G711 working but not G729

Unanswered Question
Jun 9th, 2010
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HI all,

Got a questions regarding the codec. I got two sites:

Site A, CUCM 7.1 and one 2911 as H323 gateway.

Site B, CME on 2811.

Site B has recently joined the CUCM as a site. the CUCM is using CME as h323 gateway, inter site calling working fine using G711, just don't wanna talk G729 ?!. but I have set in the reigon settings to use g729 between site A and B... and set the CME dial peer to use G729 as first preference.

Other findings:

If I remove codec setting on the dial peer on CME, or hard coded to G729.. call from B to A, will just work using G729, but call from A to B will fail with debug ccapi disconnect code 65.

there is no transcoder resouces available, but I don't think it's needed.

What else I need to do to get G729 going both ways??


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Tracy Larson Thu, 06/10/2010 - 06:49
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Verify your regions one more time and make sure that you have the correct device pools assigned to the gateways and phones that are trying to talk to each other. I am assuming you are using Cisco phones on both ends, if so no transcoding is needed as the phones can handle both 729 and 711 natively.

minghui.qi Thu, 06/10/2010 - 09:52
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thanks for the reply, I have just done more testing and found the problem. On the Site B gateway setting in CUCM, there is a Outbounf Faststart feature, it is enabled and set the codec to g711u. I am not 100% about the real effect of this feature, when I set the codec to g729 or others, it doesn't make a difference - call still connects using g711 or fail if no g711 is available on the CME matching dial peer.

I end up disabling this feature (by default it is disabled), then G729 works as well as other codecs, the codec for the call can be controlled by the codec set on the matching incoming dial peer on the CME.

the only thing now is that if I use g729 for the call from A to B, if the phone in site B don't answer, it can't reach voice mail as CUE only supports g711. I need to create a transcoder on the CME to handle that..

any idea on the real effect of the codec setting on the Outbound faststart and how does it affect the codec setting on the Reigon??


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