CCME support for G.729

[rafacampos]

Hi. I have two 3725 routers connected through a VPN. One of them (RA) is running CCME 3.1, the other one (RB) is connected to a Nortel PBX via a T1 CAS interface.

When I place a call from an IP Phone registered to CCME in RA to a phone in the PBX connected to RB, the call is set up via Skinny between the IP Phone and RA, and then via H.323 between RA and RB. The codec used is G.729 (I sniffed the packets and noticed it).

However, I was told by Cisco than the current version of CCME only supports G.711.

It seems to me that I was misinformed. If this is true, how can I specify the codec I want to use? Does the voice comes compressed from the IP Phone? Or is the router doing transcoding?

[anup.anand]

I have seen the same behaviour. Well, CCME does not do transcoding. In this case, what happens is that the routers will negotiate G729 via H323 and CME would instruct IP Phones to use G729 for that call. Since the IP Phones also support G729, everything works fine.

You cannot change the codec used by the CME IP Phones when they talk to each other, or then they dial the PSTN using the CME Router as the PSTN gateway.

Regards,

Anup

[rafacampos]

Thank you Anup,

It's fine, I only need G.729 for calls placed over the VPN, in order to save bandwidth and to improve voice quality.

By the way, I'm experiencing some voice quality issues (jitter, choppyness, distortion) in this same scenario. I configured both routers with LLQ. Does anyone have any further suggestions to improve voice quality?

Thanks,

Rafa

[thisisshanky]

What type of internet connection do you have on either ends ?? (as its a VPN)..Once the packet leaves your router, there is no guarantee on bandwidth allocation/delay for your voice packets. What is the RTT for ping response between the two routers ??