No Audio between IP Phones and PSTN using codec g729

[ochalmers]

Hi Everyone,

I working with a CUCM 4.1.3 with a MGCP  gateway with access to PSTN,  i have a region using codec g729 and when i try to call to pstn from that site the call is established but no audio in both ways, even when the DP have a transcoder and it's registered in the cucm, but if i put on hold the call the party can hear the music, i changed the codec to g711 and every works fine, but i really need to use g729 because of lack of bandwith of the remote site.

Please Help.

Thanks in advance

Oscar

[Gajanan Pande]

Oscar, Please clarify on following points..

1. Is the caller & MGCP gateway at different sites or same ?

2. For the calling user, Is the CUCM acting as MOH source or the gateway ?

GP.

[ochalmers]

Hi Gajanan,

The caller and MGCP Gw are on different sites, We have only one CUCM so it acts as MOH too.

Thanks

Oscar

[Gajanan Pande]

Thanks.

1. Do you have any CAC ( call admission control ) in place between those 2 sites ? Did you configure Location for those 2 sites ?

2. Did you try making a PSTN call, when there are absolutely no calls in progress between 2 sites ? Is the observation different ?

3. Otherwise also, does this issue occur to every PSTN call made from that remote site ?

4. What does the remote site IP Phone show when " i " or " ? " button pressed after the call gets established ? The transmitted & received packet count should give some hint.

5. Finally, is the phone running with latest firmware ?

GP.

[ochalmers]

Hi Gajanan,

     I could solve my problem by doing this, it is suppose to be a bug

#Symptoms: Calls on an MGCP gateway negotiating the g729br8 codec may fail to have audio in one or both directions.

#Conditions: This occurs on MGCP gateways with the fix for CSCsu66759 when the g729br8 codec is being negotiated.

#Workaround: Any of the following will be sufficient to get around this issue:

#1. Configure the gateway for static payload type using the following commands on the gateway:

#mgcp behavior g729-variants static-pt

mgcp behavior dynamically-change-codec-pt disable

Now I can hear audio in both directions.

Thanks

Oscar

[Gajanan Pande]

Oscar,

Thanks for posting back the resolution to the forum. (+5)

GP.