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TS 26.453
Codec for Enhanced Voice Services (EVS) –
Speech Codec Frame Structure

3GPP‑Page   ETSI‑search   CONTENT↓
V17.0.0 (PDF)  2022/03  10 p.
V16.0.0  2019/03  10 p.
V15.0.0  2018/06  10 p.
V14.0.0  2017/03  10 p.
V13.0.0  2016/03  10 p.
Rapporteur:
Mr. Varga, Imre
Qualcomm CDMA Technologies

Content for  TS 26.451  Word version:  16.0.0

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1  Scope  Word‑p. 5

The Enhanced Voice Services (EVS) Codec is specified in the series of Technical Specifications TS 26.441, TS 26.442, TS 26.443, TS 26.444, TS 26.445, TS 26.446, TS 26.447, TS 26.448, TS 26.449, TS 26.450, TS 26.451 and TS 26.452. The EVS Codec is characterized in TR 26.952.
The present document describes the "generic frame format" for the EVS Codec for the application in 3G Circuit-Switched Networks. This format is based on the RTP framing, as specified in TS 26.445. This generic frame format will be used as a common reference point, when interfacing speech frames between different elements of the 3G system. Appropriate mappings to and from this generic frame format will be used within and between each system element.
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2  References  Word‑p. 5

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]
TR 41.001: "GSM Specification set".
→ to date, withdrawn by 3GPP
[3]
TS 26.441: "Codec for Enhanced Voice Services (EVS); General overview".
[4]
TS 26.442: "Codec for Enhanced Voice Services (EVS); ANSI C code (fixed-point)".
[5]
TS 26.443: "Codec for Enhanced Voice Services (EVS); ANSI C code (floating-point)".
[6]
TS 26.444: "Codec for Enhanced Voice Services (EVS); Test Sequences".
[7]
TS 26.445: "Codec for Enhanced Voice Services (EVS); Detailed algorithmic description".
[8]
TS 26.446: "Codec for Enhanced Voice Services (EVS); Adaptive Multi-Rate - Wideband (AMR-WB) backward compatible functions".
[9]
TS 26.447: "Codec for Enhanced Voice Services (EVS); Error concealment of lost packets".
[10]
TS 26.448: "Codec for Enhanced Voice Services (EVS); Jitter buffer management".
[11]
TS 26.449: "Codec for Enhanced Voice Services (EVS); Comfort Noise Generation (CNG) aspects".
[12]
TS 26.450: "Codec for Enhanced Voice Services (EVS); Discontinuous Transmission (DTX)".
[13]
TS 26.451: "Codec for Enhanced Voice Services (EVS); Voice Activity Detection (VAD)".
[14]
TR 26.952: "Codec for Enhanced Voice Services (EVS); Performance Characterization".
[15]
TS 26.452: "Codec for Enhanced Voice Services (EVS); ANSI C code; Alternative fixed-point using updated basic operators".
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3  Abbreviations  Word‑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
CMR
Codec Mode Request (for AMR and AMR-WB and EVS)
CS
Circuit Switched
EVS
Enhanced Voice Services
EVS-CMR
CMR for EVS
EVS-SID
SID for EVS
FQC
Frame quality Classification
EVS AMR-WB IO
EVS AMR-WB Inter Operable (mode of operation)
MSB
Most Significant Bit
RTP
Real Time Protocol
SID
Silence Insertion Descriptor (for AMR and AMR-WB)
ToC
Table of Contents
WB-CMR
CMR for AMR-WB
WB-SID
SID for AMR-WB (and for EVS AMR-WB IO)
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4  EVS Codec generic frame format in CS Networks  Word‑p. 6

4.1  General  Word‑p. 6

This clause describes the "generic frame format" of the EVS Codec in 3G CS networks for the Speech and SID frames of the primary modes of operation and the Speech and SID frames of the EVS AMR-WB IO mode of operation.
This generic frame format is illustrated in Figure 4.1-1 and it is based on the RTP format specified in TS 26.445, Annex A, Figure A.3 (c), "Payload structure of Header-Full format with CMR + ToC single frame" and in TS 26.445, Annex A, Figure A.6, "Payload structure for EVS AMR-WB IO SID (56 bit) payload" with the following modifications:
  • The leading "1" bit, d(0), in the CMR octet (MSB) is omitted in CS networks;
    bits d(1) ... d(7) are copied bit by bit in the same order. EVS-CMR has therefore 7 bits.
  • The ToC octet is omitted (Table of Contents in RTP).
  • The Speech data or SID of the EVS primary and the EVS AMR-WB IO modes are copied bit by bit.
    Each rate has its own, unique number of bits (n+1).
  • The 40 bits of the AMR-WB SID, d(0) ... d(39), are copied bit by bit into the generic frame format.
Note that the order of Speech data or SID bits is the same as in in TS 26.445.
Copy of original 3GPP image for 3GPP TS 26.453, Figure 4.1-1: EVS Generic Frame Format in CS Networks
Figure 4.1-1: EVS Generic Frame Format in CS Networks
(⇒ copy of original 3GPP image)
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4.2  EVS payload sizes in CS Networks  Word‑p. 6

Table 4.2-1 lists all EVS Primary rates for the application in CS Networks, including No_Data. These payload sizes are always integer multiples of 8 bits (excluding the 7-bit EVS-CMR).
Rate Payload Size (bits) Net bit rate for active speech (kbps)
No_Data0-
EVS Primary SID48-
EVS Primary 2.8562,8
EVS Primary 7.21447,2
EVS Primary 8.01608,0
EVS Primary 9.61929,6
EVS Primary 13.226413,2
EVS Primary 16.432816,4
EVS Primary 24.448824,4
 
Table 4.2-2 lists all EVS AMR-WB IO rates for the application in CS Networks. In contrast to the payload sizes used in RTP, these payloads do not include any CMR overhead. These payload sizes are not always integer multiples of 8 bits (excluding the 7-bit EVS-CMR).
Rate Payload Size (bits) Net bit rate for active speech (kbps)
EVS-AMR-WB IO SID40-
EVS AMR-WB IO 6.61326,6
EVS AMR-WB IO 8.851778,85
EVS AMR-WB IO 12.6525312,65
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4.3  EVS generic frame header  Word‑p. 7

The EVS Codec generic frame format in CS networks has no header. The payload size defines the used Codec rate. Parameters inside this EVS payload differentiate the EVS audio bandwidth and the EVS mode of operation. For details, see TS 26.445.

4.4  EVS frame quality classification  Word‑p. 7

The EVS Codec generic frame format has no own Frame Quality Indicator. If transported on Iu and Nb the "Frame Quality Classification" (FQC) of the Iu and Nb framing protocol is used.

4.5  EVS codec mode request in CS Networks  Word‑p. 7

The EVS Codec Mode Request (EVS-CMR) is specified in TS 26.445, Annex A, Table A.3: Structure of CMR. The EVS-CMR has a size of 7 bits. The Header bit (MSB), specified in TS 26.445, is omitted in CS networks.

$  Change history  Word‑p. 8

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