Saturday, April 16, 2011

Voice Class Codec for H323 Gateways

One important aspect that I lately discovered is the necessity of having voice class codec if you are using H323 gateways in the lab/environment. VoIP Dial Peers (DP) by default employ G729 Codec. So when you are creating the VoIP Dial Peers to sent the incoming calls to the CUCM, by default they will start using G729. This can lose you marks in the Lab as you might be asked to have G711 within a site.

Having Voice Class Codec enables you to have your VoIP DPs negotiate both G711 & G729 Codecs. This comes especially handy when you transfer the calls to other site, say Branch 1 phone to whom you must talk G729.

Here is a working config:
!
voice class codec 1
 codec preference 1 g711ulaw
 codec preference 2 g729r8

!
voice class h323 1
  h225 timeout tcp establish 3
!
dial-peer voice 1000 voip
 incoming called-number .
 destination-pattern 3...$
 voice-class codec 1
 voice-class h323 1
 session target ipv4:177.1.10.20  // Subscriber
 dtmf-relay h245-alphanumeric
 no vad
!
dial-peer voice 1001 voip
 preference 1
 destination-pattern 3...$
 voice-class codec 1
 voice-class h323 1
 session target ipv4:177.1.10.10 // Publisher
 dtmf-relay h245-alphanumeric
 no vad
!

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