Post : The Cacophony of Digital Voice Continues (Part 2)
URL : http://www.k0nr.com/wordpress/2016/1...tinues-part-2/
Posted : November 3, 2016 at 12:00 pm
Author : Bob K0NR
Categories : DMR

http://www.k0nr.com/wordpress/wp-con...l-transmission
..png This post is a continuation of The Cacophony of Digital Voice Continues
(Part 1) (
http://www.k0nr.com/wordpress/2016/1...ontinues-part-
1/ ) , so you probably should read that one first.

All of the popular amateur digital voice (DV) systems (D-STAR (
https://en.wikipedia.org/wiki/D-STAR ) , DMR (
https://en.wikipedia.org/wiki/Digital_mobile_radio ) and YSF (
http://www.yaesu.com/pdf/System_Fusion_text.pdf ) ) use the AMBE vocoder (
https://en.wikipedia.org/wiki/Vocoder ) (voice codec) technology. This
technology was developed by Digital Voice Systems, Inc. (
http://www.dvsinc.com/papers/iambe.htm ) and is proprietary technology
covered by various patents. The use of proprietary technology on the ham
bands causes some folks to get worked up about it, especially proponents of
an open source world. See my blog posting: Digital Voice at Pacificon (
http://www.k0nr.com/wordpress/2013/1...-at-pacificon/ ) and this
presentation by Bruce Parens K6BP: AMBE Exposed (
http://www.qsl.net/kb9mwr/projects/d...BE_Exposed.pdf ) . Codec2 (
http://www.rowetel.com/?page_id=452 ) is an alternative open voice codec
developed by David Rowe, VK5DGR. David is doing some excellent work in this
space, which has already produced an open codec that is being used on the ham
bands. FreeDV ( http://www.freedv.org ) is an umbrella term for this open
codec work. Here's a recent video of a presentation on FreeDV (
https://www.youtube.com/watch?v=nAJ9s2Di084 ) by VK5DGR.

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