G.711 or G.729

[graydon]

Good Afternoon,

Will I notice a difference in call quality if I use G.711 instead of G.729. I know it is lighter compression, but will it help with volume and echo issues?

Thanks

[fbadr]

Hi

well you will definitly notice a difference in quality using G711 but the only issue is you need higher bandwidth as G711 need around 64k for each call

Fadi

[Chris Deren]

The difference is not that significant for g711 the advertised MOS score is 4.1 for g729 it is 3.92 (4.0 is toll quality). The bandwidth consumption is around 87kbps per call leg over ethernet (layer 2) for g711, compared to 31kbps for g729. The best practice is to use g711 in your LAN and g729 in WAN. Keep in mind that g711 uses CPU and memory intensive algorithm to digitize the signal, so it puts a lot of stress on your router. Hope this helps.

[teodorgeorgiev]

I doubt that if you switch to G711, the echo issue will disappear. Better try to fix it with the echo-cancellation command on the voice port.

And to improve the quality a bit, try disabling VAD.

[graydon]

Thanks for the tip. I'll give it a shot.

[p.sylvester]

hi,

if we need a good voice quality, we need round trip delay 400ms, anything about 500ms is not at all acceptable.

take example between US and India. 350ms is the delay for intnet, the protocols we use will add addtional delay on 75ms on both ends "codec add addtional burden 75 ms onboth end" (because of compression and de-compression)

g729 takes up 14.3 kbps bandwidth,result voice being segmented in 30 byte payload (over head can chew up bandwidth)

G711 which operates at 64 kbps (std)

Voice quality is determined primarily by three major factors:- delay, packet loss, and jitter. That is, the lower the delay, the less the packet loss and the smaller the jitter, and the better the voice quality. The low delay, packet loss and jitter simply requires sufficient Internet bandwidth between the originating and destination gateways.

[teodorgeorgiev]

Hi Prasanth,

your words are true, however from my personal experience, jitter problem is worse than high delay on the link. The UN troops in Eritrea and Afganistan, in example, have installed IP telephony over frame-relay via satellite dishes. Two way satellite link has in ideal 600ms delay. However since the channel is 100% dedicated with good QoS policy implemented (frame-relay, as I said), the quality of the conversation is fair good.

Trust me, I would prefer to speak via two way satellite link, but 100% dedicated, rather than via 150ms fiber line with a lot of jitter on it.

[ilkeryilmaz]

Yes you're right, during jitter and packet loss over 150msec i choose satellite backup with 600 msec. We're a voip carrier and that means dead end when experiencing packet loss + jitter :) 600 msec works fine with two-way and dedicated clear line. Further, even asynchronous ip traffic is more applicable during packet loss. You may prepend to your outgoing fiber line and use satellite one-way link when ip packets coming back.