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Community Member

Software CFB and transcoding


I have a problem with setting up a conference bridge with transcoding. The setup is following:

IP Phone -> SCCP -> CUCM -> SIP -> VGW ->SIP -> PSTN

IP phones are in one region - R_PHONES

VGW is in region - R_VGW

HW transcoder on VGW is in region - R_XCODE

SW CFB on CallManager is in region - R_CFB

                         R_PHONES     R_VGW     R_XCODE     R_CFB

R_PHONES          G711               G729          G729          G729

R_VGW                G729               G711          G711          G711              

R_XCODE             G729               G711          G711          G711 

R_CFB                  G729               G711          G711          G711

I want to make a conference between 3 phones in region R_PHONES.

Phone A calls phone B. Phone B answers the phone. Phone A tries to connect the phone C into the conference so the user press conference button and dial phone C(phone B has a MOH). Phone C answers, they can hear each other, but after pressing the conference button again on phone A to connect all 3 phones together , the phone C have a "to conference" message on display but gets a fast busy tone. Phones A and B can talk to each other again.  

According to everything I've read, the phones should use a transcoder, because the SW CFB can only do G711 conference. But they don't. I can see that no DSPs are in use on VGW. I have all resources (SW ANN, CFB, MOH, MTP and HW XCODER) assigned to one MRGL and all devices are using this MRGL.

I have to use G729 outside a R_PHONES because of network bandwith.

Does anyone have an idea how to solve this?


Re: Software CFB and transcoding

Make sure you assgin a Media Resource Group List (MGRL) to the phones and the gateway, or to the device pool to which your gateway or phones belong. Also make sure the MRGL contains the Confernece Bridges.

Do you have any voice class configured in the VGW?

voice class codec 1

codec preference 1 g711ulaw

codec preferece 2 g729r8

codec preference 3 g729b38

dial-peer voice X voip

voice-class codec 1


Community Member

Re: Software CFB and transcoding


As I wrote before:  I have all resources (SW ANN, CFB, MOH, MTP and HW XCODER) assigned to one MRGL and all devices are using this MRGL, so it should be no problem here.

I have voice class codec:

voice class codec 1
codec preference 1 g711alaw
codec preference 2 g711ulaw
codec preference 3 g729r8
codec preference 4 g729br8

and it is assigned to dial-peers. But I think this is not relevant here as I am making local conference.

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