rtl_fm

rtl_fm is a command-line utility from the RTL-SDR toolset that tunes an SDR to a specific frequency and demodulates FM, outputting raw audio suitable for piping to audio players and processing tools.

https://manpages.ubuntu.com/manpages/trusty/man1/rtl_fm.1.html

https://github.com/osmocom/rtl-sdr/blob/master/src/rtl_fm.c

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