Folks, I know a lot about vhf and uhf communications, ssb, too. But audio
codecs is something I just don't know much about. Having' said that, I
want you all to know that I am enjoying the posts, and picking up a thing
here or there. Keep up the great work people. That's what Amateur Radio
and open source stuff is all about. I wish I could help more.
73, Larry KL7IBV
On Sun, Jul 8, 2012 at 3:34 AM, David Rowe <[email protected]> wrote:
> Hello,
>
> I have been building some GUI displays for the FDMDV/Codec2 system to
> help test and prototype various chunks of code.
>
> I have attached a screen shot from the latest version of fl_fdmdv that
> plots various fdmdv modem parameters, and can accept an input signal
> from the default sound card microphone. The screen shot shows a signal
> I am transmitting from another PC across a simple audio cable. The
> different view (spectrum, scatter diagram), were helpful in adjusting
> the microphone and speaker levels. I have also picked up a few minor
> bugs using this real time view.
>
> It can also run with a file input and looks really interesting with data
> from fading channels (let me know if any one wants those fading channel
> fdmdv files for testing). The screen shot doesn't really capture how
> cool it looks in real time.
>
> I found one of the best ways to adjust the levels was based on
> maximising the SNR, which is > 20dB in this screenshot.
>
> Next step is to add the Codec 2 decoder and output speech from the sound
> card. We will then be ready for some on air tests. I want to use this
> code to tweak the user experience, e.g. optimise the sync code, make
> sure R2D2 noises are minimised when out of sync, and develop tuning aids
> (like SNR).
>
> The A/D - demod - decoder - D/A "main loop" code in this program could
> also be adapted to run as a daemon on platforms without a GUI.
>
> I am using the fltk and portaudio libraries so this code could be easily
> ported to Windows if anyone is interested.
>
> Bye,
>
> David
>
>
>
>
>
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