Transcoding on Unity or DSPs: Best practice?

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Sep 6th, 2007
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unity 5.0 speaks G.729.

I implemented Unity 5.0 and use G729 over the WAN.

I use G711 for intra-calls.

What are the factors/numbers that determine whether to use Unity or DSP ressources to transcode?

If I choose Unity to do the transcoding, are there any constraints like:

Let Unity do transcoding is not possible with SCCP endpoints or sth like that?

Many thanks guys


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espereir Sat, 09/08/2007 - 23:38
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If Unity has the Enable G729 coded option enabled, Unity will either use G711 or 29 depending on the endpoint codec supported codecs and advertisement, that will be based on CCM regions and when CCM negotiates the codec, you will save some Xcode sessions on the DSPs, but you will increase the server load since it is doing transcoding.

It will work, as long as Unity only receives calls from those codecs, just make sure that Unity VM ports in CallManager has a region that specifies G711 within the Unity region and either 29 or 11 between the other regions.

Hope this helps!

gary.mattson Tue, 09/11/2007 - 08:44
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I find that voice quality can be hit or miss if using Unity's transcoding because CPU and memory competition can slow down the compression rate. Best practice for me is to either install with G.729 prompts or use hardware transcoders for your remote site calls (my preference if the bulk of users ar G.711). You only need the transcode resources at the site where Unity is installed.

hoschmid Tue, 09/11/2007 - 08:47
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hi guys,

thanks for your answers. If I really find out if there is a way to calculate the best deployment model, I let you know.


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