Thetis and FreeDV important settings to get a good SNR

[Frank Rode]

Hello everyone,

I have various transceivers that I use for FreeDV. Flex-6500, IC-705 with amp, and a Hermes Lite 2 with amp. I noticed that with the Hermes Lite 2, when the signal was very good and the QRG was undisturbed, I got a 10dB worse SNR in FreeDV with Thetis under Windows, and there were also synchronization problems at the beginning. This did not happen under Linux in pihpsdr with the same hardware. I then carried out some tests without external influences. I found the cause. It is due to the DSP settings in Thetis. The default setting for the filter type in Digital is Low Latency. It must be changed to Linear Phase.

I would appreciate feedback if anyone else can confirm this.

73 Frank, DL2GRF

[Alan Beard]

Having run FreeDV mode 700D or 700E for years now on OpenWebRX, do we have a

command line decode script for RADE V1?

8k samples in from the RF DSP, 8k voice audio samples out 

Currently "freedv_rx 700E - -"

And I'll put it on our Men's Shed WebSDR:

shed.nepeanshed.org.au:8073

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[ea8ee]

Mooneer Salem K6AQ:

… there’s also a new receive-only integration available that’s intended for web-based SDRs. Originally intended for ka9q-radio, this is an application that accepts audio samples on standard input and outputs decoded audio on standard output. An SDR or other application would simply start this application and route audio through it whenever a user wants to decode FreeDV. The hope is that with this integration, many preexisting web-based SDRs will add support for FreeDV and allow people to listen to contacts over the internet, even if they don’t have a radio or the needed setup to run the FreeDV application.

To view this discussion visit https://groups.google.com/d/msgid/digitalvoice/CAKVz7kbp_QS-b%3D4juOkBR4MzydjP9DiNnc%2B7pukmigtWk124%3DA%40mail.gmail.com.

[Mooneer Salem]

Hi all,

More information on the command line application mentioned previously can be found in the respective README: https://github.com/drowe67/freedv-gui/blob/master/src/integrations/ka9q/README.md

Thanks,

-Mooneer K6AQ

To view this discussion visit https://groups.google.com/d/msgid/digitalvoice/CADJ3RdTuMP%3D1%3DxbuHqaiST_L87Be9jPoivTwT_6%2BktyckBbXHw%40mail.gmail.com.

[Alan Beard]

Thanks Mooneer,

> More information on the command line application mentioned previously can be found in the respective README

On changing to the "build_linux" directory, "make -j2 freedv-ka9q" worked, but on running it:

cat ../wav/all_radev1.wav | PYTHONPATH=$(pwd)/rade_src src/integrations/ka9q/freedv-ka9q -i 8000 -o 8000 > aaa.wav

First I get: rtkit could not make high priority: Permission denied    --- and my user is in the "audio" group now.

OS here: Linux Mint 22.1 Xia   (My target machine,  Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz)

Also the output wav file varies in size almost randomly:

-rw-r--r-- 1 alanb tims 562560 Nov 18 12:02 aaa.wav
-rw-r--r-- 1 alanb tims 347200 Nov 18 12:04 bbb.wav
-rw-r--r-- 1 alanb tims 562560 Nov 18 12:07 ccc.wav
-rw-r--r-- 1 alanb tims 650880 Nov 18 12:08 ddd.wav

Always with the same input ../wav/all_radev1.wav

So I'm not confident in implementing it.

To view this discussion visit https://groups.google.com/d/msgid/digitalvoice/CAAzDfxOKpYzgfKHR52mZWXo0M8PuCNXOmfkhavdq0J_n24pEWQ%40mail.gmail.com.

[Mooneer Salem]

Hi Alan,

The rtkit thing is optional IIRC; I think it's even logged as a warning instead of an error.

Also, have you tried to listen to any of the output files yet to see if they sound as expected? If decode is working properly they should sound fairly close to the version in the RADE repo (https://github.com/drowe67/radae/blob/main/wav/all.wav).

Thanks,

-Mooneer K6AQ

To view this discussion visit https://groups.google.com/d/msgid/digitalvoice/CAKVz7kbo7nV-xmyTN%3DGdQxmRZLEJWaztBWc%3D5-FZpnA8LmbCLA%40mail.gmail.com.