redsea is a lightweight command-line RDS decoder for Linux/macOS.
It can be used with any RTL-SDR USB radio stick with the rtl_fm tool.
It can also decode raw ASCII bitstream, the hex format used by RDS Spy,
and audio files containing multiplex signals (MPX).

RDS groups are printed to the terminal as line-delimited JSON objects
or, optionally, undecoded hex blocks (-x).