IP phones in g728 region

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Jul 11th, 2007
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This is not for a production design, just want to verify some concepts.

If the codec between region is G.728, do we need transcoder dsp for the calls between the region?

Have anybody tried this? We did test with phones in G728 region and calls are ok without transcoder, but phone shows g729. How to expain this?

1. does it still use G729? call manager jsut ignore G728 region and use g729?

2. or call actually does use g728 but shows g729?

I think 1 is the result. But any thoughts from you guys?

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Overall Rating: 5 (1 ratings)
Brandon Buffin Wed, 07/11/2007 - 08:11
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When you set the codec for a region, you are not setting the only codec that can be used. You are setting the maximum codec that can be used. Since Cisco phones do not support g.728, the phones are negotiating and using a lower supported codec, g.729.

Hope this helps. If so, please rate the post.


AJAZ NAWAZ Wed, 07/11/2007 - 08:48
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That's right. Just for the sake of completeness the other codec supported by Cisco IP phones is G711.

ciscoforum Wed, 07/11/2007 - 09:44
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Thanks guys. this is really good information to me.

Got one more question:

If that's the case, I have one real scenario: my customer is running g726 for this: pbx-PRI-r0-g726(IP)-r1-PRI-PBX. They will integrate CCM into it with IP Phones.I do not see ccm supports g726. With your concept, can I make IP phones talk to PBX phone? CCM will use H323 to PBX gw. Thanks

mchandak Wed, 07/11/2007 - 09:50
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If CM is connected to the 3rd Party PBX with a PRI in between, you dont need to do anything as long as the Router to which the PRI is connected is talking to the CM using G729/G711. If the 3rd Party PBX is connected to the CM through IP ONLY, then you will need a transcoder here.

Brandon Buffin Wed, 07/11/2007 - 09:50
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If the PBX speaks only g.726, you will need a transcoder to translate between g.726 and g.711/g.729.

Hope this helps.



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