The folks at Compandent have this to say about their product: Compandent’s ComPacketer is a voice coder which achieves a breakthrough in quality/bit rate/complexity tradeoff. Compandent’s novel technology, the ComPacketer that operates at 2.8 kb/s, produces speech with quality which exceeds that of ITU-T G.723.1 at 6.3 kb/s. Using the ComPacketer, only graceful degradation is introduced in frame erasure environment, as compared to the higher quality degradation introduces by the common standards used for VoIP.

http://www.compandent.com/products_compacketer.htm