Trusted Relay Point and Transcoder.

[markbatts]

We have a setup here where we use Software IOS MTP's for IP communicators.We have two IOS MTP's one for g711 and one for g729.

It works but we have an issue when we want to call from one site to another which would normally use the g729 , but  the device we're calling is Meeting place that only supports g711.

The call hits the g729 MTP and then originates out to meeting place but then fails because it won't allow g711 , which is what I would expect , however I'm surprised that an additional transcoder is not inserted into the stream to deal with this as they are available on both side.

My question is can you have multiple MTP's inserted into an RTP stream when its all on the same cluster?

[Chris Deren]

CUCM is not intelligent enough to allocate specific MTP with specific codec if both are in the same MRG, so having MTPs with different codecs assigned to common MRGs is normally not a good idea.  You will need to have a transcoder available to bridge calls with different codecs including MTP call legs.  And yes, you could have multiple MTPs in the same RTP stream.

[markbatts]

Thanks for the reply Chris, yep I have the different MTP's in different MRG's as I was aware of this as an issue.

I guess you have answered my main question of can I have additional MTP's in the stream which I thought would be possible.

Do the MTP's need to be assigned to a MRGL which contains transcoders for this to work , or is it ok for just the endpoints to have access to them?

[Chris Deren · Accepted solution]

It depends on the call flow, and what device needs to engage the transcoder, you will need to make sure the MRGL assigned to the device pool used by MTPs has transcoders in it in case MTPs need to trigger the transcoder.

[markbatts · Accepted solution]

actually , that was a stupid question from my behalf. :-) sorry I knew that already but I think you may have helped me find the issue as it looks like the MTP's do not have access to a XCDer so updating that should hopefully fix it.