1. Configuration Guide
  2. Transcoding
  3. AMR-NB and AMR-WB Specifications
  4. Examples and Explanations
  5. Advanced Scenarios

Advanced Scenarios

Examples provided in this first section are supported by the following codec policy and media profile. 

codec-policy
        name                      net182
        allow-codecs              *
        add-codecs-on-egress      AMR::PT97-5-6-7
        order-codecs
        force-ptime               disabled
        packetization-time        20
        dtmf-in-audio             disabled


media-profile
        name                      AMR
        subname                   PT97-5-6-7
        media-type                audio
        payload-type              97
        transport                 RTP/AVP
        req-bandwidth             0
        frames-per-packet         0
        parameters                mode-set="5,6,7"
        average-rate-limit        0
        peak-rate-limit           0
        max-burst-size            0
        sdp-rate-limit-headroom   0
        sdp-bandwidth             disabled
        police-rate               0
        standard-pkt-rate         0

The following SDP reflects the case where the offer and answer specify non-matching mode-sets.

SDP Contents
Offer received from session initiator
  • m=audio xx RTP/AVP 96
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 mode-set=0,1,2,3,4
  • INVITE SDP (partial, codec information only)
Offer sent to responder (per the net192 codec policy)
  • m=audio xx RTP/AVP 97 96
from AMR/PT97-5-6-7 media profile
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=5,6,7
initiator offer
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 mode-set=1,2,3,4
Answer received from responder
  • m=audio xx RTP/AVP 97
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=5,6,7
Answer sent to initiator
  • m=audio xx RTP/AVP 96
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 mode-set=0,1,2,3,4
Codecs Match Values
codecs match AMR/AMR
payload formats match bandwidth-efficient (default value)
mode-sets no match (1,2,3,6) / (5,6,7)
payload mapping no match 96/97

Here, given that the offer mode-set (1,2,3,4) does not intersects with the answer mode-set (5,6,7), transcoding is required.

The following SDP reflects the case where the offer and answer specify intersecting mode-sets.

SDP Contents
Offer received from session initiator
  • m=audio xx RTP/AVP 96
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 mode-set=0,1,2,3,4
  • INVITE SDP (partial, codec information only)
Offer sent to responder (per the net192 codec policy)
  • m=audio xx RTP/AVP 97 96
from AMR/PT97-5-6-7 media profile
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=5,6,7
initiator offer
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 mode-set=1,2,3,4
Answer received from responder
  • m=audio xx RTP/AVP 97
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=4,5,6,7
Answer sent to initiator
  • m=audio xx RTP/AVP 96
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 mode-set=0,1,2,3,4
Codecs Match Values
codecs match AMR/AMR
payload formats match bandwidth-efficient (default value)
mode-sets no match (1,2,3,4) / (4,5,6,7)
payload mapping no match 96/97

Here, given that the offer mode-set (1,2,3,4) intersects with the answer mode-set (4,5,6,7), transcoding is not required; payload type mapping is used.

Examples provided in this next section are supported by the following codec policy and media profiles. 

codec-policy
        name                      net192
        allow-codecs              *
        add-codecs-on-egress      AMR::PT96-MAXRED AMR::PT97-BE-0257
                                  AMR::PT98-OA AMR::PT99-OA-0257
        order-codecs                   
        force-ptime               disabled
        packetization-time        20
        dtmf-in-audio             disabled


media-profile
        name                      AMR
        subname                   PT96-MAXRED
        media-type                audio
        payload-type              96
        transport                 RTP/AVP
        req-bandwidth             0
        frames-per-packet         0
        parameters                max-red=220
        average-rate-limit        0
        peak-rate-limit           0
        max-burst-size            0
        sdp-rate-limit-headroom   0
        sdp-bandwidth             disabled
        police-rate               0
        standard-pkt-rate         0


media-profile
        name                      AMR
        subname                   PT97-BE-0257
        media-type                audio
        payload-type              97
        transport                 RTP/AVP
        req-bandwidth             0
        frames-per-packet         0
        parameters                mode-set="0,2,5,7"
        average-rate-limit        0
        peak-rate-limit           0
        max-burst-size            0
        sdp-rate-limit-headroom   0
        sdp-bandwidth             disabled
        police-rate               0
        standard-pkt-rate         0


        media-profile
        name                      AMR
        subname                   PT98-OA
        media-type                audio
        payload-type              98
        transport                 RTP/AVP
        req-bandwidth             0
        frames-per-packet         0
        parameters                octet-align=1
        average-rate-limit        0
        peak-rate-limit           0
        max-burst-size            0
        sdp-rate-limit-headroom   0
        sdp-bandwidth             disabled
        police-rate               0
        standard-pkt-rate         0


media-profile
        name                      AMR
        subname                   PT99-OA-0257
        media-type                audio
        payload-type              99
        transport                 RTP/AVP
        req-bandwidth             0
        frames-per-packet         0
        parameters                mode-set="0,2,5,7",octet-align=1
        average-rate-limit        0
        peak-rate-limit           0
        max-burst-size            0
        sdp-rate-limit-headroom   0
        sdp-bandwidth             disabled
        police-rate               0
        standard-pkt-rate         0

The following SDP reflects the case where the offer and answer differ only in the inclusion of an AMR/AMR-WB parameter in the answer.

SDP Contents
Offer received from session initiator
  • m=audio xx RTP/AVP 96
  • a=rtpmap:96 AMR/8000
  • INVITE SDP (partial, codec information only)
Offer sent to responder (per the net192 codec policy)
  • m=audio xx RTP/AVP 97 98 99 96
from AMR/PT97-BE-0257 media profile
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=0,2,5,7
from AMR/PT98-OA media profile
  • a=rtpmap:98 AMR/8000
  • a=fmtp:98 octet-align=1
from AMR/PT99-OA-0257 media profile
  • a=rtpmap:99 AMR/8000
  • a=fmtp:99 mode-set=0,2,5,7 octet-align=1
initiator offer
  • a=rtpmap:96 AMR/8000
Answer received from responder
  • m=audio xx RTP/AVP 96
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 max-red=220
Answer sent to initiator
  • m=audio xx RTP/AVP 96
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 max-red=220
Codecs Match Values
codecs match AMR/AMR
payload formats match bandwidth-efficient (default value)
mode-sets match inclusive mode-set (0,1,2,3,4,5,6,7)
payload mapping match 96/96

Here, given that the offer/answer are identical except for the AMR max-red parameter, neither transcoding nor payload type matching is required.

The following SDP reflects the case where the offer and answer differ only in the inclusion of an AMR/AMR-WB parameter in the offer.

SDP Contents
Offer received from session initiator
  • m=audio xx RTP/AVP 97
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=0,2,5,7
  • a=fmtp:97 max-red=220
  • INVITE SDP (partial, codec information only)
Offer sent to responder (per the net192 codec policy)
  • m=audio xx RTP/AVP 96 98 99 97
from AMR/PT96-MAXRED media profile
  • a=rtpmap:96 AMR/8000
  • a=fmtp:96 max-red=220
from AMR/PT98-OA media profile
  • a=rtpmap:98 AMR/8000
  • a=fmtp:98 octet-align=1
from AMR/PT99-OA-0257 media profile
  • a=rtpmap:99 AMR/8000
  • a=fmtp:99 mode-set=0,2,5,7 octet-align=1
initiator offer
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=0,2,5,7 max-red=220
Answer received from responder
  • m=audio xx RTP/AVP 97
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=0,2,5,7
Answer sent to initiator
  • m=audio xx RTP/AVP 97
  • a=rtpmap:97 AMR/8000
  • a=fmtp:97 mode-set=0,2,5,7
Codecs Match Values
codecs match AMR/AMR
payload formats match bandwidth-efficient (default value)
mode-sets match (0,2,5,7) / (0,2,5,7)
payload mapping match 97/97

Here, given that the offer/answer are identical except for the AMR max-red parameter, neither transcoding nor payload type matching is required.