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New Member

Unity G729a vs G711 Questions?

Current Setup:

Call Manager (3.1.2c): Mix of G729 and G711 regions

Unity (3.1.3): G729a support enabled in Registry – G711 is used for prompts and recording format

Is enabling G729a support in Unity required in order for a G729 call to get through to Unity?

Since we’ve had some complaints re: garbled prompts and/or recordings especially on incoming calls from outside, we are thinking about installing the G729a prompts.

If we do so:

Will the users have to re-record their greetings and names for quality purposes?

What will happen for G711 calls into Unity, will they be garbled?

Do we have to change the recording format to G729a when we change the prompts?

We were looking at changing the recording format to GSM 6.10 in order to support unity message playback on IPAQs, where does this fit into the above?

Thanks in advance,


Cisco Employee

Re: Unity G729a vs G711 Questions?

Yes, the G729a codec must be installed and the support enabled in the registry or Unity will not indicate a 729a call will be accepted when it attempts to connect to our port. In later versions of the TSP that comes with 3.1(5) and later the 729a support is on by default (without the need for the registry key) but you can still force it to not accept 729a calls at all by putting the key in there with a "0".

Unity will transcode from 711 to 729a or vice versa as necessary depending on the format of the file being played (prompt, greeting, voice name, message) and the connection type established with the call. This isn't normally the source of garbled playback reports, however - it does chew a vew CPU cycles (though not that bad) - installing the 729a prompts will prevent the ranscoding from having to be done.

So no, users will not have to rerecord their greetings and voice names, the proper format will be played out as needed. No, the messages should not be garbled (I suspect other issues are at play here).

Changing the recording format to GSM will result in _all_ recordings being in that format regardless... again, though, Unity will transcode into the proper format of all files during playback depending on the codec established by the incoming call. Same deal with recordings - it'll be transcoded from 711/729a to GSM on the fly. It chews a few CPU cycles and you get some quality loss but not significant on either count.


Re: Unity G729a vs G711 Questions?

What kind of gateway do you have? You might be running into CSCea35850.

Check out the workarounds...

Hope this helps,


New Member

Re: Unity G729a vs G711 Questions?

Thanks for the replies.

We have 6608s as gateways. A couple of followup questions:

Do you know if the Engineering special for the 6608 is available for download on CCO or only via TAC?

Are the G729a prompts the ones recommended for use in a mix environment (G711 & G729)? or depending on amount of Xcoding being done? I am trying to decide whether to convert to G729a prompts or keep them G711.



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