Transcode a G729 Call using Early offer to a CUBE ITSP SIP trunk only supporting G711

[Lee Marson]

Hello all,

I have an ITSP provided SIP Trunk that will only allow the use of G711 codec.

I have some ip phones on remote sites that need to break out over this and the links are low bw so need to use G729 only

If I use Early Offer on the SIP trunk towards the CUBE via SIP Profile (mandatory insert MTP if required) then the call fails with a 488 media non-acceptable error because I offer G729 but the voice class codec on the Dial-peers facing CUCM only allow G711. Which is what you would expect.

So I need a transcoder and the only ways I can get the transcoder to invoke are:

• Use Delayed offer on the SIP profile - this way CUCM is in control of the codec negotiation and successfully inserts the XCODE (this is the way I have opted to go for)
• Tick MTP Required on the SIP trunk and set it to G711 only (undesirable as this means every call requires an MTP not just G729 calls)
• Configure a non sccp transcoder (LTI) that the CUBE can control (I prefer cucm to be in control of resources than the CUBE and you have to add G729 to the codec pref list on the dial-peers)

Just wondering if anyone else has had this issue and has a better option ie where I can use Early Offer (mandatory insert MTP if required) but still have CUCM in charge of inserting the codec before the call fails?

Cheers

[Ayodeji Okanlawon · Accepted solution]

I will always go with Option 1. If you must use Early offer on CUCM, then use option 3.