What audio codec you using in multi-site deploiment?

[Timur Karimov]

Hi all!

For one site we have simple answer on this question - G.711 a or u-law. But for multi-site deployment where media gateway can place on diferent site rafer then contact centre operators - what codecs r u using guys ? My point, what g.711 it's a not goog solution for throw it in a VPN or  leased line to remote location? We test g.723, GSM, g.729 and found what only g.729 bring to us good voice quality. But for g.729 we have not good situation with license restriction.  Is anynody try G.729? What phone - soft or hard u using for operators ?
Any other advice ?


WBR Timur.

[Steve]

Timur, we use G.729 to our agents, who all have Nortel i2002 turrets.

Whilst G.729 saves on bandwidth, it is not without issue.

Some of the issues are -
Outbound in ASM mode, where the outward leg is G.711 but we need to transcode to G.729 for the agent leg. We also have to stop the Agents cannot transfer calls back into the GVP platform, to transfer to a different service line.
If calls start on net as G.729 they have to be transcoded to G.711 for GVP and then back to G.729 for the agent, this results in poor voice quality.

[cavagnaro]

I will have to raise my hand here.
G711 is like a TDM voice, almost no compression and ideal for voice analyzis (VAD).
G729 and G723 will add compression, however, it is not as easy as select which one has better results than the other. If it is true that both codecs differ mainly on which one has more compression than the other, there are other differences as for example how long will it take for a package to be transmitted, the delay allowed, retransmission, and more. If G729 is working fine even when it consumes more bandwidth than G723 is maybe because your link has a lot of delay, and as G729 transmits packets slower than G723 will work fine and G723 will fail because it requires by default a high speed link. However this doesn't means that G723 is not able to work, with some adjustments on the codec you will be able to handle it. This is why I always recommend to go with the hand of a network guy and analyze the network before a complete deployment, why is it slow? retransmition packets? dead packets? Many possibilities that in a long term may end affecting seriously the performance of the solution.
So, to end, if you want to select which codec is good for your multienviroment, take a moment to analyze the network and point possible points of failure.

Regards