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Surfin’: Developing New Digital Voice Software


By Stan Horzepa, WA1LOU
Contributing Editor

This week, Surfin’ looks at the results of one year of codesmithing on the digital voice front.

One year ago, David Rowe, VK5DGR, decided to begin work on a free, low bit rate speech codec with an initial target of communications quality speech at 2400 bit/s.

One year later, David announced the Version 0.1 alpha release: “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. It fills a gap in open source, free-as-in-speech voice codecs beneath 5000 bit/s. It is released under the GNU Lesser General Public License (LGPL).”

V0.1 alpha is a fully functional 2550 bit/s codec (51 bits/frame at a 20-ms frame rate). Visit the David’s Codec 2 Web page to download the software and learn more -- including how it works.

According to digital voice expert Mel Whitten, K0PFX, in TAPR’s Packet Status Register, “Codec2 will fill the need for a low bit rate speech codec with an open source codec for HF/VHF DV applications. David’s goal is to provide a codec with speech quality performance between LPC and MELP/AMBE without infringing upon any of their patents. A challenging task, to say the least, but David believes it is doable.”

Mel, myself and the ham radio digital voice community wish David the best of luck in succeeding.

Until next time, keep on surfin’!

Editor’s note: Stan Horzepa, WA1LOU, prefers his digital voice over his analog voice. To contact Stan, send him e-mail or add comments to his blog.



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