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

Project: Codec 2

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).

Speex and the other open video and audio codecs have proven it’s possible to create a patent free, high quality codec. There is an important social theme behind these technical projects. A free codec helps a large amount of people and promotes development and innovation. A closed codec helps a small number people make money at the expense of stifled business and technical development for the majority.

One important part of Codec 2 is the use of open source and community development techniques. The net result was access to a world wide "brains trust" and network of beta testers that has resulted in swift development of effective DSP algorithms.

This presentation will explain the advanced DSP techniques used in Codec 2 in terms the average Linux user can understand, plus give examples of end user applications.

David Rowe

David Rowe has 20 years experience in the development of DSP-based telephony and sat-com hardware/software. In January 2006 he quit corporate life as an Engineering Manager to become an open source developer. He now develops open telephony hardware and software full time. He likes to build advanced telephony technology – then give it away. David has pioneered the field of open hardware and has built several open hardware products including the IP04 IP-PBX and the Mesh Potato (a mesh Wifi router with telephony). David also writes open source DSP code for echo cancellation (Oslec, included in the Linux kernel) and is developing a 2400 bit/s speech codec (Codec 2). David drives an Electric Car he built himself and is passionate about developing world telephony.