I've been trying to decide which codec I want to run my VoIP system off.  There seem to be two that are the most popular.  The G.729 codec is certainly very appealing as far as bandwidth is concerned - it runs at only 8 kilobits - that's kilobits, not kilobytes! - per second.  It does have some limitations, however.

Asterisk servers have a nifty feature that lets me download recordings of voicemail in *.wav format.  I decided to call my voicemail a few different ways so that I could compare.


The first limitation with G.729 that comes to mind is quality.  There is a noticeable quality difference between it and G.711.  The second limitation has to do with processing power.  That much compression is apparently rather processor intensive, and interestingly enough, not all two-line VoIP adapters can handle a G.729 conversation on each line.  The PAP2T cannot; I am told the SPA2102 can.  Here's an example of a call I made with the G.729 codec.

As a benchmark, I decided to make a recording of me talking on an analog phone, and here it is.

The G.711 codec uses more bandwidth than the G.729 - 64kbits/sec or 8kbytes/sec.  But just listen to the quality!  Here's the G.711 codec recording.  It sounds even better than the analog phone line!!!

Personally, with only six phone lines on a 10Mbit/1Mbit connection, I have bandwidth to spare, so I'll be opting for G.711.  G.729 does appear to be a workable alternative though.

For more information about these codecs, there is a Wikipedia article on G.729 and also a Wikipedia article on G.711.