G.711 -> G.729

[brewerdude]

We're looking to implement G.729 for voice calls on a MPLS WAN link we have between two offices (it's currently running G.711)

Was wondering if anyone had any comments on the voice quality between the two, and if we what we could expect to hear from our users once we make the switch (if anything at all)

 

[ptdog]

You will not have a problem with doing this at all. It is done all the time. Whether you will need a transcoder is up to your environments and if you have end points that can only G711. If it is between ip phones, you can just use Regions. Between Cisco gateways and IP Phones, it is a matter of regions and possibly using voice class codecs to specify the preferred codecs.

We use G729 here across MPLS and it is fine. MOS scores are 3.7 and 3.6 consistently. QOS is a must so you must mark things to get them to the correct queues your carrier will give you.

 

[brewerdude]

We have MGCP gateways on both ends (going into Nortel PBX's). They'll be running over an MPLS network with QOS enabled for voice.

 

[HmmG3]

We do it all the time for our overseas offices and N. America field offices. Some users notice it and say it kind of sounds like a cell phone, but most don't notice it. However, you should try to avoid putting music on hold over it. G.729 was designed for speech, not music so MoH will sound really bad.

 

[brewerdude]

I did actually do a test with the MOH. It was actually OK. It's mostly somone speaking with a little bit of music in the background.

 

[whykap]

So Nortel supports MGCP? You mentioned Nortel PBX on both ends so there must be no call manager in the picture.

 

[brewerdude]

They are Cisco MGCP gateways that connect to legacy Nortel PBX's. The calls route from the nortel to gateway to gateway to Nortel.

There is definitely a call manager involved for the routing from gateway to gateway.