Content for TS 23.334 Word version: 18.1.0

1… 4… 5… 5.11… 5.12… 5.14… 5.18… 5.19… 5.20… 5.21… 6… 6.1.6… 6.1.11… 6.2… 6.2.10… 6.2.10.3.1.2 6.2.10.3.2 6.2.10.4… 6.2.10.4.3… 6.2.10.5 6.2.10.6… 6.2.10A… 6.2.13… 6.2.14… 6.2.14.3 6.2.14.4… 6.2.15… 6.2.17… 6.2.17.3… 6.2.17.5… 6.2.18… 6.2.20 6.2.21… 6.2.22… 6.2.22.3… 6.2.22.3.2 6.2.23 6.2.24 6.2.25 7 8… 8.3 8.4 8.5… 8.23…

5.12 Explicit Congestion Notification support 5.12.1 General 5.12.2 Incoming SDP offer with ECN 5.12.3 Incoming SDP offer without ECN 5.12.4 Detection of ECN failures by IMS-AGW 5.13 Transcoding 5.13.1 General 5.13.2 Handling of common codec parameters 5.13.3 Handling of the EVS speech codec 5.13.4 Handling of the OPUS speech and audio codec for WebRTC 5.13.5 Handling of the IVAS speech and audio codec
...

5.12 Explicit Congestion Notification support |R10| p. 29

5.12.1 General p. 29

An IMS-ALG and IMS-AGW may support Explicit Congestion Notification (see RFC 3168, RFC 6679 and TS 26.114).

An IMS-ALG and IMS-AGW which supports ECN shall support the ECN transparent procedure i.e. the transparent forwarding of ECN bits in the IP header (see RFC 3168). If the IMS-AGW does not support the transparent forwarding of ECN bits then the IMS-ALG shall not permit ECN in the SDP Offer/Answer negotiation.

The IMS-AGW shall treat RTCP for ECN as a RTP translator with no media translation.

An IMS-ALG and IMS-AGW which supports ECN may then act as an ECN endpoint to enable ECN towards the IMS access network or/and towards the IMS Core Network. The subsequent clauses describe the general support for ECN, further details on the support of ECN during PS to CS access transfer is described in clause 6.2.14.3.

An IMS-ALG and IMS-AGW that support ECN Transparent as well as transcoding shall also support the ECN endpoint procedure.

An IMS-ALG/IMS-AGW supporting the ATCF/ATGW function and ECN shall support ECN Endpoint (see clause 6.2.14).

When acting as an ECN endpoint, the IMS-AGW shall be capable of enabling end-to-end rate adaptation between the local terminal and the remote entity by performing the following towards the ECN-capable peer:

trigger rate adaptation request towards the ECN-capable peer when receiving in the incoming IMS media flow IP packets marked with ECN-CE, regardless of whether the IMS-AGW applies or does not apply transcoding;
forward adaptation requests between the local and the remote peer when the IMS-AGW bridges compatible codec configurations between the interfaces without applying a transcoding function;
perform media adaptation (e.g. reduce media bit-rate) towards the ECN-capable peer when receiving from the latter an adaptation request. and the IMS-AGW applies transcoding.

5.12.2 Incoming SDP offer with ECN p. 29

The IMS-ALG and IMS-AGW shall apply the requirements specified in clause 10.2.13.2 of TS 29.162 replacing the IBCF and TrGW with IMS-ALG and IMS-AGW respectively.

5.12.3 Incoming SDP offer without ECN p. 29

The IMS-ALG and IMS-AGW shall apply the requirements specified in clause 10.2.13.3 of TS 29.162 replacing the IBCF and TrGW with IMS-ALG and IMS-AGW respectively with the following additions:

if the IMS-ALG or IMS-AGW does not support the procedure to act as an ECN endpoint, the IMS-ALG shall not include the "a=ecn-capable-rtp" attribute in the SDP offer it forwards to the succeeding node.

5.12.4 Detection of ECN failures by IMS-AGW p. 29

An IMS-ALG and IMS-AGW that support the procedure to act as an ECN endpoint shall support the requirements specified in clause 10.2.13.3a of TS 29.162 replacing the IBCF and TrGW with IMS-ALG and IMS-AGW respectively.

5.13 Transcoding |R10| p. 30

5.13.1 General |R12| p. 30

The transcoding functionality, where the IMS-AGW processes and possibly converts media data (like e.g. RTP payload) is optional for the P-CSCF and IMS-AGW to support. Transcoding should be supported if the IMS-ALG and IMS-AGW support the ATCF and ATGW functions for use after an SRVCC handover if the media that was used prior to the access transfer is not supported by the MSC Server.

An IMS-ALG and IMS-AGW that support transcoding shall support the requirements specified for Media Control in clause 10.2.5 of TS 29.162 respectively for the IBCF and TrGW, with the following additions:

During an originating or terminating PS session establishment, the IMS-ALG (ATCF) may remove codecs when passing SDP offers (e.g. codecs known not to be supported by either the IMS-AGW (ATGW) or the MSC Server), but the IMS-ALG (ATCF) should pass SDP offers without adding codecs to the SDP offer and pass SDP answers without modification to the contained codecs to avoid the potential need for transcoding in the IMS-AGW (ATGW) before the PS to CS access transfer;
During the PS to CS access transfer procedure, the IMS-ALG (ATCF) shall preferentially select from the SDP offer it receives from the MSC Server the codec already configured on the corresponding remote leg, if available.

The procedures for the IMS-ALG (ATCF) and IMS-AGW (ATGW) are further detailed in clause 6.2.14.

5.13.2 Handling of common codec parameters |R12| p. 30

When receiving an SDP offer, the IMS-ALG may add a payload type to offer transcoding before forwarding the SDP offer (denoted as "codec 3" in Figure 10.2.5.1 and Figure 10.2.5.2 of TS 29.162). If that payload type is selected in the SDP answer, the IMS-ALG needs to transcode. Table 5.13.2.1 describes the IMS-ALG handling of codec related parameters applicable to multiple codecs when the IMS-ALG adds the payload type to the SDP offer, and that payload type is selected in the SDP answer.

Table 5.13.2.1: IMS-ALG handling of common codec parameters for transcoding.

Parameter	Handling of common codec parameter in the sent SDP offer	Handling of common codec parameter in the received SDP answer
ptime (NOTE)	If the ptime parameter is included in the received SDP offer, the IMS-ALG shall supply the parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the value is supported by the IMS-AGW for receiving media, the IMS-ALG should keep the value from the received SDP offer unchanged in the SDP offer it sends. If the IMS-AGW only supports a lower ptime value, the IMS-ALG shall supply the ptime value according to configured preferences in the SDP offer it forwards. If no ptime value was contained in the received SDP offer, the IMS-ALG may add the parameter with a value according to configured preferences to the SDP offer.	If the ptime parameter is included in the received SDP answer, the IMS-ALG shall supply the parameter to the IMS-AGW for the termination towards the SDP answerer in the remote descriptor. If the value is supported by the IMS-AGW for receiving media, the IMS-ALG should keep the value from the received SDP answer unchanged in the SDP answer it sends. If the IMS-AGW only supports a lower ptime value, the IMS-ALG shall supply the ptime value according to configured preferences in the SDP answer it forwards. If no ptime value was contained in the received SDP answer, the IMS-ALG may add the parameter with a value according to configured preferences to the SDP answer.
maxptime (NOTE)	If the maxptime parameter is included in the received SDP offer, the IMS-ALG shall supply the parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the value is supported by the IMS-AGW for receiving media, the IMS-ALG should keep the value from the received SDP offer unchanged in the SDP offer it sends. If the IMS-AGW only supports a lower maxptime value, the IMS-ALG shall supply the maxptime value according to the IMS-AGW capabilities in the SDP offer it forwards. If no maxptime value was contained in the received SDP offer, the IMS-ALG may add the parameter with a value according to the IMS-AGW capabilities to the SDP offer.	If the maxptime parameter is included in the received SDP answer, the IMS-ALG shall supply the parameter to the IMS-AGW for the termination towards the SDP answerer in the remote descriptor. If the value is supported by the IMS-AGW for receiving media, the IMS-ALG should keep the value from the received SDP answer unchanged in the SDP answer it sends. If the IMS-AGW only supports a lower maxptime value, the IMS-ALG shall supply the maxptime value according to the IMS-AGW capabilities in the SDP answer it forwards. If no maxptime value was contained in the received SDP answer, the IMS-ALG may add the parameter with a value according to the IMS-AGW capabilities to the SDP answer.
NOTE: This SDP attribute is defined in RFC 4566. It applies to all codecs offered in an SDP media line.

Table 5.13.2.2 describes the IMS-AGW handling of codec related parameters applicable to multiple codecs.

Table 5.13.2.2: IMS-AGW handling of common codec parameters

Parameter	Handling in local descriptor	Handling in remote descriptor
ptime (NOTE)	The IMS-AGW should expect to receive packets with this ptime value and may use this information when deciding upon the required resources.	The IMS-AGW should use this ptime value when sending packets.
maxptime (NOTE)	The IMS-AGW should expect to receive packets with this maxptime value and may use this information when deciding upon the required resources.	The IMS-AGW shall use this maxptime value when sending packets.
NOTE: This SDP attribute is defined in RFC 4566. It applies to all codecs offered in an SDP media line.

5.13.3 Handling of the EVS speech codec |R12| p. 31

The Enhanced Voice Services (EVS) speech codec is defined in TS 26.441. Its RTP payload type is defined in TS 26.445, and procedures for its usage as IMS Multimedia Telephony speech codec are defined in TS 26.114.

The IMS-ALG and the IMS-AGW may support transcoding to and from the EVS speech codec. If they do so, the procedures in the present clause apply.

When receiving an SDP offer, the IMS-ALG may add an EVS codec payload type before forwarding the SDP offer (denoted as "codec 3" in Figure 10.2.5.1 and Figure 10.2.5.2 of TS 29.162). If that EVS payload type is selected in the SDP answer, the IMS-ALG needs to transcode the EVS codec. Table 5.13.3.1 describes the IMS-ALG handling of EVS codec parameters when the IMS-ALG adds the EVS payload type to the SDP offer, and that EVS payload type is selected in the SDP answer. In addition, rules for the parameter handling in TS 26.445 shall apply.

Table 5.13.3.1: IMS-ALG handling of EVS related SDP parameters when the IMS-ALG adds the EVS payload type to the SDP offer.

Parameter	Handling for EVS payload type added to the SDP offer to offer transcoding	Handling if offered EVS payload type is accepted in the SDP answer
evs-mode-switch (NOTE 1)	If the IMS-ALG expects that interworking between AMR-WB and EVS is required (e.g. because AMR-WB was the first payload type in the received SDP offer), it shall include the evs-mode-switch with value 1. Otherwise the IMS-ALG shall not include the evs-mode-switch.	If the evs-mode-switch parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
hf-only (NOTE 1)	If the IMS-ALG is configured to negotiate using only the header-full EVS RTP payload format, the IMS-ALG shall include the hf-only parameter with a value 1.	If the hf-only parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
dtx (NOTE 1)	If the usage of DTX is not desired in the sending and receiving direction (e.g. due to DTX capabilities of expected codecs to transcode with, e.g. other codecs in the received SDP offer), the IMS-ALG shall include the dtx parameter with a value 0.	If the dtx parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
dtx-recv (NOTE 1)	If receiving DTX is not desired and the dtx parameter is not included, the IMS-ALG shall include the dtx-recv parameter with a value 0. If both the dtx and dtx-recv parameters are included, those parameters shall have the same value; however, inclusion of the dtx-recv parameter is not required if the dtx parameter is included.	If the dtx-recv parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
br (NOTE 1)	If the IMS-ALG desires the same bit rate range for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range to match IMS-AGW capabilities and possible configured policies, it shall supply the br parameter in the SDP offer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP offer. If the IMS-ALG also supplies the bw, bw-send or bw-recv parameter, the value of the br parameter shall be compatible with the values of those parameters.	If the br parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
br-send (NOTE 1)	If the IMS-ALG desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the send direction to match IMS-AGW capabilities and possible configured policies, it shall supply the br-send parameter in the SDP offer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP offer. If the IMS-ALG also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters.	If the br-send parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
br-recv (NOTE 1)	If the IMS-ALG desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the receive direction to match IMS-AGW capabilities and possible configured policies, it shall supply the br-recv parameter in the SDP offer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP offer. If the IMS-ALG also supplies the bw or bw-recv parameter, the value of the br-recv parameter shall be compatible with the values of those parameters.	If the br-recv parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
bw (NOTE 1)	If the IMS-ALG desires the same sampling bandwidth(s) for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths to match IMS-AGW capabilities, sampling bandwidths of expected codecs EVS will be transcoded to (e.g. the first payload type in the received SDP offer), and possible configured policies, it shall supply the bw parameter in the SDP offer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP offer.	If the bw parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
bw-send (NOTE 1)	If the IMS-ALG desires different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths in the send direction to match IMS-AGW capabilities, sampling bandwidths of expected codecs EVS will be transcoded to (e.g. the first payload type in the received SDP offer) and possible configured policies, it shall supply the bw-send parameter in the SDP offer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP offer.	If the bw-send parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
bw-recv (NOTE 1)	If the IMS-ALG desires different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths in the receive direction to match IMS-AGW capabilities, sampling bandwidths of expected codecs EVS will be transcoded to (e.g. the first payload type in the received SDP offer), and possible configured policies, it shall supply the bw-recv parameter in the SDP offer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP offer.	If the bw-recv parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
cmr (NOTE 1)	If the IMS-ALG desires to disable codec mode requests within the RTP payload of the EVS primary mode (due to the IMS-AGW capabilities or policies), it shall include the cmr parameter with value -1 in the SDP offer it sends.	If the cmr parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
ch-aw-recv (NOTE 1)	The IMS-ALG shall include the ch-aw-recv parameter in the SDP offer if it desires to control the channel-aware mode of EVS in the receive direction, e.g. to disable it with value -1. The IMS-ALG shall consider the capabilities of the IMS-AGW when it chooses an appropriate value.	If the ch-aw-recv parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
number of channels (NOTE 2)	The IMS-ALG shall only include the "number of channels" parameter in the SDP offer if it desires to send or receive multiple channels. If the desired number of channels in the send and receive direction differs, the IMS-ALG shall include the higher value. The IMS-ALG should consider the number of channels of expected codecs EVS will be transcoded to (e.g. the first payload type in the received SDP offer).	If the "number of channels" parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
ch-send (NOTE 1)	The IMS-ALG shall only include the ch-send parameter in the SDP offer if it desires to send multiple channels, with different numbers of channels in the send and receive direction. The IMS-ALG should consider the number of channels of expected codecs EVS will be transcoded to (e.g. the first payload type in the received SDP offer).	If the ch-send parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
ch-recv (NOTE 1)	The IMS-ALG shall only include the ch-recv parameter in the SDP offer if it desires to receive multiple channels, with different numbers of channels in the send and receive direction. The IMS-ALG should consider the number of channels of expected codecs EVS will be transcoded to (e.g. the first payload type in the received SDP offer).	If the ch-recv parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
mode-set (NOTE 3)	The IMS-ALG shall only include the mode-set parameter in the SDP offer if it desires to restrict the mode-set of AMR-WB IO mode. The IMS-ALG should only restrict the mode-set if the expected codec EVS will be interworked with (e.g. the first payload type in the received SDP offer) is AMR-WB and has a restricted mode-set.	If the mode-set parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor. If the IMS-ALG decides that EVS will be transcoded to AMR-WB, the IMS-ALG should include the mode-set parameter for the AMR-WB payload in the SDP offer it forwards if this is permissible by AMR-WB offer answer rules in RFC 4867.
mode-change-period (NOTE 3)	The IMS-ALG shall only include the mode-change-period parameter with value 2 in the SDP offer if it desires to restrict the mode-change-period of received packets in AMR-WB IO mode. The IMS-ALG should only restrict the mode-change-period if the expected codec EVS will be interworked with (e.g. the first payload type in the received SDP offer) is AMR-WB and has such a restriction.	If the mode-change-period parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor. If the IMS-ALG decides that EVS will be transcoded to AMR-WB, the IMS-ALG should include the mode-change-period parameter for the AMR-WB payload in the SDP offer it forwards.
mode-change-capability (NOTE 3)	The IMS-ALG shall include the mode-change-capability parameter with value 2 in the SDP offer if it is capable of restricting the mode-change-period of packets it sends in AMR-WB IO mode. The IMS-ALG should consider the mode-change-period of the expected codec EVS will be interworked with (e.g. the first payload type in the received SDP offer) if this is AMR-WB.	If the mode-change-capability parameter is contained in the SDP answer, the IMS-ALG may forward this parameter to the IMS-AGW in the remote descriptor. If the IMS-ALG decides that EVS will be transcoded to AMR-WB, the IMS-ALG should include the mode-change-capability parameter for the AMR-WB payload in the SDP offer it forwards.
mode-change-neighbor (NOTE 3)	The IMS-ALG shall only include the mode-change-neighbor parameter in the SDP offer if it desires to restrict the mode-change within received packets of AMR-WB IO mode to neighboring modes. The IMS-ALG should consider the mode-change-neighbor parameter of the expected codec EVS will be interworked with (e.g. the first payload type in the received SDP offer) if this is AMR-WB.	If the mode-change-neighbor parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor. If the IMS-ALG decides that EVS will be transcoded to AMR-WB, the IMS-ALG should include the mode-change-neighbor parameter for the AMR-WB payload in the SDP offer it forwards.
max-red (NOTE 5)	The IMS-ALG shall only include the max-red parameter in the SDP offer if it desires to restrict the maximum redundancy of received packets. IMS-ALG shall consider the capabilities of the IMS-AGW, and should consider the max-red parameter of the expected codec EVS will be interworked with (e.g. the first payload type in the received SDP offer) if this is AMR-WB.	If the max-red parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor. If the IMS-ALG decides that EVS will be interworked with AMR-WB, the IMS-ALG should include the max-red parameter for the AMR-WB payload in the SDP offer it forwards.
3gpp_mtsi_app_adapt (NOTE 4)	If the IMS-AGW supports RTCP APP based adaptation messages defined in TS 26.114, and the IMS-ALG has a policy to negotiate the usage of those messages, the IMS-ALG shall include the 3gpp_mtsi_app_adapt SDP attribute indicating the supported APP messages in the SDP offer.	If the 3gpp_mtsi_app_adapt attribute is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.
NOTE 1: This MIME parameter of the EVS RTP payload type is defined in TS 26.445. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 2: This number of channels are encoded as "encoding parameters" of the SDP "a=rtpmap" attribute defined in RFC 4566. NOTE 3: This MIME parameter of the EVS RTP payload type relates to AMR-WB IO mode and is defined in RFC 4867. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 4: This SDP attribute is defined in TS 26.114. It applies to all codecs offered in an SDP media line. However, some values are specific to EVS. NOTE 5: This MIME parameter of the EVS RTP payload type is defined in RFC 4867. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566.

When receiving an SDP offer that contains an EVS codec payload type (denoted as "codec 1" in Figure 10.2.5.2 of TS 29.162), the IMS-ALG may add other payload types before forwarding the SDP offer (denoted as "codec 3" in Figure 10.2.5.2 of TS 29.162). If that added payload type is selected in the SDP answer, the IMS-ALG needs to transcode, and may select to transcode to the EVS codec. Table 5.13.3.2 describes the IMS-ALG handling of EVS codec parameters when the IMS-ALG receives an EVS payload type in an SDP offer, and selects to transcode between the EVS codec and some other codec. In addition, rules for the parameter handling in TS 26.445 shall apply.

Table 5.13.3.2: IMS-ALG handling of EVS related SDP parameters when the IMS-ALG receives the EVS payload type in the SDP offer and decides to transcode between the EVS payload type and some other codec.

Parameter	Handling of EVS payload type parameter received in the SDP offer	EVS payload type supplied in the SDP answer
evs-mode-switch (NOTE 1)	If the evs-mode-switch parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the evs-mode-switch parameter is contained in the SDP offer, the IMS-ALG shall include the evs-mode-switch parameter with unmodified value in the SDP answer. Otherwise, if the IMS-ALG decides to interwork between AMR-WB and EVS (e.g. because AMR-WB was selected in the received SDP answer), it shall include the evs-mode-switch with value 1. Otherwise the IMS-ALG shall not include the evs-mode-switch. If the IMS-ALG supplies the evs-mode-switch in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
hf-only (NOTE 1)	If the hf-only parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the hf-only parameter is contained in the SDP offer, the IMS-ALG shall include the hf-only parameter with unmodified value in the SDP answer. Otherwise, if the IMS-ALG is configured to negotiate using only the header-full EVS RTP payload format, the IMS-ALG shall include the hf-only parameter with a value 1. If the IMS-ALG supplies the hf-only parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
dtx (NOTE 1)	If the dtx parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the dtx parameter is contained in the SDP offer, the IMS-ALG shall include the dtx parameter with unmodified value in the SDP answer. If the dtx parameter is not contained in the SDP offer and if a dtx-recv parameter is contained in the SDP offer, the IMS-ALG may include the dtx parameter in the SDP answer, and the value of the dtx parameter shall then be identical to that of the dtx-recv parameter in the SDP offer (e.g, if that value matches DTX capabilities of expected codecs to transcode with). If the dtx parameter is not contained in the SDP offer and if the dtx-recv parameter is not contained in the SDP offer, and if the usage of DTX is not desired (e.g. due to DTX capabilities of expected codecs to transcode with, e.g. other codecs in the received SDP answer), the IMS-ALG shall include in the SDP answer the dtx parameter with a value 0. If the IMS-ALG supplies the dtx parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
dtx-recv (NOTE 1)	If the dtx-recv parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If no dtx parameter is included in the SDP answer and if the reception of DTX is not desired, the IMS-ALG shall include in the SDP answer the dtx-recv parameter with a value 0. If both the dtx and dtx-recv parameters are included, those parameters shall have the same value; however, inclusion of the dtx-recv parameter is not required if the dtx parameter is included. If the IMS-ALG supplies the dtx-recv parameter in the SDP answer, it should also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
br (NOTE 1)	If the br parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, in EVS primary mode in the send and receive direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the br parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received br value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the br parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires the same bit rate range for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range to match IMS-AGW capabilities and possible configured policies, it shall supply the br parameter in the SDP answer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG also supplies the bw, bw-send or bw-recv parameter, the value of the br parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the br parameter in the SDP answer, it shall also supply to the IMS-AGW the br parameter in the local descriptor for the termination towards the offerer with the same value.
br-send (NOTE 1)	If the br-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, in EVS primary mode in the receive direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the br-recv parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received br-recv value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the br-send parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the send direction to match IMS-AGW capabilities and possible configured policies, it shall supply the br-send parameter in the SDP answer it sends. Otherwise the IMS-ALG shall not include the br-send parameter in the SDP answer. If the IMS-ALG also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the br-send parameter in the SDP answer, it shall also supply to the IMS-AGW the br-send parameter in the local descriptor for the termination towards the offerer with the same value.
br-recv (NOTE 1)	If the br-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, in EVS primary mode in the send direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the br-send parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received br-send value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the br-recv parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the receive direction to match IMS-AGW capabilities and possible configured policies, it shall supply the br-recv parameter in the SDP answer it sends. Otherwise the IMS-ALG shall not include the br-recv parameter in the SDP answer. If the IMS-ALG also supplies the bw or bw-recv parameter, the value of the br-recv parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the br-recv parameter in the SDP answer, it shall also supply to the IMS-AGW the br-recv parameter in the local descriptor for the termination towards the offerer with the same value.
bw (NOTE 1)	If the bw parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated sampling bandwidth(s), or a subset of them, in EVS primary mode in the send and receive direction. If the indicated sampling bandwidth(s), and even each subset of them, are not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the bw parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidth value, which is either the received bw value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the bw parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires the same sampling bandwidth(s) for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidth(s) to match IMS-AGW capabilities and possible configured policies, it shall supply the bw parameter in the SDP answer it sends. Otherwise the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG also supplies the br, br-send or br-recv parameter, the value of the bw parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the bw parameter in the SDP answer, it shall also supply to the IMS-AGW the bw parameter in the local descriptor for the termination towards the offerer with the same value.
bw-send (NOTE 1)	If the bw-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the receive direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the bw-recv parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidths value, which is either the received bw-recv value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the bw-send parameter with the selected value in the SDP answer. Otherwise, if the IMS-ALG desires different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths for the send direction to match IMS-AGW capabilities and possible configured policies, it shall supply the bw-send parameter in the SDP answer it sends. Otherwise the IMS-ALG shall not include the br-send parameter in the SDP answer. If the IMS-ALG also supplies the br or br-send parameter, the value of the bw-send parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the bw-send parameter in the SDP answer, it shall also supply to the IMS-AGW the bw-send parameter in the local descriptor for the termination towards the offerer with the same value.
bw-recv (NOTE 1)	If the br-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the send direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type, it shall forward the bw-recv parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the bw-send parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidths value, which is either the received bw-send value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the bw-recv parameter with the selected value in the SDP answer. Otherwise, if the IMS-ALG desires a different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths for the receive direction to match IMS-AGW capabilities and possible configured policies, it shall supply the bw-recv parameter in the SDP answer it sends. Otherwise the IMS-ALG shall not include the bw-recv parameter in the SDP answer. If the IMS-ALG also supplies the br or br-recv parameter, the value of the bw-recv parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the bw-send parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
cmr (NOTE 1)	If the cmr parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the cmr parameter is contained in the SDP offer, the IMS-ALG shall include the cmr parameter with unmodified value in the SDP answer. Otherwise, if the IMS-AGW desires to disable codec mode requests within the RTP payload of the EVS primary mode (due to the IMS-AGW capabilities or policies), it shall include the cmr parameter with value -1 in the SDP answer it sends If the IMS-ALG supplies the cmr parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
ch-aw-recv (NOTE 1)	If the ch-aw-recv parameter is contained in the SDP offer the IMS-ALG shall check if the IMS-AGW supports the indicated mode in the send direction. If the indicated mode is not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the IMS-ALG it desires to control the channel-aware mode of EVS in the receive direction, e.g. to disable it with value -1, it shall include the ch-aw-recv parameter in the SDP offer and shall also supply the ch-aw-recv parameter to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value. The IMS-ALG shall consider the capabilities of the IMS-AGW when it chooses an appropriate value.
number of channels (NOTE 2)	If the "number of channels" parameter is contained in the SDP offer the IMS-ALG shall check if the IMS-AGW supports the indicated number of channels. If the indicated number of channels is not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the "number of channels" parameter is contained in the SDP offer, the IMS-ALG shall include the "number of channels" parameter with unmodified value in the SDP answer and shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
ch-send (NOTE 1)	If the ch-send parameter is contained in the SDP offer the IMS-ALG shall check if the IMS-AGW supports the indicated number of channels in the receive direction. If the indicated number of channels is not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward the ch-send parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ch-recv parameter is contained in the SDP offer, the IMS-ALG shall include the ch-send parameter with unmodified value in the SDP answer and shall also supply the ch-send parameter to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
ch-recv (NOTE 1)	If the ch-recv parameter is contained in the SDP offer the IMS-ALG shall check if the IMS-AGW supports the indicated number of channels in the send direction. If the indicated number of channels is not supported, the IMS-ALG shall not select the EVS payload type for transcoding. If the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward the ch-recv parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ch-send parameter is contained in the SDP offer, the IMS-ALG shall include the ch-recv parameter with unmodified value in the SDP answer and shall also supply the ch-recv parameter to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
mode-set (NOTE 3)	If the mode-set parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the mode-set parameter is contained in the SDP offer and the IMS-ALG expects that EVS will be interworked with AMR-WB (e.g. if EVS is the first payload type in the received SDP offer, and the IMS-ALG adds a AMR-WB payload type), the IMS-ALG should include the mode-set parameter with the same value for the AMR-WB payload in the SDP offer it forwards.	If the mode-set parameter is contained in the SDP offer, the IMS-ALG shall include the mode-set parameter with unmodified value in the SDP answer. Otherwise, if the mode-set parameter is contained in the SDP answer for an AMR-WB payload type and the IMS-ALG decides that the EVS codec will be interworked with that AMR-WB payload type, the IMS-ALG should include that mode-set parameter for the EVS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-set parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
mode-change-period (NOTE 3)	If the mode-change-period parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the mode-change-period parameter is contained in the SDP offer and the IMS-ALG expects that EVS will be interworked with AMR-WB (e.g. if EVS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the mode-change-period parameter with the same value for the AMR-WB payload type in the SDP offer it forwards.	If the mode-change-period parameter is contained in the SDP answer for the AMR-WB payload type and the IMS-ALG decides the EVS codec will be interworked with that AMR-WB payload type, the IMS-ALG should include the mode-change-period parameter for the EVS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-change-period parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
mode-change-capability (NOTE 3)	If the mode-change-capability parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG may forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the IMS-ALG expects that EVS will be interworked with AMR-WB (e.g. if EVS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the mode-change-capability parameter with value 2 for the AMR-WB payload in the SDP offer it forwards.	If the IMS-ALG decides that the EVS codec is selected, the IMS-ALG shall either include the mode-change-capability parameter with value 2 or omit the parameter for the EVS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-change-capability parameter in the SDP answer, it may also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
mode-change-neighbor (NOTE 3)	If the mode-change-neighbor parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the mode-change-neighbor parameter is contained in the SDP offer and the IMS-ALG expects that EVS will be interworked with AMR-WB (e.g. if EVS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the mode-change-neighbor with the same value for the AMR-WB payload in the SDP offer it forwards.	If the mode-change-neighbor parameter is contained in the SDP answer for the AMR-WB payload type and the IMS-ALG decides that the EVS codec will be interworked with that AMR-WB payload type, the IMS-ALG should include the mode-change-neighbor parameter for the EVS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-change-neighbor parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
max-red (NOTE 5)	If the max-red parameter is contained in the SDP offer and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the max-red parameter is contained in the SDP offer and the IMS-ALG expects that EVS will be interworked with AMR-WB (e.g. if EVS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the max-red parameter with the same value for the AMR-WB payload in the SDP offer it forwards with a value that considers the received value and the capabilities of the IMS-AGW.	The IMS-ALG shall only include the max-red parameter in the SDP answer if it desires to restrict the maximum redundancy of received packets. When selecting the value of the max-red parameter, the IMS-ALG shall consider the capabilities of the IMS-AGW and, if the max-red parameter is contained in the SDP answer for the AMR-WB payload type and the IMS-ALG decides that the EVS codec will be interworked with that AMR-WB payload type, the received value. If the IMS-ALG supplies the max-red parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
3gpp_mtsi_app_adapt (NOTE 4)	If the 3gpp_mtsi_app_adapt parameter is contained in the SDP answer, and the IMS-ALG selects the EVS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.	If the IMS-AGW supports RTCP APP based adaptation messages defined in TS 26.114, and the IMS-ALG has a policy to negotiate the usage of those messages, the IMS-ALG shall include the 3gpp_mtsi_app_adapt SDP attribute indicating the supported APP messages in the SDP answer.
NOTE 1: This MIME parameter of the EVS RTP payload type is defined in TS 26.445. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 2: This number of channels are encoded as "encoding parameters" of the SDP "a=rtpmap" attribute defined in RFC 4566. NOTE 3: This MIME parameter of the EVS RTP payload type relates to AMR-WB IO mode and is defined in RFC 4867. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 4: This SDP attribute is defined in TS 26.114. It applies to all codecs offered in an SDP media line. However, some values are specific to EVS. NOTE 5: This MIME parameter of the EVS RTP payload type is defined in RFC 4867. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566.

Table 5.13.3.3 describes the IMS-AGW handling of EVS codec parameters. The IMS-AGW should support transcoding of EVS with bandwidths (sampling rates) which are supported by codec the IMS-AGW is capable to transcode EVS to/from (e.g. NB for AMR, and WB for AMR-WB).

Table 5.13.3.3: IMS-AGW handling of EVS codec parameters

Parameter	Handling in local descriptor	Handling in remote descriptor
evs-mode-switch (NOTE 1)	The IMS-AGW should expect to receive packets with the indicated EVS mode and may use this information when deciding upon the required resources.	The IMS-AGW shall use the indicated EVS mode (e.g. AMR-WB interoperable mode for value 1) when sending packets.
hf-only (NOTE 1)	The IMS-AGW should expect to receive packets with the indicated mode and may use this information when deciding upon the required resources.	The IMS-AGW shall use the indicated mode (e.g. header-full EVS RTP payload format for value 1) when sending packets.
dtx (NOTE 1)	The IMS-AGW should expect to receive packets with this dtx mode and may use this information when deciding upon the required resources. (NOTE 8)	The IMS-AGW shall use this dtx mode (i.e. no usage of DTX for value 0) when sending packets. (NOTE 8)
dtx-recv (NOTE 1)	The IMS-AGW should expect to receive packets with this dtx mode and may use this information when deciding upon the required resources. (NOTE 8)	The IMS-AGW shall use this dtx mode (i.e. no usage of DTX for value 0) when sending packets. (NOTE 8)
br (NOTE 1)	If different values for the br parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources. The IMS-AGW shall use this bitrate range when sending packets.	If different values for the br parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources. The IMS-AGW shall use this bitrate range when sending packets.
br-send (NOTE 1)	If different values for the br-send parameter in the local descriptor and for the br-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use this bitrate range when sending packets.	If different values for the br-send parameter in the remote descriptor and for the br-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources.
br-recv (NOTE 1)	If different values for the br-send parameter in the remote descriptor and for the br-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources.	If different values for the br-send parameter in the local descriptor and for the br-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use this bitrate range when sending packets.
bw (NOTE 1)	If different values for the bw parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these sampling bandwidth(s) and may use this information when deciding upon the required resources. The IMS-AGW shall use these sampling bandwidth(s) when sending packets.	If different values for the bw parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these sampling bandwidth(s) and may use this information when deciding upon the required resources. The IMS-AGW shall use these sampling bandwidth(s) when sending packets.
bw-send (NOTE 1)	If different values for the bw-send parameter in the local descriptor and for the bw-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use these sampling bandwidth(s) when sending packets.	If different values for the bw-send parameter in the remote descriptor and for the bw-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these sampling bandwidth(s) and may use this information when deciding upon the required resources.
bw-recv (NOTE 1)	If different values for the bw-send parameter in the remote descriptor and for the bw-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these sampling bandwidth(s) and may use this information when deciding upon the required resources.	If different values for the bw-send parameter in the local descriptor and for the bw-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use these sampling bandwidth(s) when sending packets.
cmr (NOTE 1)	For cmr with value -1 or 0, the IMS-AGW should expect to receive no RTP packets containing codec mode requests for EVS primary mode and may use this information when deciding upon the required resources. For cmr with value -1 or 0, the IMS-AGW shall also send no RTP packets containing codec mode requests for EVS primary mode. Different cmr values in the local and remote descriptors are an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.	For cmr with value -1 or 0, the IMS-AGW should expect to receive no RTP packets containing codec mode requests for EVS primary mode and may use this information when deciding upon the required resources. For cmr with value -1 or 0, the IMS-AGW shall also send no RTP packets containing codec mode requests for EVS primary mode. Different cmr values in the local and remote descriptors are an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.
ch-aw-recv (NOTE 1, NOTE 7)	The IMS-AGW should expect to receive RTP packets containing the indicated partial redundancy mode and may use this information when deciding upon the required resources.	The IMS-AGW shall send RTP packets containing the indicated partial redundancy mode.
number of channels (NOTE 2)	If no ch-recv parameter in the local descriptor and no ch-send parameter in the remote descriptors are received, the IMS-AGW should expect to receive RTP packets containing the indicated number of channels and may use this information when deciding upon the required resources. If no ch-send parameter in the local descriptor and no ch-recv parameter in the remote descriptors are received, the IMS-AGW shall also send RTP packets containing the indicated number of channels. Different number of channels values in the local and remote descriptors is an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.	If no ch-recv parameter in the local descriptor and no ch-send parameter in the remote descriptors are received, the IMS-AGW should expect to receive RTP packets containing the indicated number of channels and may use this information when deciding upon the required resources. If no ch-send parameter in the local descriptor and no ch-recv parameter in the remote descriptors are received, the IMS-AGW shall also send RTP packets containing the indicated number of channels. Different number of channels values in the local and remote descriptors is an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.
ch-send (NOTE 1)	The IMS-AGW shall send RTP packets containing the indicated number of channels. Different number of channels in the ch-send parameter in the local descriptor and the ch-recv parameter in the remote descriptors is an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.	The IMS-AGW should expect to receive RTP packets containing the indicated number of channels and may use this information when deciding upon the required resources. Different number of channels in the ch-send parameter in the local descriptor and the ch-recv parameter in the remote descriptors is an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.
ch-recv (NOTE 1)	The IMS-AGW should expect to receive RTP packets containing the indicated number of channels and may use this information when deciding upon the required resources. Different number of channels in the ch-send parameter in the local descriptor and the ch-recv parameter in the remote descriptors is an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.	The IMS-AGW shall send RTP packets containing the indicated number of channels. Different number of channels in the ch-send parameter in the local descriptor and the ch-recv parameter in the remote descriptors is an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.
mode-set (NOTE 4)	For AMR-WB IO mode, the IMS-AGW should expect to receive RTP packets using only the indicated mode-set and may use this information when deciding upon the required resources. The IMS-AGW shall also send RTP packets only using the indicated mode-set. Different mode-set values in the local and remote descriptors are an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.	For AMR-WB IO mode, the IMS-AGW should expect to receive RTP packets using only the indicated mode-set and may use this information when deciding upon the required resources. The IMS-AGW shall also send RTP packets only using the indicated mode-set. Different mode-set values in the local and remote descriptors are an error situation, but it is permissible that this parameter is only supplied in one of those descriptors.
mode-change-period (NOTE 3)	For AMR-WB IO mode, the IMS-AGW should expect to receive packets with this mode-change-period and may use this information when deciding upon the required resources.	For AMR-WB IO mode, the IMS-AGW shall use this mode-change-period when sending packets.
mode-change-capability (NOTE 6)	For AMR-WB IO mode, mode-change-capability with value 2 indicates that the IMS-AGW should expect to be requested to send packets with restricted mode-change-period and may use this information when deciding upon the required resources.	No IMS-AGW handling of this parameter id defined.
mode-change-neighbor (NOTE 3)	The IMS-AGW should expect to receive packets with this mode-change-period and may use this information when deciding upon the required resources.	The IMS-AGW shall use this mode-change-period when sending packets.
max-red (NOTE 5)	The IMS-AGW should expect to receive packets with redundancy up to the indicated max-red value and may use this information when deciding upon the required resources.	The IMS-AGW shall only send packet with redundancy up to the indicated max-red value.
3gpp_mtsi_app_adapt (NOTE 4)	The IMS-AGW should expect to receive RTCP APP packets of the indicated types and may use this information when deciding upon the required resources.	The IMS-AGW may send RTCP APP packets of the indicated types. The IMS-AGW shall not send other RTCP APP packets. If the parameter is not supplied, the IMS-AGW shall not send any RTCP APP packets.
NOTE 1: This MIME parameter of the EVS RTP payload type is defined in TS 26.445. The values and the defaults if a parameter is omitted, as defined in TS 26.445 shall apply. NOTE 2: This number of channels are encoded as "encoding parameters" of the SDP "a=rtpmap" attribute defined in RFC 4566. NOTE 3: This MIME parameter of the EVS RTP payload type relates to AMR-WB IO mode and is defined in RFC 4867. The values and the defaults if a parameter is omitted, as defined in RFC 4867 shall apply. NOTE 4: This SDP attribute is defined in TS 26.114. It applies to all codecs offered in an SDP media line. However, some values are specific to EVS. NOTE 5: This MIME parameter of the EVS RTP payload type is defined in RFC 4867. The values and the defaults if a parameter is omitted, as defined in RFC 4867 shall apply. NOTE 6: This MIME parameter of the EVS RTP payload type relates to AMR-WB IO mode and is defined in RFC 4867. The values and the defaults if a parameter is omitted, as defined in TS 26.445, shall apply. NOTE 7: The frame erasure rate indicator for the channel-aware mode has two permissible values (LO, HI) and this indicator has to be initialized to HI, as specified in clause 5.8.4 of TS 26.445. NOTE 8: If both the dtx and the dtx-recv parameter are provided either in the local or in the remote descriptor, both parameters will have the same value within that descriptor.

5.13.4 Handling of the OPUS speech and audio codec for WebRTC |R12| p. 44

The OPUS speech and audio codec is defined in RFC 6716. Its RTP payload type is defined in RFC 7587.

The eP-CSCF and the eIMS-AGW should support transcoding to and from the OPUS speech codec. If they do so, the procedures in the present clause apply.

When receiving an SDP offer from the core network, the IMS-ALG may add an OPUS codec payload type (as specified in RFC 7587) before forwarding the SDP offer towards the served WebRTC UE (denoted as "codec 3" in Figure 10.2.5.2 of TS 29.162). If that OPUS payload type is selected in the SDP answer, the IMS-ALG needs to transcode the OPUS codec. Table 5.13.4.1 describes the IMS-ALG handling of the OPUS codec parameters when the IMS-ALG adds an OPUS payload type to the SDP offer, and that OPUS payload type is selected in the SDP answer. In addition, rules for the parameter handling in RFC 7587 shall apply.

Table 5.13.4.1: IMS-ALG handling of OPUS related SDP parameters when the IMS-ALG adds the OPUS payload type to the SDP offer.

Parameter	Handling for OPUS payload type added to the SDP offer to offer transcoding	Handling if offered OPUS payload type is accepted in the SDP answer
maxplaybackrate (NOTE)	Should be set according to IMS-AGW capabilities and sampling rates of expected codecs to transcode with (E.g. other codecs in the received SDP offer).	If parameter is contained in the SDP answer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
sprop-maxcapturerate (NOTE)	Should be set according to IMS-AGW capabilities and sampling rates of expected codecs to transcode with (E.g. other codecs in the received SDP offer).	If parameter is contained in the SDP answer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
maxaveragebitrate (NOTE)	Should be set according to IMS-AGW capabilities and sampling rates of expected codecs to transcode with (E.g. other codecs in the received SDP offer), see RFC 7587.	If parameter is contained in the SDP answer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
stereo (NOTE)	Should be set to 0 or omitted, unless the expected codecs to transcode with (E.g. other codecs in the received SDP offer) support stereo and the IMS-AGW supports stereo transcoding.	If parameter is contained in the SDP answer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
sprop-stereo (NOTE)	Should be set to 0 or omitted, unless the expected codecs to transcode with (E.g. other codecs in the received SDP offer) support stereo and the IMS-AGW supports stereo transcoding.	If parameter is contained in the SDP answer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
cbr (NOTE)	Should be set or omitted according to IMS-AGW capabilities and used encryption.	If parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
useinbandfec (NOTE)	Should be set or omitted according to IMS-AGW capabilities and delay budget.	If parameter is contained in the SDP answer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
usedtx (NOTE)	Should be set according to IMS-AGW preferences and DTX capabilities of expected codecs to transcode with (E.g. other codecs in the received SDP offer).	If parameter is contained in the SDP answer, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the answerer in the remote descriptor.
NOTE: This MIME parameter of the OPUS RTP payload type is defined in RFC 7587. It is encapsulated within the SDP "a=fmtp" attribute defined in RFC 4566.

When receiving an SDP offer from the served WebRTC UE that contains an OPUS codec payload type, the IMS-ALG may add other payload types before forwarding the SDP offer (denoted as "codec 3" in Figure 10.2.5.2 of TS 29.162). If that added payload type is selected in the SDP answer, the IMS-ALG needs to transcode, and may select to transcode to the OPUS codec. Table 5.13.4.2 describes the IMS-ALG handling of the OPUS codec parameters when the IMS-ALG receives the OPUS payload type in the SDP offer, and selects to transcode between the OPUS codec and some other codec. In addition, rules for the parameter handling in RFC 7587 shall apply.

Table 5.13.4.2: IMS-ALG handling of OPUS related SDP parameters when the IMS-ALG receives the OPUS payload type to the SDP offer and decides to transcode between the OPUS payload type and some other codec.

Parameter	Handling of OPUS payload type parameter received in the SDP offer	OPUS payload type supplied in the SDP answer
maxplaybackrate (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set according to IMS-AGW capabilities and sampling rates of expected codecs to transcode with (E.g. other codecs in the received SDP offer).
sprop-maxcapturerate (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set according to IMS-AGW capabilities and sampling rates of expected codecs to transcode with (E.g. other codecs in the received SDP offer).
maxaveragebitrate (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set according to IMS-AGW capabilities and sampling rates of expected codecs to transcode with (E.g. other codec s in the received SDP offer), see RFC 7587.
stereo (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set to 0 or omitted, unless the expected codecs to transcode with (E.g. other codecs in the received SDP offer) support stereo and the IMS-AGW supports stereo transcoding.
sprop-stereo (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set to 0 or omitted, unless the expected codecs to transcode with (E.g. other codecs in the received SDP offer) support stereo and the IMS-AGW supports stereo transcoding.
cbr (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set or omitted according to IMS-AGW capabilities and used encryption.
useinbandfec (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG should forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set or omitted according to IMS-AGW capabilities and delay budget.
usedtx (NOTE)	If parameter is contained in the SDP offer, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	Should be set according to IMS-AGW preferences and DTX capabilities of expected codecs to transcode with (E.g. other codecs in the received SDP offer).
NOTE: This MIME parameter of the OPUS RTP payload type is defined in RFC 7587. It is encapsulated within the SDP "a=fmtp" attribute defined in RFC 4566.

Table 5.13.4.3 describes the IMS-AGW handling of the OPUS codec parameters. The IMS-AGW should support transcoding of OPUS with at least the bandwidths (sampling rates) which are supported by codec the IMS-AGW is capable to transcode OPUS to/from (e.g. NB for AMR, and WB for AMR-WB).

Table 5.13.4.3: IMS-AGW handling of OPUS codec parameters.

Parameter	Handling in local descriptor	Handling in remote descriptor
maxplaybackrate (NOTE)	The IMS-AGW should expect to receive RTP packets with sampling rates up to the indicated maximum and may use this information when deciding upon the required resources.	The IMS-AGW should send RTP packets with the indicated sampling rate.
sprop-maxcapturerate (NOTE)	No IMS-AGW handling of this parameter is defined.	The IMS-AGW should expect to receive RTP packets with sampling rates up to the indicated maximum and may use this information when deciding upon the required resources.
maxaveragebitrate (NOTE)	The IMS-AGW should expect to receive RTP packets with average bit rates up to the indicated maximum and may use this information when deciding upon the required resources.	The IMS-AGW shall send RTP packets with average bit rates up to the indicated maximum.
stereo (NOTE)	The IMS-AGW should expect to receive RTP packets containing the indicated stereo mode and may use this information when deciding upon the required resources.	The IMS-AGW should send RTP packets containing the indicated stereo mode.
sprop-stereo (NOTE)	No IMS-AGW handling of this parameter is defined.	The IMS-AGW should expect to receive RTP packets containing the indicated stereo mode and may use this information when deciding upon the required resources.
cbr (NOTE)	The IMS-AGW should expect to receive RTP packets containing the indicated constant bit rate mode and may use this information when deciding upon the required resources.	The IMS-AGW should send RTP packets containing the indicated constant bit rate mode.
useinbandfec (NOTE)	The IMS-AGW should expect to receive RTP packets containing the indicated forward error correction mode and may use this information when deciding upon the required resources.	The IMS-AGW should send RTP packets containing the indicated forward error correction mode.
usedtx (NOTE)	The IMS-AGW should expect to receive RTP packets containing the indicated DTX mode and may use this information when deciding upon the required resources.	The IMS-AGW should send RTP packets using the indicated DTX mode.
NOTE: This MIME parameter of the OPUS RTP payload type is defined in RFC 7587. The default value if a parameter is omitted, as defined in RFC 7587, shall apply.

5.13.5 Handling of the IVAS speech and audio codec |R18| p. 47

The Immersive Voice and Audio Services (IVAS) speech and audio codec is defined in TS 26.250. Its RTP payload type is defined in TS 26.253, and procedures for its usage as IMS Multimedia Telephony speech codec are defined in TS 26.114.

The IMS-ALG and the IMS-AGW may support transcoding the IVAS speech and audio codec to and from another (mono-format) codec (e.g. AMR-WB or EVS). If they do so, the IMS-ALG and the IMS-AGW shall support transcoding to and from the IVAS codec using EVS Primary or AMR-WB IO mode, shall support transcoding from the IVAS codec using the IVAS Immersive mode (i.e. decoding the IVAS codec using the IVAS Immersive mode) and they may support transcoding to the IVAS codec using the IVAS Immersive mode, and the procedures in the present clause apply.

When receiving an SDP offer without the IVAS codec, the IMS-ALG should not add an IVAS codec payload type to the SDP offer it forwards to avoid the need for transcoding between IVAS immersive mode and another codec in this scenario. The IMS-ALG may add an EVS codec payload type to the SDP offer it forwards (see Table 5.13.3.1).

When receiving an SDP offer that contains an IVAS codec payload type (denoted as "codec 1" in figure 10.2.5.2 of TS 29.162), the IMS-ALG may add other payload types before forwarding the SDP offer (denoted as "codec 3" in figure 10.2.5.2 of TS 29.162). If that added payload type is selected in the SDP answer, the IMS-ALG needs to transcode, and may select to transcode to the IVAS codec. Table 5.13.5.1 describes the IMS-ALG handling of IVAS codec parameters when the IMS-ALG receives an IVAS payload type in an SDP offer and selects to transcode between the IVAS codec and some other codec. In addition, rules for the parameter handling in TS 26.253 shall apply.

Table 5.13.5.1: IMS-ALG handling of IVAS related SDP parameters when the IMS-ALG receives the IVAS payload type in the SDP offer and decides to transcode between the IVAS payload type and some other codec

Parameter	Handling of IVAS payload type parameter received in the SDP offer	IVAS payload type supplied in the SDP answer
ivas-mode-switch (NOTE 2)	If the ivas-mode-switch parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ivas-mode-switch parameter is contained in the SDP offer, the IMS-ALG shall include the ivas-mode-switch parameter with unmodified value in the SDP answer. Otherwise, if the IMS-ALG decides to interwork between AMR-WB or EVS and IVAS using EVS Primary or AMR-WB IO mode (e.g. because AMR-WB or EVS was selected in the received SDP answer), it shall include the ivas-mode-switch with value 1. Otherwise, the IMS-ALG shall not include the ivas-mode-switch. If the IMS-ALG supplies the ivas-mode-switch in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
evs-mode-switch (NOTE 1)	If the evs-mode-switch parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the evs-mode-switch parameter is contained in the SDP offer, the IMS-ALG shall include the evs-mode-switch parameter with unmodified value in the SDP answer. Otherwise, if the IMS-ALG decides to interwork between AMR-WB and IVAS using AMR-WB IO mode (e.g. because AMR-WB was selected in the received SDP answer), it shall include the evs-mode-switch with value 1. Otherwise, the IMS-ALG shall not include the evs-mode-switch. If the IMS-ALG supplies the evs-mode-switch in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
hf-only (NOTE 1)	If the hf-only parameter is contained in the SDP offer and set to 1 and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the hf-only parameter is contained in the SDP offer and set to 1, the IMS-ALG shall include the hf-only parameter with unmodified value in the SDP answer. If the IMS-ALG supplies the hf-only parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
dtx (NOTE 1)	If the dtx parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the dtx parameter is contained in the SDP offer, the IMS-ALG shall include the dtx parameter with unmodified value in the SDP answer. If the dtx parameter is not contained in the SDP offer and if a dtx-recv parameter is contained in the SDP offer, the IMS-ALG may include the dtx parameter in the SDP answer, and the value of the dtx parameter shall then be identical to that of the dtx-recv parameter in the SDP offer (e.g, if that value matches DTX capabilities of expected codecs to transcode with). If the dtx parameter is not contained in the SDP offer and if the dtx-recv parameter is not contained in the SDP offer, and if the usage of DTX is not desired (e.g. due to DTX capabilities of expected codecs to transcode with, e.g. other codecs in the received SDP answer), the IMS-ALG shall include in the SDP answer the dtx parameter with a value 0. If the IMS-ALG supplies the dtx parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
dtx-recv (NOTE 1)	If the dtx-recv parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If no dtx parameter is included in the SDP answer and if the reception of DTX is not desired, the IMS-ALG shall include in the SDP answer the dtx-recv parameter with a value 0. If both the dtx and dtx-recv parameters are included, those parameters shall have the same value; however, inclusion of the dtx-recv parameter is not required if the dtx parameter is included. If the IMS-ALG supplies the dtx-recv parameter in the SDP answer, it should also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
br (NOTE 1)	If the br parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, in EVS primary mode in the send and receive direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select the IVAS payload type for transcoding. If the IMS-ALG selects the IVAS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the br parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received br value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the br parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires the same bit rate range for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range to match IMS-AGW capabilities and possible configured policies, it shall supply the br parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG also supplies the bw, bw-send or bw-recv parameter, the value of the br parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the br parameter in the SDP answer, it shall also supply to the IMS-AGW the br parameter in the local descriptor for the termination towards the offerer with the same value.
br-send (NOTE 1)	If the br-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, in EVS primary mode in the receive direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select the IVAS payload type for transcoding. If the IMS-ALG selects the IVAS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the br-recv parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received br-recv value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the br-send parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the send direction to match IMS-AGW capabilities and possible configured policies, it shall supply the br-send parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the br-send parameter in the SDP answer. If the IMS-ALG also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the br-send parameter in the SDP answer, it shall also supply to the IMS-AGW the br-send parameter in the local descriptor for the termination towards the offerer with the same value.
br-recv (NOTE 1)	If the br-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, in EVS primary mode in the send direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select the IVAS payload type for transcoding. If the IMS-ALG selects the IVAS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the br-send parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received br-send value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the br-recv parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the receive direction to match IMS-AGW capabilities and possible configured policies, it shall supply the br-recv parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the br-recv parameter in the SDP answer. If the IMS-ALG also supplies the bw or bw-recv parameter, the value of the br-recv parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the br-recv parameter in the SDP answer, it shall also supply to the IMS-AGW the br-recv parameter in the local descriptor for the termination towards the offerer with the same value.
bw (NOTE 1)	If the bw parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated sampling bandwidth(s), or a subset of them, in EVS primary mode in the send and receive direction. If the indicated sampling bandwidth(s), and even each subset of them, are not supported, the IMS-ALG shall not select the IVAS payload type for transcoding. If the IMS-ALG selects the IVAS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the bw parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidth value, which is either the received bw value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the bw parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires the same sampling bandwidth(s) for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidth(s) to match IMS-AGW capabilities and possible configured policies, it shall supply the bw parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG also supplies the br, br-send or br-recv parameter, the value of the bw parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the bw parameter in the SDP answer, it shall also supply to the IMS-AGW the bw parameter in the local descriptor for the termination towards the offerer with the same value.
bw-send (NOTE 1)	If the bw-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the receive direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the IMS-ALG shall not select the IVAS payload type for transcoding. If the IMS-ALG selects the IVAS payload type, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the bw-recv parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidths value, which is either the received bw-recv value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the bw-send parameter with the selected value in the SDP answer. Otherwise, if the IMS-ALG desires different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths for the send direction to match IMS-AGW capabilities and possible configured policies, it shall supply the bw-send parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the br-send parameter in the SDP answer. If the IMS-ALG also supplies the br or br-send parameter, the value of the bw-send parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the bw-send parameter in the SDP answer, it shall also supply to the IMS-AGW the bw-send parameter in the local descriptor for the termination towards the offerer with the same value.
bw-recv (NOTE 1)	If the br-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the send direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the IMS-ALG shall not select the IVAS payload type for transcoding. If the IMS-ALG selects the IVAS payload type, it shall forward the bw-recv parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the bw-send parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidths value, which is either the received bw-send value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the bw-recv parameter with the selected value in the SDP answer. Otherwise, if the IMS-ALG desires a different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths for the receive direction to match IMS-AGW capabilities and possible configured policies, it shall supply the bw-recv parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the bw-recv parameter in the SDP answer. If the IMS-ALG also supplies the br or br-recv parameter, the value of the bw-recv parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the bw-recv parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
cmr (NOTE 2)	If the cmr parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the cmr parameter is contained in the SDP offer, the IMS-ALG shall include the cmr parameter with unmodified value in the SDP answer. Otherwise, if the IMS-AGW desires to disable codec mode requests within the IVAS RTP payload (due to the IMS-AGW capabilities or policies), it shall include the cmr parameter with value -1 in the SDP answer it sends. If the IMS-ALG supplies the cmr parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
ch-aw-recv (NOTE 1)	If the ch-aw-recv parameter is contained in the SDP offer the IMS-ALG shall check if the IMS-AGW supports the indicated mode in the send direction. If the indicated mode is not supported, the IMS-ALG shall not select the IVAS payload type for transcoding. If the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the IMS-ALG it desires to control the channel-aware mode of IVAS in EVS Primary mode in the receive direction, e.g. to disable it with value -1, it shall include the ch-aw-recv parameter in the SDP offer and shall also supply the ch-aw-recv parameter to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value. The IMS-ALG shall consider the capabilities of the IMS-AGW when it chooses an appropriate value.
mode-set (NOTE 3)	If the mode-set parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the mode-set parameter is contained in the SDP offer and the IMS-ALG expects that IVAS using AMR-WB IO mode will be interworked with AMR-WB (e.g. if IVAS is the first payload type in the received SDP offer, and the IMS-ALG adds a AMR-WB payload type), the IMS-ALG should include the mode-set parameter with the same value for the AMR-WB payload in the SDP offer it forwards.	If the mode-set parameter is contained in the SDP offer, the IMS-ALG shall include the mode-set parameter with unmodified value in the SDP answer. Otherwise, if the mode-set parameter is contained in the SDP answer for an AMR-WB payload type and the IMS-ALG decides that the IVAS codec using AMR-WB IO mode will be interworked with that AMR-WB payload type, the IMS-ALG should include that mode-set parameter for the IVAS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-set parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
mode-change-period (NOTE 3)	If the mode-change-period parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the mode-change-period parameter is contained in the SDP offer and the IMS-ALG expects that IVAS using AMR-WB IO mode will be interworked with AMR-WB (e.g. if IVAS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the mode-change-period parameter with the same value for the AMR-WB payload type in the SDP offer it forwards.	If the mode-change-period parameter is contained in the SDP answer for the AMR-WB payload type and the IMS-ALG decides the IVAS codec using AMR-WB IO mode will be interworked with that AMR-WB payload type, the IMS-ALG should include the mode-change-period parameter for the IVAS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-change-period parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
mode-change-capability (NOTE 3)	If the mode-change-capability parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG may forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the IMS-ALG expects that IVAS using AMR-WB IO mode will be interworked with AMR-WB (e.g. if IVAS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the mode-change-capability parameter with value 2 for the AMR-WB payload in the SDP offer it forwards.	If the IMS-ALG decides that the IVAS codec using AMR-WB IO mode is selected, the IMS-ALG shall either include the mode-change-capability parameter with value 2 or omit the parameter for the IVAS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-change-capability parameter in the SDP answer, it may also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
mode-change-neighbor (NOTE 3)	If the mode-change-neighbor parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the mode-change-neighbor parameter is contained in the SDP offer and the IMS-ALG expects that IVAS using AMR-WB IO mode will be interworked with AMR-WB (e.g. if IVAS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the mode-change-neighbor with the same value for the AMR-WB payload in the SDP offer it forwards.	If the mode-change-neighbor parameter is contained in the SDP answer for the AMR-WB payload type and the IMS-ALG decides that the IVAS codec using AMR-WB IO mode will be interworked with that AMR-WB payload type, the IMS-ALG should include the mode-change-neighbor parameter for the IVAS payload in the SDP answer it forwards. If the IMS-ALG supplies the mode-change-neighbor parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
max-red (NOTE 5)	If the max-red parameter is contained in the SDP offer and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor. If the max-red parameter is contained in the SDP offer and the IMS-ALG expects that IVAS using AMR-WB IO mode will be interworked with AMR-WB (e.g. if IVAS is the first payload type in the received SDP offer, and the IMS-ALG adds the AMR-WB payload type), the IMS-ALG should include the max-red parameter with the same value for the AMR-WB payload in the SDP offer it forwards with a value that considers the received value and the capabilities of the IMS-AGW.	The IMS-ALG shall only include the max-red parameter in the SDP answer if it desires to restrict the maximum redundancy of received packets. When selecting the value of the max-red parameter, the IMS-ALG shall consider the capabilities of the IMS-AGW and, if the max-red parameter is contained in the SDP answer for the AMR-WB payload type and the IMS-ALG decides that the IVAS codec using AMR-WB IO mode will be interworked with that AMR-WB payload type, the received value. If the IMS-ALG supplies the max-red parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
3gpp_mtsi_app_adapt (NOTE 4)	If the 3gpp_mtsi_app_adapt parameter is contained in the SDP offer, and the IMS-ALG selects the IVAS payload type for transcoding, the IMS-ALG shall forward this parameter to the IMS-AGW in the remote descriptor.	If the IMS-AGW supports RTCP APP based adaptation messages defined in TS 26.114, and the IMS-ALG has a policy to negotiate the usage of those messages, the IMS-ALG shall include the 3gpp_mtsi_app_adapt SDP attribute indicating the supported APP messages in the SDP answer.
ibr (NOTE 2)	If the ibr parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, for IVAS immersive operation in the send and receive direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ibr parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received ibr value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the ibr parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires the same bit rate range for the send and receive direction for IVAS immersive operation, and wants to restrict the bit rate range to match IMS-AGW capabilities and possible configured policies, it shall supply the ibr parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG also supplies the ibw, ibw-send or ibw-recv parameter, the value of the ibr parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the ibr parameter in the SDP answer, it shall also supply to the IMS-AGW the ibr parameter in the local descriptor for the termination towards the offerer with the same value.
ibr-send (NOTE 2)	If the ibr-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, for IVAS immersive operation in the receive direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ibr-recv parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received ibr-recv value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the ibr-send parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires a different bit rate (range) for the send and receive direction for IVAS immersive operation, and wants to restrict the bit rate range for the send direction to match IMS-AGW capabilities and possible configured policies, it shall supply the ibr-send parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the ibr-send parameter in the SDP answer. If the IMS-ALG also supplies the ibw or ibw-send parameter, the value of the ibr-send parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the ibr-send parameter in the SDP answer, it shall also supply to the IMS-AGW the ibr-send parameter in the local descriptor for the termination towards the offerer with the same value.
ibr-recv (NOTE 2)	If the ibr-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bitrates, or a subset of them, for IVAS immersive operation in the send direction. If the indicated bitrates, and even each subset of them, are not supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ibr-send parameter is contained in the SDP offer, the IMS-ALG shall select a bitrate value, which is either the received ibr-send value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the ibr-recv parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires a different bit rate (range) for the send and receive direction for IVAS immersive operation, and wants to restrict the bit rate range for the receive direction to match IMS-AGW capabilities and possible configured policies, it shall supply the ibr-recv parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the ibr-recv parameter in the SDP answer. If the IMS-ALG also supplies the ibw or ibw-recv parameter, the value of the ibr-recv parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the ibr-recv parameter in the SDP answer, it shall also supply to the IMS-AGW the ibr-recv parameter in the local descriptor for the termination towards the offerer with the same value.
ibw (NOTE 2)	If the ibw parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bandwidth(s), or a subset of them, for IVAS immersive operation in the send and receive direction. If the indicated sampling bandwidth(s), and even each subset of them, are not supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ibw parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidth value, which is either the received ibw value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the ibw parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, if the IMS-ALG desires the same sampling bandwidth(s) for the send and receive direction for IVAS immersive operation, and wants to restrict the sampling bandwidth(s) to match IMS-AGW capabilities and possible configured policies, it shall supply the bw parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG also supplies the ibr, ibr-send or ibr-recv parameter, the value of the ibw parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the ibw parameter in the SDP answer, it shall also supply to the IMS-AGW the ibw parameter in the local descriptor for the termination towards the offerer with the same value.
ibw-send (NOTE 2)	If the ibw-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bandwidths, or a subset of them, for IVAS immersive operation in the receive direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ibw-recv parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidths value, which is either the received ibw-recv value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the ibw-send parameter with the selected value in the SDP answer. Otherwise, if the IMS-ALG desires different sampling bandwidths for the send and receive direction for IVAS immersive operation, and wants to restrict the sampling bandwidths for the send direction to match IMS-AGW capabilities and possible configured policies, it shall supply the ibw-send parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the ibr-send parameter in the SDP answer. If the IMS-ALG also supplies the ibw or ibw-send parameter, the value of the ibr-send parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the ibw-send parameter in the SDP answer, it shall also supply to the IMS-AGW the ibw-send parameter in the local descriptor for the termination towards the offerer with the same value.
ibw-recv (NOTE 2)	If the ibr-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated bandwidths, or a subset of them, for IVAS immersive operation in the send direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the ibw-send parameter is contained in the SDP offer, the IMS-ALG shall select a sampling bandwidths value, which is either the received ibw-send value or a subset of it, based on IMS-AGW capabilities and possible configured policies, and shall include the ibw-recv parameter with the selected value in the SDP answer. Otherwise, if the IMS-ALG desires a different sampling bandwidths for the send and receive direction for IVAS immersive operation, and wants to restrict the sampling bandwidths for the receive direction to match IMS-AGW capabilities and possible configured policies, it shall supply the ibw-recv parameter in the SDP answer it sends. Otherwise, the IMS-ALG shall not include the ibw-recv parameter in the SDP answer. If the IMS-ALG also supplies the ibr or ibr-recv parameter, the value of the ibw-recv parameter shall be compatible with the values of those parameters. If the IMS-ALG supplies the ibw-send parameter in the SDP answer, it shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
cf (NOTE 2)	If the cf parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated IVAS coded-formats, or a subset of them, for IVAS immersive operation in the send and receive direction. The IMS-ALG shall remove from the received list the coded-formats not supported by the IMS-AGW. If none of the indicated IVAS coded-formats are supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the cf parameter is contained in the SDP offer, the IMS-ALG shall select the list of IVAS coded-format, based on the received list, IMS-AGW capabilities and possible configured policies, and shall include the cf parameter with the resulting list in the SDP answer. If the IMS-ALG supplies the cf parameter in the SDP answer, the IMS-ALG shall also supply it to the IMS-AGW in the local descriptor for the termination towards the offerer with the same value.
cf-send (NOTE 2)	If the cf-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated IVAS coded-formats, or a subset of them, for IVAS immersive operation in the receive direction. The IMS-ALG shall remove from the received list the coded-formats not supported by the IMS-AGW. If none of the indicated IVAS coded-formats are supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the cf-recv parameter is contained in the SDP offer, the IMS-ALG shall select the list of IVAS coded-format, based on the received list, IMS-AGW capabilities and possible configured policies, and shall include the cf-send parameter with the resulting list in the SDP answer. If the IMS-ALG supplies the cf-send parameter in the SDP answer, the IMS-ALG shall also supply to the IMS-AGW the cf-send parameter in the local descriptor for the termination towards the offerer with the same value.
cf-recv (NOTE 2)	If the cf-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated IVAS coded-formats, or a subset of them, for IVAS immersive operation in the send direction. The IMS-ALG shall remove from the received list the coded-formats not supported by the IMS-AGW. If none of the indicated IVAS coded-formats are supported, the IMS-ALG shall not select transcoding with IVAS. If the IMS-ALG selects transcoding with IVAS, it shall forward this parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the cf-send parameter is contained in the SDP offer, the IMS-ALG shall select the list of IVAS coded-format, based on the received list, IMS-AGW capabilities and possible configured policies, and shall include the cf-recv parameter with the resulting list in the SDP answer. If the IMS-ALG supplies the cf-recv parameter in the SDP answer, the IMS-ALG shall also supply to the IMS-AGW the cf-recv parameter in the local descriptor for the termination towards the offerer with the same value.
pi-types (NOTE 2)	If the pi-types parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the received PI data types, for IVAS immersive operation in the send and receive direction. The IMS-ALG shall set the pi-types parameter based on the received value and the IMS-AGW capabilities. If the IMS-ALG selects transcoding with IVAS, it shall forward the resulting parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the pi-types parameter is contained in the SDP offer, the IMS-ALG shall set the pi-types parameter based on the received value and the IMS-AGW capabilities, and shall include the resulting pi-types parameter in the SDP answer. If none of the received PI data types are supported, the IMS-ALG shall not include the pi-types parameter in the SDP answer. If the IMS-ALG supplies the pi-types parameter in the SDP answer, it shall also supply to the IMS-AGW the pi-types parameter in the local descriptor for the termination towards the offerer with the same value.
pi-types-send (NOTE 2)	If the pi-types-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the received PI data types, for IVAS immersive operation in the receive direction. The IMS-ALG shall set the pi-types-send parameter based on the received value and the IMS-AGW capabilities. If the IMS-ALG selects transcoding with IVAS, it shall forward the resulting parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the pi-types-recv parameter is contained in the SDP offer, the IMS-ALG shall set the pi-types-send parameter based on the received value and the IMS-AGW capabilities, and shall include the resulting pi-types-send parameter in the SDP answer. If none of the received PI data types are supported, the IMS-ALG shall not include the pi-types-send parameter in the SDP answer. If the IMS-ALG supplies the pi-types-send parameter in the SDP answer, it shall also supply to the IMS-AGW the pi-types-send parameter in the local descriptor for the termination towards the offerer with the same value.
pi-types-recv (NOTE 2)	If the pi-types-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the received PI data types, for IVAS immersive operation in the send direction. The IMS-ALG shall set the pi-types-recv parameter based on the received value and the IMS-AGW capabilities. If the IMS-ALG selects transcoding with IVAS, it shall forward the resulting parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the pi-types-send parameter is contained in the SDP offer, the IMS-ALG shall set the pi-types-recv parameter based on the received value and the IMS-AGW capabilities, and shall include the resulting pi-types-recv parameter in the SDP answer. If none of the received PI data types are supported, the IMS-ALG shall not include the pi-types-recv parameter in the SDP answer. If the IMS-ALG supplies the pi-types-recv parameter in the SDP answer, it shall also supply to the IMS-AGW the pi-types-recv parameter in the local descriptor for the termination towards the offerer with the same value.
pi-br (NOTE 2)	If the pi-br parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated maximum bitrate, for IVAS immersive operation in the send and receive direction. If the indicated maximum bitrate is not supported, the IMS-ALG shall return the pi-br parameter with the maximum bit rate supported by the IMS-AGW for PI data. If the IMS-ALG selects transcoding with IVAS, the IMS-ALG shall forward the resulting pi-br parameter to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the pi-br parameter is contained in the SDP offer, the IMS-ALG shall select the maximum bit rate value for PI data, based on the received value, IMS-AGW capabilities and possible configured policies, and shall include the pi-ibr parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG supplies the pi-br parameter in the SDP answer, it shall also supply to the IMS-AGW the pi-br parameter in the local descriptor for the termination towards the offerer with the same value.
pi-br-send (NOTE 2)	If the pi-br-send parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated maximum bitrate, for IVAS immersive operation in the receive direction. If the indicated maximum bitrate is not supported, the IMS-ALG shall return the pi-br-recv parameter in the SDP answer with the maximum bit rate supported by the IMS-AGW for PI data. If the IMS-ALG selects transcoding with IVAS, the IMS-ALG shall forward the pi-br-send parameter (possibly modified to the maximum bit rate supported by the IMS-AGW for PI data) to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the pi-br-recv parameter is contained in the SDP offer, the IMS-ALG shall select the maximum bit rate value for PI data, based on the received value, IMS-AGW capabilities and possible configured policies, and shall include the pi-ibr-send parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG supplies the pi-br-send parameter in the SDP answer, it shall also supply to the IMS-AGW the pi-br-send parameter in the local descriptor for the termination towards the offerer with the same value.
pi-br-recv (NOTE 2)	If the pi-br-recv parameter is contained in the SDP offer, the IMS-ALG shall check if the IMS-AGW supports the indicated maximum bitrate, for IVAS immersive operation in the send direction. If the indicated maximum bitrate is not supported, the IMS-ALG shall return the pi-br-send parameter in the SDP answer with the maximum bit rate supported by the IMS-AGW for PI data. If the IMS-ALG selects transcoding with IVAS, the IMS-ALG shall forward the pi-br-recv parameter (possibly modified to the maximum bit rate supported by the IMS-AGW for PI data) to the IMS-AGW for the termination towards the offerer in the remote descriptor.	If the pi-br-send parameter is contained in the SDP offer, the IMS-ALG shall select the maximum bit rate value for PI data, based on the received value, IMS-AGW capabilities and possible configured policies, and shall include the pi-br-recv parameter with the selected value that is also supplied towards the IMS-AGW in the SDP answer. Otherwise, the IMS-ALG shall not include this parameter in the SDP answer. If the IMS-ALG supplies the pi-br-recv parameter in the SDP answer, it shall also supply to the IMS-AGW the pi-br-recv parameter in the local descriptor for the termination towards the offerer with the same value.
NOTE 1: This MIME parameter of the IVAS RTP payload type is defined in TS 26.445. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 2: This MIME parameter of the IVAS RTP payload type is defined in TS 26.253. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 3: This MIME parameter of the IVAS RTP payload type relates to AMR-WB IO mode and is defined in RFC 4867. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 4: This SDP attribute is defined in TS 26.114. It applies to all codecs offered in an SDP media line. However, some values are specific to IVAS. NOTE 5: This MIME parameter of the IVAS RTP payload type is defined in RFC 4867. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566.

Table 5.13.5.2 describes the IMS-AGW handling of IVAS codec parameters. The IMS-AGW should support transcoding of IVAS with bandwidths (sampling rates) which are supported by codec the IMS-AGW is capable to transcode IVAS to/from (e.g. AMR-WB or EVS).

Table 5.13.5.2: IMS-AGW handling of IVAS codec parameters

Parameter	Handling in local descriptor	Handling in remote descriptor
ivas-mode-switch (NOTE 2)	The IMS-AGW should expect to receive packets using EVS Primary or AMR-WB IO mode (as defined by the evs-mode-switch parameter) and may use this information when deciding upon the required resources.	The IMS-AGW shall use the EVS Primary or AMR-WB IO mode (as defined by the evs-mode-switch parameter) when sending packets.
evs-mode-switch (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
hf-only (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
dtx (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
dtx-recv (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
br (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
br-send (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
br-recv (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
bw (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
bw-send (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
bw-recv (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
cmr (NOTE 2)	For IVAS in EVS Primary or WB-AMR IO mode: see Table 5.13.3.3. Additionally, for IVAS immersive modes: For cmr with value -1, the IMS-AGW should expect to receive no RTP packets containing codec mode requests and may use this information when deciding upon the required resources. For cmr with value -1 the IMS-AGW shall also send no RTP packets containing codec mode requests.	For IVAS in EVS Primary or WB-AMR IO mode: see Table 5.13.3.3. Additionally, for IVAS immersive modes: For cmr with value -1, the IMS-AGW should expect to receive no RTP packets containing codec mode requests and may use this information when deciding upon the required resources. For cmr with value -1 the IMS-AGW shall also send no RTP packets containing codec mode requests.
ch-aw-recv (NOTE 1)	See Table 5.13.3.3.	See Table 5.13.3.3.
mode-set (NOTE 4)	See Table 5.13.3.3.	See Table 5.13.3.3.
mode-change-period (NOTE 3)	See Table 5.13.3.3.	See Table 5.13.3.3.
mode-change-capability (NOTE 6)	See Table 5.13.3.3.	See Table 5.13.3.3.
mode-change-neighbor (NOTE 3)	See Table 5.13.3.3.	See Table 5.13.3.3.
max-red (NOTE 5)	See Table 5.13.3.3.	See Table 5.13.3.3.
3gpp_mtsi_app_adapt (NOTE 4)	See Table 5.13.3.3.	See Table 5.13.3.3.
ibr (NOTE 2)	If different values for the ibr parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources. The IMS-AGW shall use this bitrate range when sending packets.	If different values for the ibr parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources. The IMS-AGW shall use this bitrate range when sending packets.
ibr-send (NOTE 2)	If different values for the ibr-send parameter in the local descriptor and for the ibr-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use this bitrate range when sending packets.	If different values for the ibr-send parameter in the remote descriptor and for the ibr-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources.
ibr-recv (NOTE 2)	If different values for the ibr-send parameter in the remote descriptor and for the ibr-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with this bitrate range and may use this information when deciding upon the required resources.	If different values for the ibr-send parameter in the local descriptor and for the ibr-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use this bitrate range when sending packets.
ibw (NOTE 2)	If different values for the ibw parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these bandwidth(s) and may use this information when deciding upon the required resources. The IMS-AGW shall use these bandwidth(s) when sending packets.	If different values for the ibw parameter are provided in the local and remote descriptors, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these sampling bandwidth(s) and may use this information when deciding upon the required resources. The IMS-AGW shall use these sampling bandwidth(s) when sending packets.
ibw-send (NOTE 2)	If different values for the ibw-send parameter in the local descriptor and for the ibw-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use these bandwidth(s) when sending packets.	If different values for the ibw-send parameter in the remote descriptor and for the ibw-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these sampling bandwidth(s) and may use this information when deciding upon the required resources.
ibw-recv (NOTE 2)	If different values for the ibw-send parameter in the remote descriptor and for the ibw-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets with these sampling bandwidth(s) and may use this information when deciding upon the required resources.	If different values for the ibw-send parameter in the local descriptor and for the ibw-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall use these sampling bandwidth(s) when sending packets.
cf (NOTE 2)	The IMS-AGW should expect to receive packets using the IVAS coded-formats indicated by this parameter. The IMS-AGW shall only send packets using the IVAS coded-formats indicated by this parameter.	The IMS-AGW should expect to receive packets using the IVAS coded-formats indicated by this parameter. The IMS-AGW shall only send packets using the IVAS coded-formats indicated by this parameter.
cf-send (NOTE 2)	If different values for the cf-send parameter in the local descriptor and for the cf-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall only send packets using the IVAS coded-formats indicated by this parameter.	If different values for the cf-send parameter in the remote descriptor and for the cf-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets using the IVAS coded-formats indicated by this parameter.
cf-recv (NOTE 2)	If different values for the cf-send parameter in the remote descriptor and for the cf-recv parameter in the local descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW should expect to receive packets using the IVAS coded-formats indicated by this parameter.	If different values for the cf-send parameter in the local descriptor and for the cf-recv parameter in the remote descriptor are provided, one will be a subset of the other, and the smaller range shall apply. The IMS-AGW shall only send packets using the IVAS coded-formats indicated by this parameter.
pi-types (NOTE 2)	The IMS-AGW should expect to receive PI data with the PI data types indicated by this parameter. The IMS-AGW may send PI data with the PI data types indicated by this parameter.	The IMS-AGW should expect to receive PI data with the PI data types indicated by this parameter. The IMS-AGW may send PI data with the PI data types indicated by this parameter.
pi-types-send (NOTE 2)	If different values for the pi-types-send parameter in the local descriptor and for the pi- types-recv parameter in the remote descriptor are provided, only PI data types present in both parameters should be used. The IMS-AGW may send PI data with the PI data types indicated by this parameter.	If different values for the pi-types-send parameter in the remote descriptor and for the pi-types-recv parameter in the local descriptor are provided, the IMS-AGW should expect to receive PI data with the PI data types present in both parameters. The IMS-AGW should expect to receive PI data with the PI data types indicated by this parameter.
pi-types-recv (NOTE 2)	If different values for the pi-types-send parameter in the remote descriptor and for the pi-types-recv parameter in the local descriptor are provided, the IMS-AGW should expect to receive PI data with the PI data types present in both parameters. The IMS-AGW should expect to receive PI data with the PI data types indicated by this parameter.	If different values for the pi-types-send parameter in the local descriptor and for the pi- types-recv parameter in the remote descriptor are provided, only PI data types present in both parameters should be used. vThe IMS-AGW may send PI data with the PI data types indicated by this parameter.
pi-br (NOTE 2)	The IMS-AGW should expect to receive PI data with the maximum bit rate indicated by this parameter. The IMS-AGW may send PI data with the maximum bit rate indicated by this parameter.	The IMS-AGW should expect to receive PI data with the maximum bit rate indicated by this parameter. The IMS-AGW may send PI data with the maximum bit rate indicated by this parameter.
pi-br-send (NOTE 2)	If different values for the pi-br-send parameter in the local descriptor and for the pi-br-recv parameter in the remote descriptor are provided, the smallest value of the parameters should be used. The IMS-AGW may send PI data with the maximum bit rate indicated by this parameter.	If different values for the pi-br-send parameter in the remote descriptor and for the pi-br-recv parameter in the local descriptor are provided, the smallest value of the parameters should be used. The IMS-AGW should expect to receive PI data with the maximum bit rate indicated by this parameter.
pi-br-recv (NOTE 2)	If different values for the pi-br-send parameter in the remote descriptor and for the pi-br-recv parameter in the local descriptor are provided, the smallest value of the parameters should be used. The IMS-AGW should expect to receive PI data with the maximum bit rate indicated by this parameter.	If different values for the pi-br-send parameter in the local descriptor and for the pi-br-recv parameter in the remote descriptor are provided, the smallest value of the parameters should be used. The IMS-AGW may send PI data with the maximum bit rate indicated by this parameter.
NOTE 1: This MIME parameter of the IVAS RTP payload type is defined in TS 26.445. The values and the defaults if a parameter is omitted, as defined in TS 26.445 shall apply. NOTE 2: This MIME parameter of the IVAS RTP payload type is defined in TS 26.253. It is encapsulated within the SDP "a=fmtp" attribute defined RFC 4566. NOTE 3: This MIME parameter of the IVAS RTP payload type relates to AMR-WB IO mode and is defined in RFC 4867. The values and the defaults if a parameter is omitted, as defined in RFC 4867 shall apply. NOTE 4: This SDP attribute is defined in TS 26.114. It applies to all codecs offered in an SDP media line. However, some values are specific to IVAS. NOTE 5: This MIME parameter of the IVAS RTP payload type is defined in RFC 4867. The values and the defaults if a parameter is omitted, as defined in RFC 4867 shall apply. NOTE 6: This MIME parameter of the IVAS RTP payload type relates to AMR-WB IO mode and is defined in RFC 4867. The values and the defaults if a parameter is omitted, as defined in TS 26.445, shall apply.