rdahl

Can anyone tell me which compression mode in the VoIP tab under line comfiguration gives the best call quality? Seems like there are so many to choose from. I currently have a T-1 frame-relay connection and it seems to be somewhat quiet between VoIP lines. I currently have the compression mode set to automatic.

Thanks,

Rich

lmonzon

The best quality is provided using G711 but it takes 64K of your bandwidth so i suggest u use G729 simple.

PBXtech.info

 

sizbut

In Auto mode the IP Office tries to negotiate 729, then 723 and finally 711.

And that's a pretty good indication of the quality divided by bandwidth performance of each. Thinks G711 = CD, 729 = FM radio, 723 = AM radio - each on its days can be perfect but each is increasingly prone to potential probelms.

G729 gives better quality than G723 for not much bandwidth difference. For example on Ethernet 30Kbps versus 21Kbps (that may seems a big difference but not against full quality G711 at 86Kbps).

Over G723, G729 has better sound quality and a shorter conversion delay (40ms vs 80ms) which can be a factor since total latency becomes apparent to callers at 150ms.

Cephas

Another consideration is whether you have IP hardphones on any of your systems. If you do, or might in the future, I urge you to ensure the same codec will be used across the board. Since IP hardphones support only a small sample of the codecs the IPO offers, choose accordingly. Ie don't pick G.729 simple, but rather go for G.729(a)

Or G.711 if you can afford the bandwidth on your WAN :-)

Peter