I recently wondered why we are still using narrow band speech codecs for VoIP calls between two SIP devices. There were a number of interesting answers and as always the issue is multi-faceted. However, it seems that wideband codec capable devices are now appearing on the market and SIP phones such as the Siemens Gigaset 6XX are actually advertised with superior voice quality between two 'High Definition Sound Performance' (HDSP) phones these days. Here's a link to a web page that demonstrates the difference between today's voice quality and the wideband codec used by Siemens.
While it is difficult (but not impossible) to introduce wideband codecs in fixed and wireless circuit switched networks (e.g. due to the required tandem/transcoder free operation) things are pretty much straight forward in IP based networks. Here, devices negotiate the speech codec to be used directly and no interworking-, transcoding- and digitizing functions are required beyond the user's device that would force the use of a specific speech codec.
Let's hope we don't have to go through many years of fragmentation
where each vendor implements his own set of wideband codecs,
incompatible with those of the competition. But in the end I can very well imagine that wideband
codecs are the missing piece to bring a real breakthrough for
VoIP. So far, VoIP offers little to nothing beyond circuit switched telephony to the average user. With wideband codecs, however, I am sure most people will start convincing others to switch once they've been on a wideband conversation with someone.
For true success, an important additional requirement is that VoIP providers connect their registrar servers with each other to avoid the call being routed into the circuit switched national network first before being thrown back into the VoIP domain. When this happens, there is no transparent VoIP connection in place and consequently the smallest common denomitator, today's G.711 narrow band voice codec, is used for the call.
Well, maybe it's not so straight forward after all… As always, theory and practice…