, the AMR-WB backward compatible functions in the EVS coder provide the following extra functionalities compared to the AMR-WB coder specified in [11] to [17] and [20]:
  • Support of input and output sampling frequencies other than 16 kHz (i.e. 8, 32, 48 kHz)
  • Inclusion of jitter buffer management for AMR-WB backward compatible functions
  • Switching between AMR-WB IO bit rates and primary EVS bit rates at any 20 ms speech frame boundary
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 codec backward compatible functions 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 procedure described in the present document and its ANSI-C code specification contained in [4] the procedure defined by [4] prevails. In the case of discrepancy between the procedure described in the present document and its ANSI-C code specification contained in [22] the procedure defined by [22] prevails.
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5  AMR-WB backward compatible transcoding functionsWord‑p. 7
The AMR-WB backward compatible transcoding functions of the EVS coder are described in [2].

6  AMR-WB backward compatible ANSI-C code

The ANSI C-code of the EVS codec, including backward compatible functions, is described in [3] and [22] for fixed point arithmetic operation, using different sets of basic operators, and is described in [4] for floating point arithmetic operation.

7  AMR-WB backward compatible error concealment of erroneous or lost frames

The EVS coder AMR-WB backward compatible error concealment of erroneous or lost frames is described in [2], [6] and [7].

8  AMR-WB backward compatible comfort noise aspects

The AMR-WB backward compatible comfort noise aspects of EVS coder are described in [2] and [8].

9  AMR-WB backward compatible source controlled rate operation

The EVS coder AMR-WB backward compatible source controlled rate operation of the Enhanced Voice Services codec is defined in [2] and [9]. This DTX operation is compliant with [16].

10  AMR-WB backward compatible Voice Activity Detector (VAD)

The AMR-WB backward compatible VAD function of EVS coder is described in [2] and [10].
The VAD algorithm description is detailed in [2], and the corresponding C-code is defined in [3], [4] and [22].
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11  AMR-WB backward compatible frame structure and interface to Iu, Uu, and Nb

The EVS coder AMR-WB backward compatible part of the EVS coder supports the formats (IF1, IF2, MIME, RFC 4867 [21]) defined in [18] and [19].

A  Change historyWord‑p. 8

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