Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Cucm MTP and transcoder


I been reading cisco documents about mtp on call manager and transcoder with mtp.  My understanding that mtp is run on call manager to have different devices codecs such as g711 and g729 deceives communicate with other. Also a transcoder is hardware with dsp and mtp if I'm wrong please correct me. Would anyone be able to give me an example of when mtp on a call manager is used and how it works as well as an example of how a transcoder with mtp is used and what devices might use this?


Cisco Employee

Cucm MTP and transcoder


Just go through once this thread  and SRND it will help

let me know if you have any question further.


Please rate all useful post.

Br, Nadeem Please rate all useful post.
New Member

Cucm MTP and transcoder

Hello Ahmed,

I read those two documents you mention before I posted this discussion and I'm a bit still confuse.  What devices use mtp and how does mtp work. Like if you give an example with call manager running mtp which has conference call involved it would make more sense?


Cisco Employee

Re: Cucm MTP and transcoder

Hi Horacio,

MTP can be allocated by configuration or dynamically. When "MTP required" is checked for SIP or H.323 endpoint, a MTP will be allocated for the SIP or H.323 endpoint. MTP may also be allocated due to DTMF profile mismatched between two endpoints, or due to transcoding need, or due to v4/v6 address translation need.

To make a call between two devices that are using a low bit rate code (such as G.729 and G.723) that do not support the same codec, you need a transcoder resource. Assume that Cisco CallManager has been configured such that the codec between Region-A and Region-B is G.729. The following scenarios apply:

* If caller on Phone A initiates a call, Cisco CallManager realizes it is a Cisco IP Phone 7960, which supports G.729. After the digits have been collected, the Cisco CallManager determines that the call is destined for User D who is in Region-B. Because the destination device also supports G.729, the call gets set up, and the audio flows directly between Phone A and Phone D.

* If a caller on Phone B, who suppose has a Cisco IP Phone 12SP+, initiates a call to Phone D, this time the Cisco CallManager would realize that the originating phone only supports G.723 or G.711. Cisco CallManager would need to allocate a transcoding resource so audio would flow as G.711 between Phone B and the transcoder but as G.729 between the transcoder and Phone D. If no transcoder were available, Phone D would ring, but as soon as the call was answered, the call would disconnect.

* If a user on Phone B calls Phone F, which is a Cisco IP Phone 12SP+, the two phones would actually use G.723, even though G.729 is configured as the codec to use between the regions. G.723 gets used because both endpoints support it, and it uses less bandwidth than G.729.



CreatePlease login to create content