Does any one use or evaluate the free speech coder --speex? How about the quality compared to G.729 ? Is it really patent free? It seems to me that the Line Spectral Frequence (LSF) was patented by NTT. The LSF is another representation of linear prediction coefficient (LPC) for effcient quatization.
Speex uses almost the same algrithm as G.723.1. Someone says that it is because the guy is from the Lab. AFAIK it's patent free. When in the same rate, not much different among G.729 or G.723.1, they all use acelp(723 5.3k).
