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Question about transcoding


Hi there,

I have a question about transcoding on a callmanager express...

I try to build a situation with normal cisco sccp phones and sip phones..

The thing is..that the sip phones are going to use the codec G729 because of the smaller bandwith..

However...i configured transcoding on the cme,this is up and running but still i cannot call between cisco phone and sip phone..

Is it only possible to trancode between phones and gateways or sip trunks? and this situation not working for sip phones to sccp phones with different codecs?

And is there some other configure this?? so that the sip phones can use codec G729 and the sccp phones G711ulaw...????


1 Reply 1


When you configure a trunk or third-party phone to use the SIP protocol and Media Termination Point Required is enabled, Cisco Unified CallManager Administration only allows you to choose a G.711 codec in the MTP Preferred Originating Codec field. When you assign the SIP trunk or third-party SIP phone with the MTP required option enabled to the device pool for that region, you must verify that the region relationship between the SIP device and the MTP device is configured to use a codec with equal or greater bandwidth (G.711 or Wideband codec). MTP is not supported on SIP trunk while using codec g729.

SIP Trunk using G711 works with and without MTP

SIP Trunk using G729 works without MTP

SIP Trunk using G729 does not work with MTP enabled, even with transcoders.

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