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SIP AMR-WB invoking transcoder

Hi,

I have a scenario where outbound to SIP ITSP I’m using early offer (no CUBE, direct SIP trunks on the CUCM).  The IP Phone to the SIP Trunk is configured with Region relationship of a maximum bandwidth of 8k.

 

Outbound to the ITSP I have the below attributes in the INVITE SDP:

b=TIAS:8000

b=AS:8

t=0 0

m=audio 23004 RTP/AVP 113 115 18 101

b=TIAS:8000

a=rtpmap:113 AMR-WB/16000/2

a=fmtp:113 mode-change-capability=2

a=rtpmap:115 AMR-WB/16000

a=fmtp:115 octet-align=1;mode-change-capability=2

a=rtpmap:18 G729/8000

a=ptime:20

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15

 

The ITSP is replying with a Session 183 with the following SDP:

a=sendrecv

m=audio 33636 RTP/AVP 115

b=RS:375

b=RR:1125

a=maxptime:40

a=rtpmap:115 AMR-WB/16000

a=fmtp:115 octet-align=1;mode-set=0,1,2;mode-change-period=2;mode-change-capability=2;mode-change-neighbor=1;max-red=0

 

CUCM then errors in the log stating unable to parse bandwidth elements – which look to be the RS and RR RTCP statements:

 

96587296.010 |11:33:20.535 |AppInfo  |//SIP/SDPLib/Warning/0x0/sdp_parse_bandwidth:  Warning: BW Modifier type unsupported (RS).

 

96587296.011 |11:33:20.535 |AppInfo  |//SIP/SDPLib/Warning/0x0/sdp_parse_bandwidth:  Warning: BW Modifier type unsupported (RR).

 

CUCM then tries to allocate a transcoder. 

96587330.014 |11:33:20.538 |AppInfo  |DET-MediaManager-(897449)::preCheckCapabilities, caps mismatch! Xcoder Reqd. kbps(8), filtered A[capCount=6 (Cap,ptime)= (98,0) (98,0) (11,20) (12,20) (15,20) (16,20)], B[capCount=0 (Cap,ptime)=] allowMTP=0 numXcoderRequired=1 xcodingSide=2

 

96587331.000 |11:33:20.538 |SdlSig   |MrmAllocateXcoderResourceReq           |waiting                        |MediaResourceManager(2,100,131,1) |MediaManager(2,100,133,897449)   |2,100,13,15442316.116659^193.113.149.54^* |[R:N-H:0,N:0,L:0,V:0,Z:0,D:0]  CI=38972224 MRGLPkid=13ea34b5-71fb-9408-4333-baeb2c893968 Kpbs=0 RegionA=RE-UK-YABL CapA=10 RegionB=RE-UK-YCEN CapB=1 SuppressFlag=0 Type=1 DeviceCapablity= [0x0]0 MandatoryCapabilties= [0x0]0 Count=1

 

My transcoder has no ability to transcode AMR-WB therefore the call fails. 

Why is a transcoder required??

Is it because AMR-WB may use more than 8kbps?

Is it because it couldn’t determine the bandwidth required by the ITSP as it was unable to parse some of the SDP content?

Or is it because of a packertization mis-match, I see the cap,ptime states 98,0 – which confuses me.

 

Any thoughts?

 

 

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