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<H1><FONT face=Verdana>WinDRM, <STRONG>DRMDV</STRONG> and
<STRONG>FDMDV</STRONG></FONT> sound card programs get codec change </H1>
<P><FONT face=Verdana>Several popular digital voice programs that were pulled
from distribution have returned with a different digital coding and decoding
scheme. This following major rewrites to avoid problems dealing with
intellectual property rights.</FONT></P>
<P><FONT face=Verdana>Amateur Radio Newsline's <STRONG>Gary Pearce,
KN4AQ</STRONG>, is in Cary, North Carolina, with the details:</FONT></P>
<P><FONT face=Verdana>Hams who tried to download any of the sound-card based
Digital Voice programs - <STRONG>WinDRM</STRONG>, <STRONG>DRMDV</STRONG> and
<STRONG>FDMDV</STRONG> - this past week, found them gone, as were the
Google-Groups message boards that supported them.</FONT></P>
<P><FONT face=Verdana>The problem was licensing, or lack of it, for the codec
that all the programs shared. That codec was developed for the US military and
NATO, but was never licensed for free distribution. Several companies shared the
intellectual property rights, and finally, one of them complained.</FONT></P>
<P><FONT face=Verdana>This caused a quick re-write of WinDRM and FDMDV with an
open-source codec. At air-time, the new version of FDMDV was available again at
the download site, N1SU dot COM, and WinDRM is expected to be back soon. DRMDV,
little used since FDMDV was developed, has been dropped.</FONT></P>
<P><FONT face=Verdana>Digital Voice users will need to download the new version
of FDMDV to maintain compatibility. </FONT></P>
<P><FONT face=Verdana>The new codec isn't quite as good as the old one, so audio
quality, a hallmark of the Digital Voice programs, will suffer a bit. The old
codec, called MELP, was designed for high quality, low data-rate communication,
and was particularly well suited for HF radio applications. </FONT></P>
<P><FONT face=Verdana>WinDRM occupies about 2.5 kHz of spectrum and sounds like
FM with few artifacts when signals are good. FDMDV, uses only 1.1 kHz of
spectrum. It sounds a little rougher, but still remarkable for that low
bandwidth. It works closer to the noise level, and has almost no latency. Both
programs use OFDM multiple carrier modulation schemes, and work with ordinary
single-sideband transceivers.</FONT></P>
<P><FONT face=Verdana>This episode points out the need for someone - somewhere -
to develop a codec for low-bandwidth digital voice on Amateur Radio. The
sound-card based digital-voice programs have been a continuous "work in
progress." But they need a codec for that work to continue.</FONT></P>
<P><FONT face=Verdana>Note that the AOR digital voice modems, and D-STAR radios,
use a commercial product, the AMBE 2020 vocoder, so they are
<EM><STRONG>not</STRONG></EM> affected by this license situation.</FONT></P>
<P><FONT face=Verdana><STRONG><EM>Gary Pearce, KN4AQ</EM></STRONG></FONT></P>
<P><FONT face=Verdana><STRONG><EM><BR></EM></STRONG>Fonte: Amateur Radio
Newsline</FONT> <BR></P></BODY></HTML>