A.14 SDP offers and answers for speech sessions with EVS

26.1143GPPIP Multimedia Subsystem (IMS)Media handling and interactionMultimedia telephonyRelease 18TS

These examples show SDP offers and answers for speech sessions where EVS is negotiated. These SDP offer and answer examples are designed to highlight the respective area that is being described and should therefore not be considered as complete SDP offers and answers.

A.14.1 SDP offers initiated by MTSI client in terminal

The SDP offers below can be used by MTSI client in terminal, depending on the access technology or the number of audio channels.

A.14.1.1 Unknown access technology

When the access technology is unknown to MTSI client in terminal, the SDP offer below can be used to initiate a speech session. In this example, RTP Payload Type 97 is defined for EVS, and two sets of RTP Payload Types, 98 and 99, and 100 and 101 are defined for AMR-WB and AMR respectively.

Table A.14.1: SDP example

SDP offer

m=audio 49152 RTP/AVP 97 98 99 100 101 a=tcap:1 RTP/AVPF a=pcfg:1 t=1 b=AS:145 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 max-red=220 a=rtpmap:98 AMR-WB/16000/1 a=fmtp:98 mode-change-capability=2; max-red=220 a=rtpmap:99 AMR-WB/16000/1 a=fmtp:99 mode-change-capability=2; max-red=220; octet-align=1 a=rtpmap:100 AMR/8000/1 a=fmtp:100 mode-change-capability=2; max-red=220 a=rtpmap:101 AMR/8000/1 a=fmtp:101 mode-change-capability=2; max-red=220; octet-align=1 a=ptime:20 a=maxptime:240

Comments:

Since the MTSI client in terminal is not aware of the access technology it uses, all bit-rates of EVS are offered in the session.

The MTSI client in terminal supports all bandwidths, up to fullband.

Regardless of the bandwidth used in the session, clock rate of EVS shall be set to 16 kHz.

Media level b=AS is computed for the highest bit-rate of EVS, 128 kbps, with IPv4 and Header-full payload format, which is greater than the b=AS values of other RTP Payload Types.

A.14.1.2 EGPRS

When the access technology is EGPRS, the SDP offer below can be used to initiate a speech session. In this example, RTP Payload Type 97 is defined for EVS, and two sets of RTP Payload Types, 98 and 99, and 100 and 101 are defined for AMR-WB and AMR respectively.

Table A.14.2: SDP example

SDP offer

m=audio 49152 RTP/AVP 97 98 99 100 101 a=tcap:1 RTP/AVPF a=pcfg:1 t=1 b=AS:33 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=5.9-24.4; bw=nb-wb; max-red=200 a=rtpmap:98 AMR-WB/16000/1 a=fmtp:98 mode-change-capability=2; max-red=200 a=rtpmap:99 AMR-WB/16000/1 a=fmtp:99 mode-change-capability=2; max-red=200; octet-align=1 a=rtpmap:100 AMR/8000/1 a=fmtp:100 mode-change-capability=2; max-red=200 a=rtpmap:101 AMR/8000/1 a=fmtp:101 mode-change-capability=2; max-red=200; octet-align=1 a=ptime:40 a=maxptime:240

Comments:

It is assumed that the modulation and coding scheme (MCS) of EGPRS used in this session is MCS-7 [132] or higher, which supports at least 44.8 kbps. The bit-rate available for data will be reduced further from the overhead for RLC and MAC headers.

All bit-rates of EVS from 5.9 (SC-VBR) to 24.4 kbps are offered in the session.

The MTSI client in terminal supports narrowband and wideband.

Media level b=AS is computed for 24.4 kbps of EVS with Header-full payload format, or for 23.85 which results in a b=AS value of 33 kbps. MCS lower than MCS-7 would necessitate the use of mode-set parameter for AMR-WB as MCS-6 supports only 29.6 kbps. However, higher MCS values would leave lower overhead for channel coding.

A.14.1.3 NR/E-UTRAN/HSPA

When the access technology is E-UTRAN or HSPA, the SDP offer below can be used to initiate a speech session. In this example, RTP Payload Type 97 is defined for EVS, and two sets of RTP Payload Types, 98 and 99, and 100 and 101 are defined for AMR-WB and AMR respectively.

Table A.14.3: SDP example

SDP offer

m=audio 49152 RTP/AVP 97 98 99 100 101 a=tcap:1 RTP/AVPF a=pcfg:1 t=1 b=AS:42 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=5.9-24.4; bw=nb-swb; max-red=220 a=rtpmap:98 AMR-WB/16000/1 a=fmtp:98 mode-change-capability=2; max-red=220 a=rtpmap:99 AMR-WB/16000/1 a=fmtp:99 mode-change-capability=2; max-red=220; octet-align=1 a=rtpmap:100 AMR/8000/1 a=fmtp:100 mode-change-capability=2; max-red=220 a=rtpmap:101 AMR/8000/1 a=fmtp:101 mode-change-capability=2; max-red=220; octet-align=1 a=ptime:20 a=maxptime:240

Comments:

It is assumed that 42 kbps is reserved for speech by the radio access technology.

All bit-rates of EVS from 5.9 (SC-VBR) to 24.4 kbps are offered in the session.

The MTSI client in terminal supports all bandwidths, up to super-wideband.

Media level b=AS is computed for 24.4 kbps of EVS with Header-full payload format.

A.14.1.4 Dual-mono

When dual-mono is offered, the SDP offer below can be used to initiate a speech session. In this example in Table A.14.4a, RTP Payload Types 97 and 98 are defined for EVS, and two sets of RTP Payload Types, 99 and 100, and 101 and 102 are defined for AMR-WB and AMR respectively.

Table A.14.4a: SDP example

SDP offer

m=audio 49152 RTP/AVP 97 98 99 100 101 102 a=tcap:1 RTP/AVPF a=pcfg:1 t=1 b=AS:50 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/2 a=fmtp:97 br=16.4; bw=swb; max-red=220 a=rtpmap:98 EVS/16000/1 a=fmtp:98 br=5.9-24.4; bw=nb-swb; ch-aw-recv=-1; max-red=220 a=rtpmap:99 AMR-WB/16000/1 a=fmtp:99 mode-change-capability=2; max-red=220 a=rtpmap:100 AMR-WB/16000/1 a=fmtp:100 mode-change-capability=2; max-red=220; octet-align=1 a=rtpmap:101 AMR/8000/1 a=fmtp:101 mode-change-capability=2; max-red=220 a=rtpmap:102 AMR/8000/1 a=fmtp:102 mode-change-capability=2; max-red=220; octet-align=1 a=ptime:20 a=maxptime:240

Comments:

It is assumed that 50 kbps is reserved for speech by the radio access technology.

Dual-mono session consisting of two 16.4 kbps SWB channels is offered for the send and the receive directions.

In addition, all bit-rates of EVS from 5.9 (SC-VBR) to 24.4 kbps are offered in the session. Channel-aware mode is disabled in the session for the receiving direction.

Media level b=AS is computed for a dual-mono session including 16.4 kbps of EVS with IPv4 and Header-full payload format which results in a b=AS value of 50 kbps.

In the example in Table A.14.4b, RTP Payload Types 97 and 98 are defined for EVS, and two sets of RTP Payload Types, 99 and 100, and 101 and 102 are defined for AMR-WB and AMR respectively.

Table A.14.4b: SDP example

SDP offer

m=audio 49152 RTP/AVP 97 98 99 100 101 102 a=tcap:1 RTP/AVPF a=pcfg:1 t=1 b=AS:66 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/2 a=fmtp:97 br=13.2-24.4; bw=nb-swb; ch-aw-recv=3; max-red=220 a=rtpmap:98 EVS/16000/1 a=fmtp:98 br=13.2-24.4; bw=nb-swb; ch-aw-recv=3; max-red=220 a=rtpmap:99 AMR-WB/16000/1 a=fmtp:99 mode-change-capability=2; max-red=220 a=rtpmap:100 AMR-WB/16000/1 a=fmtp:100 mode-change-capability=2; max-red=220; octet-align=1 a=rtpmap:101 AMR/8000/1 a=fmtp:101 mode-change-capability=2; max-red=220 a=rtpmap:102 AMR/8000/1 a=fmtp:102 mode-change-capability=2; max-red=220; octet-align=1 a=ptime:20 a=maxptime:240

Comments:

It is assumed that 66 kbps is reserved for speech by the radio access technology.

Dual-mono session consisting of two NB-SWB channels is offered for the send and the receive directions. All bit-rates of EVS from 13.2 to 24.4 kbps are offered in the session. Partial redundancy (channel-aware mode) is used at the start of the session for the receive direction.

Media level b=AS is computed for a dual-mono session including 24.4 kbps of EVS with IPv4, Header-full payload format which results in a b=AS value of 66 kbps.

A.14.2 SDP offers initiated by media gateway

The SDP offer below can be used by media gateway.

A.14.2.1 Network between MTSI using fixed access and MTSI modifying SDP offer to configure EVS AMR-WB IO mode

This example shows the SDP offer when the session is initiated from MTSI client in terminal using fixed access, which supports AMR (all modes) and AMR-WB (all modes). In addition, EVS, G.722, and PCM codecs are supported by the MTSI client in terminal.

The offers for AMR, AMR-WB and EVS codecs are changed by the network to include AMR {12.2, 7.4, 5.9, 4.75}, AMR-WB {12.65, 8.85, 6.60}, EVS AMR-WB IO {12.65, 8.85, 6.60}. For payload type 98, the network also changes the offer to start the session with EVS in EVS AMR-WB IO mode if it is agreed to use the codec.

For EVS, RTP Payload Types 97 and 98 are defined, for example, to initiate a speech session with another MTSI client in terminal using fixed access supporting a bit-rate of 64 kbps or radio access supporting all bit-rates from 5.9 to 24.4 kbps respectively.

The MTSI client in terminal does not include the evs-mode-switch parameter in the initial SDP offer, see Table 6.2a. The SDP is instead changed by the network.

Table A.14.5: SDP example

SDP offer from MTSI client in terminal using fixed access

m=audio 49152 RTP/AVP 97 98 99 9 100 0 8 a=tcap:1 RTP/AVPF a=pcfg:1 t=1 b=AS:81 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=64; bw=wb; mode-change-capability=2; max-red=220 a=rtpmap:98 EVS/16000/1 a=fmtp:98 br=5.9-24.4; bw=nb-wb; mode-change-capability=2; max-red=220 a=rtpmap:99 AMR-WB/16000/1 a=fmtp:99 mode-change-capability=2; max-red=220 a=rtpmap:100 AMR/8000/1 a=fmtp:100 mode-change-capability=2; max-red=220 a=rtpmap:9 G722/8000/1 a=rtpmap:0 PCMU/8000/1 a=rtpmap:8 PCMA/8000/1 a=ptime:20 a=maxptime:240

SDP offer modified by network

m=audio 49152 RTP/AVP 97 98 99 9 100 0 8 a=tcap:1 RTP/AVPF a=pcfg:1 t=1 b=AS:81 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=64; bw=wb; mode-set=0,1,2; mode-change-capability=2; max-red=220 a=rtpmap:98 EVS/16000/1 a=fmtp:98 br=5.9-24.4; bw=nb-wb; evs-mode-switch=1; mode-set=0,1,2; mode-change-capability=2; \ max-red=220 a=rtpmap:99 AMR-WB/16000/1 a=fmtp:99 mode-set=0,1,2; max-red=0 a=rtpmap:100 AMR/8000/1 a=fmtp:100 mode-set=0,2,4,7; max-red=0 a=rtpmap:9 G722/8000/1 a=rtpmap:0 PCMU/8000/1 a=rtpmap:8 PCMA/8000/1 a=ptime:20 a=maxptime:80

Comments:

For EVS, narrowband and wideband are supported for Payload Type 98 while only wideband is supported for Payload Type 97.

If Payload Type 97 is negotiated, EVS Primary mode will be used at the start or update of the session, at 64 kbps wideband. EVS AMR-WB IO mode can be used in the middle of session, which can be switched by the sender, or the receiver with CMR.

If Payload Type 98 is negotiated, EVS AMR-WB IO mode will be used at the start or update of the session, at 6.60, 8.85, or 12.65 kbps.

A.14.3 SDP answers from MTSI client in terminal

The SDP answers below can be used by MTSI client in terminal, depending on access technology or service policy. It is assumed that SDP offers such as Tables A.14.1, A.14.2, A.14.3, A.14.4, or A.14.5 are received.

A.14.3.1 SDP answer from MTSI client in terminal when narrowband speech is negotiated

In this example, the MTSI client in terminal includes only narrowband speech in the SDP answer.

Table A.14.6: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:30 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=5.9-13.2; bw=nb; mode-set=0,1,2; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains all bit-rates from 5.9 to 13.2 kbps, with IPv4 for the send and the receive directions.

Media level b=AS is computed for 13.2 kbps of EVS Primary mode, or 12.65 kbps of EVS AMR-WB IO mode, with Header-full payload format, either of which results in 30 kbps.

A.14.3.2 SDP answer from MTSI client in terminal when up to wideband speech is negotiated

In this example, the MTSI client in terminal includes narrowband and wideband speech in the SDP answer.

Table A.14.7: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:49 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=7.2-32; bw=nb-wb; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains all bit-rates from 7.2 to 32 kbps, with IPv4 for the send and the receive directions.

As neither br-send nor br-recv of the SDP answer includes 5.9 kbps, source controlled variable bit-rate (SC-VBR) coding is not used for the session.

A.14.3.3 SDP answer from MTSI client in terminal when only wideband speech is negotiated

In this example, the MTSI client in terminal includes only wideband speech in the SDP answer.

Table A.14.8: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:49 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=9.6-32; bw=wb; mode-set=0,1,2; hf-only=1; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains all bit-rates from 9.6 to 32 kbps, with IPv4 for the send and the receive directions.

In EVS AMR-WB IO mode, only 6.60, 8.85, and 12.65 kbps are used.

Only Header-full format is used in the session.

A.14.3.4 SDP answer from MTSI client in terminal when up to super-wideband speech is negotiated

In this example, the MTSI client in terminal includes narrowband, wideband, and super-wideband speech in the SDP answer.

Table A.14.9: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:65 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br-send=8-48; br-recv=32-48; bw-send=nb-swb; bw-recv=swb; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains bit-rates from 8 to 48 kbps for the send direction, and bit-rates from 32 to 48 kbps for the receive direction, with IPv4.

The SDP answer contains bandwidths from narrowband to super-wideband for the sending direction, and only super-wideband for the receiving direction.

A.14.3.5 SDP answer from MTSI client in terminal when only super-wideband speech is negotiated

In this example, the MTSI client in terminal includes only super-wideband speech in the SDP answer.

Table A.14.10: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:65 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=16.4-48; bw=swb; cmr=-1; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains bit-rates from 16.4 to 48 kbps, with IPv4 for the send and the receive directions.

CMR is not used in this session.

A.14.3.6 SDP answer from MTSI client in terminal using WLAN

This example shows the SDP answer when the MTSI client in terminal is using WLAN as the access technology.

Table A.14.11: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:37 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=13.2-32; ch-aw-recv=3; max-red=160 a=ptime:80 a=maxptime:240

Comments:

The SDP answer contains all bit-rates from 13.2 to 32 kbps, with IPv4 for the send and the receive directions. Channel-aware mode with offset 3 is enabled for the receiving direction.

A.14.3.7 SDP answer from MTSI client in terminal supporting dual-mono

This example shows the SDP answer when the MTSI client in terminal supports dual-mono.

Table A.14.12: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:50 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/2 a=fmtp:97 br=16.4; bw=swb; ch-send=2; ch-recv=2; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains a dual-mono session consisting of two 16.4 kbps SWB channels, for the send and the receive directions, with IPv4.

A.14.3.8 SDP answer from MTSI client in terminal supporting dual-mono for send direction

This example shows the SDP answer when the MTSI client in terminal supports dual-mono only for the send direction.

Table A.14.13: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:42 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/2 a=fmtp:97 br-send=16.4; br-recv=24.4; bw-send=swb; bw-recv=nb-swb; ch-send=2; ch-recv=1; \ max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains a dual-mono session consisting of two 16.4 kbps SWB channels for the send direction, and a mono session consisting of 24.4 kbps for the receive direction, with IPv4.

In the usage of the channels parameter, "/n," n represents the number of audio channels, see [125].

‘ch-send=2’ indicates that the answerer will include two audio channels (dual-mono) in the RTP packets in the sending direction, see Clause 7.5.2.1.9. ‘ch-recv=1’ indicates that the answerer expects that only one audio channel will be included in the RTP packets in the receiving direction.

A.14.3.9 SDP answer from MTSI client in terminal when SC-VBR is negotiated

In this example, the MTSI client in terminal includes narrowband and wideband speech in the SDP answer. This SDP answer is used to negotiate the lowest possible bit-rate of EVS Primary, for example, due to limited network capacity.

Table A.14.13a: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:25 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=5.9; bw=nb-wb; mode-set=0; max-red=220 a=ptime:20 a=maxptime:240

Comments:

Media level b=AS of SC-VBR is computed for the b=AS of its highest component bit-rate, 8 kbps. Therefore br=5.9, 5.9-7.2, and 5.9-8 result in the same b=AS value of 25, with IPv4.

If frame aggregation is not used, no codec mode of EVS AMR-WB IO other than 6.6 kbps can be used at this b=AS value, whether mode-set is included or not,

A.14.4 SDP answers from MTSI client in terminal using fixed access

These examples show the SDP answers when the MTSI client in terminal is using fixed access.

A.14.4.1 SDP answer from MTSI client in terminal using fixed access when narrowband speech is negotiated

In this example, the MTSI client in terminal includes only narrowband speech in the SDP answer.

Table A.14.14: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:30 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=13.2; bw=nb; dtx=0; mode-set=0,1,2; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains only 13.2 kbps.

DTX is disabled in the session.

Media level b=AS with IPv4 is computed for 13.2 kbps of EVS Primary mode, or 12.65 kbps of EVS AMR-WB IO mode, with Header-full payload format, either of which results in 30 kbps.

A.14.4.2 SDP answer from MTSI client in terminal using fixed access when only wideband speech is negotiated

In this example, the MTSI client in terminal includes only wideband speech in the SDP answer.

Table A.14.15: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:81 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=64; bw=wb; dtx=0; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains only 64 kbps.

DTX is disabled in the session.

A.14.4.3 SDP answer from MTSI client in terminal using fixed access when only super-wideband speech is negotiated

In this example, the MTSI client in terminal includes only super-wideband speech in the SDP answer.

Table A.14.16: SDP example

SDP answer

m=audio 49152 RTP/AVPF 97 a=acfg:1 t=1 b=AS:113 b=RS:0 b=RR:2000 a=rtpmap:97 EVS/16000/1 a=fmtp:97 br=96; bw=swb; dtx=0; max-red=220 a=ptime:20 a=maxptime:240

Comments:

The SDP answer contains only 96 kbps.

DTX is disabled in the session.