cropinghigh / stdcdec

Open-source inmarsat-C cli decoder, based on inmarsatc library.

stdcdec

Set of programs to receive Inmarsat-C signals

Related projects:

inmarsatc: library with all functions to receive Inmarsat-C signals
https://github.com/cropinghigh/inmarsatc

qstdcdec: qt version of stdcdec_parser
https://github.com/cropinghigh/qstdcdec

sdrpp-inmarsatc-demodulator: SDR++ module, which replaces stdcdec_demod and stdcdec_decoder
https://github.com/cropinghigh/sdrpp-inmarsatc-demodulator

Building:

0. If you have an arch-like system, just install stdcdec-git with all dependencies

1. Install inmarsatc library(libinmarsatc-git for arch-like systems)

2. Build

   mkdir build
   cd build
   cmake ..
   make
   sudo make install
   

Usage:

1. Run stdc_demod to demodulate symbols from audio stream(you need additional program to move RF signal to audio zone, like SDR++ or gqrx, Inmarsat-C signal are usually around 1539MHz).

   Available arguments:

   --lo-freq <freq>           - set the minimum audio frequency in Hz where demodulator will search for the signal, default=500Hz
   --hi-freq <freq>           - set the maximum audio frequency in Hz where demodulator will search for the signal, default=4500Hz
   --cent-freq <freq>         - set the initial audio center frequency in Hz to tune demodulator to, default=2600Hz; Because demodulator is not very good, it requires to be set quite precisely and a bit higher than actual signal center frequency(~100 Hz)
   --stats                    - demodulator will print statistics(frequency and lock status). Useful for tuning
   --source-file <file path>  - use the audio file as the source for the demodulator
   --source-udp <port>        - receive audio samples via udp. Compatible with gqrx, default argument=7355
   --source-alsa <device>     - read audio samples from specified alsa device, default argument=default
   --out-udp <ip> <port>      - send demodulated symbols to specified ip and port, default arguments=127.0.0.1 15003
   

   Note that exactly one source and one out arguments should be used.

2. Run stdc_decoder to decode symbols to get the frames

   Available arguments:

   --verbose              - print all frames to the stdout, useful for tuning
   --in-udp <port>        - receive demodulated symbols via udp, default argument=15003
   --out-udp <ip> <port>  - send decoded frames to specified ip and port, default arguments=127.0.0.1 15004
   

   Note that exactly one in and one out arguments should be used.

3. Run stdc_parser to extract packets and messages from the frames

   Available arguments:

   --verbose              - print all data for all parsed packets
   --print-all-packets    - print all packets, not only messages
   --in-udp <port>        - receive decoded frames via udp, default argument=15003(should be changed to 15004)
   --out-udp <ip> <port>  - send parsed packets to specified ip and port in JSON, default arguments=127.0.0.1 15005
   

   Note that exactly one in argument should be used

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