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Codec2 — an Open Source, Low-Bandwidth Voice Codec

Posted by Soulskill on from the sound-of-efficiency dept.

Bruce Perens writes "Codec2 is an Open Source digital voice codec for low-bandwidth applications, in its first Alpha release. Currently it can encode 3.75 seconds of clear speech in 1050 bytes, and there are opportunities to code in additional compression that will further reduce its bandwidth. The main developer is David Rowe, who also worked on Speex. Originally designed for Amateur Radio, both via sound-card software modems on HF radio and as an alternative to the proprietary voice codec presently used in D-STAR, the codec is probably also useful for telephony at a fraction of current bandwidths. The algorithm is based on papers from the 1980s, and is intended to be unencumbered by valid unexpired patent claims. The license is LGPL2. The project is seeking developers for testing in applications, algorithmic improvement, conversion to fixed-point, and coding to be more suitable for embedded systems."

3 of 179 comments (clear)

  1. Original Rationale by Bruce+Perens · · Score: 5, Informative

    The original rationale for Codec2 is at Codec2.org. I've been promoting this issue for about four years, as I was bothered by the proprietary nature of the AMBE codec in D-STAR. But I didn't have the math, etc., to do the work myself. It was really fortunate that David became motivated to do the work without charge. He has a Ph.D. in voice coding. By the way, look over his web site rowetel.com for the other work he's done: two really nice Open Hardware projects - a PBX and a mesh telephony device, an Open Source echo canceler for digital telephony, used in Asterisk and elsewhere, and his own electric car conversion. He'd be my nomination for the MacArthur grant.

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    Bruce Perens.
    1. Re:Original Rationale by jmv · · Score: 5, Informative

      The fundamental difference is not that much the lossless vs lossy transmission, but the actual bit-rate. I designed Speex with a "sweet spot" around 16 kb/s, whereas David designed codec for a sweet spot around 2.4 kb/s. Speex does have a 2.4 kb/s mode, but the quality isn't even close to what David was able to achieve with codec2.

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      Opus: the Swiss army knife of audio codec
  2. Re:Mumble integration ? by Inda · · Score: 5, Insightful

    Is this really Slashdot? Do I have a DNS error?

    These are the stories I used to enjoy. I don't realy understand them, but they make a good read.

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    This post contains benzene, nitrosamines, formaldehyde and hydrogen cyanide.