Hi David
fair enough
here is some good and reasonable recent work by one of your own.....
http://search.ror.unisa.edu.au/record/UNISA_ALMA11140739050001831/media/digital/open/9916110811201831/12140739040001831/13140739030001831/pdf
Maybe build into freeDV some sort of recording to disk and FTP upload to
codec2 server....
On 7/05/2018 9:02 AM, David Rowe wrote:
The 700D waveform is designed for subset of those paths. As part of
the testing I'd like to crowd source some samples of where it works
and were it doesn't.
Long term - if the average SNR is there, a waveform can be designed to
pass DV over it. Eventually.
DV over HF is a tough problem, and every development consumes 1000's
of volunteer man-hours (mainly mine). So I'm taking a tractable path
through the problem.
Currently the focus is on low SNR HF channels. I'll make incremental
improvements from there, e.g. rarer HF paths, higher speech quality at
higher SNRs etc.
- David
On 07/05/18 07:45, glen english wrote:
SSB sometimes wins because the brain picks up the slack. like with a
0.5 second fade.
In my opinion, for HF paths, to be broadly useful , voice DV modes
need to pass an HF fading simulator, targeted at vertical incidence
work, and bear in mind, that the channel profiles are quite different
for Equatorial, Mid latitude and high latitude locations. And they
must have minimal conversational delay, , < 0.25 seconds.
take a look at
https://www.itu.int/dms_pubrec/itu-r/rec/f/R-REC-F.1487-0-200005-I!!PDF-E.pdf
several languages :
https://www.itu.int/rec/R-REC-F.1487-0-200005-I/en
This article, is useful for its 127 excellent references,
https://link.springer.com/article/10.1007/s11235-017-0287-2#CR38
and has some excellent channel profile references .
From the DRM spec, Annex B Definition of channel profiles
Channel 6, path 4
delta delay : 6mS, path gain RMS = 0.0625, dopplershift : 3.6Hz,
dopper spread 7.2Hz
Some paths are worse than that .. especially vertical incidence paths
what have values almost triple the above numbers....
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