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Design Guide Recommendation for G.729 and Transcoding

The Unity 4.0 Design guide http://www.cisco.com/univercd/cc/td/doc/product/voice/c_unity/design/udg/udg_040.htm#1103357 has as a recommendation for installations utilizing mixed codecs to disable g.729a in Unity and utilize a hardware transcoder:

"If it is necessary to use G.729a over WAN connections or remote IPT sites, use Transcoders (Cisco hardware) to do the transcoding for Cisco Unity. In this circumstance, Cisco Unity should not have to do any transcoding whatsoever. Utilize other Cisco resources for codec such as transcoders and G.729a WAN partitions for Cisco CallManager servers"

I'm guessing this is primarily to reduce CPU utilization in larger implementations but my question is what is the best practice for ensuring the best voice quality for WAN deployments and what testing has been done of the scenarios with and without transcoders.

Thanks,

Chris

7 REPLIES
Gold

Re: Design Guide Recommendation for G.729 and Transcoding

CPU is one reason, silence detection doesn't work with g.729 either and some people like the sounds of hardware transcoded g.729 better than software. To me it sounds the same.

The largest deployment of Unity currently uses g.729 everywhere so it is definitely safe to run it without transcoders.

Thanks,

Keith

Community Member

Re: Design Guide Recommendation for G.729 and Transcoding

So Unity be set up to support g.729 only without transcoders?

Blue

Re: Design Guide Recommendation for G.729 and Transcoding

Unity will transcode on its own,,,,so how do you force it to use a hardware transcoder if you want to go that route?

Community Member

Re: Design Guide Recommendation for G.729 and Transcoding

Go to the Advanced Settings Tool for Unity, and change the Enable G.729a codec support to off, this forces Unity to only 'allow' G.711, which forces the call setup to pass through a hardware transcoder.

Cisco Employee

Re: Design Guide Recommendation for G.729 and Transcoding

Note, it seems that as of TSP 8.0(1), you need to reboot the Unity server to have this change take effect. Simply restarting the Unity software won't have the change take effect.

Blue

Re: Design Guide Recommendation for G.729 and Transcoding

So, let me make sure I understand this correctly. If I disable G.729 and a call comes over the WAN to Unity. The remote site is setup to talk to the region that Unity resides in using G.729. If the prompt was recorded using G.711 (the Unity server default prompts are G.711 because we selected G.711 in the setup) any calls to Unity from over the WAN should invoke the hardware transcoder assigned to the Unity Port MRGL?

Thanks,

Andy

Community Member

Re: Design Guide Recommendation for G.729 and Transcoding

Your Correct disable G729 on Unity under register to force to use G711. Basically you will then need to create a device pool and region called e.g. Unity on Callmanager and then make sure you have assigned them to your VM ports. You will need to have your regions set in a way that so that we can invoke the H/W transcoder from remote phones talking g729 over the WAN to central site (unity).

Please refer to the CIPT troubleshooting book on Transcoding if you have it, its got a great example. Otherwise let me know if it still does not make sense.

Ah yes once configured you will need to reboot unity, restart device pool and IP Voice media straming app services on all servers.

Cheers!

Yavuz

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