VoIP codecs Day Four: Does VoIP sound bad?

Adam Turner asks the question most VoIP sceptics want answered as we continue our look at VoIP codecs.

PREVIOUSLY: Low bandwidth codecs

People have very low expectations when it comes to VoIP and therefore tend to accept poor call quality, but even highly compressed codecs such as G.729 can offer very good results, says Steve Ikeda - chief technology officer of consumer grade VoIP provider engin.

"G.729 is rated a bit lower than G.711 but, thanks to some of the configuration we've done with engin, it's ironic that a good majority of our customers at one point rated us as better than PSTN quality. This makes some sense because over PSTN you're also introducing a lot of line noise and other factors with the copper pair," Ikeda says.

engin also supports G.711, G.726 and a few other codecs, but the service defaults to G.729.

"We tend to suggest sticking with G.729 because of the bandwidth requirements but users can ask to try G.711. If their VoIP device is configured for G.711 then our system will talk G.711 back to it," Ikeda says.

"Still, we would only recommend G.711 if a users complained about G.729."

For organisations running their own internal VoIP service, Ikeda recommends looking for an IP PABX with the ability to switch codecs to allow for different conditions, such as network conditions or long haul links between offices. Features such as silence suppression and echo cancelation can also improve call quality.

Organisations shouldn't be afraid to look beyond G.711 and G.729 to explore different codecs, says James Spenceley - chief technology officer of business grade VoIP provider ISPhone.

"People often go to the extremes of trying to running G.711 over a link that's not up to the job, or else they automatically choose a low grade codec - because it's VoIP and they think it's supposed to be poor quality. They think you're supposed to cram as many channels down the pipe as you can and often don't realise VoIP can be better than your PSTN at home."

NEXT: VoIP - Better than PSTN?


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