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)
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.
Figure 4.1-1: EVS Generic Frame Format in CS Networks
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_Data | 0 | - |
EVS Primary SID | 48 | - |
EVS Primary 2.8 | 56 | 2,8 |
EVS Primary 7.2 | 144 | 7,2 |
EVS Primary 8.0 | 160 | 8,0 |
EVS Primary 9.6 | 192 | 9,6 |
EVS Primary 13.2 | 264 | 13,2 |
EVS Primary 16.4 | 328 | 16,4 |
EVS Primary 24.4 | 488 | 24,4 |
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 SID | 40 | - |
EVS AMR-WB IO 6.6 | 132 | 6,6 |
EVS AMR-WB IO 8.85 | 177 | 8,85 |
EVS AMR-WB IO 12.65 | 253 | 12,65 |
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.
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.
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.