David Rowe is working on a very cool project that should be of interest to hams with an interest in digital communications. He’s creating an open source, low bit rate speech codec. His target is a usable 2400 bps codec that is free from patent issues, and that can be used in situations similar to the patented algorithm AMBE that is currently used in D-Star networks. He’s not quite at the point where he has a full codec yet, but he’s begun to make some code available that can encode and decode using his sinusoidal encoder. He’s also writing up a lot of the theory behind the encoder on his blog, which is frankly a bit beyond me, but not a huge amount beyond me, which means that it’s very interesting reading.
David has also done some very interesting VOIP work, including a high quality echo canceler. His blog is always worth reading.