MIME media type name : Audio
MIME subtype name : Standards Tree - EVS
Required parameters : None
Optional parameters :
These parameters apply to RTP transfer only.
ptime: defined in section 6 of RFC-ietf-mmusic-rfc4566bis-37
maxptime: defined in section 6 of RFC-ietf-mmusic-rfc4566bis-37
evs-mode-switch: Permissible values are 0 and 1. If evs-mode-switch is 0 or not present, EVS primary mode is used at the start or update of the session for the send and the receive directions. If evs-mode-switch is 1, EVS AMR-WB IO mode is used at the start or update of the session for the send and the receive directions.
hf-only: Permissible values are 0 and 1. If hf-only is 0 or not present, both Compact and Header-Full formats can be used in the session for the send and the receive directions. If hf-only is 1, only Header-Full format without zero padding for size collision avoidance is used.
NOTE 1: The hf-only parameter applies to both directions in the session, including when hf-only is 1.
dtx: Permissible values are 0 and 1. If dtx is 0, DTX is disabled in the session for the send and the receive directions. If dtx is 1 or not present, DTX is enabled. If dtx is included, dtx-recv is redundant but if dtx-recv is included, it shall be identical to dtx.
NOTE 2: If dtx is not present, DTX can still be disabled by the inclusion of dtx-recv=0 for the direction indicated by dtx-recv. See also clause A.3.3.1 and clause A.3.3.3 of 3GPP TS 26.445.
dtx-recv: Permissible values are 0 and 1. If dtx-recv=0 is included for a payload type in the received SDP offer or the received SDP answer, and the payload type is accepted, the receiver shall disable DTX for the send direction. If dtx-recv=1 is included for a payload type in the received SDP offer or the received SDP answer, and this payload type is accepted, or if dtx-recv is not present for an accepted payload type, DTX is enabled.
NOTE 3: dtx-recv only applies for the media direction towards the SDP sender. If dtx-recv is not present, dtx determines if DTX is enabled or disabled. See also clause A.3.3.1 and clause A.3.3.3 of 3GPP TS 26.445.
max-red: defined in RFC 4867
channels: The number of audio channels. See RFC 3551. If channels is not present, its default value is 1. If both ch-send and ch-recv are included in the SDP with different numbers of channels for sending and receiving directions, channels is set to the larger of the two parameters.
cmr: Permissible values are -1, 0, and 1. If cmr is -1 and the session is in the EVS primary mode, CMR on the RTP payload header is disabled in the session. If cmr is -1 and the session is in the EVS AMR-WB IO mode, CMR in the CMR byte is restricted to the values of EVS AMR-WB IO bit-rates and NO_REQ as specified in Table A.3 of 3GPP TS 26.445. If cmr is 0 or not present, the values of CMR specified in Table A.3 of 3GPP TS 26.445 are enabled. If cmr is 1, CMR shall be present in each packet. CMR shall be compliant with the negotiated bit-rate and bandwidth media type attributes for EVS primary and EVS AMR-WB IO modes.
br: Specifies the range of source codec bit-rate for EVS Primary mode (see Table 1 of 3GPP TS 26.441) in the session, in kilobits per second, for the send and the receive directions. The parameter can either have: a single bit-rate (br1); or a hyphen-separated pair of two bit-rates (br1-br2). If a single value is included, this bit-rate, br1, is used. If a hyphen-separated pair of two bit-rates is included, br1 and br2 are used as the minimum bit-rate and the maximum bit-rate respectively. br1 shall be smaller than br2. br1 and br2 have a value from the set: 5.9, 7.2, 8, 9.6, 13.2, 16.4, 24.4, 32, 48, 64, 96, and 128. 5.9 represents the average bit-rate of source controlled variable bit rate (SC-VBR) coding, and 7.2, ..., 128 represent the bit-rates of constant bit-rate source coding. Only bit-rates supporting at least one of the allowed audio bandwidth(s) shall be used in the session (see clause A.3.3.1 of 3GPP TS 26.445). If br is not present, all bit-rates consistent with the negotiated bandwidth(s) are allowed in the session unless br-send or br-recv is present. If br is included, br-send or br-recv is redundant but if either br-send or br-recv, or both are included, they shall be identical to br. If br-send and br-recv are not identical, br shall not be used.
br-send: Specifies the range of source codec bit-rate for EVS Primary mode (see Table 1 of 3GPP TS 26.441) in the session, in kilobits per second, for the send direction. The parameter can either have: a single bit-rate (br1); or a hyphen-separated pair of two bit-rates (br1-br2). If a single value is included, this bit-rate, br1, is used. If a hyphen-separated pair of two bit-rates is included, br1 and br2 are used as the minimum bit-rate and the maximum bit-rate respectively. br1 shall be smaller than br2. br1 and br2 have a value from the set: 5.9, 7.2, 8, 9.6, 13.2, 16.4, 24.4, 32, 48, 64, 96, and 128. 5.9 represents the average bit-rate of source controlled variable bit-rate (SC-VBR) coding, and 7.2, ..., 128 represent the bit-rates of constant bit-rate source coding. Only bit-rates supporting at least one of the allowed audio bandwidth(s) shall be used in the session (see clause A.3.3.1 of 3GPP TS 26.445). If br-send is not present, all bit-rates consistent with the negotiated bandwidth(s) are allowed in the session unless br is present.
br-recv: Specifies the range of source codec bit-rate for EVS Primary mode (see Table 1 of 3GPP TS 26.441) in the session, in kilobits per second, for the receive direction. The parameter can either have: a single bit-rate (br1); or a hyphen-separated pair of two bit-rates (br1-br2). If a single value is included, this bit-rate, br1, is used. If a hyphen-separated pair of two bit-rates is included, br1 and br2 are used as the minimum bit-rate and the maximum bit-rate respectively. br1 shall be smaller than br2. br1 and br2 have a value from the set: 5.9, 7.2, 8, 9.6, 13.2, 16.4, 24.4, 32, 48, 64, 96, and 128. 5.9 represents the average bit-rate of source controlled variable bit-rate (SC-VBR) coding, and 7.2, ..., 128 represent the bit-rates of constant bit-rate source coding. Only bit-rates supporting at least one of the allowed audio bandwidth(s) shall be used in the session (see clause A.3.3.1 of 3GPP TS 26.445). If br-recv is not present, all bit-rates consistent with the negotiated bandwidth(s) are allowed in the session unless br is present.
bw: Specifies the audio bandwidth for EVS Primary mode (see Table 1 of 3GPP TS 26.441) to be used in the session for the send and the receive directions. bw has a value from the set: nb, wb, swb, fb, nb-wb, nb-swb, and nb-fb. nb, wb, swb, and fb represent narrowband, wideband, super-wideband, and fullband respectively, and nb-wb, nb-swb, and nb-fb represent all bandwidths from narrowband to wideband, super-wideband, and fullband respectively. If bw is not present, all bandwidths consistent with the negotiated bit-rate(s) are allowed in the session unless bw-send or bw-recv is present. If bw is included, bw-send or bw-recv is redundant but if either bw-send or bw-recv, or both are included, they shall be identical to bw. If bw-send and bw-recv are not identical, bw shall not be used.
bw-send: Specifies the bandwidth (see Table 1 of 3GPP TS 26.441) to be used in the session for the send direction. bw-send has a value from the set: nb, wb, swb, fb, nb-wb, nb-swb, and nb-fb. nb, wb, swb, and fb represent narrowband, wideband, super-wideband, and fullband respectively, and nb-wb, nb-swb, and nb-fb represent all bandwidths from narrowband to wideband, super-wideband, and fullband respectively. If bw-send is not present, all bandwidths consistent with the negotiated bit-rate(s) are allowed in the session unless bw is present.
bw-recv: Specifies the bandwidth (see Table 1 of 3GPP TS 26.441) to be used in the session for the receive direction. bw-recv has a value from the set: nb, wb, swb, fb, nb-wb, nb-swb, and nb-fb. nb, wb, swb, and fb represent narrowband, wideband, super-wideband, and fullband respectively, and nb-wb, nb-swb, and nb-fb represent all bandwidths from narrowband to wideband, super-wideband, and fullband respectively. If bw-recv is not present, all bandwidths consistent with the negotiated bit-rate(s) are allowed in the session unless bw is present.
ch-send: Specifies the number of audio channels to be used in the session for the send direction. ch-send has an integer value from 1 to the maximum number of audio channels (see also clause A.3.2 of 3GPP TS 26.445). If ch-send is not present, ch-send=1, mono, is supported.
ch-recv: Specifies the number of audio channels to be used in the session for the receive direction. ch-recv has an integer value from 1 to the maximum number of audio channels (see also clause A.3.2 of 3GPP TS 26.445). If ch-recv is not present, ch-recv=1, mono, is supported.
ch-aw-recv: Specifies how channel-aware mode is configured or used for the receive direction. Permissible values are -1, 0, 2, 3, 5, and 7. If ch-aw-recv is -1, channel-aware mode is disabled in the session for the receive direction. If ch-aw-recv is 0 or not present, partial redundancy (channel-aware mode) is not used at the start of the session for the receive direction. If ch-aw-recv is positive (2, 3, 5, or 7), partial redundancy (channel-aware mode) is used at the start of the session for the receive direction using the value as the offset (See NOTE below). Partial redundancy is supported only when the bit-rate is 13.2 kbps and the bandwidth is wb or swb.
mode-set: Restricts the active codec mode set to a subset of all modes when the EVS codec operates in AMR-WB IO, for example, to be able to support transport channels such as GSM or UMTS networks. Possible value is a comma-separated list of modes from the set: 0, ..., 8 (see Table 1a of 3GPP TS 26.201). If mode-set is specified, it must be abided, and frames encoded with AMR-WB IO outside of the subset must not be sent in any RTP payload or used in codec mode request signal. If not present, all codec modes of AMR-WB IO are allowed for the payload type.
NOTE 4: If a positive (2, 3, 5, or 7) value of ch-aw-recv is declared for a payload type and the payload type is accepted, the receiver of the parameter shall send partial redundancy (channel-aware mode) at the start of the session using the value as the offset. If ch-aw-recv=0 is declared or not present for a payload type and the payload type is accepted, the receiver of the parameter shall not send partial redundancy (channel-aware mode) at the start of the session. If ch-aw-recv=-1 is declared for a payload type and the payload type is accepted, the receiver of the parameter shall not send partial redundancy (channel-aware mode) in the session. If ch-aw-recv is not present or a non-negative (0, 2, 3, 5, or 7) value of ch-aw-recv is declared for a payload type and the payload type is accepted, partial redundancy (channel-aware mode) can be activated or deactivated during the session based on the expected or estimated channel condition through adaptation signaling, such as CMR (see clause A.2 of 3GPP TS 26.445) or RTCP based signaling (see clause 10.2 of 3GPP TS 26.114). If ch-aw-recv is not present or a non-negative (0, 2, 3, 5, or 7) value of ch-aw-recv is declared for a payload type and the payload type is accepted, the partial redundancy offset value can also be adjusted during the session based on the expected or estimated channel condition through adaptation signaling.
NOTE 5: 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 3GPP TS 26.445.
mode-change-period: defined in section 8.1 of RFC 4867
mode-change-capability: defined in section 8.1 of RFC 4867, except that the default and the only allowed value of mode-change-capability is 2 for EVS AMR-WB IO. As the default and the only allowed value of mode-change-capability is 2 in EVS AMR-WB IO, it is not required to include this parameter in the SDP.
mode-change-neighbor: defined in section 8.1 of RFC 4867
Encoding considerations : This media type is framed and binary; see Section 4.8 in RFC 6838
