brainwagon

This month’s QST had a pointer to a potentially interesting voice codec that I hadn’t seen before. It appears that Broadcom has developed a voice codec, and released it under the terms of the GPL for royalty-free use. It’s actually two codecs: one at 32kbps, and the other at only 16kbps. I haven’t done much reading on them yet, but there are certainly a number of possible applications that I can think of where having open codecs like this would be useful. Unfortunately, we probably need a codec with a data rate more down in the 2400 baud range to make digital voice on VHF comparable to DStar, but it’s still interesting.

Check out the links:

Broadcom.com – BroadVoice® Speech Codec Open Source C Code.

Addendum: In listening to the voice samples, I must say that they seem quite good, although not perhaps any better than the already free Speex based codecs. It’d be interesting to do an apples/apples comparison of the two, but look at these Speex encoded examples which sound very good at approximately half the bitrates of the BroadVoice codecs.

Addendum²: K3NG mentions the “white elephant in the room” with respect to D-Star: namely that it uses a proprietary codec. I must admit that I’d probably own a D-Star radio if the speech codecs were open. I find it really annoying when amateur radio adopts techniques which are covered by patents: they serve only to protect business interests, and to discourage free experimentation and deployment of new radio techniques. If D-Star used a freely available audio codec, there would be less to keep other manufacturers from supplying compatible radios (they wouldn’t need to license technology or single source chips from a single manufacturer) and there would be a great deal more experimentation (echolink->D-Star gateways anyone?). As cool as D-Star is, I can’t help but think that we are sending the wrong message to equipment manufacturers by adopting them widely.