On Codecs and High-Definition VoIP

Lately, there's been a lot of buzz in the VoIP community about high-definition telephony. The first time we heard about it, we all raised our eyebrows since high-definition is a term that gets overused in technology. But we're open-minded geeks, so we tried it...and it's really, really cool. The audio has so little distortion compared to a traditional telephony call that it's slightly unnerving at first because the vocal clarity approaches stereo quality. So what is it? High-definition telephony comes down to the G.722 codec. In pragmatic terms, the codec is responsible for the compression and decompression of the media stream (i.e., your voice) that comprises a VoIP phone call. One of the first things a SIP phone does when it talks to a SIP proxy is to negotiate which codecs both support so that when the media stream comes, it is compressed and decompressed at the same rate and overhead. G.722 is one of the most efficient codecs out there, so it does a very good job. Voila, high-definition. (For more information on codecs, Voip-Info has a thorough list.) The OnSIP Hosted PBX already has high-definition functionality for extension-to-extension dialing. Both parties will need a phone that supports G.722, such as the Polycom IP 560 or the SNOM 320. (Please note, the Grandstream 2000 has support for G.722, but it's problematic.) But we won't stop there, of course - we're currently testing moving some of our other applications to high-definition. We'll announce their launch in this blog, so stay tuned!