g729 vs g711 in ccx

[vatter]

I am working on installing CCX 8.5 standard edition. I use Verizon SIP trunk to connect to the PSTN.

Verizon supports either G729 or G711 codec. In order for my company to save Bandwidth and money, it is probably good idea to configure G729 but not sure what kind of issues we are going to encounter if we use G729 Codec? I know converting prompts to G729 is a pain.. other than that do you see any issue?

thanks,

[Steven Griffin]

I've setup over 30+ UCCX systems in the last four years.  I can say that I always prefer G.711 over G.729.  IVR prompts just sound horrible at G.729 whereas a live person is not as bad.  Thus, if you can have end-to-end G.711 calls on your contact center, that is the best way to go. 

However, since you are using a SIP trunk with UCCX you are going to need to run your calls through a transcoder anyway in order to handle DTMF.  Just increase the number of DSPs in your voice gateway(s) and transcode from G.729 to G.711 for the time the calls spends in the UCCX IVR Menu or Queue.  Once the calls get to agents they can be answered in G.729 and the transcoder will drop out of the call.

Just my two cents...

-Steven

[Jonathan Schulenberg · Accepted solution]

However, since you are using a SIP trunk with UCCX you are going to need to run your calls through a transcoder anyway in order to handle DTMF. 

I think an MTP handle RFC2833 to KPML conversion which can be done in CPU, not DSP.

Otherwise I agree that G.711 is easier. The biggest issue in my opinion is that you have to keep careful documentation on what each prompt actually says since you can't just play it back on your computer.

[Steven Griffin]

Jonathan,

True you can use an MTP but when using a SIP trunk from a carrier I've found hardware trancoders to provide the best results when it comes to UCCX. YMMV, but in my experience the DSPWare that runs the PVDM modules has tended to be more reliable than IOS.  If can use one codec (G.711 for instance) between UCCX and the SIP provider then setting up a transcoder for just the DTMF capture purpose isn't too expensive from a DSP perspective.

Also, if you want to play G.729 on your PC, look at Unity.  There is a G.729 codec for Windows you can install.  Look for sl_g729a_setup.exe on your Unity Install DVD.   This assumes you are licensed to run Unity.

-Steven

[vatter]

Thanks for your reply guys...

I have one CUBE router at my office here and this CUBE router handles calls to different locations.

I will probably will use G729.. Do you know how to convert G711 prompts to G729?

thanks,

[Steven Griffin · Accepted solution]

Transcoding prompts tends to insert unwanted pops and crackles into the audio file. Your best option is to record / re-record natively in the codec you want to use.  If you need to record or transcode, you can use the program I mentioned in my previous post.  Use MS Sound Recorder to save the prompt as G.729.  I've yet to find a professional audio software package that does a decent job of G.729. 

-Steven