Transcoding in a centeralized call processing enviroment

[ben]

Hello,

i have a VG200 with a DSP farm in it. i have configured the Call Manager with a Transcoder and have added it to the media list. but when calling between Regions it does not use the transcoder. I have followed all the directions i 've found on CCO. what am i missing? this is Call Manager 3.1.3a

[jpstott]

If you are calling between regions from an IP Phone to an IP Phone, then you do not need transcoding, as both G.711 and G.729 CODECs are built into the phones.

If you are calling from a region that is G.729 to an endpoint that only supports G.711 for instance, then you will need a Transcoder. Does the VG200 transcoder show up as registered to the Call Manager? If not, you may want to look at your configuration on the VG200 or in CCM.

[ben]

the VG200 does register with te call manager. it is the Media Resource Group but it still does not use it.

[gary.shaw]

But like John says, does it actually need to use it in your case?

Example One

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IP Phone A (Location - Central, Codec G.711) calls IP Phone B (Location - Branch, Codec G.729) a transcoding resource its not needed as the IP Phone can sort out the codec difference between themselves.

Example Two

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IP Phone A (Location - Central, Codec G.711) calls IP Phone B (Location - Branch, Codec G.729), but Phone B is on the phone and the call has to go to Unity Voicemail, by default Unity only understands G.711, so.. for the call to complete a transcoding resource must be used to handle the G.729 to G.711 conversion (A VG200 in your case).

Hope that helps

Gary

[kennethh]

HI,

How about the Unity Voicemail located at IP Phone A?? So VG200 should be located at IP Phone A, right??

1. What I mean is that IP Phone A(G.711) call IP Phone B(G.729) -->no problem(dont need VG200).

2. IP Phone B(G.729) want to reach Unity Voicemail that located in A. If you put VG200 at location B. So it will convert G.729 to G.711 at location B and then use G.711 to reach Voicemail. IT will take up a lot of bandwidth from B to A.

3. If put VG200 at location A, IP Phone B will use G.729 to reach location A(saving bandwidth). Then use VG200 at location A, then transcode to G.711 to reach voice mail.

AM I RIGHT??? please advise!!!

Ken

[gary.shaw]

Yes. :)

3. Is correct.

The transcoder gets used at the destination end, so the stream between location B to A is G.729, Phone A is diverted to Unity, CallManager detects a mismatch in codec's and uses a transcoding resource, the same G.729 stream from B is terminated into the local transcoder in location A.

Then the local transcoder at A sets up a second stream to Unity, but uses G.711 instead, it sits in the path until the call is complete.

Hope that makes more sense.

Gary