05-02-2011 08:07 AM - edited 03-16-2019 04:45 AM
05-05-2011 10:52 AM
Hi Javier! Looking at the issue you are encountering, I am wondering why you would not want the phones to negotiate a common codec. This is the default behavior in order to avoid using transcoding resources (which involve costly DSPs). At what point in your topology are you trying to use the transcoding? You could force your ephone's to use a specific codec on your CME, then force your dial-peers to and from CUCM to use a different codec. That would effectively force the use of transcoding, but I am still not sure what would be accomplished by doing this. On the CUCM side remember that the region settings do not specifically hard code codecs, as they do in CME/gateways. The region relationship settings allow CUCM to negotiate codecs down to the complexity chosen. CUCM will attempt to seek the highest bandwidth codec within the range but will allow lower bandwidth codecs to be used. For example if two regions are set to use G729, they will only be able to use G729 (nothing is lower). However if they are set to G711 they can negotiate G711 and G729, but G711 will be preferred. Therefore the best place to hard code your codecs would be on the gateway side of your configuration, because you have more options to hard set codec use.
So in the above mentioned idea of hard coding the ephones and dial-peers in the CME, you could force the use of transcoding. However, remember that your voice quality on a given call will only be as good as the worst quality leg of that call. So if you have one leg using a high quality codec and another using a low quality codec with transcoding inbetween your quality will only end up being perceived as being as good as the low quality leg. I hope this helps a bit.
If this answers the question, or if the problem has already been resolved, please mark it as such. That will avoid others on the forum from continuing to respond if it is no longer an issue for you. Thanks!
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