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?