VoIP And Codecs

I received a question via email that was roughly as follows: “I currently use Vonage VOIP to provide voice and fax lines to remote construction sites via VSAT satellites. The problem is that each port requires a lot of bandwidth (90 kbps). Is there a solution that would require much less bandwidth (@20 kbps) per voice line?”

To which I responded by explaining what codecs are. Codec stands for coder and decoder. It is a method to take your audio or video stream and encode it in a specific format…avi, mp3, etc. When talking about our VoIP codecs there really are only a handful to choose from.

In the above case, a lot of devices run on G.711, which is the default standard for many VoIP systems (Cisco, Vonage). My suggestion was to run a codec that is leaner, like G.729 which will get you around the 20Kb mark. I then found a handy forum post that shows you how change Vonage between it’s 3 available codecs…one of which is G.729 😉

Cisco has a concept of locations. You can specify what protocol is used between locations. For example, you can use 711 inside the company and if you want to go to the remote location, you will use the 729 codec. Pretty nifty. If you need to transcode between one codec and another, be sure you have some available DSP resources, though 🙂