Codec 2 - Open Source Speech Coding at 2400 bit/s and Below - David Rowe

Codec2 is an open source low bit rate speech codec designed for communications quality speech at around 2400 bit/s. Applications include low bandwidth HF/VHF digital radio and VOIP trunking. Codec 2 operating at 2000 bit/s can send 32 phone calls using the bandwidth required for one 64 kbit/s uncompressed phone call. It fills a gap in open source, free-as-in-speech voice codecs beneath 5000 bit/s and is released under the GNU Lesser General Public License (LGPL).

• Category

  Science & Technology

[Mike Trieu]

Awesome development! These are heady times for open source and I feel so fortunate to be alive in it. It's a shame the video got truncated so early, but I feel I got the gist out of it, regardless =)

[overand]

Love it. Really hope the codec2 site improves a bit - I'll be *very* happy if this gains traction.

[Sterling Coffey]

This is pretty bloody awesome. I don't watch many videos over 7 minutes. I can't wait to get this on the ham bands...I moreover can't wait to learn how to program.

[Bruce Perens]

Follow our progress at Codec2.org

[Bruce Perens]

8100 Hz, not KHz.

[Bruce Perens]

8 KHz is more than twice the telephone-quality speech band that is actually encoded, so we're sure we're getting all of the sound. It turns out that in practice we generally do convert up to 48 KHz, but only because many PC sound cards and AC97-derived embedded sound chips work correctly at 48 KHz and don't work correctly at other clock rates. We found one that clocked at 8100 KHz when we told it 8 KHz, etc.

[TimmmmCam]

Good work. Why is it 8 kHz when it is model based though? You could use 48 kHz with no cost right (apart from maybe processing cost)?