MSK144 Stream Decoder.

Input: Reads audio stream from stdin. Format: 12000 samples per second, 16 bits signed, mono.
Output: Prints decoded lines to stdout, optionally writes log files and posts results to a specific HTTP service.

Despite the repository has name msk144* it also includes jt65decoder and q65decoder. These decoders act in the similar way. They accept infinite stream at input, start recording at proper T/R interval, feed the consumed stream to decoder, repeat that process again in the loop.

How to compile:

Prereqirements:

sudo apt-get install build-essential
sudo apt-get install cmake
sudo apt-get install gfortran
sudo apt-get install libfftw3-dev
sudo apt-get install libboost-dev
sudo apt-get install libcurl4-openssl-dev

The project utilizes original WSJT decoder. WSJTX repository linked as git submodule.
After cloning this repository, execute the following commands:

cd msk144decoder
git submodule init
git submodule update --progress

Commands to build:

mkdir build
cd build
cmake ..
cmake --build . 

Executable file msk144decoder will appear at the current directory.

To install the binaries for system-wide use, you can additionally run the following command:

sudo cmake --install .

(sudo can be omitted if run as root)

Wav-file reading example:

cat ../demo/000000_000001.wav | ./msk144decoder
# Actually, when using cat command the wav header is also read. Not a big problem for decoder.

Get brief help:

./msk144decoder --help

./jt65decoder --help

./q65decoder --help

Getting stream from rtl_tcp example:

nc 192.168.1.200 2223 | ./csdr convert_u8_f | ./csdr shift_addition_cc 0.312451171875 | ./csdr fir_decimate_cc 64 0.005 HAMMING | ./csdr bandpass_fir_fft_cc 0.0 0.12 0.06 | ./csdr realpart_cf | ./csdr rational_resampler_ff 3 8 | ./csdr gain_ff 100.0 | ./csdr limit_ff | ./csdr convert_f_s16 | ./msk144decoder

Script ./scripts/generate_cmd_line.py will help you build csdr commands chain. Just make necessary changes in it and run.

cd scripts
python generate_cmd_line.py

Links:

• WSJT-X Software by Joe K1JT
• WSJT Git Repository at sourceforge
• Spot Reporter Discussion Thread (in Russian)

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Acknowledgements to K1JT Joe Taylor and WSJT Development Group. The algorithms, source code, and protocol specifications for the mode MSK144, JT65, Q65 are Copyright © 2001-2021 by one or more of the following authors: Joseph Taylor, K1JT; Bill Somerville, G4WJS; Steven Franke, K9AN; Nico Palermo, IV3NWV; Greg Beam, KI7MT; Michael Black, W9MDB; Edson Pereira, PY2SDR; Philip Karn, KA9Q; and other members of the WSJT Development Group.

Alexander, RA9YER.
ra9yer@yahoo.com